Double-wheel dry fractionation process for lard oil

Abstract

The invention discloses a double-wheel dry fractionation process for lard oil, and relates to the technical field of grease fractionation, the double-wheel dry fractionation process for lard oil comprises the following steps: (1) heating and melting lard oil, cooling and crystallizing, growing crystal, and carrying out solid-liquid separation to obtain liquid lard oil; and (2) carrying out heating melting, cooling crystallization, crystal growing and solid-liquid separation on the residual material after liquid lard fractionation in the step (1) to obtain solid lard. According to the method, the lard is subjected to dry fractionation twice, high-quality liquid lard and solid lard are prepared by controlling the cooling rate, the crystallization temperature and the crystal growing time, the content of unsaturated fatty acid in the liquid lard can reach up to 80%, and the heat value is low; the content of saturated fatty acid in the solid lard oil can reach 76% or above, and the solid lard oil is good in crispness.

Description

Technical Field

[0001] The invention relates to the technical field of oil fractionation, and in particular to a lard double-wheel dry fractionation process. Background Art

[0002] Animal fats and oils are obtained from fat-rich tissues in animals. They are one of the main sources of edible fats and oils. They mainly include lard, beef tallow, mutton fat, chicken fat, duck fat, fish oil, etc. They are usually solid or solidified at room temperature. Most animal fats and oils contain a large amount of saturated fatty acids, unsaturated fatty acids, oleic acid, cholesterol, vitamins and other ingredients. At present, animal fats and oils are widely used in food, daily chemicals and industrial fields.

[0003] The processing of animal fats can be divided into three levels: crude extraction, refining and deep processing. The main purpose of crude extraction is to separate fats from animal tissues. Refining is to degumming, deacidification, decolorization and deodorization of crude animal fats. Deep processing is to better serve the food industry and improve product quality. The deep processing of animal fats adopts extraction technology, blending technology, ester exchange rearrangement technology, hydrogenation technology, etc. Among them, the main purpose of oil extraction is to meet the requirements of food for oils. At present, there are three main ways to extract fats: ① Dry extraction. Freeze, crystallize and squeeze the melted fat. ② Wet extraction. Dissolve the fat in a large amount of solvent (water or organic solvent), then crystallize some high-melting-point triglycerides at a suitable temperature, and then separate them by decantation, filtration and centrifugation. Wet extraction has a higher liquid oil yield than dry extraction, but the production cost is higher. ③ Surfactant extraction. An aqueous solution containing a surfactant and an electrolyte is added to the partially crystallized oil phase. The crystallized solid fat is preferentially wetted by the surfactant and enters the aqueous solution. Centrifugal separation is then used to separate the solid fat and liquid oil. The separated solid fat is melted into liquid oil and centrifuged to obtain liquid and solid fats, thereby expanding the scope of use of animal fats.

[0004] Liquid lard and solid lard are obtained by dry fractionation, and the theoretical basis of the fractionation is the homogeneous polymorphism of oils and fats. Triglycerides exist in three different crystalline forms: α, β, and β'. Among them, the α type has the lowest melting point, the worst stability, and is not easy to filter; the β' type has a moderate stability and is easy to filter; the β type has the highest melting point, with coarse crystals and is easy to filter. Different crystal forms have different enthalpy changes when melting, and the β type has the largest enthalpy change. At the same time, the three crystal forms can be converted, but can only be converted from α type to β type, β' type, or from β' type to β type. If α and β' type crystals need to be obtained again, the oil needs to be reheated to melt and cooled to crystallize. Generally speaking, after the oil is rapidly cooled, the unstable α type is first generated, and then the crystal form gradually turns to β type and β' type. In the crystallization process, different thermodynamic conditions are required to induce the formation of different crystals. Rapid cooling with a large temperature difference will produce the α type and produce a very fine crystalline dense material, which is not conducive to the formation of the β type. The corresponding crystal form can only be obtained by slowly cooling to a certain crystallization humidity and a certain crystal growth time. The ultimate goal of dry fractionation is to convert the original oil into two groups of oils with different melting points, namely the high melting point group and the low melting point group, by cooling and crystallizing the oil. In order to obtain a better separation effect, the oil must be converted into β and β' types.

