Clarified ghee and preparation method thereof

Abstract

The invention relates to the field of food, in particular to clarified ghee and a preparation method thereof. The method comprises the following steps: heating and carrying out solid-liquid separation on ghee in sequence to obtain clarified ghee; wherein the milk fat content of the clarified ghee is not lower than 99.0 wt% under the heating condition; wherein the heating conditions comprise that the temperature ranges from 100 DEG C to 160 DEG C, and the time ranges from 10 min to 25 min. According to the clarified ghee prepared by the method disclosed by the invention, the milk fat content is ensured, the Maillard reaction can be effectively controlled, excessive increase of a peroxide value is prevented, and the clarified ghee is relatively good in sense. Meanwhile, beta-cyclodextrin or lactococcus is further preferably adopted to remove cholesterol in the clarified ghee, the removal efficiency can reach 55% or above, and under the condition that lactococcus 3 is adopted, the removal efficiency can reach 70% or above.

Description

Technical Field

[0001] The invention relates to the field of food, in particular to clarified ghee and a preparation method thereof. Background Art

[0002] Clarified ghee is fat that has been heated and filtered to remove protein, lactose, and water. Clarified ghee is used as a food in Asia, the Middle East, and Africa. In Ayurveda, the traditional Indian system of medicine, clarified ghee is used in both food and medicine, as a base for topical medications such as nose drops, eye baths, and skin remedies, and as a base for internal medications. In Ayurvedic texts such as the Charaka Samhita and the Ashtanga Khedayam, ghee is described as the best of all fats and oils and can be made from the milk of animals such as cows, buffaloes, and goats; Ayurveda considers cow's milk to be the best.

[0003] Ghee, as an important source of energy food in pastoral areas, is carefully extracted from yak milk. Its fat content is extremely high, usually in the range of 80%-90%, and is mainly composed of various fatty acids, including saturated fatty acids and unsaturated fatty acids. Among them, saturated fatty acids such as palmitic acid and stearic acid account for a large proportion, making ghee solid or semi-solid at room temperature. In the dietary system of plateau pastoral areas, ghee, as an important source of high calories, can help plateau residents resist the cold and meet the energy needs of daily activities. It also gives a rich and mellow taste to traditional foods such as butter tea and tsampa. The moisture content of ghee is relatively low, roughly between 10% and 20%. The lower moisture content helps the preservation of ghee and can reduce the growth and reproduction of microorganisms. This low moisture characteristic works together with the high fat content to affect the physical properties of ghee, which in turn determines its texture and stability.

[0004] Yak milk is the raw material for preparing ghee, which contains lactose and proteins, including casein. When heated, the Maillard reaction occurs, producing a brown substance called melanoidin. Melanoidin, the final product of the Maillard reaction, is reported to have antioxidant properties, so the Maillard reaction is believed to affect the quality preservation of clarified ghee. At the same time, heating will also promote the oxidation of oils, which will deteriorate the quality, flavor and nutritional value.

[0005] Therefore, the present invention aims to develop a preparation method that effectively ensures the milk fat content after clarification while limiting the negative effects of Maillard reaction and oil oxidation on quality as much as possible. Summary of the invention

[0006] In order to achieve the above objectives, the present invention provides a clarified ghee and a preparation method thereof. The clarified ghee prepared by the method of the present invention can effectively control the occurrence of the Maillard reaction, prevent excessive increase of the peroxide value, and has better sensory properties while effectively ensuring the milk fat content.

[0007] In a first aspect, the present invention provides a method for preparing clarified ghee, the method comprising: heating and solid-liquid separation of ghee in sequence to obtain clarified ghee;

[0008] wherein the heating conditions are such that the milk fat content of the clarified ghee is not less than 99.0% by weight;

[0009] Wherein, the heating conditions include: temperature of 100-160°C and time of 10-25min.

[0010] Preferably, the method further comprises adding β-cyclodextrin to the clarified ghee to remove cholesterol from the clarified ghee.

