Preparation method of nutritious anti-melting ice cream with increased agglomeration degree of fat part

Abstract

The present invention belongs to the field of food, and discloses a method for preparing a nutritious anti-melting ice cream with increased agglomeration degree of the fat part. The method comprises the following steps: preparing coconut oil or palm kernel oil stearin diglyceride; heating and stirring the diglyceride to completely melt it to obtain an oil phase; adding skimmed milk powder, guar gum and sucrose to deionized water and heating to dissolve to obtain an aqueous phase; then slowly adding the oil phase to the aqueous phase while stirring, premixing with a stirrer and performing high-speed shear emulsification to obtain a crude emulsion; and then pasteurizing, high-pressure homogenizing, aging, freezing whipping and hardening to obtain an ice cream product. Using diglyceride to replace anhydrous milk fat, coconut oil, palm kernel oil, etc. in ice cream can effectively increase the degree of agglomeration of the fat part on the surface of the ice cream bubbles, forming a fat crystal network structure with strong rigidity, and the ice cream is not easy to melt at room temperature and has good shape retention.

Description

Technical Field

[0001] The invention belongs to the field of food, and particularly relates to a method for preparing nutritious anti-melting ice cream with increased agglomeration degree of a fat part. Background Art

[0002] Ice cream is a frozen snack food made from one or more of water, dairy products, sweeteners, oils and fats as raw materials and auxiliary materials, with appropriate amounts of spices, stabilizers, emulsifiers and other food additives added. It is made through processes such as mixing, pasteurization, homogenization, cooling and aging, frozen whipping and hardening. It is a complex colloidal system containing ice crystals, bubbles, oil crystals, milk solids, etc.

[0003] Commonly used fats in ice cream include anhydrous milk fat, coconut oil, palm oil series, palm kernel oil series, etc. These fats have low-temperature crystallization characteristics. During the aging process of ice cream slurry, fat crystallization occurs and continues to grow to a certain extent. The fat crystals penetrate the interfacial membrane of the fat globules, causing the fat globules to become unstable and partially coalesce. Part of the coalesced fat is adsorbed onto the surface of the bubbles during the freezing and whipping process to form a fat crystal network structure. This rigid network structure can stabilize the bubbles. And when the degree of partial coalescence of fat globules is high, the rigidity of the fat crystal network structure is stronger, and the anti-melting characteristics of ice cream are significantly improved.

[0004] Ice cream is loved by consumers for its delicate and smooth taste and rich flavor. However, traditional ice cream is a high-sugar, high-fat, high-calorie and low-protein food, and the fat in ice cream is mostly saturated fat or hydrogenated oil. The high content of saturated fat and possible trans fat can easily increase the risk of cardiovascular disease and other metabolic diseases. With the rise of economic level, consumers' consumption direction of ice cream has also changed, from delicious to healthy, from the pursuit of sensory to high quality. In the context of consumers' nutritional and healthy diet requirements, ice cream has gradually developed towards low-calorie, nutritious and healthy. Due to the particularity of ice cream structure, it needs to be strictly frozen at low temperature from the product to the hands of consumers, and large temperature fluctuations will seriously reduce the quality of the product. Therefore, there is an urgent need to seek new healthy raw materials to replace traditional saturated fats and hydrogenated oils to produce healthy and nutritious anti-melting ice cream, while reducing storage and transportation costs and improving quality.

[0005] The Chinese invention patent application (publication number CN102100298A) discloses an emulsifier for improving the melting resistance of ice cream and a method for preparing ice cream using the emulsifier. The method uses unsaturated monoglycerides with a specific fatty acid carbon number ratio to prepare ice cream, which effectively improves the melting resistance of ice cream, but requires the addition of more edible colloids.

[0006] The Chinese invention patent application (publication number CN110122649A) discloses an anti-melting fresh milk ice cream and a preparation method thereof. The method improves the anti-melting performance of fresh milk ice cream, but requires the addition of a high content of fresh milk and sugar, resulting in high preparation costs and high product calories.