[0005] At present, the liquid lard obtained by the existing dry fractionation technology has the problem of low yield or low unsaturated fatty acid content, and it is impossible to achieve a balance between improving the yield and the unsaturated fatty acid content. The solid lard also has the problem of low saturated fatty acid content. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a double-wheel dry fractionation process for lard, so as to respectively prepare liquid lard with high unsaturated fatty acid content and solid lard with high saturated fatty acid content, thereby promoting high-value utilization of liquid lard and solid lard in different fields and improving the market potential of lard.

[0007] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0008] The present invention provides a lard double-wheel dry fractionation process, comprising the following steps:

[0009] (1) heating and melting lard, cooling and crystallizing, growing crystals, and separating solid from liquid to obtain liquid lard;

[0010] (2) The remaining material after the liquid lard is fractionated in step (1) is heated to melt, cooled for crystallization, grown for crystallization, and separated from the solid and the liquid to obtain solid lard.

[0011] In steps (1) and (2), the heating and melting temperature is 50-70°C; preferably, the heating and melting temperature is 55-65°C. The melting point of lard is different for different parts of pig fat. When setting the heating temperature, it is necessary not only to ensure that all crystal forms of lard are destroyed, but also to avoid oxidation of lard. Oxidation of lard will destroy the nutritional components and even produce harmful substances.

[0012] In steps (1) and (2), the cooling rate is 2-10°C / h; preferably, the cooling rate is 2-6°C / h. The cooling rate directly affects the number of crystal nuclei, crystal morphology and crystal size.

[0013] In steps (1) and (2), the crystal growing time is 2 to 14 hours; preferably, the crystal growing time is 6 to 10 hours. As the crystal growing time increases, the yield of liquid lard increases, and a long crystal growing time makes solid-liquid separation easier, but too long a crystal growing time will lead to a longer fractionation cycle, so it is necessary to reasonably control the crystal growing time.

[0014] In step (1), the crystallization temperature is 15-25° C. In the present invention, the crystallization temperature is set based on the comprehensive consideration of increasing the yield of liquid lard and the unsaturated fatty acid content.

[0015] In step (2), the crystallization temperature is 30-40° C. In the present invention, the crystallization temperature is set based on the comprehensive considerations of reducing energy consumption, improving lard utilization, and increasing the saturated fatty acid content of solid lard.

[0016] In steps (1) and (2), the solid-liquid separation method is at least one of filtration and centrifugation. Filtration is to achieve solid-liquid separation by means of the mesh structure of the filter medium, and centrifugation is to separate solids and liquids with different densities by centrifugal force.

[0017] The beneficial effects of the present invention are as follows: the present invention performs dry fractionation on lard twice, and prepares high-quality liquid lard and solid lard by controlling the cooling rate, crystallization temperature and crystal growing time; the content of unsaturated fatty acids in the liquid lard can be as high as 80%, and the calorific value is low; the content of saturated fatty acids in the solid lard can reach more than 76%, and the shortening property is good. DETAILED DESCRIPTION

[0018] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0019] The raw material lard in the following examples is lard provided by Anhui Tianxiang Cereals, Oils and Foodstuffs Co., Ltd. and prepared from the same batch of lard through the same crude extraction and refining process.

[0020] Example 1

[0021] (1) The lard is heated to 55°C to completely melt it, cooled to 15°C at a cooling rate of 2°C / h to crystallize, grown for 6 hours, and centrifuged to obtain liquid lard.

[0022] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 55° C. to completely melt it, cooled to 30° C. at a cooling rate of 4° C. / h for crystallization, grown for 8 hours, and centrifuged to obtain solid lard.