[0011] Preferably, the method further comprises inoculating lactococci into the clarified ghee and fermenting the ghee to remove cholesterol from the clarified ghee, wherein the lactococci are at least one of lactococci with a preservation number of CGMCC No.32756, lactococci with a preservation number of CGMCC No.32757 and lactococci with a preservation number of CGMCC No.32758.

[0012] The present invention can achieve the following beneficial effects:

[0013] (1) The clarified ghee prepared by the method of the present invention can effectively control the occurrence of the Maillard reaction and prevent the excessive increase of the peroxide value while ensuring its milk fat content (the milk fat content is not less than 99.0 weight %) and controlling the water content (the water content is not higher than 1.0 weight %), and has a better sensory experience.

[0014] (2) The present invention further preferably uses β-cyclodextrin or lactococcus to remove cholesterol from clarified ghee, and the removal efficiency can reach more than 55%. When lactococcus 3 is used, the removal efficiency can reach more than 70%.

[0015] Biological Deposit

[0016] The lactococcus 1 provided by the present invention is Lactococcus formosensis, which was deposited in the General Microbiology Center of the China Culture Collection Administration on November 25, 2024, with a deposit number of CGMCC No. 32758, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences (abbreviated as CGMCC).

[0017] The lactococcus 3 provided by the present invention is Lactococcus garvieae, which was deposited in the General Microbiology Center of the China Culture Collection Administration on November 25, 2024, with a deposit number of CGMCC No. 32756, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences (abbreviated as CGMCC).

[0018] The lactococcus 5 provided by the present invention is Lactococcus garvieae, which was deposited in the General Microbiology Center of the China Culture Collection Administration on November 25, 2024, with a deposit number of CGMCC No. 32757, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences (abbreviated as CGMCC). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 Cholesterol standard curve.

[0021] Figure 2 The effect of β-cyclodextrin addition on cholesterol removal from clarified ghee was shown.

[0022] Figure 3 The effect of β-cyclodextrin on the acid value and peroxide value of clarified shortening at 3 wt% addition is shown. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] In a first aspect, the present invention provides a method for preparing clarified ghee, wherein the ghee is heated and solid-liquid separated in sequence to obtain clarified ghee;

[0025] wherein the heating conditions are such that the milk fat content of the clarified ghee is not less than 99.0% by weight;

[0026] Wherein, the heating conditions include: temperature of 100-160°C and time of 10-25min.

[0027] The invention can effectively control the occurrence of Maillard reaction and prevent excessive increase of peroxide value by reasonably controlling the temperature and time in the preparation process of clarified ghee, while effectively ensuring the milk fat content, and has better sensory experience.

[0028] In the present invention, the heating temperature can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, preferably 110-120°C, for example, 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C, 120°C, more preferably 113-117°C.

[0029] In the present invention, the heating time can be 10-25min, for example, it can be 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min, 25min, preferably 12-17min, for example, it can be 12min, 12.5min, 13min, 13.5min, 14min, 14.5min, 15min, 15.5min, 16min, more preferably 12.5-16min.

[0030] In some preferred embodiments, the heating temperature is 113-117°C and the time is 12.5-16 min. In some more preferred embodiments, the heating temperature is 114-116°C and the time is 14.5-15.5 min. In the most preferred embodiment, the heating temperature is 115°C and the time is 15 min.

[0031] The preparation of clarified ghee by the method provided by the present invention can also effectively ensure the low moisture content characteristics of clarified ghee, thereby helping to preserve the clarified ghee. In some embodiments, the moisture content of the clarified ghee provided by the present invention is not higher than 1.0 weight %. In some embodiments, the moisture content of the clarified ghee provided by the present invention is not higher than 0.8 weight %. In some embodiments, the moisture content of the clarified ghee provided by the present invention is not higher than 0.6 weight %. In some embodiments, the moisture content of the clarified ghee provided by the present invention is not higher than 0.4 weight %. In some embodiments, the moisture content of the clarified ghee provided by the present invention is not higher than 0.3 weight %.