[0007] The Chinese invention patent application (publication number CN113133493A) discloses an ice cream composition and a preparation method thereof. The ice cream prepared by the method has a high sliding melting point, but the raw material soybean oil-based diglyceride needs to be fractionated, does not involve melting time, and needs to add a high content of stabilizer.

[0008] The Chinese invention patent application (publication number CN104026326A) discloses a method for preparing low-fat nutritional ice cream. The method adds Haematococcus pluvialis powder and astaxanthin, which have the function of lowering blood lipids, to achieve low-fat and nutritional requirements. However, the system adds a large amount of sugar and needs to add a large amount of flavor ingredients to improve the sensory quality.

[0009] The Chinese invention patent application (publication number CN107549433A) discloses a method for preparing anti-melting ice cream. The method uses microcrystalline fibers extracted from potatoes and is applied to the ice cream system to form a gel-stable structure, but the system does not involve the improvement of fat aggregation and does not contain nutritional functional ingredients.

[0010] The Chinese invention patent application text (publication number CN108041181A) discloses a preparation method and application of a special oil for fortified plant sterol ester ice cream. The method improves the melting characteristics of ice cream, but requires the addition of more emulsifiers. Summary of the invention

[0011] In order to overcome the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing a nutritious anti-melting ice cream with an increased degree of agglomeration of the fat part. The diglyceride derived from coconut oil or palm kernel oil stearin provided by the present invention can significantly increase the degree of agglomeration of the fat part compared to traditional coconut oil, palm kernel oil stearin, anhydrous milk fat, etc., improve the formation of a rigid fat crystal network structure, effectively stabilize the bubble structure, and can also better maintain its shape at room temperature and is not easy to melt. While effectively replacing saturated fats and hydrogenated oils in the ice cream system, it can maintain product quality, eliminate the risks of saturated lipids and trans fats, retain the flavor of the raw oils, reduce calories, and improve nutritional value.

[0012] Another object of the present invention is to provide a nutritious anti-melting ice cream with increased agglomeration degree of the fat part prepared by the above method.

[0013] Another object of the present invention is to provide an application of the above-mentioned nutritional anti-melting ice cream.

[0014] The purpose of the present invention is achieved through the following solutions:

[0015] A method for preparing a nutritious anti-melting ice cream with increased agglomeration degree of a fat part comprises the following steps:

[0016] (1) Raw material preparation and purification: vegetable oil and glycerol are used as raw materials, and diglyceride is prepared by reaction under the action of lipase and water. After the reaction is completed, the mixture is centrifuged and the upper layer is taken to obtain a crude diglyceride product; the crude diglyceride product is purified by molecular distillation to obtain mixed fatty acid monoglycerides (distillation light phase) and diglycerides (distillation heavy phase);

[0017] (2) Preparation of O / W emulsion: heat and stir the diglyceride to completely melt it to obtain an oil phase; heat and stir the dairy product, stabilizer, sweetener and water to obtain an aqueous phase; add the oil phase to the aqueous phase while stirring, premix with a stirrer, and then shear and emulsify to obtain a crude emulsion; pasteurize the crude emulsion, and then homogenize to obtain a final emulsion; and finally cool and age.

[0018] (3) Preparation of ice cream: The aged O / W emulsion sample obtained in step (2) is subjected to freeze whipping treatment, and then hardened at low temperature to finally obtain the nutritious anti-melting ice cream with increased agglomeration degree of the fat part.

[0019] Diaceryl is a structural lipid in which a fatty acid residue in triglyceride is replaced by a hydroxyl group. There are two main isomers, 1,3-diaceryl and 1,2-diaceryl. It exists naturally in oils and fats and is a functional lipid that can be prepared in large quantities by chemical or enzymatic methods. It has physiological functions such as lowering postprandial blood lipids and blood sugar and inhibiting visceral fat accumulation. Coconut oil diglyceryl and palm kernel oil stearin diglyceryl are prepared and purified by enzymatic methods using coconut oil or palm kernel oil stearin as raw materials. They not only retain the flavor of the raw oil but also have the excellent physiological functions of diglyceryl. The melting point range is 10-40°C. Solid fat can form fat agglomeration at low temperatures, and quickly melt at high temperatures to make the product have good mouth-melting properties. The crystallization characteristics and nutritional characteristics of diglyceryl provide a strong basis for its application in ice cream. In the method of the present invention, the preparation and purification process of diglyceryl is simple, easy to operate, does not involve organic reagents, is safe and pollution-free, and has high nutritional characteristics. The purity is greater than 40%. At low temperatures, a certain amount of solid fat crystallizes and can form large fat aggregates adsorbed on the surface of liquid droplets. The resulting product has good stability at room temperature and excellent meltability in the mouth.

