MLCT grease for improving stability of milk base of ice cream as well as preparation method and application of MLCT grease

Abstract

The invention discloses MLCT grease for improving the stability of an ice cream milk base and a preparation method of the MLCT grease. The MLCT grease is prepared by directionally hydrolyzing grease containing conjugated linolenic acid and then directionally esterifying medium-chain fatty acid and palmitic acid at sn-1 and sn-3 positions. In the CLnA-enriched sn-2 MLCT structure ester constructed by the invention, sn-2 site fatty acid is mainly CLnA and accounts for 13-15% of the total amount of fatty acid, medium-chain fatty acid accounts for more than 30% of the total amount of fatty acid, and the content of MLCT accounts for more than 93% of the total amount of fatty acid. The CLnA-enriched sn-2 MLCT structure ester prepared by the invention is added into a basic formula of ice cream, so that the bleeding rate of the ice cream can be reduced by 10% or more, the expansion rate can be increased by 8% or more, and the melting rate is also improved.

Description

Technical Field

[0001] This invention relates to the field of food nutritional fats, specifically to an MLCT fat for improving the stability of ice cream emulsions, its preparation method, and its application. Background Technology

[0002] Ice cream is a popular frozen dairy product. Its typical structure is a complex multiphase system composed of air bubbles, ice crystals, partially solidified fat globules, and a concentrated unfrozen phase. An ideal ice cream should possess excellent characteristics such as a smooth and delicate texture, good melt resistance, and minimal ice crystal growth and structural shrinkage during storage.

[0003] Milk fat plays a crucial role in the composition of ice cream. It not only imparts the rich, creamy flavor and full-bodied texture of ice cream, but more importantly, the fat globule network structure formed during emulsification and homogenization is key to maintaining the overall stability of ice cream (including melt resistance, shape retention, and texture). The solid fat content (SFC) and crystallization characteristics of milk fat directly affect the water separation rate, melt resistance, and overrun of ice cream.

[0004] However, traditional ice cream typically uses animal milk fat or partially hydrogenated vegetable fat as its fat source. With the increasing demand for healthy eating among modern consumers, traditional milk fat-based ice cream, due to its high content of saturated fatty acids and cholesterol, contradicts the current consumer trend towards low-calorie, healthy nutrition. Therefore, developing healthy fats that can replace milk fat while maintaining or improving the quality of ice cream has become a hot research topic in the industry.

[0005] Medium- and long-chain fatty acid esters (MLCTs) are structured lipids whose glycerol backbone combines both medium-chain fatty acids (MCFA, C6-C12) and long-chain fatty acids (LCFA, C14-C24). MCFAs are characterized by rapid metabolism and low susceptibility to accumulation in the body, while LCFAs provide essential fatty acids and maintain normal physiological functions. Therefore, MLCTs are considered a type of oil that combines nutritional and health benefits, providing energy while helping to control weight and reduce body fat accumulation.

[0006] Applying MLCT to ice cream could theoretically replace some or all of the milk fat, thereby developing low-calorie functional ice cream products with specific health claims to meet the needs of specific consumer groups (such as fitness enthusiasts and weight managers).

[0007] Despite the significant nutritional advantages of MLCT (milk fat substitute), its direct application in ice cream systems faces numerous technical challenges. Firstly, existing MLCTs exhibit poor antioxidant properties, and their crystallization characteristics, melt flow curves, and solid fat content differ significantly from milk fat. The strength of the fat globule membranes formed by MLCTs and their partial aggregation behavior also differ from milk fat, making it difficult to form a stable and robust fat network structure in ice cream systems. This directly manifests as poor water separation, melt resistance, and overrun in ice cream. Secondly, natural plant oils such as pomegranate seed oil are rich in conjugated linolenic acid (CLnA), which also exhibits physiological activities such as fat reduction and anti-inflammation, and has potential metabolic regulatory functions. However, there are currently few technologies for constructing fat substitutes using CLnA. Therefore, utilizing CLnA to construct fat substitutes to replace fat in ice cream and prepare an ice cream that combines health benefits, structural stability, and sensory palatability to meet the nutritional and health needs of modern consumers is crucial. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide an MLCT fat for improving the stability of ice cream milk base and its preparation method. This involves directional esterification of conjugated linolenic acid (CLnA) at the sn-2 position to construct a sn-2 position-enriched structural ester, which, together with milk fat, serves as a fat source, replacing part or all of the milk fat. This forms a fat composition with superior metabolic properties and structural stability. When applied to ice cream, this composition maintains good taste and emulsifying properties while reducing the proportion of saturated fat, meeting modern consumers' demands for a balance of nutrition, health, and taste. Simultaneously, it solves the problem of poor stability found in existing medium- and long-chain fatty acid esters used as milk fat substitutes in ice cream.

