POLYUNSATURATED FATTY ACID CONTAINING A FOOD INGREDIENT WITH IMPROVED PALATABILITY AND METHOD FOR MANUFACTURING THE SAME

Abstract

This disclosure comprises a refined PUFA oil with improved palatability compared to the same unrefined PUFA oil. It also discloses a pet food or human food composition comprising the aforementioned refined PUFA oil and thus having improved palatability. A further disclosure herein is a method for manufacturing the aforementioned refined PUFA oil, which includes a deodorization step.

Description

POLYUNSATURATED FATTY ACID CONTAINING A FOOD INGREDIENT WITH IMPROVED PALATABILITY AND METHOD FOR MANUFACTURING THE SAME nzAann / lzaz / b / yl FIELD OF INVENTION The present invention relates to a pet food and a human food with improved palatability, whereby said food contains polyunsaturated fatty acids. The present invention relates to a method for manufacturing the aforementioned food ingredient. BACKGROUND OF THE INVENTION Pet food manufacturers have a business incentive to produce a food that meets the following three criteria: high nutritional value, high palatability, and low production cost. The nutritional value of polyunsaturated fatty acids (PUFAs), such as omega-3 fatty acids, is well established. PUFAs are biologically important molecules that affect molecular physiology due to their presence in the cell membrane, regulate the gene expression of biologically active compounds, and serve as biosynthetic substrates. For example, docosahexaenoic acid (DHA) constitutes approximately 15–20% of the lipids in the animal brain and 30–60% of the lipids in the retina. Since omega-3 fatty acids cannot be synthesized by de novo terrestrial animals, these fatty acids must be obtained from dietary sources. Polyunsaturated fatty acids are synthesized by microbes such as microalgae and fungi. Fish acquire polyunsaturated fatty acids by feeding on these microbes. Commercially, polyunsaturated fatty acids are obtained by extracting them from fish, as well as by harvesting microalgae or fungi through fermentation and extraction. Many chemicals are used in the PUFA oil extraction process to accelerate the extraction process through chemical reactions. Volatile byproducts are generated during these reactions. Many volatile byproducts, such as lipid oxidation products and Maillard reaction products, are produced in the extraction process. When PUFA oil is initially extracted from fish or microalgae without any further refining, it is called crude oil. Crude oil has an unpleasant odor and taste and is therefore not well received and is even rejected by humans and animals. When designing food for humans and companion animals such as cats and dogs, providing a high level of nutrition is an important goal. However, if the human or animal refuses to eat the food because they find it unappealing, that food will have no value for them. The food product will also be worthless to the manufacturer, as there will be no market for it. Therefore, there is a strong incentive to produce a palatable food ingredient containing PUFAs. Crude oil needs to be purified before it is ready for human consumption. Generally, the purification process involves the steps of refining, bleaching, winterizing, and deodorizing. Refining involves the removal of free fatty acids, phospholipids, oil-soluble material, trace metals, and water-soluble molecules. Bleaching removes pigments, secondary oxidation products, trace metals, vitamins, environmental contaminants, and other polar components. Winterizing is the process of removing sediment that will appear in oils at low temperatures. Deodorizing refers to the removal of volatile components, secondary oxidation products, free fatty acids, mono- and diglycerides, aldehydes, ketones, chlorinated hydrocarbons, pigments, and persistent organic contaminants.The above process is also called the RBWD process for the initial letter in English (refinement, bleaching, winterization, deodorization) of the four steps. It is costly to perform the four steps of refining, bleaching, winterizing, and deodorizing in a reverse robbed water (RBWD) process due to the equipment, energy, labor, and time involved. Additionally, up to 55–60% of the PUFA oil can be lost during a full RBWD process. Therefore, although the unpleasant odor and taste of crude PUFA oil can be eliminated through a full RBWD process, the cost of producing such oil is high. Consequently, it is typically used to produce purified PUFA oil for human consumption. This makes selling and manufacturing pet food that is palatable and contains a nutritionally significant amount of PUFA economically challenging. Therefore, there is a need for a PUFA oil that has high nutritional value and high palatability, while also being produced at a low cost. Historically, efforts to produce a low-cost yet reasonably palatable PUFA-containing food ingredient have focused on creating palatability enhancers. For example, U.S. Patent Application No. 12 / 442,828 discloses an algae-based biofood palatability enhancer that is said to improve the texture and taste of pet food. U.S. Patent Application No. 15 / 038545 discloses a method for formulating a palatability enhancer by including suitable fat sources and edible agents in the food. However, formulating a separate palatability enhancer and blending it into the food has proven costly. Additionally, the palatability enhancer sometimes has an adverse impact or compromises the nutritional quality or other characteristics of the underlying pet food.Therefore, there is still a need to find a new approach to solving this problem. The goal of this invention is to find a method that makes PUFA oil highly palatable while keeping production costs low. BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the palatability of a polyunsaturated fatty acid (PUFA) oil for a pet, wherein said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming or refining the PUFA oil using a short-path evaporator (SPE), or both degumming and refining it using an SPE, after step a); c) deodorizing the PUFA oil from step b); wherein the yield of PUFA oil after step c) is not less than 85% of the amount of crude oil used in step a), wherein said palatability is measured by an animal feed preference test, and wherein the palatability score of the PUFA oil obtained after step c) is at least 10 percentage points higher than the crude oil used in step a). In one embodiment, the PUFA oil yield is not less than 90% of the crude oil used in step a). In one embodiment, the preceding animal feed preference test is a two-bowl test. In other embodiments, the palatability score of the PUFA oil obtained after step c) is at least 20, at least 30, at least 40, or at least 45 percentage points higher than the crude oil used in step a). In some models, step c) of deodorization is carried out using a VTA deodorizer or a DeSmet deodorizer. In some forms, PUFA oil is derived from fish, microorganisms, or plants. In one form, the microorganisms are algae. In another form, the algae are Schizochytrium, Aurantiochytrium, or Thraustochytrium. In some forms, PUFA oil comprises one or more compounds of DHA, EPA, ARA, and DPA. The present invention is also directed to a polyunsaturated fatty acid (PUFA) oil, wherein said PUFA oil comprises less than 10 ppb of one or more Maillard reaction compounds and more than 1.5 ppb of one or more lipid oxidation products, when qualified as ethyl heptanoate. In some forms, PUFA oil comprises less than 1 ppb, less than nzAann / Lznz / E / YiAi 0.5 ppb or less than 0.3 ppb Maillard reaction compounds when graded as ethyl heptanoate. In one embodiment, the amount of Maillard reaction compounds in said PUFA oil is not detectable when it is classified as ethyl heptanoate. In one embodiment, the Maillard reaction compounds are selected from a group consisting of: trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, tetramethylpyrazine, 2-hydroxy-3-methyl-2-cyclopenten-1-one, methyl-1H-pyrrole-2-carboxaldehyde, and indole. In another embodiment, the lipid oxidation products are selected from a group consisting of: 1-penten-3-one, 4-heptenal, and 2,6-nonadienal. The present invention also relates to a pet food composition comprising a PUFA oil produced by the method described above. The present invention further relates to a pet food composition wherein said food composition comprises the PUFA oil comprising less than 10 ppb of one or more Maillard reaction compounds and more than 1.5 ppb of one or more lipid oxidation products, when qualified as ethyl heptanoate. In some cases, the aforementioned pets are a dog or a cat. In some forms, the aforementioned food composition is dog food, cat food, a dog treat, or a cat treat. In one form, the food composition is a nutritional supplement. The present invention also relates to a food composition for human consumption comprising a PUFA oil produced by the method described above. The present invention further relates to a food composition for human consumption wherein said food composition comprises the PUFA oil comprising less than 10 ppb of one or more Maillard reaction compounds and more than 1.5 ppb of one or more lipid oxidation products, when qualified as ethyl heptanoate. The present invention is further directed to a method for increasing the yield of a polyunsaturated fatty acid (PUFA) oil over a control oil which is the same oil, but which has been refined, bleached, winterized and deodorized (RBWD oil), wherein said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming said PUFA oil, or refining it using a short path evaporator (SPE) for said PUFA oil or both degumming and refining said PUFA oil using an SPE after step a); and c) deodorizing the PUFA oil of step b); wherein the yield of the PUFA oil after step c) is more than 5 percentage points higher than the yield of the RBWD oil. In some configurations, the PUFA oil yield after step c) is 10 or 20 percentage points higher than the RBWD oil yield. In some formulations, the difference between the palatability scores of PUFA oil after step c) and RBWD oil is less than 10% in an animal feed preference test using a common control sample oil. In another formulation, PUFA oil after step c) has a higher palatability score than RBWD oil in an animal feed preference test using a common control sample oil. In one formulation, the animal feed preference test is a two-bowl test. In one modality, step c) of deodorization is carried out using a VTA deodorizer or a DeSmet deodorizer. In some forms, PUFA oil is derived from fish, microorganisms, or plants. In one form, the microorganisms are algae. In another form, the algae are Schizochytrium, Aurantiochytrium, or Thraustochytrium. In some forms, PUFA oil comprises one or more compounds of DHA, EPA, ARA, and DPA. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph showing the human sensory result of samples of PUFA oil from algae, showing the aroma score of deodorized and non-deodorized algae oils and the palatability score of some oils. DETAILED DESCRIPTION OF THE INVENTION The features and advantages of the invention can be more easily understood by those of ordinary skill in the art after reading the following detailed description. It should be appreciated that certain features of the invention, described above and below in the context of separate embodiments for the sake of clarity, can also be combined to form subcombinations thereof. The modalities identified here as examples are intended to be illustrative and not limiting. Another objective of the present invention is to provide a PUFA oil that is palatable for consumption by pets and / or humans and that, at the same time, requires minimal treatment and can therefore be produced at a low cost. Another objective of the present invention is to develop a method for producing a palatable PUFA oil more efficiently than a method using the conventional processing steps of refining, bleaching, winterizing and deodorizing. The present invention has the additional objective of identifying a group of compounds or an individual compound that is the primary cause of unpleasant odor and taste for pets, and the removal of which from crude PUFA oil would significantly improve the palatability of the PUFA oil. The above objectives are achieved in accordance with the present invention. Crude microbial PUFA oil and raw fish oil are rich in polyunsaturated fatty acids, especially omega-3 polyunsaturated fatty acids such as DHA and EPA. It is widely recognized that omega-3 polyunsaturated fatty acids, particularly DHA and EPA, are essential nutrients for animals. Mammals such as humans and pets must obtain omega-3 polyunsaturated fatty acids from external sources, as they cannot synthesize these nutrients internally. However, unprocessed crude microbial PUFA oil and raw fish oil have a strong, unpleasant odor that needs to be removed before they are suitable for consumption by pets and humans. Traditionally, the refining process is complex, involving at least four steps, including refining, bleaching, winterizing, and deodorizing, and is therefore very expensive and low-yield.This makes pet food production economically challenging, as it contains sufficient PUFAs while remaining competitively priced. As a result, some pets have access to a diet rich in beneficial nutrients such as PUFAs. Surprisingly, this invention found that, among the four processing steps for PUFA oil—refining, bleaching, winterizing, and deodorizing—deodorizing is the most effective step in improving the palatability of PUFA oil for a pet. It was also found that adding either a degumming step or a refining step further increases the palatability of the PUFA oil without significant loss in oil production yield. Therefore, palatable PUFA oil can be produced at low cost by treating crude PUFA oil with a deodorizing step and, optionally, an additional degumming step or an additional refining step, or both. Changes in palatability are measured using an animal food preference test. The animal food preference test used in this invention is a two-bowl test. The two-bowl test (or paired test or comparison test) compares how much of two foods, presented simultaneously, is eaten within a defined time period. This is a common test used by expert panels for palatability evaluation studies in dogs and cats. In the present invention, two pet food samples, each containing a different PUFA oil, are compared to each other. The first food contains a control PUFA oil. The second food contains a test PUFA oil. The control PUFA oil can be any PUFA oil sample, whether crude or processed.A control PUFA oil commonly used in this invention is a commercially available fish oil that has been treated by refining, bleaching, and deodorizing. In another embodiment, the control PUFA oil is a commercially available fish oil that has been treated by refining, bleaching, winterizing, and deodorizing. In one embodiment, the test PUFA oil is a sample PUFA oil whose palatability is measured against the control PUFA oil. This test PUFA oil may be a crude, unprocessed algae oil or an algae oil that has been processed by one or more steps of degumming, short-path evaporation, refining, bleaching, winterizing, and deodorizing. The palatability of a test PUFA oil is considered superior to the other PUFA oil it is paired with in a two-bowl test when the palatability score of the test PUFA oil is above 50%. This means that the test PUFA oil is preferred by the experimental animal more than 50% more than the control PUFA oil. The two-bowl test and its scoring method are described in detail in Example 2 of this application. The two-bowl test is a type of animal feed preference test and provides a quantitative measurement of an animal's feed preference. The sum of the palatability scores of the two compared samples is always 100%. For example, if the palatability score of one test PUFA oil is 56%, the palatability score of the other PUFA oil is 44%. When several different test PUFA oils are measured against the same PUFA oil, which in this case is called the control PUFA oil or simply the control oil, the relative preferences among the test PUFA oil samples can be observed. For example, if the palatability scores of test PUFA oil samples A, B, and C are 56%, 64%, and 74%, respectively, and all are higher than the control oil, it can be concluded that sample C is the most palatable among the three samples. In this case, the identity of the control oil becomes irrelevant. This method is used in this invention to evaluate the effect of different processing steps on palatability improvement. The palatability of a first test PUFA oil is considered to have been significantly improved over a second test PUFA oil when the palatability score of the first test PUFA oil is 20 percentage points or nzfiann / Lznz / E / YiAi higher than the second PUFA oil. For example, if the palatability score of a test PUFA oil that has been refined, bleached, and winterized is 46% and another test PUFA oil that has been refined, bleached, winterized, and deodorized is 74%, the palatability of the test PUFA oil is considered to have been significantly improved by the additional deodorization step, since the increase in palatability score is 38%. PUFA oil yield is defined as the percentage of PUFA oil remaining after one or more processing steps compared to the amount at the start of the process. Since each processing step will remove some amount of the oil along with the impurities it is designed to remove, PUFA oil yield is generally expected to decrease as more processing steps are added to the purification process. It is surprising to find in this invention that the deodorization step is much more effective in improving the palatability of a PUFA oil for a pet than any of the refining, bleaching, winterizing, or even all three steps combined. It is also surprising to find that by adding either a degumming step or a refining step, or both, a high yield of 90% or more of the crude oil is obtained after these processing steps. The resulting oil has an increased palatability at least 45 percentage points higher than the palatability score of the crude oil. A common control oil sample is used to measure the palatability score of the processed oil and the crude oil. In one embodiment, the present invention relates to a method for improving the palatability of a polyunsaturated fatty acid (PUFA) oil for a pet, wherein said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming, or refining, or both degumming and refining, the PUFA oil from step a); c) deodorizing the PUFA oil from step b); wherein the yield of PUFA oil after step c) is not less than 85% of the amount of crude oil with which it was started in step a), wherein said palatability is measured by an animal feed preference test, and wherein the palatability score of the PUFA oil obtained after step c) is at least 10 percentage