[0020] Preferably, the vegetable oil in step (1) is at least one of coconut oil and palm kernel oil stearin; the enzymatic method is a glycerol hydrolysis method, the catalytic enzyme of the reaction is phospholipase A1, the amount of the catalytic enzyme added is 2-6% of the total mass of the substrate (glycerol and vegetable oil), the water is deionized water, the amount of deionized water added is 6-10% of the total mass of the substrate (glycerol and vegetable oil), and the molar ratio of glycerol to vegetable oil is 10:1-20:1.

[0021] Preferably, the reaction temperature in step (1) is 30-50° C. and the reaction time is 3 h.

[0022] More preferably, the reaction temperature in step (1) is 40°C.

[0023] Diacylceride can be synthesized in large quantities by enzymatic method. It has good crystallization, emulsification and nutritional properties. It can be used as a functional special oil to replace hydrogenated oil or other saturated fats commonly used in ice cream systems.

[0024] Preferably, the mixture in step (1) is centrifuged at a speed of 8000 to 12000 rpm for 8 to 12 min.

[0025] Preferably, the distillation temperature selected for the molecular distillation method in step (1) is 140-180°C.

[0026] The mass content of diglyceride in the diglyceride in step (2) is greater than 40%.

[0027] Preferably, the diglyceride in step (2) is at least one of coconut oil diglyceride or palm kernel oil stearin diglyceride, and the addition amount is 8-16wt%; the dairy product is skimmed milk powder, and the addition amount is 8-16wt%; the stabilizer is at least one of gelatin, guar gum, locust bean gum, alginate, carrageenan, gum arabic, xanthan gum, konjac gum, pectin, and carboxymethyl cellulose, and the addition amount is 0.0-0.3wt%; the sweetener is sucrose, and the addition amount is 15-16%; the water is deionized water, and the addition amount is 51.7-69wt%.

[0028] Preferably, the step (2) of adding the oil phase to the water phase while stirring means first preheating the oil phase to 50-80°C, preheating the water phase to the same temperature, and adding the oil phase to the water phase while stirring; the premixing means premixing the mixture with a stirrer at a speed of 500-1000 rpm for 8-12 minutes.

[0029] Preferably, the shear rate of the shear emulsification in step (2) is 8000-15000 rpm, the processing time is 2-5 min, and the temperature of the mixture of the water phase and the oil phase is maintained at 50-80°C during the process.

[0030] Preferably, the pasteurization temperature in step (2) is 60-80° C., and the treatment time is 8-12 min.

[0031] Preferably, the homogenization treatment in step (2) refers to two-stage high-pressure homogenization, with a first-stage homogenization pressure of 15 to 20 MPa, a second-stage homogenization pressure of 4 to 6 MPa, and homogenization for 2 to 3 times.

[0032] Preferably, the aging temperature in step (2) is 0 to 5° C. and the time is 4 to 10 hours.

[0033] Preferably, the freezing and whipping temperature in step (3) is -6 to -20°C and the time is 10 to 30 minutes.

[0034] Preferably, the hardening temperature in step (3) is -16 to -22°C and the hardening time is 24 to 48 hours.

[0035] A nutritious anti-melting ice cream prepared by the method.

[0036] Application of the above-mentioned nutritional anti-melting ice cream in the food field.