[0009] To achieve the above objectives, the present invention first provides a method for preparing MLCT fats for improving the stability of ice cream emulsion base, the steps of which are as follows: (1) Pomegranate seed oil was mixed with phosphate buffer, and a specific lipase at the sn-1 and 3 positions was added for enzymatic hydrolysis. The product was separated to obtain glycerol monoester with CLnA retained at the sn-2 position, namely CLnA-sn-2 MAG. (2) The CLnA-sn-2 MAG obtained in step (1) is mixed with lauric acid oil and palm oil, and sn-1,3 specific lipase is added to carry out esterification reaction to obtain MLCT structure ester enriched with CLnA at sn-2 position.

[0010] In one embodiment of the present invention, in step (1), the pomegranate seed oil is pomegranate seed oil with a CLnA content of 80-85%.

[0011] In one embodiment of the present invention, in step (1), the pH of the phosphate buffer is 6.5 to 7.0, the concentration is 0.03 to 0.07 mol / L, and the mass ratio of pomegranate seed oil to phosphate buffer is 1:0.15 to 0.45.

[0012] In one embodiment of the present invention, in step (1), the sn-1,3-position specific lipase includes at least one of pancreatic lipase, gastric lipase, Lipozyme 435, Lipozyme RM IM, Lipozyme TL IM or Aspergillus oryzae lipase, and the amount of sn-1,3-position specific lipase added is 5 to 15% of the weight of pomegranate seed oil.

[0013] In one embodiment of the present invention, in step (1), the pancreatic lipase has an enzyme activity of 35 units / mg, the gastric lipase has an enzyme activity of 10-100 U / mg, the Lipozyme 435 has an enzyme activity of 9000-10000 PLU / g, the Lipozyme RM IM has an enzyme activity of 255-275 IUN / g, and the Lipozyme TL IM has an enzyme activity of 230-280 IUN / g.

[0014] In one embodiment of the present invention, in step (1), the temperature during enzymatic hydrolysis is 45-50°C and the hydrolysis time is 4-12 hours.

[0015] In one embodiment of the present invention, in step (2), the lauric acid oils include at least one of coconut oil, palm kernel oil, camphor seed oil and their fractionated or hydrogenated products, and the palm oil includes at least one of palm oil and its fractionated or hydrogenated products.

[0016] In one embodiment of the present invention, in step (2), the mass ratio of CLnA-sn-2 MAG to lauric acid oil is 23-26:44-48, and the mass ratio of CLnA-sn-2 MAG to palm oil is 23-26:28-32.

[0017] In one embodiment of the present invention, in step (2), the sn-1,3 specific lipase includes at least one of pancreatic lipase, gastric lipase, Lipozyme TL IM, Lipozyme RM IM or Lipozyme 435, and the amount of sn-1,3 specific lipase added is 5 to 15% of the total weight of CLnA-sn-2 MAG, lauric acid oil and palm oil.

[0018] In one embodiment of the present invention, in step (2), the pancreatic lipase has an enzyme activity of 35 units / mg, the gastric lipase has an enzyme activity of 10-100 U / mg, the Lipozyme 435 has an enzyme activity of 9000-10000 PLU / g, the Lipozyme RM IM has an enzyme activity of 255-275 IUN / g, and the Lipozyme TL IM has an enzyme activity of 230-280 IUN / g.