points higher than the PUFA oil obtained after step c).In another embodiment, the PUFA oil yield is not less than 80%, or less than 81%, or less than 82%, or less than 83%, or less than 84%, or less than 85%, or less than 86%, or less than 87%, or less than 88%, or less than 89%, or less than 90%, or less than 91%, or less than 92%, or less than 93%, or less than 94%, or less than 95% when comparing the amount of PUFA oil obtained after step c) with the amount of crude oil with which it started in step a). In another modality, the PUFA oil yield is between 85% and 99%, between 85% and 95%, between 87% and 93%, between 90% and 95%, and between 92% and 95% when comparing the amount of PUFA oil obtained after step c) with the amount of crude oil with the start in step a). In another modality, the increase in the palatability score of PUFA oil at the previous performance level is at least 10 percentage points higher, at least 15 percentage points higher, at least 25 percentage points higher, at least 30 percentage points higher, at least 35 percentage points higher, at least 40 percentage points higher, at least 45 percentage points higher, at least 50 percentage points higher, at least 55 percentage points higher, at least 60 percentage points higher, at least 65 percentage points higher than the palatability score of the crude oil before processing.In another modality, the increase in the palatability score of PUFA oil at the previous yield level is 20% to 65%, 30% to 65%, 40% to 65%, 20% to 65%, 30% to 50%, 40% to 50%, 30% to 60%, 40% to 60%, 20% to 30%, 10% to 20%, or 30% to 40% percentage points higher than the palatability score of the crude oil before processing. Furthermore, it is remarkable to find in this invention that by replacing the conventional processing steps of refining, bleaching, and winterizing (RBWD oil) with a degumming step or a short-path evaporation step, or both, while retaining the deodorization step, the yield of the resulting oil is more than 20 percentage points higher than that of RBDW oil. The resulting oil has an increased palatability score at least 10 percentage points higher than that of RBWD oil. A common control oil sample is used to measure the palatability score of the deodorized oil and the RBWD oil. In one embodiment, the invention relates to a method for increasing the yield of a polyunsaturated fatty acid (PUFA) oil over a control oil that is the same oil that has been refined, bleached, winterized, and deodorized (RBWD oil), wherein said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming, refining, or both degumming and refining said PUFA oil; c) deodorizing the PUFA oil from step b); wherein the yield of the PUFA oil after step c) is more than 30 percentage points higher than the yield of the RBWD oil. The yield of the RBWD oil is calculated as the percentage ratio between the amount of oil remaining after the crude oil in step a) is processed by the refining, bleaching, winterizing, and deodorizing steps and the amount of crude oil in step a).In other variations, the PUFA oil yield after step c) is more than 25 percentage points higher, more than 25 percentage points higher, more than 19 percentage points higher, more than 18 percentage points higher, more than 15 percentage points higher, more than 13 percentage points higher, more than 10 percentage points higher, or more than 5 percentage points higher than the RBWD oil yield. In one variation, the palatability score of the above oil after step c) and the control oil are the same. In one variation, the palatability score of the above oil and the control oil differs by no more than 10%. In another modality, the difference in palatability score of no more than 9%, no more than 8%, no more than 7%, no more than 6%, no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%.In another scenario, the difference in palatability score is between 1% and 10%, between 2% and 10%, between 3% and 10%, between 4% and 10%, between 5% and 10%, between 6% and 10%, between 7% and 10%, and between 4% and 7%. In another scenario, the PUFA oil after step c) has a higher palatability score than the RBWD oil in an animal preference test using a common control sample oil. In another scenario, the PUFA oil after step c) has a palatability score 1 to 10, 5 to 10, or 7 to 10 percentage points higher than the RBWD oil in an animal preference test using a common control sample oil.In another modality, PUFA oil after step c) has a higher palatability score of between 1% and 10%, between 2% and 10%, between 3% and 10%, between 4% and 10%, between 5% and 10%, between 6% and 10%, between 7% and 10% and between 4% and 7% than that of RBWD oil. In one embodiment, the above objectives are achieved by a method for improving the palatability of a PUFA oil comprising the step of treating said oil with a deodorizer. In a preferred embodiment, the deodorizer is a VTA deodorizer. In another preferred embodiment, the deodorizer is a DeSmet deodorizer. In another embodiment, the above method further comprises a degumming step and / or a short-path evaporation step. In yet another preferred embodiment, the method does not comprise any refining, bleaching, or winterizing steps and, therefore, significantly increases the yield of PUFA oil in the process and reduces the production cost. The degumming step and the short-path evaporation step result in a slight loss of oil yield. The refining, bleaching, and winterizing steps result in a significant loss of yield. nzAann / Lznz / E / YiAi Without being bound by theory, it is hypothesized that the deodorizer removes Maillard reaction compounds and thus helps eliminate unpleasant odor(s) and taste(s) from the PUFA oil and improves its palatability. It is further hypothesized that degumming removes materials from the PUFA oil, such as phospholipids and other compounds, and any that might clog the deodorizer in the subsequent deodorization step. It is also hypothesized that the short-path evaporation (SPE) step removes free fatty acids from the PUFA oil and thus prevents oxidation of the resulting PUFA oil. In the present invention, the degumming and refining steps are optional, as their application depends on the quality of the crude oil being processed. If the starting crude PUFA oil contains few free fatty acids, the refining step can be omitted.Similarly, if the starting crude oil contains few phospholipids or other impurities and is therefore unlikely to clog the deodorizer, the degumming step can also be omitted. It was known that volatiles produced during the extraction of PUFA oil from its source, whether algae or fish, generally cause unpleasant odor(s) and flavor(s). Examples of volatiles that cause unpleasant odors include, but are not limited to, lipid oxidation products such as 1-penten-3-one, 4-heptenal, and 2,6-nonadienal, and Maillard reaction compounds such as trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, tetramethylpyrazine, 2-hydroxy-3-methyl-2-cyclopenten-1-one, 1H-pyrrole-2-carboxaldehyde, and indole. Surprisingly, it was found in this invention that removing the Maillard reaction products, but not the lipid oxidation products, can significantly improve the palatability of PUFA oil.Deodorizers were found to be very effective in removing Maillard reaction products from crude PUFA oils and thus improving the palatability of these oils. In one embodiment, crude PUFA oil is treated to remove all or substantially all Maillard reaction compounds, whereby the resulting oil has a significantly higher palatability score than the crude PUFA oil. In one embodiment, the aforementioned Maillard reaction compounds are reduced to the following list: trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, tetramethylpyrazine, 2-hydroxy-3-methyl-2-cyclopenten-1-one, methyl-1H-pyrrole-2-carboxaldehyde, and indole. It was found in the present invention that the removal of the above seven compounds from a crude algae oil or a crude fish oil can significantly increase the palatability of said oil to pets. It was also found in the present invention that the level of lipid oxidation products in the non-NZAann / Lznz / E / YiAi PUFA oil significantly improves the palatability of the oil.Examples of lipid oxidation products include, but are not limited to: 1-penten-3-one, 4-heptenal, and 2,6-nonadienal. In one embodiment, the palatability of PUFA oil is significantly improved by removing Maillard reaction compounds from crude PUFA oil to undetectable levels. In one embodiment, the method for detecting Maillard reaction compounds and lipid oxidation products is a gas chromatography-mass spectrometry-solid-phase microextraction (SPME-GCMS) analysis method. In another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the PUFA oil to less than 10 ppb when graded as ethyl heptanoate.In another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the PUFA oil to less than 10 ppb when graded as ethyl heptanoate, while lipid oxidation products in the PUFA oil are found at a level of more than 1.5 ppb when graded as ethyl heptanoate. In another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the crude oil to less than 1 ppb when graded as ethyl heptanoate. In yet another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the crude oil to less than 0.5 ppb of Maillard reaction compounds when graded as ethyl heptanoate. In another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the crude oil to less than 0.3 ppb when graded as