[0037] The above-mentioned nutritional anti-melting ice cream uses functional structural lipid diglyceride, whose crystallization characteristics play a very important role in the formation of ice cream structure. During the aging stage, fat crystallizes. When fat globules approach each other, the crystals inside the fat globules can pierce the interface membrane between the fat globules, and the crystallized fat is moistened by the non-crystallized part. Bridges are formed between the fat globules, and partial fat aggregation occurs. The partially aggregated fat will be adsorbed on the surface of the bubbles to form a crystalline fat network structure. This structure can stabilize the bubbles and significantly improve the anti-melting properties of the ice cream. In addition, diglyceride replaces traditional saturated oils and hydrogenated oils with excellent nutritional properties and biological activity. The ice cream has a delicate and smooth taste and excellent product quality. The preparation process is simple and easy to operate, and it is very popular in the food field.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] (1) The raw materials used in the product preparation process of the present invention are all natural and healthy ingredients, the preparation process does not involve complicated steps, does not involve large-scale instruments, is simple to operate, safe and pollution-free, and is low-cost and suitable for large-scale industrial production;

[0040] (2) The diglyceride added in the present invention is a functional structural lipid, which reduces the intake of saturated oil and trans fat, has excellent biological activity and functionality, prevents atherosclerosis, has the effects of lowering blood lipids and controlling weight gain, etc. It improves the defects of traditional ice cream that are high in fat, high in calories and low in nutrition, and gives the product better nutritional functional characteristics.

[0041] (3) The nutritional anti-melting ice cream of the present invention does not require the addition of additional surfactants, and can achieve good emulsification and stabilization effects when less colloid is added. The product has excellent quality and stability, effectively reduces the use of emulsifiers, improves product safety and reduces production costs.

[0042] (4) The diglyceride in the present invention has excellent crystallization characteristics and surface activity, and the prepared O / W emulsion has high stability. Compared with traditional coconut oil, anhydrous milk fat, etc., it can effectively improve the fat aggregation degree of ice cream, and the network structure of the fat part aggregation body around the bubbles is complete and has a certain strength. The product is not easy to melt at room temperature, and can also maintain a good structural shape under high temperature conditions of 50°C. It is easy to melt in the mouth without a sticky feeling and has a good flavor, which improves the disadvantage of common ice cream on the market that it is easy to melt at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the process of the present invention.

[0044] Figure 2 It is a solid fat content diagram of coconut oil diglyceride and palm kernel oil stearin diglyceride prepared by the present invention at different temperatures.

[0045] Figure 3 Laser confocal microstructure images of ice cream prepared in Examples 1, 2, 3 and 4 and Comparative Example 1.

[0046] Figure 4 This is a laser confocal microstructure image of the ice cream prepared in Comparative Examples 2, 3, and 4.

[0047] Figure 5 The shapes and appearances of the ice creams prepared in Examples 3 and 4 and Comparative Examples 1, 2, 3 and 4 under different temperatures and storage times. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0049] Unless otherwise specified, the reagents used in the examples can be purchased from the market.

[0050] Example 1

[0051] (1) Preparation and purification of diglyceride raw materials: Glycerol and coconut oil were mixed in a molar ratio of 15:1, phospholipase A1 (added amount was 4% of the total mass of the substrate) and deionized water (added amount was 8% of the total mass of the substrate) were added at 40°C, and the catalytic reaction was carried out under vacuum for 3 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes. The upper layer was a crude diglyceride product. The crude product was purified using a molecular distillation device at 160°C to obtain purified diglyceride.

[0052] The content and components of the obtained coconut oil diglyceride (CO-DAG) product were detected by gas chromatography, wherein the purity of the diglyceride was 44%.

[0053] The solid fat content of diglyceride in the examples is analyzed as follows: measured by NM-2 nuclear magnetic resonance analyzer. 1.5000 g of oil sample is weighed into a nuclear magnetic resonance test tube, maintained at 80°C for 30 minutes to melt the sample and eliminate crystal memory, then maintained at 0°C for 30 minutes, and finally measured at a constant temperature of 5°C from 5 to 80°C for 30 minutes.