[0019] In one embodiment of the present invention, in step (2), the temperature of the esterification reaction is 45-55°C and the time is 5-15 hours. The esterification reaction is carried out in an anhydrous or low-aqueous-activity system.

[0020] The present invention also provides an MLCT structure ester enriched with CLnA at the sn-2 position, prepared according to the above preparation method.

[0021] The present invention also provides an application of the above-mentioned MLCT structure ester enriched with CLnA at the sn-2 position in ice cream, wherein the application is to replace part or all of the milk fat with the above-mentioned MLCT structure ester enriched with CLnA at the sn-2 position.

[0022] In one embodiment of the invention, the application includes replacing 40-70% of the milk fat with an MLCT structure ester enriched with CLnA at the sn-2 position.

[0023] The present invention also provides an ice cream containing the above-mentioned MLCT structure ester enriched with CLnA at the sn-2 position, the components of which include 8-12% milk powder, 10-15% sucrose, 0.2-0.5% emulsifier, 0.2-0.4% stabilizer, 1%-10% milk fat, 1%-10% MLCT structure ester enriched with CLnA at the sn-2 position, and the remainder being water.

[0024] In one embodiment of the present invention, the emulsifier is selected from one or more of mono- and di-fatty acid glycerides, sucrose esters, Tween, and Span, and the stabilizer is selected from one or more of sodium carboxymethyl cellulose, microcrystalline cellulose, carrageenan, xanthan gum, guar gum, and red bean gum.

[0025] The present invention also provides a method for preparing the above-mentioned ice cream, comprising selecting the above-mentioned raw materials and performing homogenization, sterilization, aging and freezing steps in sequence according to conventional ice cream production process to obtain ice cream product.

[0026] Beneficial effects: (1) This invention utilizes sn-1,3 position specific lipases to enzymatically hydrolyze pomegranate seed oil rich in conjugated linolenic acid (CLnA), and then directionally esterifies the obtained CLnA-retained glycerol monoester at the sn-2 position with medium-chain fatty acids and palm oil to construct a sn-2 CLnA-enriched MLCT structure ester. Adding the sn-2 CLnA-enriched MLCT structure ester prepared in this invention to the basic formula of ice cream can significantly reduce the water separation rate and melting rate of ice cream, and greatly improve its overrun.

[0027] (2) In the sn-2-enriched CLnA MLCT structure ester constructed in this invention, the fatty acid at the sn-2 position is mainly CLnA, accounting for 13-15% of the total fatty acid content, while the medium-chain fatty acid accounts for more than 30% of the total fatty acid content, and the MLCT content accounts for more than 93%. Adding the sn-2-enriched CLnA MLCT structure ester prepared in this invention to the basic formula of ice cream can reduce the water separation rate of ice cream by more than 10 percentage points, increase the overrun by more than 8 percentage points, and also improve the melting rate.

[0028] (3) The sn-2 enriched CLnA MLCT structure ester prepared by the method of the present invention can realize the metabolic and functional advantages of CLnA and medium chain fatty acids, and improve the absorption and utilization efficiency of CLnA. It has both structural functionality and good dairy taste, and is suitable for the development of nutritious and healthy ice cream. Detailed Implementation

[0029] To better understand the present invention, the following specific embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0030] The sn-1,3 specific lipases involved in the embodiments and comparative examples of this invention are all commercially available products: (1) Lipozyme 435 (trade name: Novozym 435), purchased from Novozymes A / S (Novozymes), is lipase B from immobilized Candida antarctica, with a batch-labeled enzyme activity of 10,000 PLU / g; (2) Lipozyme RM IM, purchased from Novozymes A / S, is lipase from immobilized Rhizomucor miehei, with a batch-labeled enzyme activity of 275 IUN / g; (3) Lipozyme TL IM, purchased from Novozymes A / S, is lipase from immobilized Thermomyces lanuginosus, with a batch-labeled enzyme activity of 250 IUN / g; (4) Pancreatic lipase, purchased from Aladdin, is a free enzyme powder, and the batch used has a nominal enzyme activity of 35 units / mg.