ethyl heptanoate. In other embodiments, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the crude oil to less than 500, less than 200, less than 100, less than 50, less than 20, less than 5, less than 2, less than 0.2, less than 0.1 ppb when graded as ethyl heptanoate. In other formulations, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the crude oil to between 500 and 0.1 ppb, between 200 and 0.1, between 200 and 0.1, between 100 and 0.1, between 50 and 0.1, between 10 and 0.1, between 2 and 0.1, between 1 and 0.1, between 20 and 1, between 10 and 1 when classified as ethyl heptanoate. The numerical value of the level of Maillard reaction compounds and lipid oxidation products referred to in this application (in the unit of ppb) is the total amount of Maillard reaction compounds and lipid oxidation products detected in the PUFA oil, unless specifically designated as the level of an individual Maillard reaction compound and lipid oxidation product. In another embodiment, the palatability of PUFA oil for humans and pets is significantly improved by reducing the level of Maillard reaction compounds in the PUFA oil to less than 10 ppb, whereas the PUFA oil comprises more than 1.5 ppb of one or more lipid oxidation products when graded as ethyl heptanoate. In one embodiment, the lipid oxidation products are selected from a group consisting of 1-penten-3-one, 4-heptenal, and 2,6-nonadienal. In other forms, lipid oxidation products in PUFA oil are found at a level of more than 1 ppb, more than 2 ppb, more than 3 ppb, more than 4 ppb, more than 5 ppb, more than 20 ppb, more than 50 ppb, more than 100 ppb, when rated as ethyl heptanoate.In other formulations, lipid oxidation products in PUFA oil are found at levels between 100 and 1 ppb, between 50 and 1 ppb, between 20 and 1 ppb, and between 15 and 1 ppb, when graded as ethyl heptanoate. In other formulations, the level of Maillard reaction compounds in crude oil is less than 500, less than 200, less than 100, less than 50, less than 20, less than 5, less than 2, less than 0.2, and less than 0.1 ppb when graded as ethyl heptanoate. In another embodiment, the palatability of PUFA oil is significantly improved by removing not only Maillard reaction compounds from crude PUFA oil to a low or undetectable level, but also all or substantially all free fatty acids. In another embodiment, crude oil is treated to remove all or substantially all Maillard reaction compounds, free fatty acids, phospholipids, and cations. In one embodiment, free fatty acids are removed from PUFA oil to a level of less than 0.1% by weight of the oil.In some embodiments, the level of Maillard reaction compounds in the crude oil is less than 500, less than 200, less than 100, less than 50, less than 20, less than 5, less than 2, less than 0.2, and less than 0.1 ppd when graded as ethyl heptanoate. In one embodiment, free fatty acids are removed from the PUFA oil at a level between 1% and 0.01% by weight of the oil. In another embodiment, free fatty acids are removed from the PUFA oil at a level of less than 0.01% by weight of the oil. In one embodiment, phospholipids are removed from the PUFA oil at a level of less than 0.1% by weight of the oil. In one embodiment, phospholipids are removed from the oil of nzAann / Lznz / E / YiAi. PUFAs are removed from the oil at a level between 1% and 0.01% by weight of the oil. In another embodiment, phospholipids are removed from the PUFA oil at a level of less than 0.01% by weight of the oil. In one embodiment, cations are removed from the PUFA oil at a level of less than 0.1% by weight of the oil. In another embodiment, cations are removed from the PUFA oil at a level of less than 0.01% by weight of the oil. In one embodiment, cations are removed from the PUFA oil at a level between 1% and 0.01% by weight of the oil. Furthermore, the method disclosed herein is for improving the palatability of a PUFA oil, where the PUFA oil is treated with a deodorizer. In one embodiment, the deodorizer is a DeSmet deodorizer. In another embodiment, the deodorizer is a VTA deodorizer. In yet another embodiment, the deodorizer can be any type of equipment capable of effectively removing Maillard reaction compounds. In a further embodiment, the deodorizer can be any type of equipment capable of effectively removing a list of Maillard reaction compounds comprising: trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, tetramethylpyrazine, 2-hydroxy-3-methyl-2-cyclopenten-1-one, methyl-1H-pyrrole-2-carboxaldehyde, and indole. Furthermore, what is disclosed here is a method to improve the palatability of a PUFA oil where the PUFA oil is treated using a short path evaporator.Furthermore, what is disclosed here is a method to improve the palatability of a PUFA oil where the PUFA oil is treated through a degumming process. In general, a pet food containing PUFAs is made from a mixture of pet food ingredients with PUFA oil or PUFA powder. Similarly, a food containing PUFAs for human consumption is made from a mixture of a human food ingredient with PUFA oil or PUFA powder. The present invention provides a pet food with improved palatability by mixing pet food ingredients with the deodorized PUFA oil described above. The invention further provides a human food with improved palatability by mixing human food ingredients with the deodorized PUFA oil described above. The invention further provides a nutritional supplement composition with improved palatability by mixing human nutritional supplement ingredients with the deodorized PUFA oil described above. The PUFA oil described herein refers to an oil comprising PUFAs. In one embodiment, the PUFA oil described herein refers to an oil comprising a significant amount of PUFAs. In some embodiments, the oil comprises at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% by weight of PUFAs. The source of such PUFAs in PUFA oil nzRonn / Lznz / E / YiAi may be fish or microbes. In some embodiments, the microbes are algae, bacteria, fungi, yeast, or protists. If a significant amount of the PUFAs are derived from microbes, it is called microbial oil. If a significant amount of the PUFAs are derived from microalgae, it is called algal oil. If a significant amount of the PUFAs are derived from fish, it is called fish oil. Polyunsaturated fatty acids (PUFAs) are classified based on the position of the first double bond at the methyl end of the fatty acid. Omega-3 (n-3) fatty acids have their first double bond at the third carbon, while omega-6 (n-6) fatty acids have their first double bond at the sixth carbon. For example, docosahexaenoic acid (DHA) is a long-chain omega-3 polyunsaturated fatty acid (LCPUFA) with a chain length of 22 carbons and 6 double bonds, often designated as “22:6n-3”. In one embodiment, the PUFA is selected from an omega-3 fatty acid, an omega-6 fatty acid, and mixtures of these. In another embodiment, the PUFA is selected from LC-PUFAs. In yet another modality, PUFA is selected from docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), arachidonic acid (ARA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA), stearidonic acid (SDA) and mixtures of these.In another formulation, the PUFA is selected from DHA, EPA, DPA, ARA, and mixtures thereof. In yet another formulation, the PUFA is DHA. In yet another formulation, the PUFA is EPA. In yet another formulation, the PUFA is ARA. PUFAs can be in the form of a fatty acid, salt, fatty acid ester (e.g., methyl or ethyl ester), monoacylglycerol (MAG), diacylglycerol (DAG), triacylglycerol (TAg) and / or phospholipid (PL). Free fatty acids are polyunsaturated fatty acids that have lost their triacylglycerol structure or broken off from oil molecules. Reducing free fatty acids in PUFA oil is expected to reduce long-term oxidation and thus extend the shelf life of the PUFA oil. Crude microbial PUFA oil is typically extracted from microbial cells. As used herein, a “cell” refers to an oil-containing biomaterial, such as a biomaterial derived from oleaginous microorganisms. In one embodiment, crude microbial oil refers to crude oil extracted from the microbial biomass without further processing. Crude microbial oil is usually treated before use in pet food or human food. As used herein, a “microbial cell” or “microorganism” refers to organisms such as algae, bacteria, fungi, yeast, protists, and combinations thereof, e.g., unicellular organisms. In some forms, a microbial cell is a eukaryotic cell. A microbial cell includes, but is not limited to, golden algae (e.g., nzfiann / Lznz / E / YiAi e.g., microorganisms of the kingdom of stramenopiles); green algae; diatoms; dinoflagellates (e.g., microorganisms of the order Dinophyceae including members of the genus Crypthecodinium such as, for example, Crypthecodinium cohnii or C. cohnii), microalgae of the order Thraustochytriales\ yeast (ascomycetes or basidiomycetes); and fungi of the genera Mucor, Mortierella, including, but not limited to, Mortierella alpina and Mortierella sect, schmuckeriy Pythium, including, but not limited to, Pythium insidiosum. In one modality, the microbial cells are from the genus Mortierella, the genus Crypthecodinium, or the order Thraustochytriales. In a further modality, the microbial cells are from Crypthecodinium cohnii. In yet another modality, the microbial cells are selected from Crypthecodinium cohnii, Mortierella alpina, the genus Aurantiochytrium, the genus Thraustochytrium, the genus Schizochytrium, and