[0023] Example 2

[0024] (1) The lard is heated to 55°C to completely melt it, cooled to 20°C at a cooling rate of 2°C / h to crystallize, grown for 8 hours, and centrifuged to obtain liquid lard.

[0025] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 55° C. to completely melt it, cooled to 35° C. at a cooling rate of 4° C. / h for crystallization, grown for 8 hours, and centrifuged to obtain solid lard.

[0026] Example 3

[0027] (1) The lard is heated to 60°C to completely melt it, cooled to 25°C at a cooling rate of 2°C / h to crystallize, grown for 10 hours, and centrifuged to obtain liquid lard.

[0028] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 60° C. to completely melt it, cooled to 40° C. at a cooling rate of 4° C. / h for crystallization, grown for 8 hours, and centrifuged to obtain solid lard.

[0029] Example 4

[0030] (1) The lard is heated to 65°C to completely melt it, cooled to 15°C at a cooling rate of 4°C / h to crystallize, grown for 8 hours, and centrifuged to obtain liquid lard.

[0031] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 2° C. / h for crystallization, grown for 6 hours, and centrifuged to obtain solid lard.

[0032] Example 5

[0033] (1) The lard is heated to 65°C to completely melt it, cooled to 20°C at a cooling rate of 4°C / h to crystallize, grown for 10 hours, and centrifuged to obtain liquid lard.

[0034] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 35° C. at a cooling rate of 2° C. / h for crystallization, grown for 8 hours, and centrifuged to obtain solid lard.

[0035] Example 6

[0036] (1) The lard is heated to 60°C to completely melt it, cooled to 25°C at a cooling rate of 4°C / h to crystallize, grown for 6 hours, and centrifuged to obtain liquid lard.

[0037] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 60° C. to completely melt it, cooled to 40° C. at a cooling rate of 2° C. / h for crystallization, grown for 10 hours, and centrifuged to obtain solid lard.

[0038] Example 7

[0039] (1) The lard is heated to 65°C to completely melt it, cooled to 15°C at a cooling rate of 6°C / h to crystallize, grown for 10 hours, and centrifuged to obtain liquid lard.

[0040] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 6° C. / h to crystallize, grown for 10 hours, and centrifuged to obtain solid lard.

[0041] Example 8

[0042] (1) The lard is heated to 60°C to completely melt it, cooled to 20°C at a cooling rate of 6°C / h to crystallize, grown for 6 hours, and centrifuged to obtain liquid lard.

[0043] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 60° C. to completely melt it, cooled to 35° C. at a cooling rate of 6° C. / h to crystallize, grown for 10 hours, and centrifuged to obtain solid lard.

[0044] Example 9

[0045] (1) The lard is heated to 60°C to completely melt it, cooled to 25°C at a cooling rate of 6°C / h to crystallize, grown for 8 hours, and centrifuged to obtain liquid lard.

[0046] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 60° C. to completely melt it, cooled to 40° C. at a cooling rate of 6° C. / h for crystallization, grown for 10 hours, and centrifuged to obtain solid lard.

[0047] The masses of the liquid lard and solid lard obtained by the extraction in Examples 1 to 9 and the masses of the unsaturated fatty acids and saturated fatty acids in the obtained liquid lard and solid lard were measured, and the liquid lard yield, solid lard yield, unsaturated fatty acid content and saturated fatty acid content were calculated according to the following formulas. The results are shown in Table 1.

[0048] Calculation formula:

[0049] Liquid lard yield = liquid lard (g) / refined lard (g) * 100%

[0050] Solid lard yield = solid lard (g) / refined lard (g) * 100%

[0051] Unsaturated fatty acid content = unsaturated fatty acid (g) / total fatty acid (g) * 100%

[0052] Saturated fatty acid content = saturated fatty acid (g) / total fatty acid (g) * 100%

[0053] Table 1

[0054]

[0055]

[0056] As can be seen from Table 1, the present invention prepares liquid lard with a high unsaturated fatty acid content and solid lard with a high saturated fatty acid content by two dry fractionation steps and controlling the cooling rate, crystallization temperature and crystal growing time, and the yield of the liquid lard is relatively high.