[0032] In the present invention, in the absence of contrary instructions, the term "ghee" has the broadest meaning in the art, and refers to fat extracted from yak milk, cow milk, and goat milk. In some embodiments, the ghee is clarified ghee, which refers to a liquid obtained by heating the fat extracted from yak milk, cow milk, and goat milk at high temperature. In some embodiments, the ghee refers to a product obtained by fermenting the fat extracted from yak milk, cow milk, and goat milk. In a specific example, the preparation process of the ghee includes: first centrifuging and defatting yak milk / cow milk and / or goat milk, fermenting the defatted fat for 48 to 72 hours, washing and kneading, and finally making the finished ghee. In a preferred example, ghee is prepared using cow milk as a raw material. In a more preferred example, ghee is prepared using yak milk as a raw material. The ghee can be commercially available. In a specific example of the present invention, the ghee is a finished yak ghee purchased from Shangri-La, Yunnan.

[0033] In the present invention, the method for determining the milk fat content in the clarified ghee can be a method known in the art. In a specific embodiment, the milk fat content in the clarified ghee is calculated according to the following formula.

[0034]

[0035] The milk fat can also be extracted from clarified ghee in a conventional manner in the art. A preferred extraction method includes: extracting the clarified ghee to be tested with methanol and chloroform, then performing solid-liquid separation to obtain a clear liquid, washing the clear liquid with water, and finally drying the washed product to obtain a residual weight.

[0036] In some embodiments, the water content can be obtained by drying clarified ghee and measuring the weight difference before and after heating. In a preferred embodiment, the drying conditions include: a temperature of 60-80° C. and a drying time of 4-6 hours.

[0037] Many researchers have shown in the past that people with elevated cholesterol levels in their blood are more susceptible to coronary heart disease, also known as coronary artery disease. And the increased risk of cardiovascular disease is associated with an increased intake of high-cholesterol foods. Animal studies support the fact that dietary cholesterol intake can induce atherosclerosis. In addition, during the processing and storage of cholesterol-rich foods, oxidation products of cholesterol may form. Few of them have further harmful effects, such as mutagenicity, cytotoxicity and carcinogenicity. Therefore, in some embodiments, in order to make the clarified ghee of the present invention more healthy, the method of the present invention also includes a step of removing cholesterol from the clarified ghee.

[0038] In a preferred embodiment, the method for removing cholesterol comprises: adding β-cyclodextrin to the clarified ghee to remove cholesterol from the clarified ghee.

[0039] The inventors of the present invention found that in the process of removing cholesterol by β-cyclodextrin, the addition amount of β-cyclodextrin increases with the increase of the addition amount of β-cyclodextrin before 3% by weight, reaches a maximum value at 3% by weight, and then enters a plateau period. Therefore, considering the removal effect of cholesterol and the input-output ratio, the addition amount of β-cyclodextrin is not less than 2.5g relative to 100g of clarified ghee, for example, it can be 2.5g, 2.7g, 3g, 3.2g, 3.4g, 3.5g, 3.6g, 3.8g, 4g, 4.2g, 4.4g, 4.5g, 4.6g, 4.8g, 5g, preferably 3-5g.

[0040] In the present invention, in order to further improve the cholesterol removal effect, it is also preferred to control the water-to-oil ratio in the system, and the water refers to the water added to the system additionally, and does not include the water in the system. In some preferred embodiments, the method further includes adding water to the clarified ghee, and the amount of water used is such that the water-to-oil ratio in the system is (0.8-1.5):1; for example, it can be 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, preferably (1.1-1.3):1, and more preferably (1.15-1.25):1.

[0041] The method of adding water is not particularly limited, as long as the above water-to-oil ratio is satisfied. In some preferred embodiments, water is added in the form of a β-cyclodextrin aqueous solution.

[0042] In some preferred embodiments, the temperature for removing cholesterol from clarified ghee using β-cyclodextrin is 40-60°C, for example, 40°C, 42°C, 44°C, 45°C, 46°C, 48°C, 50°C, 52°C, 54°C, 55°C, 56°C, 58°C, 60°C, preferably 45-55°C.