mixtures thereof. Raw fish oil is typically extracted from fish without further processing. In one form, this fish may be sardines, anchovies, mackerel, and / or tuna. Raw fish oil is usually treated before being used in pet food or human food. Vegetable oil is usually extracted from plant seeds. Examples of oil-producing plants include canola, soybean, sunflower, flax, and camelina. In some embodiments, the plant referred to in this invention is a plant that has been genetically modified to produce PUFA oil. As used herein, a “companion animal” refers to domesticated or domesticated animals whose physical, emotional, behavioral, and social needs can be readily met as companions in the home or in close daily contact with humans. Examples of companion animals include dogs, cats, guinea pigs, rabbits, rats, mice, and horses. The terms “pet” and “domestic animal” are used interchangeably in this application. A “treated PUFA oil” or a “processed PUFA oil” or simply a “treated oil” or a “processed oil” as used in this application refers to a PUFA oil that has been processed from a crude PUFA oil. In one embodiment, such treatment includes one or more steps of refining, bleaching, winterizing, deodorizing, degumming, or short-path evaporation. In another embodiment, such treatment includes only the deodorizing step. The treated PUFA oil of the present invention can be mixed with a base pet food product, such as dry pet food. The pet food composition of the present invention includes various wet, oily, powdered, or granular flavor additive compositions. In one embodiment, the treated PUFA oil can be incorporated into the pet food as part of the manufacturing process. nzfiann / Lznz / E / YiAi In the present method, pet food products comprise PUFA oil treated from microbes or fish. The present invention relates to a food product composition for non-human or human animals, comprising any of the microbial oils of the invention. In some embodiments, the food product is an additive for non-human or human animal food. In some embodiments, the food product is a nutritional supplement. In some embodiments, the food product is animal feed. In some embodiments, the animal feed is pet food. EXAMPLES Example 1 PUFA oil samples and processing methods A crude algae oil in this invention was extracted from the biomass of the Schizochytrium ATOO PTA-10208 strain without further processing. Different batches of this crude algae oil were produced and used in this invention. Purification processes The above crude algae oil was processed using one or more of the purification steps described below. Refinement In this refining step, crude algal PUFA oil(s) were heated to 5055 °C under nitrogen. Approximately 2% phosphoric acid was then added and mixed for 15 minutes. Based on the amount of crude free fatty acids (crude FFAs) in the crude algal oil, the amount of 50% caustic solution and soft water needed to create a caustic / H₂O solution was calculated using the following formula. The excess caustic factor was increased to account for the neutralizing phosphoric acid. Caustic at 50% = [(0.142 x crude FFA) +3.7] x weight of crude algal PUFA oil (kg) / 50 H2O = 0.05 X weight of crude algal PUFA oil (kg) The caustic solution / H₂O was added to the algae oil / phosphoric acid mixture and retained for 30 minutes. A 2.5% saline solution and 2.5% H₂O were then added. The resulting solution was heated to 80–85 °C and subsequently centrifuged. The resulting oil was isolated and either analyzed for palatability or further processed using additional steps. Teeth whitening Under nitrogen, the algal PUFA oil from the previous processing step, as in the refining step, was heated to 50–55 °C. 0.25–1.4% Trisyl®-based soaps (manufactured by WR Grace Co. USA) were added to the heated solution, and the solution was held for 15 minutes. A 2% F-72FF type bleaching clay was added under vacuum. The oil was heated to 90–95 °C, and once the oil reached the set point, it was held for 60 minutes. After holding the remaining oil, it was filtered at 91–95 °C using a vertical leaf filter (VLF). The resulting oil was isolated and analyzed for palatability or further processed using additional steps. Preparing for winter The algal PUFA oil from the previous processing step, such as the bleaching step, was heated to 60°C if it was at 45°C. The oil was then cooled to 19°C or 7°C and held at that temperature for 4 hours. Afterward, 1% Celpure® (filter medium from Imerys Filtration Minerals Inc., USA) was added, and the oil was mixed for 15 minutes. The filter used in this step was a membrane filter press. The resulting oil was isolated and either analyzed for palatability or further processed using additional steps. degumming Under nitrogen, the algal PUFA oil from the previous processing step was heated to 90–95 °C. Three percent citric acid (50% solution) and 10% water were added, and the mixture was stirred for 4 hours. After the retention time, the oil solution was decanted for another 4 hours. The oil was then washed with water containing 10% degummed oil by weight. The mixture was stirred for 4 hours and decanted for another 4 hours. The oil was dried under vacuum and nitrogen at 50–60 °C until the moisture content was <0.5%. A membrane filter press was used in this step. The resulting oil was isolated and either analyzed for palatability or further processed using additional steps. Short path evaporation Short-path evaporation, or SPE, is a specific type of refining. It was carried out using a commercially available short-path evaporator acquired from LCI Corporation, USA. In this short-path evaporator, the rotor cage assembly surrounds an internal condenser and rotates at moderate speeds. The feed is introduced through the nozzle at the top of the unit and spread in a thin film on the inner surface of the housing by the rotor blades. The cage-type construction and internal condenser location create a short steam flow path. The operating pressure was set to 0.1 mbar relative. The heating media temperature was set to 240 °C. The flow rate was 13 L / hour. The distillate and remaining liquid concentrate were drained through separate outlets at the bottom of the unit. The resulting oil was isolated and analyzed for palatability or further processed using additional steps. Deodorization nzAann / Lznz / E / YiAi Deodorization was carried out in a VTA deodorant or a DeSmet deodorant under a continuous condition or a batch condition as shown in Table 1 below. Table 1 nzRann / Lznz / E / YiAi Deodorizer Operating Parameters Temperature Pressure Feed Rate Vapor Rate VTA Deodorizer 180 1 mbar 10 kg / h 8.3 ml / min DeSmet Continuous Deodorizer 205 4 mbar 7 kg / h 3.5 ml / min DeSmet Batch Deodorizer 170-190 4 mbar NA 3.5 ml / min The VTA deodorant was manufactured by VTA Verfahrenstechnische Anlagen GmbH & Co. KG, Germany. The DeSmet deodorant was manufactured by Desmet Ballestra Group, Belgium. The deodorization process was carried out under the conditions specified by the manufacturers. The resulting oil was collected from the deodorant and analyzed for palatability. Example 2 Animal testing of pet food palatability Pets such as domestic dogs and cats have distinct nutritional requirements and are sensitive to various palatability enhancers. The animal food preference test used here is designed to identify the preference for foods containing PUFAs by the animals tested. In preference tests, animals are given a choice between two different diets presented simultaneously. This is also called a two-bowl test. In this test, the amount of each of two foods, presented simultaneously, consumed within a defined time period is compared. This is the most common test used by expert panels for palatability assessment studies in dogs and cats. It compares two products and establishes a preference based on the difference in the amounts consumed. In these tests, two identical bowls are presented to the animal simultaneously, each bowl containing one of the two products being tested (A or B). The animal has free access to the bowls for a predetermined period. The amount available in each bowl is more than sufficient to meet the animal's energy requirements.At the end of feeding time or when a bowl is finished, the bowls are removed and weighed again to measure the amount consumed. A total of 30 dogs were included in each two-bowl test conducted for this invention. Each test lasted two days. In the test, two diets were prepared: Diet A and Diet B. Diet A is a brand-name kibble pet food mixed with a test PUFA oil sample. Diet B is the same brand-name kibble pet food mixed with a control PUFA oil sample. The brand-name kibble pet food can be either dog or cat food, depending on the type of animal being tested. In the test, the average daily consumption of Diet A and Diet B was measured for each dog or cat. The amount of Diet A and Diet B consumed by each of the 30 dogs was measured over the two-day period. The individual consumption portions of Diet A and Diet B were calculated for each of the 30 dogs.The average of the 30 individual consumption portions for each diet A and B were calculated and used as an indicator of the palatability superiority of one of the two diets. The same two-bowl tests were performed in cats following the protocols described above. The average of the individual consumption portions for each diet A and B were calculated and used as an indicator of the palatability superiority of