[0057] The present invention also provides a lard double-wheel dry fractionation process, comprising the following steps:

[0058] (1) heating and melting lard, cooling and crystallizing, adding a crystallization agent when crystals appear, growing crystals, separating solid from liquid, and separating oil from water to obtain liquid lard;

[0059] (2) The remaining material after the liquid lard is fractionated in step (1) is heated to melt, cooled for crystallization, grown for crystallization, and separated from the solid and the liquid to obtain solid lard.

[0060] In step (1), the crystal aid is a Boc-L-lysine aqueous solution; preferably, the concentration of the Boc-L-lysine aqueous solution is 0.5-1wt%, and the amount used is 0.5-1 times the mass of lard.

[0061] In step (1), the crystal aid is an aqueous solution of disodium sebacic acid; preferably, the concentration of the aqueous solution of disodium sebacic acid is 1 to 2 wt %, and the amount used is 0.5 to 1 times the mass of lard.

[0062] The invention uses Boc-L-lysine or disodium sebacic acid as a crystal aid, which can further improve the yield of liquid lard and the content of unsaturated fatty acids.

[0063] In steps (1) and (2), the heating and melting temperature is 50-70°C; preferably, the heating and melting temperature is 55-65°C. The melting point of lard is different for different parts of pig fat. When setting the heating temperature, it is necessary not only to ensure that all crystal forms of lard are destroyed, but also to avoid oxidation of lard. Oxidation of lard will destroy the nutritional components and even produce harmful substances.

[0064] In steps (1) and (2), the cooling rate is 2-10°C / h; preferably, the cooling rate is 2-6°C / h. The cooling rate directly affects the number of crystal nuclei, crystal morphology and crystal size.

[0065] In steps (1) and (2), the crystal growing time is 2 to 14 hours; preferably, the crystal growing time is 6 to 10 hours. As the crystal growing time increases, the yield of liquid lard increases, and a long crystal growing time makes solid-liquid separation easier, but too long a crystal growing time will lead to a longer fractionation cycle, so it is necessary to reasonably control the crystal growing time.

[0066] In step (1), the crystallization temperature is 15-25° C. In the present invention, the crystallization temperature is set based on the comprehensive consideration of increasing the yield of liquid lard and the unsaturated fatty acid content.

[0067] In step (2), the crystallization temperature is 30-40° C. In the present invention, the crystallization temperature is set based on the comprehensive considerations of reducing energy consumption, improving lard utilization, and increasing the saturated fatty acid content of solid lard.

[0068] In steps (1) and (2), the solid-liquid separation method is at least one of filtration and centrifugation. Centrifugation is the preferred solid-liquid separation method for oils and fats, and filtration and centrifugation can also be combined to improve the separation effect.

[0069] Example 10

[0070] The difference between Example 10 and Example 4 is that Boc-L-lysine is added as a crystallization aid in step (1).

[0071] (1) The lard is heated to 65°C to completely melt it, and then cooled to 15°C at a cooling rate of 4°C / h to crystallize. When crystals appear, a Boc-L-lysine aqueous solution is added, wherein the concentration of the Boc-L-lysine aqueous solution is 0.5wt%, and the amount used is 1 times the mass of the refined lard. The crystals are grown for 8 hours, and then centrifuged to separate the oil and water to obtain liquid lard.

[0072] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 2° C. / h for crystallization, grown for 6 hours, and centrifuged to obtain solid lard.

[0073] Embodiment 11

[0074] The difference between Example 11 and Example 4 is that Boc-L-lysine is added as a crystallization aid in step (1).