[0043] In some preferred embodiments, the temperature and time for removing cholesterol from clarified ghee using β-cyclodextrin is 30-50 min, for example, 30 min, 32 min, 34 min, 35 min, 36 min, 38 min, 40 min, 42 min, 44 min, 45 min, 46 min, 48 min, 50 min, preferably 35-45 min.

[0044] In some preferred embodiments, cholesterol is removed under stirring conditions, and the stirring speed can be selected within a wide range. Taking 10g clarified ghee as an example, the stirring speed is 500-1500rpm, for example, it can be 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm, 1300rpm, 1400rpm, 1500rpm, preferably 800-1200rpm.

[0045] In some preferred alternative embodiments, the method for removing cholesterol comprises: inoculating lactococci into the clarified ghee and fermenting to remove cholesterol from the clarified ghee, wherein the lactococci are at least one of lactococci with a preservation number of CGMCC No. 32756, lactococci with a preservation number of CGMCC No. 32757 and lactococci with a preservation number of CGMCC No. 32758. In some more preferred embodiments, lactococci with a preservation number of CGMCC No. 32756 are inoculated. In some preferred embodiments, Lactococcus with a preservation number of CGMCC No. 32756 and Lactococcus with a preservation number of CGMCC No. 32757, or Lactococcus with a preservation number of CGMCC No. 32756 and Lactococcus with a preservation number of CGMCC No. 32758, or Lactococcus with a preservation number of CGMCC No. 32756, Lactococcus with a preservation number of CGMCC No. 32757 and Lactococcus with a preservation number of CGMCC No. 32758 are inoculated.

[0046] In the present invention, the inoculation amount of the lactococcus is not particularly limited, as long as it can reduce the cholesterol content in clarified ghee. In some preferred embodiments, the inoculation amount of the lactococcus calculated as OD value 1 is 0.4-0.6 ml for every 10 g of clarified ghee.

[0047] In the present invention, the fermentation time is not particularly limited, as long as the cholesterol content in the clarified ghee can be reduced. In some preferred embodiments, the fermentation time is not less than 40 hours, preferably 45-72 hours, and more preferably 46-50 hours, calculated based on the above inoculum amount. In a specific embodiment, the fermentation time is 48 hours.

[0048] In a second aspect, the present invention provides clarified shortening prepared by the method described above.

[0049] Example

[0050] Ghee was purchased from finished yak butter in Shangri-La, Yunnan.

[0051] β-Cyclodextrin, food grade, was purchased from Shandong Aicai Biotechnology Co., Ltd.

[0052] Example 1 is used to illustrate the preparation of clarified ghee

[0053] Yak butter (milk fat content 85.2 wt %, water content 14.7 wt %) was heated for 10-20 minutes according to the conditions in Table 1. The clear liquid obtained by filtration was clarified butter, which were named C1, C2, C3 and C4 respectively.

[0054] Determination of moisture content: Take about 1.0 g of each clarified ghee sample and put it into a weighing bottle, dry it at 70°C for 5 hours, and then calculate the mass (g) of the moisture content. Repeat three times for each sample and take the average value.

[0055] Residual weight determination: About 1.0g of each clarified ghee sample is placed in a 10mL centrifuge tube, 6mL of methanol:chloroform mixed reagent is added, vortexed and then 4mL is added. The sample is allowed to stand for 1h, filtered through quantitative filter paper, and the filtered solution is retained. 8ml of distilled water is added to the solution, placed in a centrifuge and centrifuged at 5000r / min for 5min, and the supernatant is discarded. The lower layer of fat is evaporated to dryness at 60℃ under negative pressure in a water bath. Then the fat content (g) is calculated according to the following formula, and each sample is repeated three times and the average is taken.

[0056]

[0057]

[0058] Example 2 is used to illustrate the preparation of clarified ghee

[0059] Clarified ghee was prepared according to the method of Example 1, except that the temperature was 100° C. and the time was 20 min. The obtained clarified ghee had a milk fat content of 99.1% by weight and a water content of 0.8% by weight.