one of the two diets. Example 3 In order to identify the impact of each step in the PUFA oil purification process, samples of algae oil were collected using one or more of the refining, bleaching, winterizing, and deodorizing steps described in Example 1. The palatability of these oil samples was measured using the test protocol described in Example 2. The test samples included a raw, unprocessed algae oil as described in Example 1 and oils that were refined and / or bleached and / or winterized. A sample of commercial fish oil was purchased from a pet food producer and was labeled “RC fish oil”. This oil was refined, bleached, and deodorized by its manufacturer before being purchased. RC fish oil was used as a control oil and compared to the test oil samples described above. The test results are summarized in Table 2. nzAann / Lznz / E / YiAi Table 2 Base feed and control oil Crude algae oil Refining Bleached Winterized Deodorized VTA Dog food and fish oil RC Process Palatability score (% consumption) 22.9 Process Palatability score (% consumption) 26.8 Process Palatability score (% consumption) 31.8 Process Palatability score (% consumption) 46.4 Process Palatability score (% consumption) 74 nzfiann / Lznz / E / YiAi The data in Table 2 show that when raw, unprocessed algae oil was refined, bleached, and winterized, but not yet deodorized, the improvement in oil palatability increased. For example, the consumption ration for raw algae oil (compared to the RC fish oil control sample) increased from 22.9% to 26.8% after refining, to 31.8% after both refining and bleaching, and to 46.4% after refining, bleaching, and winterization. The RC fish oil control sample was still preferred by the dogs in the test over the test sample that underwent triple processing (refining, bleaching, and winterization). However, when the additional deodorization step was performed, the oil's palatability score increased by 27.6 percentage points, from 46.4% to 74%.This increase is greater than the combined effect of the three refining, bleaching, and winterizing steps, which is 23.5 percentage points. This demonstrates that the deodorizing step is significantly more effective than the refining, bleaching, and winterizing steps in improving the palatability of algal PUFA oil. Example 4 In the following experiment, the performance loss for each of the processing steps was examined and the optimal combination of processing steps was identified. The yield of a crude algal PUFA oil was examined after one or more processing steps were added to the purification process, including refining, bleaching, winterizing, and deodorizing. Additionally, the oil yield after undergoing two further processing steps—degumming and short-path evaporation (SPE)—was also examined. Palatability scores of the previously processed oils were measured and compared. Oil processing was carried out based on the methods described in Example 1. The palatability test was conducted as described in Example 2, using RC fish oil as the control oil. The crude algal oil used in this example is unprocessed and not as described in Example 1. The test results are presented in Table 3. Table 3 nzfiann / Lznz / E / YiAi Control Oil Experiment No. Test Algal Oil Name and Processing Steps % Yield % Palatability Fish Oil RC 1 Crude Algal Oil NA 24.8 2 Refined + bleached + winterized at 11°C + DeSmet continuous deodorizing 74.5 63.6 3 Refined + bleached + DeSmet continuous deodorizing 83.9 56.8 4 Refined + DeSmet continuous deodorizing 90.7 61.4 5 Refined + VTA 90.8 71.9 6 SPE 94.6 56.5 7 SPE + DeSmet continuous deodorizing 90.1 78.6 8 SPE + DeSmet batch deodorizing 94.3 62.4 9 Degummed, SPE + DeSmet continuous deodorizing 92.2 73.2 10 Degumming, SPE + VTA 92.0 60.1 The test results showed that, when the steps of In the purification of crude kelp oil, common oil processing steps such as refining, bleaching, and winterizing resulted in the loss of up to 25.5% of the original crude kelp oil during the process (Experiment 1). Eliminating one more processing step, such as winterizing, improved the oil yield but worsened the oil's palatability (Experiment 2). However, replacing the three refining, bleaching, and winterizing steps with a degumming and / or SPE step while retaining the deodorizing step resulted in a yield exceeding 90% while maintaining a palatability score similar to or better than RBWD oil (Experiments 7-10). Surprisingly, a degummed, SPE and deodorized oil was found to have a yield of 92.2% (Experiment No.9), which is an increase of approximately 24% over the 74.5% yield of the RBWD oil (Experiment No. 1). The palatability of this oil is 73.2% (Experiment No. 9), which is more than 9% higher than the palatability score of 63.6% for the RBWD oil (Experiment No. 1). Example 5 SPME-GCMS analysis of volatiles in PUFA oil samples To identify and quantify the compounds removed from algal PUFA oil samples during the deodorization process, which supposedly contributed to improved palatability, SPME-GCMS analysis was performed using ethyl heptanoate as an internal standard. This analysis identified approximate concentrations in parts per billion (ppb) for specific odor-related volatiles in algal PUFA oil and fish PUFA oil. A list of ten volatiles commonly detected in raw fish PUFA oil and raw algae PUFA oil is described in Table 4. Lipid oxidation products such as 1-penten-3-one, 4-heptenal, and 2,6-nonadienal are commonly found in raw fish oils and cause an unpleasant taste. The Maillard reaction products in Table 4 are commonly found in extracted and aqueous algae oil and also cause an unpleasant taste. In order to quantify the amount of nine lipid oxidation products and Maillard reaction products in the PUFA oil samples, an eleventh sample of ethyl heptanoate was added as an internal standard to the target volatiles list. nzAann / Lznz / E / YiAi Table 4 Volatile Compound Reaction Source Quantification Ion (m / z) 1-penten-3-one lipid oxidation product 84 4-heptenal lipid oxidation product 84 2,6-nonadienal lipid oxidation product 70 Trimethylpyrazine Maillard reaction product 122 2-ethyl-3,5-dimethylpyrazine Maillard reaction product 135 2-ethyl-3,6-dimethylpyrazine Maillard reaction product 135 Tetramethylpyrazine Maillard reaction product 136 2-hydroxy-3-methyl-2-cyclopenten-1-one Maillard reaction product 112 Methyl-1,1-H-pyrrole-2-carboxaldehyde Maillard reaction product 109 Indole Maillard reaction product 90 Ethyl heptanoate Internal Standard (added) 88 Ten samples of PUFA oil from algae and PUFA oil from fish, either crude or refined, were analyzed for the ten volatiles listed in Table 4. Each of the ten PUFA oil samples was analyzed in duplicate. For each replicate, 3 g of oil were placed in a 20 mL headspace vial along with 0.05 g of an internal standard solution of 123 ppb ethyl heptanoate in miglyol. The samples were thoroughly vortexed, and the final concentration of the internal standard was approximately 2 ppb in each oil sample. The weights of the sample and internal standard were accurately recorded for each replicate. A 2 cm hand-sifted SPME “triple-phase” fiber (PDMS (polydimethylsiloxane) / carboxene / DVB (divinylbenzene)) was exposed in the vial for 30 minutes at 75 °C after a 2-minute equilibration period. The instrument and method used were the GCO apparatus, but only the mass spectral data were recorded.The volatiles that were measured are listed in Table 4. The peak ion areas, sample weights, and internal weights recorded, along with the concentration of the internal standard, were used to calculate the approximate concentration for each volatile of interest (see Equation 1). This assumes an equivalent response to the internal standard of ethyl heptanoate. Therefore, these approximate concentrations are reported as ppb (parts per billion) as ethyl heptanoate. Equation 1: Volatile concentration (ppb) = volatile ion peak area / IS ion peak area * IS concentration in sample Where IS ion peak area = peak area for 88 m / z ethyl heptanoate ion And volatile ion peak area = peak area for selected ion for each volatile of interest (listed in Table 1) And IS concentration in sample = peak IS concentration (123 ppb) * peak IS weight / (sample weight + peak IS weight) The average concentrations in ppb (as ethyl heptanoate) for each volatile and each sample are listed in Table 5 below, along with palatability data where available. A few were measured down to 0.1 ppb, while others were detected but could not be readily quantified at even lower levels and were therefore reported as <0.1 ppb. Peaks below the detection limit (0.1 ppb as ethyl heptanoate) were labeled as not detected (nd). The sample “Crude Algae Oil Sample 1” refers to an unprocessed crude algae oil extracted from the Schizochytrium ATOO PTA-10208 strain. The sample “RBDW deo VTA algae oil sample” refers to the resulting oil after the crude algae oil sample “Crude Algae Oil Sample 1” was refined, bleached, winterized, and deodorized using a VTA deodorizer. nzfiann / Lznz / E / YiAi The sample “Algal oil sample 1 RBDW deso desmet” refers to the resulting oil after the crude algae oil sample “Crude algae oil sample 2” was refined, bleached, winterized, and deodorized using a DeSmet deodorizer. The sample “Algal oil sample 1 RBDW deso desmet” refers to the resulting oil after the crude algae oil sample “Crude algae oil sample 1” was bleached, winterized, and deodorized using a DeSmet deodorizer. The sample “Algal oil