[0031] The present invention relates to a method for testing parameters: Water separation rate: The proportion of water separated during the storage process of the milk substrate (-18℃, 7 days) (centrifugation at 3000 rpm, 15 min), reflecting its stability.

[0032] Ice cream overrun: Using plastic tasting cups of the same size, weigh the same volume of aged emulsion and frozen and churned ice cream samples, and calculate the overrun: Overrun / % = (W0 - W1) / W1 × 100, where W0 is the mass of the aged ice cream emulsion, g; and W1 is the mass of the frozen ice cream sample, g.

[0033] Ice cream melting rate: Weigh a certain mass of hardened ice cream and place it on a 10-mesh sieve. Place a beaker below the sieve and maintain the temperature at about 25 ℃. Record the mass of ice cream that melts in the beaker within 20 min. Calculate the melting rate / % = m1 / m0 ×100, where m0 is the total mass of ice cream (g) and m1 is the mass of melted ice cream (g).

[0034] Example 1 A method for preparing MLCT-structured esters for improving the stability of ice cream emulsion bases includes the following steps: (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 6h to obtain CLnA-sn-2 MAG with a yield of 80% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 80g of CLnA-sn-2 MAG was obtained.

[0035] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 8 hours with lipase Lipozyme 435 (10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0036] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0037] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0038] Example 2 A method for preparing a sn-2 conjugated linolenic acid MLCT structured ester for use in ice cream includes the following steps: (1) 100g of pomegranate seed oil with 80% CLnA content was mixed with 0.05 mol / L pH 7.0 phosphate buffer (30% w / w oil weight) to form an emulsion. Lipozyme RM IM (12% of the pomegranate seed oil mass) was added to the sn-1,3 position specific lipase and reacted at 50℃ for 4h to obtain CLnA-sn-2 MAG with a yield of 75% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 70g of CLnA-sn-2 MAG was obtained.

[0039] (2) Take 25g of the obtained CLnA-sn-2 MAG, mix it with 48g of camphor seed oil and 32g of palm oil, and react it under anhydrous conditions at 45℃ for 6 hours under the catalysis of lipase Lipozyme TL IM (the amount added is 10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0040] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-obtained structural ester and dehydrated butter, and prepare a fat composition for ice cream at a total fat ratio of structural ester: milk fat = 60:40.

[0041] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 6%. The formula also includes 10% milk powder, 14% sucrose, 0.4% stabilizer (xanthan gum + carrageenan), 0.3% emulsifier, and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0042] Example 3 A method for preparing a sn-2 conjugated linolenic acid MLCT structured ester for use in ice cream includes the following steps: (1) 100g of pomegranate seed oil with a CLnA content of 85% was mixed with 0.05 mol / L pH 7.0 phosphate buffer (30% w / w oil weight) to form an emulsion. Pancreatic lipase, a specific lipase at the sn-1,3 position (6% of the pomegranate seed oil mass), was added and reacted at 50℃ for 8 h to obtain CLnA-sn-2 MAG with a yield of 70% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 70g of CLnA-sn-2 MAG was obtained.

[0043] (2) Take 25 g of the obtained CLnA-sn-2 MAG, mix it with 44 g of palm kernel oil and 28 g of palm liquid oil, and react it under anhydrous conditions at 50°C for 5 hours with lipase Lipozyme RM IM (added at 12% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0044] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-obtained structural ester and dehydrated butter, and prepare a fat composition for ice cream at a total fat ratio of structural ester: milk fat = 40:60.

[0045] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 6%. The formula also includes 8% milk powder, 10% sucrose, 0.4% stabilizer (xanthan gum + carrageenan), 0.5% emulsifier, and 75.1% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes with stirring. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the pomegranate seed oil used in step (1) contains 75% CLnA.

[0047] (1) 100g of pomegranate seed oil with a CLnA content of 75% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 6h to obtain CLnA-sn-2 MAG with a yield of 75% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 70g of CLnA-sn-2 MAG was obtained.