[0060] Comparative Example 1 is used to illustrate the preparation of clarified ghee

[0061] Clarified ghee was prepared according to the method of Example 1, except that the temperature was 85° C. and the time was 20 min. The obtained clarified ghee had a milk fat content of 94.9% by weight and a water content of 5.0% by weight.

[0062] Example 3 is used to illustrate the preparation of clarified ghee

[0063] Clarified ghee was prepared according to the method of Example 1, except that the temperature was 130° C. and the time was 20 min. The obtained clarified ghee had a milk fat content of 99.2% by weight and a water content of 0.7% by weight.

[0064] Example 4 is used to illustrate the preparation of clarified ghee

[0065] Clarified ghee was prepared according to the method of Example 1, except that the temperature was 160° C. and the time was 25 min. The obtained clarified ghee had a milk fat content of 99.2% by weight and a water content of 0.4% by weight.

[0066] Example 5 is used to illustrate the measurement of the peroxide value of clarified ghee

[0067] The peroxide value was determined by the indicator titration method according to GB 5009.227-2023 national food safety standard. Specifically, 1G C3 group clarified ghee sample was weighed and 25ml of a mixture containing acetic acid and chloroform solution (3:2) was added. 1ml of saturated potassium iodide solution was added, and the flask was immediately covered, shielded from light, and allowed to stand at room temperature for 10 minutes. Then, 30ml of water was added. Free iodine was then titrated using 0.01mol / L Na2S2O3 and 1mL5mg / mL starch as indicators, and the results are shown in Table 2.

[0068] Peroxide value (mEq / kg) = (ab) × f × 10 / m

[0069] Where M = grams of sample, a = volume of titrant; mL sample, b = volume of titrant; mL blank, f = 0.01 mol / L Na2S2O3.

[0070] Table 2

[0071] Peroxide value (mEq / kg) raw materials 3.23±0.06 C3 (115℃, 15min) 3.37±0.06

[0072] As can be seen from Table 2, although the peroxide value of the clarified ghee obtained by heating through this process is slightly higher than that of the raw material, the difference is not significant. Therefore, this process will not significantly cause oil oxidation while increasing the fat content of ghee.

[0073] Example 6 is used to illustrate the Maillard reaction during the preparation of clarified ghee

[0074] Spectrophotometer is used to measure the ghee chromaticity value. When using spectrophotometer to measure the ghee chromaticity value, representative and uniform C3 group ghee sample 5g is prepared, and it is appropriately softened and placed in a cuvette for measurement, and the absorbance value under different wavelengths is recorded to reflect the color characteristics of ghee. According to the absorbance value, chromaticity parameters such as L*, a*, b*, etc. are calculated, and the CIE 1976Lab color space method is commonly used, and the measurement data is statistically analyzed at the same time to evaluate the accuracy and reliability of the measurement result. The chromaticity value of ghee can be accurately measured using a spectrophotometer, and by comparing the chromaticity parameters before and after heating, the influence of heating on the ghee color is analyzed, and the results are shown in Table 3.

[0075] Table 3

[0076] L* a* b* C3 (115℃, 15min) 79.93±1.99 -9.95±0.12 45.92±2.54 raw materials 86.56±3.38 -7.48±0.30 33.78±2.45

[0077] As can be seen from Table 3, the ghee clarified by this process is yellower in color than the raw material. This is because there is a certain degree of Maillard reaction in the processing, which has little effect on the quality.

[0078] Example 7 Sensory evaluation of clarified ghee

[0079] A sensory evaluation table was drawn based on the sensory descriptors created by Kiwanuka et al., and a panel of 10 food major students who had systematically studied sensory evaluation conducted sensory evaluation on the final product. The sensory evaluation table of the raw materials and clarified ghee is shown in Table 4.

[0080] Table 4

[0081]

[0082] It can be seen from Table 4 that although the color of clarified ghee is slightly yellow due to the Maillard reaction and other reasons, the sensory panel members generally believe that after ghee is clarified, the butter aroma of ghee is enhanced, the acetic acid taste is reduced, the texture is firmer, and the taste is more oily and smooth.