sample 2 RBDW deso desmet” refers to the resulting oil after a second sample of unprocessed crude algae oil extracted from the Schizochytrium ATOO PTA-10208 strain was bleached, winterized, and deodorized using a DeSmet deodorizer. An RC fish oil was used as the control oil sample for the 5 above algae oil samples in the two-bowl food preference tests. A sample of commercial fish oil was purchased from Ocean Nutrition Corp. and labeled “Fish Oil Sample 3.” This oil was refined, bleached, and deodorized. This oil was used as the control oil sample for “Fish Oil Sample 3 RBWD” in the two-bowl food preference test. The sample “Fish Oil Sample 3 RBDW” refers to the resulting oil after “Fish Oil Sample 3” was refined, bleached, winterized, and deodorized using a DeSmet deodorizer. The sample “Crude Algal Oil Sample 4” refers to a fourth sample of unprocessed crude algae oil extracted from the Schizochytrium ATCC PTA-10208 strain. The sample “Algal oil sample 4 RBDW deso desmet” refers to the resulting oil after the crude algae oil sample “Crude algae oil sample 4” was refined, bleached, winterized, and deodorized using a DeSmet deodorizer. Crude algae oil samples 1, 2, and 4 are from separate batches of crude algae oil extracted from the Schizochytrium ATCC strain PTA-10208. As shown in Table 5, the crude oils are clearly distinct from their corresponding deodorized oils, for both fish and algae oils. The deodorization results in some oils show a decrease in the approximate concentration of all volatiles compared to their crude state. Crude algae oils, as shown in “Crude Algal Oil Sample 1” and “Crude Algal Oil Sample 4,” have much higher concentrations of Maillard reaction products than their deodorized counterparts, such as “Algal Oil Sample 2 BWD deo desmet” and “Algal Oil Sample 4 RBWD,” respectively. The concentration of pyrazines is particularly high, reaching hundreds to thousands of ppb (as ethyl heptanoate). In deodorized oils, these pyrazines are either not detected or detected at <0.3 ppb (as ethyl heptanoate). The other Maillard reaction products also had significantly higher concentrations in the crude seaweed oils (in the range of 10 to 100 ppb), while they were not detected in most of the deodorized oils. Deodorized algae oils show significantly smaller peaks for most compounds compared to crude algae oils, with many Maillard reaction products no longer detected after deodorization. Within the deodorized algae oil samples, the use of VTA's deodorizer (“Algal Oil Sample 1 RBWD deso VTA”) shows an even greater improvement, with fewer Maillard reaction product peaks detected and lower levels of some lipid oxidation products compared to deodorization using Desmet (“Algal Oil Sample 1 RBWD deso desmet”). Based on these data, as fewer meta volatiles are detected, the palatability score tends to improve (increase). Lipid oxidation products were detected at lower concentrations in deodorized oils compared to crude oils, but the overall concentration range of lipid oxidation products was relatively low (ranging from <0.3 ppb to approximately 20 ppb), and most were not completely removed by deodorization. The peak area of ​​the aforementioned volatiles for each sample was measured under the conditions described above. The odor impact of each volatile compound depends not only on its concentration but also on the odor threshold, which varies for each compound. Therefore, to assess odor improvement, one must consider the changes in the relative peak size for each compound and how this relates to palatability results. Data from this study showed that deodorization has a dramatic effect, reducing the relatively high concentration of Maillard reaction products by factors of 100–1000 to barely detectable levels, corresponding to a more dramatic effect on palatability.Deodorized samples show that further reductions in Maillard reaction products demonstrate a corresponding improvement in palatability results, even when similar levels of lipid oxidation products are present (i.e., comparing sample “Algal oil sample 1 RBWD deso desmet” with sample “Algal oil sample 1 RBWD deso VTA” or comparing sample “Algal oil sample 1 BWD deso desmet” with “Algal oil sample 2 BWD deso ηζβαηη / Lznz / E / YiAi desmet”). The sample “Fish Oil Sample 3” is the control for the “Fish Oil Sample RBWD”. Both fish oil samples were deodorized and therefore had low concentrations of Maillard reaction products. However, the “Fish Oil Sample 3 RBWD” sample was deodorized using a VTA deodorizer and therefore has an even lower concentration of Maillard reaction products. The “Fish Oil Sample 3 RBWD” sample showed an improved palatability score over a previously deodorized “Fish Oil Sample 3” when a VTA deodorizer was used. The sample “Crude Algal Oil Sample 4” is the control for “Crude Algal Oil Sample 4” in the two-bowl test. “Crude Algal Oil Sample 2” is another batch of crude algal oil that again demonstrated a high concentration of Maillard reaction products. After processing the crude algal oil with refining, bleaching, winterizing, and deodorizing steps, it had a low concentration of Maillard reaction products and, therefore, improved palatability compared to the control sample. nzAann / Lznz / E / YiAi Table 5 1- pentencompound 3-one 4hept enal 2,6nonadi enal trimethyl 2-ethyl-3,5pyrazin dimethylpyr azine 2-ethyl-3,6dimethylpyr azine tetramethyl pyrazine 2-hydroxy3-methyl-2cyclopent en-1 -one methyl-1Hpyrrol-2carbozal dehyde Palatabi indolity Mase ota ionm / z» 84 84 70 122 135 135 136 112 109 90 sample type RT min »8.1 nom. file 15.1 24.3 19.6 20.7 21.1 214 29.4 33.3 37.3 Algal oil sample 1 RBWD deso ®:®:®®®:®®®:®^^ Algal oil sample 1 RBWD deso desmet average 2 0.4 <0.1 PPb <0.1 ppb nd nd nd nd nd nd 74.6 dog : est. dev. 0.2 : 0.0 : 0.0 0.0 nd nd nd nd nd nd Algal oil sample 1 BWD deso <0 1 ®®®®®í®®®^ Otó Algal oil sample 2 RBWD deso desmet average 10 est. dev. 04 1 0.0 0.3 0.0 <0.1 ppb <0.1 ppb 0.0 0.0 <0.1 ppb 0.0 nd nd nd nd <0.1 ppb 0.0 nd 58.3 nd 56.9 dog duck Algal oil sample 1 Yes Yes Yes Yes Yes;est:Yes Yes Yes 3 dog Fish oil RC (control oil) average 1.8 std. dev. 0.2 0.4 O.O 0.2 0.0 <0.1 ppb 0.1 OI 00 <0.1 ppb i <0.1 ppb 0 0 0 0 nd nd <0.1 ppb 0 0 0.3 N / A oo .............. Fish oil sample <0.1 <0 1 <0.1 Otó Fish oil sample 3 (control oil) average 20 std. dev. 2 11 19 1 0 0.4 0.3 0.1 OI 0.0 00 <0.1 ppb nd 00nd <0.1 ppb 0.0 5 N / A 0 3 Algal oil sample 4 RBWD deso sssssssssssss8és»íestísssÓiiíiiiíiííííS:Sssss0í6ssssííYesYesííiíiíiííííí0í0sssíí^ Otó£ Algae oil sample 4 average crude 3 2 8 3932 2992 632 312 49 15 131 N / A dev. est. 0.1 0.2 1 375 241 51 29 7 4 55 nd = not detected Detection limit ~ <0.01 ppb ethyl heptanoate Quantification limit ~ <0.1 ppb ethyl heptanoate Concentration = ppb quantified as ethyl heptanoate. Example 6 Human sensory evaluation of refined algal PUFA oil samples In order to identify the human sensory perception of deodorized or non-deodorized algae PUFA oils, descriptive sensory profiles of these oils were obtained and measured. nzRann / Lznz / E / YiAi “Crude 1099” is an unprocessed crude algae oil extracted from the Schizochytrium ATOO PTA-10208 strain. It was used as the starting oil for refining, bleaching, cold filtration, and deodorization. “RC fish oil,” as mentioned in Example 3, was used as the control oil in the two-bowl palatability test. Sample “refined 1099” refers to the resulting oil after the “crude 1099” algae oil sample was refined, but not bleached, winterized, or deodorized. The sample “bleached 1099” refers to the resulting oil after the “raw 1099” algae oil sample was bleached, but not refined, winterized, or deodorized. The sample “cold filtered 1099A” refers to the resulting oil after the “crude 1099” algae oil sample was cold filtered at 7°C, but was not refined, bleached, winterized, or deodorized. The sample “cold filtered 1099B” refers to the resulting oil after the “crude 1099” algae oil sample was cold filtered at 19°C, but was not refined, bleached, winterized, or deodorized. Sample “deso 1099A” refers to the resulting oil after the “1099 crude” algae oil sample was deodorized by a VTA and refined, bleached and winterized at 7°C. Sample “deso 1099B” refers to the resulting oil after the “1099 crude” algae oil sample was deodorized using a VTA deodorizer and refined, bleached and winterized at 19°C. Several human sensory properties were examined and measured, including unpleasant tastes such as burnt, fish complex, green complex, meat protein, putrid, chemical / solvent, malted / granular, egg complex, skunk, cocoa, and painted. Corresponding palatability tests were also conducted on each of the five oil samples, with “RC fish oil” as the reference diet. The result of the experiment is shown in Figure 1. Deodorized algae oil exhibited the least intensity of unpleasant taste. In comparison, all deodorized algae oils showed an intensity of unpleasant taste at least five times greater. This difference is inversely correlated with the palatability scores of deodorized and non-deodorized algae oils. In other words, deodorized oil had a high palatability score and a lower intensity of unpleasant taste than non-deodorized algae oils. Non-deodorized algae oils all had a low palatability score and a high intensity of unpleasant taste. nzAann / Lznz / E / YiAi NOVELTY OF THE INVENTION Having described the present invention as above, the following is considered novel and, therefore, is claimed as property:

Claims

1. A method for improving the palatability of a polyunsaturated fatty acid (PUFA) oil for a pet, characterized in that said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming or refining using a short-path evaporator (SPE) or both degumming and refining using an SPE of said PUFA oil from step a); and c) deodorizing the PUFA oil from step b); wherein the yield of PUFA oil after step c) is not less than 85% of the amount of crude oil used in step a), wherein said palatability is measured by an animal feed preference test and wherein the palatability score of the PUFA oil obtained after step c) is at least 10 percentage points higher than the crude oil used in step a).

2. The method according to claim 1, characterized in that the yield of PUFA oil is not less than 90% of the crude oil with which it was started in step a).

3. The method according to claim 1 or claim 2, characterized in that said animal feed preference test is a two-bowl test.

4. The method according to claim 3, characterized in that the palatability score of the PUFA oil obtained after step c) is at least 20 percentage points higher than the crude oil with which it was started in step a).

5. The method according to claim 3, characterized in that the palatability score of the PUFA oil obtained after step c) is at least 30 percentage points higher than the crude oil with which it was started in step a).

6. The method according to claim 3, characterized in that the palatability score of the PUFA oil obtained after step c) is at least 40 percentage points higher than the crude oil with which it was started in step a).

7. The method according to claim 3, characterized in that the palatability score of the PUFA oil obtained after step c) is at least 45 percentage points higher than the crude oil with which it was started in step a).

8. The method according to any of claims 1 to 7, nzfionn / Lznz / Bm characterized in that said deodorization step c) is carried out using a VTA deodorizer.

9. The method according to any of claims 1 to 7, characterized in that said deodorization step c) is carried out using a DeSmet deodorizer.

10. The method according to any of claims 1 to 9, characterized in that the PUFA oil is derived from fish.

11. The method according to any of claims 1 to 9, characterized in that the PUFA oil is derived from microorganisms.

12. The method according to claim 11, characterized in that the microorganisms are algae.

13. The method according to claim 12, characterized in that the algae are Schizochytrium, Aurantiochytrium or Thraustochytrium.

14. The method according to any of claims 1 to 9, characterized in that the PUFA oil is derived from plants.

15. The method according to any of claims 1 to 14, characterized in that the PUFA oil comprises one or more of the compounds DHA, EPA, ARA and DPA.

16. A polyunsaturated fatty acid (PUFA) oil, characterized in that said PUFA oil comprises less than 10 ppb of one or more Maillard reaction compounds and more than 1.5 ppb of one or more lipid oxidation products, when qualified as ethyl heptanoate.

17. The PUFA oil according to claim 16, characterized in that said PUFA oil comprises less than 1 ppb of Maillard reaction compounds when qualified as ethyl heptanoate.

18. The PUFA oil according to claim 17, characterized in that said PUFA oil comprises less than 0.5 ppb of Maillard reaction compounds when qualified as ethyl heptanoate.

19. The PUFA oil according to claim 18, characterized in that said PUFA oil comprises less than 0.3 ppb of Maillard reaction compounds when qualified as ethyl heptanoate.

20. The PUFA oil according to claim 19, characterized in that the amount of Maillard reaction compounds in said PUFA oil is not detectable when it is classified as ethyl heptanoate.

21. The PUFA oil according to any of claims 15 to 20, characterized in that the Maillard reaction compounds are selected from a group consisting of: trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, tetramethylpyrazine, 2-hydroxy-3-methyl-2-cyclopenten-1-one, methyl-1H-pyrrole-2-carboxaldehyde, and indole.

22. The PUFA oil according to any of claims 15 to 21, characterized in that said lipid oxidation products are selected from a group consisting of: 1-penten-3-one, 4-heptenal and 2,6-nonadienal.

23. A pet food composition, characterized in that said food composition comprises a PUFA oil produced by the method according to any of claims 1 to 15.

24. A food composition for a pet, characterized in that said food composition comprises PUFA oil according to any of claims 16 to 22.

25. The food composition according to claim 23 or claim 24, characterized in that the pet is a dog.

26. The food composition according to claim 23 or claim 24, characterized in that the pet is a cat.

27. The food composition according to any of claims 23 to 26, characterized in that the food composition is a dog food or a cat food.

28. The food composition according to any of claims 23 to 26, characterized in that the food composition is a treat for dogs or a treat for cats.

29. The food composition according to any of claims 23 to 26, characterized in that the food composition is a nutritional supplement.

30. A food composition for human consumption, characterized in that said food composition comprises a PUFA oil that is processed by the method according to any of claims 1 to 15.

31. A food composition for human consumption, characterized in that said food composition comprises PUFA oil according to any of claims 16 to 22.

32. A method for increasing the yield of a polyunsaturated fatty acid (PUFA) oil above a control oil which is the same oil, but which has been refined, bleached, winterized and deodorized (RBWD oil), characterized in that said method comprises the steps of: a) obtaining a crude PUFA oil; b) optionally, degumming said PUFA oil or refining using a short path evaporator (SPE) of said PUFA oil or both degumming and refining using an SPE of said PUFA oil from step a); and c) deodorizing the PUFA oil from step b); wherein the yield of the PUFA oil after step c) is more than 5 percentage points higher than the yield of the RBWD oil.

33. The method according to claim 32, characterized in that the PUFA oil yield after step c) is more than 10 percentage points higher than the RBWD oil yield.

34. The method according to claim 32, characterized in that the PUFA oil yield after step c) is more than 20 percentage points higher than the RBWD oil yield.

35. The method according to any of claims 32 to 34, characterized in that the difference between the palatability scores of the PUFA oil after step c) and the RBWD oil is less than 10% in an animal feed preference test in which a common control sample oil is used.

36. The method according to claim 35, characterized in that the PUFA oil after step c) has a higher palatability score than the RBWD oil in an animal preference test in which a common control sample oil is used.

37. The method according to claim 35 or claim 36, characterized in that said animal feed preference test is a two-bowl test.

38. The method according to any of claims 32 to 37, characterized in that said deodorization step c) is carried out using a VTA deodorizer.

39. The method according to any of claims 32 to 37, characterized in that said deodorization step c) is carried out using a DeSmet deodorizer.

40. The method according to any of claims 32 to 39, characterized in that the PUFA oil is derived from fish.

41. The method according to any of claims 32 to 39, characterized in that the PUFA oil is derived from microorganisms.

42. The method according to claim 41, characterized in that the microorganisms are algae.

43. The method according to claim 42, characterized in that the algae are Schizochytrium, Aurantiochytrium or Thraustochytrium.

44. The method according to any of claims 32 to 39, characterized in that the PUFA oil is derived from plants.