[0048] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 8 hours with lipase Lipozyme 435 (10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0049] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0050] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0051] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the enzymatic hydrolysis time in step (1) is 2 hours.

[0052] (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 2h to obtain CLnA-sn-2 MAG with a yield of 60% and a CLnA retention rate of 55%. After separation and molecular distillation purification, 55g of CLnA-sn-2 MAG was obtained.

[0053] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 8 hours with lipase Lipozyme 435 (10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0054] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0055] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0056] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the enzymatic hydrolysis time in step (1) is 18h.

[0057] (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 18h to obtain CLnA-sn-2 MAG with a yield of 50% and a CLnA retention rate of 60%. After separation and molecular distillation purification, 45g of CLnA-sn-2 MAG was obtained.

[0058] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 8 hours with lipase Lipozyme 435 (10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0059] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0060] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0061] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that CLnA-sn-2 MAG is not constructed, and pomegranate seed oil, palm oil and coconut oil are directly mixed for esterification reaction, that is, step (1) is omitted.

[0062] 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 45g of palm oil and 30g of coconut oil, and Lipozyme 435 (10%) was added. The mixture was esterified at 50℃ for 8 hours to obtain a sn-2 conjugated linolenic acid MLCT structured ester.

[0063] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0064] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0065] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that palm oil was replaced with coconut oil in step (2).

[0066] (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 6h to obtain CLnA-sn-2 MAG with a yield of 80% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 80g of CLnA-sn-2 MAG was obtained.

[0067] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1) and mix it with 75g of coconut oil. Under the catalysis of lipase Lipozyme435 (the amount added is 10% of the total mass of the mixture), react for 8 hours at 50°C under anhydrous conditions to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0068] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0069] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0070] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that in step (2), the amount of CLnA-sn-2 MAG added is reduced and the amount of coconut oil added is increased.

[0071] (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 6h to obtain CLnA-sn-2 MAG with a yield of 80% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 80g of CLnA-sn-2 MAG was obtained.

[0072] (2) Take 15g of CLnA-sn-2 MAG obtained in step (1), mix it with 55g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 8 hours with lipase Lipozyme 435 (the amount added is 10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0073] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0074] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0075] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that in step (2), the esterification reaction time is 4 hours.

[0076] (1) 100g of pomegranate seed oil with a CLnA content of 83% was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 and stirred to form an emulsion. Lipozyme 435, a specific lipase at the sn-1,3 position (8% of the pomegranate seed oil mass), was added and reacted at 45℃ for 6h to obtain CLnA-sn-2 MAG with a yield of 80% and a CLnA retention rate of 70%. After separation and molecular distillation purification, 80g of CLnA-sn-2 MAG was obtained.

[0077] (2) Take 25g of CLnA-sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50℃ for 4 hours with lipase Lipozyme 435 (the amount added is 10% of the total mass of the mixture) to obtain sn-2 conjugated linolenic acid MLCT structure ester.

[0078] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester and milk fat, and prepare a fat composition for ice cream at a total fat ratio of structure ester: milk fat = 50:50.

[0079] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0080] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that in step (1), sunflower seed oil is used instead of pomegranate seed oil.

[0081] (1) 100g of sunflower seed oil was mixed with 0.05 mol / L pH 7.0 phosphate buffer at a mass ratio of 1:0.3 to form an emulsion under stirring. Sn-1,3 position specific lipase Lipozyme 435 (the amount of enzyme added was 8% of the mass of sunflower seed oil) was added, and the mixture was reacted at 45℃ for 6h to obtain sn-2 MAG with a yield of 80%. After separation and molecular distillation purification, 80g of sn-2 MAG was obtained.

[0082] (2) Take 25g of sn-2 MAG obtained in step (1), mix it with 45g of coconut oil and 30g of palm oil, and react it under anhydrous conditions at 50°C for 8 hours with lipase Lipozyme 435 (the amount added is 10% of the total mass of the mixture) to obtain MLCT structure ester.