[0083] Example 8 is used to illustrate the removal of cholesterol by β-cyclodextrin inclusion method

[0084] (1) Preparation of cholesterol standard curve

[0085] Pipette 0.0mL, 0.5mL, 1.0mL, 1.5mL, and 2.0mL of cholesterol standard working solution into 10mL test tubes respectively, and add glacial acetic acid to each tube to make the total volume reach 4mL. Add 2mL of iron alum colorimetric solution along the tube wall, mix well, and compare colors at a wavelength of 560nm to 575nm within 15min to 90min. Use cholesterol standard concentration as the horizontal axis and absorbance as the vertical axis to make a standard curve, such as Figure 1 The regression equation is: y = 0.1854x + 0.06 (R2 = 1).

[0086] (2) Determination of cholesterol in clarified ghee

[0087] Take 10g of C3 group clarified butter, mix different masses of β-cyclodextrin, deionized water and butter, place in a constant temperature water bath at 50°C for mechanical stirring, stir with a constant speed mixer at different stirring speeds, and take out the sample after a certain reaction time. Then centrifuge at 1000r / min and 15min, the supernatant is low-cholesterol butter, take out the upper oil sample and save it for testing. Under the conditions of water-oil ratio (B) of 1.2:1 and stirring time (C) of 40min, the addition amount of β-cyclodextrin is 1 weight %, 2 weight %, 3 weight %, 4 weight %, and 5 weight %, respectively.

[0088] Determination of cholesterol content: The cholesterol content is determined according to the method of GB / T 5009.128-2003 "Determination of cholesterol in food".

[0089] Calculation of cholesterol removal rate: Take each oil sample and determine the cholesterol content according to the method, and calculate the cholesterol removal rate according to the following formula.

[0090] Cholesterol removal rate (%) = (W1-W2) / W1×100%

[0091] Wherein: W1 is the cholesterol content of original ghee, mg / g; W2 is the cholesterol content of de-cholesterolized ghee, mg / g.

[0092] (4) Data processing: All experimental results were obtained by three parallel experiments. The average value and standard error value were obtained. Origin 8 5 was used for data processing and plotting, and Design Expert 8.0.0 was used for data analysis. The results are shown in the figure. Figure 2 shown.

[0093] Depend on Figure 2 It can be seen that the cholesterol removal rate increases with the increase of the amount of β-cyclodextrin added. When the amount of β-cyclodextrin added is 3.0%, the cholesterol removal rate is the highest, which is 67.34%. When the amount of β-cyclodextrin added exceeds 3.0%, the cholesterol removal rate tends to slowly decrease.

[0094] (3) Determination of acid value and peroxide value of clarified ghee

[0095] The determination of acid value and peroxide value is based on the method of GB / T 5009.37-2003 "Analysis method of edible vegetable oil hygienic standard". The results are as follows: Figure 3 shown.

[0096] Depend on Figure 3It can be seen that after adding 3% of β-cyclodextrin, the clarified ghee showed a phenomenon of decreased acid value and increased peroxide value. The reason for the decrease in acid value is that β-cyclodextrin has a unique ring structure, which can encapsulate the free fatty acids in the ghee, isolate them from the system, and thus reduce the acidic components that cause the increase in acid value. As for the increase in peroxide value, on the one hand, β-cyclodextrin can change the microenvironment of ghee and react with trace metal ions (such as iron and copper ions), so that these catalysts for oil oxidation are in a state that is more conducive to catalyzing the oxidation of unsaturated fatty acids. Combined with the comprehensive impact on acid value and peroxide value, adding β-cyclodextrin does not significantly promote the rancidity of the product.