[0054] (2) Take 10 g of coconut oil diglyceride, heat and stir at 60° C. to completely melt it, and obtain an oil phase; take 10 g of skimmed milk powder, 0.25 g of guar gum, 15 g of sucrose, and 64.75 g of deionized water, heat and stir at 60° C. to completely dissolve them, and obtain an aqueous phase; then slowly add the oil phase to the uniformly mixed aqueous phase while stirring, use a stirrer to fully mix the oil phase and the aqueous phase at a speed of 800 rpm for 10 minutes, and high-speed shear the mixture at a speed of 15000 rpm for 3 minutes to obtain a crude emulsion. During the emulsification process, the water bath temperature is maintained at about 60° C. The crude emulsion is pasteurized at 80° C. for 10 minutes, and then homogenized three times under high-pressure homogenization conditions with a primary pressure of 15 MPa and a secondary pressure of 5 MPa to obtain a final emulsion, and the emulsion is immediately cooled to 4° C. and aged at this temperature for 6 hours.

[0055] (3) The aged emulsion obtained in step (2) is placed in an ice cream machine and frozen and whipped at -18°C for 20 minutes, and then the frozen and whipped sample is placed in -18°C for hardening for 24 hours, and finally the ice cream product is stored at -18°C.

[0056] The whipping performance of the ice cream in the examples is expressed by overrun:

[0057] Expansion rate (%) = (m0-m) / m×100%

[0058] m0: represents the mass of a certain volume of aged emulsion sample before freezing and whipping.

[0059] m: represents the mass of ice cream of the same volume after freezing and whipping.

[0060] The method for analyzing the degree of aggregation of the fat part of the ice cream in the embodiment is as follows: when preparing the dye, 0.02% (mass percentage) of Nile red and 0.1% (mass percentage) of Nile blue are dissolved in a mixed solution of 1.2-propylene glycol and water (volume ratio is 50:1), mixed evenly and stored at 4°C in the dark. When observing, a small amount of mixed dye is added to the ice cream to make slices for observation. Select the excitation wavelength of 488nm Ar ion and 633nm He / Ne ion laser scanning to collect fluorescence images. The red area represents the degree of aggregation of the fat part. The larger the red area, the higher the degree of aggregation of the fat part. The green area represents protein and polysaccharide, and the black circle is the bubble.

[0061] The melting characteristics analysis method of the ice cream in the embodiment is as follows: 60g of ice cream sample is placed on the porous plate at the top of a plastic dish, and the ambient temperature is maintained at 20°C. The time of initial dripping of the sample and the mass of the ice cream dripping after melting are recorded every 10 minutes for a total of 120 minutes. The ratio of the amount of ice cream dripping in 60 minutes or 120 minutes to the total amount of ice cream is taken as the melting rate (%) of the ice cream. The ability of the sample to maintain its initial shape during the melting process is evaluated by monitoring the change in the shape of the sample.

[0062] By the detection method described in Example 1, the solid fat content of coconut oil diglyceride in this example changes with temperature as follows Figure 2 As shown in the figure, at 37°C, the solid fat content of coconut oil diglyceride is very low, which can give the product good melting properties and is suitable for ice cream products. By freezing and whipping, an ice cream with an expansion rate of about 66% and a fine texture can be obtained. The distribution of fat aggregates on the surface of ice cream bubbles is observed by collecting fluorescence images using laser confocal microscopy. Figure 3 It can be seen that there are large fat aggregates on the surface of the bubbles and the attachment area is wide, indicating that a complete fat crystal network structure can be formed on the surface of the bubbles, and the wrapped bubbles are highly stable. The analysis of the anti-melting properties of ice cream found that when stored at 20°C, the first drop of the sample was leaked at 98 minutes, and the sample melting rate was only 6% at 120 minutes. The sample shape was well maintained, indicating that the ice cream obtained in this example has excellent room temperature anti-melting properties. However, the product can melt quickly in the mouth and has excellent mouth-melting properties and flavor characteristics.

[0063] Example 2

[0064] (1) Preparation and purification of diglyceride raw materials: Glycerol and palm kernel oil stearin were mixed in a molar ratio of 10:1, phospholipase A1 was added at 40°C (the addition amount was 4% of the total mass of the substrate), and deionized water was added in an amount of 8% of the total mass of the substrate. The catalytic reaction was carried out under vacuum for 3 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes. The upper layer was a crude diglyceride product. The crude product was purified using a molecular distillation device at 160°C to obtain purified diglyceride.