[0083] A method for preparing ice cream containing the above-mentioned sn-2 conjugated linolenic acid MLCT structure ester includes the following steps: S1. Take the above-mentioned MLCT structural ester and milk fat and mix them together. The ratio of structural ester to milk fat is 50:50 to prepare a fat composition for ice cream.

[0084] S2. Add the above-mentioned fat composition to the basic ice cream formula to make the fat content 8%. The formula also includes 10% milk powder, 12% sucrose, 0.4% stabilizer (xanthan gum + carrageenan = 1:1), 0.3% emulsifier (mono- and diglycerides of fatty acids + Tween = 5:1), and 69.3% water. Homogenize using traditional methods (first stage pressure 15 MPa, second stage 5 MPa), sterilize at 85℃ for 15 minutes, age at 4℃ for 8 hours, then freeze in a freezer for 20 minutes. The discharge temperature is [not specified]. 6℃, freezing temperature is 5℃ to At 10℃, a structured ester-substituted ice cream product was obtained.

[0085] Table 1 shows the content of MAG and the proportion of CLnA at the sn-2 position in pomegranate seed oil after enzymatic hydrolysis and esterification. It can be seen that Lipozyme 435, Lipozyme RM IM, and Lipozyme TL IM can all prepare CLnA-sn-2-MAG with a purity higher than 70%, and the three sn-1,3 specific lipases can also esterify and synthesize esters with a high sn-2 conjugated linolenic acid (MLCT) structure (CLnA at the sn-2 position is higher than 60%). During enzymatic hydrolysis, higher temperatures (within the enzyme's optimal temperature range) and longer times resulted in a higher proportion of CLnA-sn-2-MAG obtained. During esterification, the effects of temperature and time on the degree of esterification were similar to those during enzymatic hydrolysis; higher temperatures and longer times resulted in the synthesis of more MLCT. The proportion of CLnA at the sn-2 position in MLCT after esterification is affected by the content of CLnA-sn-2 MAG obtained from enzymatic hydrolysis. The lower the content of CLnA-sn-2 MAG obtained from enzymatic hydrolysis, the lower the content of CLnA at the sn-2 position in MLCT.

[0086] Table 1. Proportion of corresponding substances after enzymatic hydrolysis and esterification in the examples and comparative examples.

[0087] Table 2. Test results of relevant indicators of ice cream in the examples and comparative examples.

[0088] The MLCT-structured esters obtained in Examples 1-3 have a high CLnA content (>65%) at the sn-2 position, resulting in ice cream with low water separation rate, high overrun, and low melting rate, indicating a stable emulsion system and a dense structure. In contrast, differences in enzymatic hydrolysis time, enzyme type, fat ratio, or raw materials can all lead to a decrease in the proportion of CLnA at the sn-2 position (<60%), resulting in uneven fat crystal distribution and a weak emulsion film structure.

[0089] The positioning of CLnA at the sn-2 position helps enhance the steric stability of glycerides, promotes partial aggregation of fat globules and the formation of a continuous network. When the proportion of CLnA decreases or the proportion of medium-chain fatty acids is abnormal, the fat globule membrane is prone to rupture, the free oil in the system increases, leading to increased water separation rate, bubble structure collapse, and decreased expansion rate. Insufficient enzymatic hydrolysis or esterification time (e.g., Comparative Examples 2 and 7) results in incomplete transesterification, uneven MLCT structure, and increased fat crystal size; while excessive time (e.g., Comparative Example 3) enhances hydrolysis side reactions, causing fatty acid migration and structural damage at the sn-2 position, ultimately leading to decreased emulsion stability and poor melt resistance.

[0090] Furthermore, completely omitting the structural construction (Comparative Example 4) or replacing it with ordinary vegetable oil (Comparative Example 8) will lose the advantages of CLnA-MLCT in stereoconfiguration and molecular polarity, resulting in fat globules being unable to form a stable three-dimensional network; using a single oil (Comparative Example 5) or changing the ratio (Comparative Example 6) will disrupt the synergistic effect of medium-chain and long-chain fatty acids, causing an imbalance in the energy distribution and crystallization rate within the ice cream system, manifested as reduced melt resistance, rough texture, and increased viscosity.