[0097] Example 9 Determination of the cholesterol-lowering ability of bacterial strains

[0098] Lactococcus 1, Lactococcus 3, Lactococcus 5, commercial bacteria and mixed bacterial liquid (Lactococcus 1, Lactococcus 3 and Lactococcus 5 were mixed in equal proportions) were inoculated into MRS liquid culture medium, placed in a shaker at 37°C, 150r / min for 8-12h to expand the bacteria, the bacterial liquid concentration was adjusted to OD600 = 1, 0.5ml of different bacterial liquids were inoculated into 10g of sterilized clarified ghee, stirred for 3min to mix, and fermented at 37°C for 24h, 48h, and 72h, respectively. The colorimetric method in the national standard "Determination of cholesterol in food GB 5009.128-2016" was used to determine the cholesterol content of the original product and the product after different fermentation times. Each group of bacterial liquids was measured 3 times at each fermentation time, and the cholesterol removal rate was calculated. The cholesterol determination results are shown in Table 5.

[0099] Table 5

[0100] Group Fermentation time / h <![CDATA[Cholesterol content / (mg·100g -1 )]]> Cholesterol removal rate / % Clarified Ghee 0 196.176 0 Commercial bacteria 24 131.474 30.43 Commercial bacteria 48 121.987 37.82 Commercial bacteria 72 121.215 38.21 Lactococcus 1 24 85.624 56.35 Lactococcus 1 48 83.153 57.61 Lactococcus 1 72 82.596 57.9 Lactococcus 3 24 54.049 72.45 Lactococcus 3 48 52.943 73.01 Lactococcus 3 72 52.178 73.4 Lactococcus 5 24 82.263 58.07 Lactococcus 5 48 79.572 59.44 Lactococcus 5 72 78.927 59.77 Mixed bacteria 24 63.234 67.77 Mixed bacteria 48 62.071 68.36 Mixed bacteria 72 61.234 68.79 Beta-cyclodextrin 3% 0 64.078 67.34

[0101] As can be seen from Table 5, adding several strains to clarified ghee shows that the cholesterol removal rate of Lactococcus 3 is the highest, with a cholesterol content of 52.718 mg / 100 g and a removal rate of 73.40%. The cholesterol removal rate of commercial bacteria is the lowest, with a cholesterol content of 121.215 mg / 100 g and a removal rate of 38.21%.

[0102] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing clarified ghee, characterized in that: The method comprises: heating and solid-liquid separation of ghee in sequence to obtain clarified ghee; wherein the heating conditions are such that the milk fat content of the clarified ghee is not less than 99.0% by weight; Wherein, the heating conditions include: temperature of 100-160°C and time of 10-25min.

2. The preparation method according to claim 1, wherein The heating conditions include: temperature of 110-120° C. and time of 10-20 min.

3. The preparation method according to claim 1 or 2, wherein The method further comprises adding beta-cyclodextrin to the clarified ghee to remove cholesterol from the clarified ghee; Preferably, relative to 100 g of clarified shortening, the added amount of the β-cyclodextrin is not less than 2.5 g, preferably 3-5 g.

4. The preparation method according to claim 3, wherein The method further comprises adding water to the clarified shortening, wherein the amount of water used is such that the water-oil ratio in the system is (0.8-1.5):1; preferably (1.1-1.3):

1.

5. The preparation method according to claim 3 or 4, wherein The conditions for removing cholesterol from clarified ghee using β-cyclodextrin also include: The temperature is 40-60°C, preferably 45-55°C; and / or The time is 30-50 min, preferably 35-45 min; and / or The stirring speed is 500-1500 rpm, preferably 800-1200 rpm.

6. The preparation method according to claim 1 or 2, wherein: The method further comprises inoculating lactococci into the clarified ghee and fermenting the ghee to remove cholesterol from the clarified ghee, wherein the lactococci are at least one of lactococci with a preservation number of CGMCC No.32756, lactococci with a preservation number of CGMCC No.32757 and lactococci with a preservation number of CGMCC No.32758.

7. The preparation method according to claim 6, wherein: Relative to every 10g of clarified ghee, calculated based on an OD value of 1, the content of the lactococcus is 0.4-0.6ml.

8. The preparation method according to claim 6 or 7, wherein: The fermentation time is not less than 40 hours, preferably 45-72 hours, and more preferably 46-50 hours.

9. The preparation method according to any one of claims 1 to 8, wherein: The ghee is yak milk ghee.

10. Clarified ghee prepared by the preparation method according to any one of claims 1 to 9.

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