[0075] (1) The lard is heated to 65°C to completely melt it, and then cooled to 15°C at a cooling rate of 4°C / h to crystallize. When crystals appear, a Boc-L-lysine aqueous solution is added, wherein the concentration of the Boc-L-lysine aqueous solution is 1 wt%, and the amount used is 0.5 times the mass of the refined lard. The crystals are grown for 8 hours, and then centrifuged to separate the oil and water to obtain liquid lard.

[0076] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 2° C. / h for crystallization, grown for 6 hours, and centrifuged to obtain solid lard.

[0077] Example 12

[0078] The difference between Example 12 and Example 4 is that an aqueous solution of disodium sebacic acid is added as a crystallization agent in step (1).

[0079] (1) The lard is heated to 65°C to completely melt it, and then cooled to 15°C at a cooling rate of 4°C / h to crystallize. When crystals appear, an aqueous solution of disodium sebacic acid is added, wherein the concentration of the aqueous solution of disodium sebacic acid is 1 wt%, and the amount used is 1 times the mass of the refined lard. The crystals are grown for 8 hours, and then centrifuged to separate the oil and water to obtain liquid lard.

[0080] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 2° C. / h for crystallization, grown for 6 hours, and centrifuged to obtain solid lard.

[0081] Embodiment 13

[0082] The difference between Example 13 and Example 4 is that an aqueous solution of disodium sebacic acid is added as a crystallization agent in step (1).

[0083] (1) The lard is heated to 65°C to completely melt it, and then cooled to 15°C at a cooling rate of 4°C / h to crystallize. When crystals appear, an aqueous solution of disodium sebacic acid is added, wherein the concentration of the aqueous solution of disodium sebacic acid is 2wt%, and the amount used is 0.5 times the mass of the refined lard. The crystals are grown for 8 hours, and then centrifuged to separate the oil and water to obtain liquid lard.

[0084] (2) The remaining material after the liquid lard is extracted in step (1) is heated to 65° C. to completely melt it, cooled to 30° C. at a cooling rate of 2° C. / h for crystallization, grown for 6 hours, and centrifuged to obtain solid lard.

[0085] The masses of the liquid lard and solid lard obtained by the fractionation in Examples 10 to 13, as well as the masses of unsaturated fatty acids and saturated fatty acids in the obtained liquid lard and solid lard were measured, and the liquid lard yield, solid lard yield, unsaturated fatty acid content and saturated fatty acid content were calculated according to the above formulas. The results are shown in Table 2.

[0086] Table 2

[0087]

[0088] As can be seen from Table 2, the present invention prepares liquid lard with a high unsaturated fatty acid content and solid lard with a high saturated fatty acid content by adding a crystallizing agent, and improves the yield of liquid lard and solid lard.

[0089] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A lard double-wheel dry fractionation process, characterized in that: The following steps are involved: (1) heating and melting lard, cooling and crystallizing, growing crystals, and separating solid from liquid to obtain liquid lard; (2) The remaining material after the liquid lard is fractionated in step (1) is heated to melt, cooled for crystallization, grown for crystallization, and separated from the solid and the liquid to obtain solid lard.

2. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In steps (1) and (2), the heating and melting temperature is 50 to 70°C.

3. The lard double-wheel dry fractionation process according to claim 2, characterized in that: In steps (1) and (2), the heating and melting temperature is 55 to 65°C.

4. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In steps (1) and (2), the cooling rate is 2 to 10°C / h.

5. The lard double-wheel dry fractionation process according to claim 4, characterized in that: In steps (1) and (2), the cooling rate is 2 to 6°C / h.

6. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In steps (1) and (2), the crystal growing time is 2 to 14 hours.

7. The lard double-wheel dry fractionation process according to claim 5, characterized in that: In steps (1) and (2), the crystal growing time is 6 to 10 hours.

8. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In step (1), the crystallization temperature is 15-25°C.

9. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In step (2), the crystallization temperature is 30-40°C.

10. The lard double-wheel dry fractionation process according to claim 1, characterized in that: In steps (1) and (2), the solid-liquid separation method is at least one of filtration and centrifugation.

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