[0091] In summary, the enrichment of CLnA at the sn-2 position in MLCT fats, the fatty acid composition ratio, and the enzymatic reaction conditions are all key factors affecting the final ice cream performance. Appropriate enzymatic hydrolysis and esterification conditions can yield MLCT-structured esters with regular structures and crystallization characteristics similar to milk fat, thereby significantly improving the stability and anti-melting properties of the milk base.

[0092] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for the preparation of an MLCT oil for improving the stability of ice cream milk bases, characterized in that, The steps are as follows: (1) mixing pomegranate seed oil with phosphate buffer, adding sn-1, 3 specific lipase for enzymolysis, and separating the product to obtain CLnA-sn-2 MAG with CLnA remaining at the sn-2 position, wherein the pomegranate seed oil is pomegranate seed oil with a CLnA content of 80-85%; (2) mixing the CLnA-sn-2 MAG obtained in step (1) with lauric acid oil and palm oil, adding sn-1, 3 specific lipase for esterification reaction to obtain MLCT structure ester with CLnA enriched at the sn-2 position.

2. The production method according to claim 1, characterized by, In step (1), the pH of the phosphate buffer is 6.5-7.0, the concentration is 0.03-0.07 mol / L, and the mass ratio of the pomegranate seed oil to the phosphate buffer is 1:0.15-0.

45.

3. The production method according to claim 1, characterized by, In step (1), the sn-1, 3 specific lipase includes at least one of pancreatic lipase, gastric lipase, Lipozyme 435, Lipozyme RM IM, Lipozyme TL IM or Aspergillus oryzae lipase, and the addition amount of the sn-1, 3 specific lipase is 5-15% of the weight of the pomegranate seed oil.

4. The production method according to claim 3, characterized by, The enzyme activity of the pancreatic lipase is ≥90 U / mg, the enzyme activity of the gastric lipase is 10-100 U / mg, the enzyme activity of the Lipozyme 435 is 9000-10000 PLU / g, the enzyme activity of the Lipozyme RM IM is 255-265 IUN / g, the enzyme activity of the Lipozyme TL IM is 230-280 IUN / g, the temperature during enzymolysis is 45-50°C, and the enzymolysis time is 4-12 h.

5. The production method according to claim 1, characterized by, In step (2), the lauric acid oil includes at least one of coconut oil, palm kernel oil, camphor seed oil and its fractionation or hydrogenation product, the palm oil includes at least one of palm oil and its fractionation or hydrogenation product, the mass ratio of the CLnA-sn-2 MAG to the lauric acid oil is 23-26:44-48, and the mass ratio of the CLnA-sn-2 MAG to the palm oil is 23-26:28-32.

6. The production method according to claim 1, characterized by, In step (2), the sn-1, 3 specific lipase includes at least one of pancreatic lipase, gastric lipase, Lipozyme TL IM, Lipozyme RM IM or Lipozyme 435, and the addition amount of the sn-1, 3 specific lipase is 5-15% of the total weight of the CLnA-sn-2 MAG, the lauric acid oil and the palm oil.

7. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the esterification reaction is 45-55°C, the time is 5-15 h, and the esterification reaction is carried out in a water-free or low-water active system.

8. The MLCT structure ester with CLnA enriched at the sn-2 position prepared by the preparation method of any one of claims 1-7.

9. Use of the sn-2 position enriched CLnA's MLCT structured ester of claim 8 in ice cream, characterized in that, The application is to replace part or all of milk fat with the MLCT structure ester with CLnA enriched at the sn-2 position.

10. An ice cream comprising the sn-2 position enriched CLnA MLCT structured ester of claim 9, characterized in that, The components include milk powder 8-12%, sucrose 10-15%, emulsifier 0.2-0.5%, stabilizer 0.2-0.4%, milk fat 1-10%, sn-2 site enriched CLnA MLCT structure ester 1-10%, and the rest is water.

Images