[0065] The content and components of the obtained palm kernel oil stearin diglyceride (PKST-DAG) were detected by gas chromatography, wherein the purity of the diglyceride was 49%.

[0066] (2) Take 10 g of palm kernel oil stearyl diglyceride, heat and stir at 60°C to completely melt it, and obtain an oil phase; take 10 g of skimmed milk powder, 0.25 g of guar gum, 15 g of sucrose, and 64.75 g of deionized water, heat and stir at 60°C to completely dissolve them, and obtain an aqueous phase; then slowly add the oil phase to the uniformly mixed aqueous phase while stirring, use a stirrer to fully mix the oil phase and the aqueous phase at a speed of 800 rpm for 10 minutes, and high-speed shear the mixture at a speed of 15000 rpm for 3 minutes to obtain a crude emulsion. During the emulsification process, the water bath temperature is maintained at about 60°C. The crude emulsion is pasteurized at 80°C for 10 minutes, and then homogenized three times under high-pressure homogenization conditions with a first-level pressure of 15 MPa and a second-level pressure of 5 MPa to obtain a final emulsion, and the emulsion is immediately cooled to 4°C and aged at this temperature for 6 hours.

[0067] (3) The aged emulsion obtained in step (2) is placed in an ice cream machine and frozen and whipped at -18°C for 20 minutes, and then the frozen and whipped sample is placed in -18°C for hardening for 24 hours, and finally the ice cream product is stored at -18°C.

[0068] The solid fat content of palm kernel oil stearyl diglyceride obtained in this example is as follows: Figure 2 As shown in the figure, at 37°C, the solid fat content of palm kernel oil stearyl diglyceride is low, which can give the product better melting properties and is suitable for ice cream products. Ice cream with an expansion rate of about 43% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles was observed by laser confocal fluorescence imaging. Figure 3 It can be seen that there are large fat aggregates on the bubble surface and the attachment area is wide, indicating that a complete fat crystal network structure can be formed on the bubble surface, and the bubble wrapping stability is high. The melting property analysis of ice cream found that when stored at 20°C, the first drop of the sample was leaked for 70 minutes, and the sample melting rate was 9% at 120 minutes. The sample shape was well maintained, indicating that the ice cream obtained in this example has excellent anti-melting properties.

[0069] Example 3

[0070] Referring to the steps and conditions of Example 1, coconut oil diglyceride was used as the oil phase, except that the amount of guar gum added in step 2 was 0 g, and the amount of deionized water added was 65 g.

[0071] By using the detection method described in Example 1, ice cream with an overrun of about 69% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by collecting fluorescence images using laser confocal microscopy. Figure 5 It was found that the fat aggregates attached to the bubble surface were larger, but the attachment area was smaller than that in Example 1 ( Figure 3 The analysis of the anti-melting properties of ice cream found that when stored at 20°C, the first drop of the sample was 28 minutes, the melting rate of the sample was 16% at 120 minutes, and the shape of the sample was well maintained, indicating that this embodiment did not add edible gum as a stabilizer, and good anti-melting properties could be obtained through the crystal network formed by diglyceride.

[0072] Example 4

[0073] Referring to the steps and conditions of Example 2, the oil phase used palm kernel oil stearin diglyceride, except that the amount of guar gum added in step 2 was 0 g, and the amount of deionized water added was 65 g.

[0074] By using the detection method described in Example 1, ice cream with an overrun of about 49% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by laser confocal microscopy. Figure 5 It was found that there were large fat aggregates on the bubble surface, and the adhesion area was larger than that of Example 2 ( Figure 3 ) is small. The anti-melting properties of ice cream were observed. It was found that when stored at 20°C, the first drop of the sample was leaked in 18 minutes, and the melting rate of the sample was 17% at 120 minutes. The shape of the sample was well maintained, indicating that this embodiment can also obtain good anti-melting properties through the crystal network formed by diglyceride without adding stabilizer.

[0075] Comparative Example 1

[0076] (1) Soybean oil diglyceride (SO-DAG) was prepared according to the method in Example 1 to obtain soybean oil diglyceride with a purity of 45%. 10 g of soybean oil diglyceride was taken and heated and stirred at 60°C to completely melt it to obtain an oil phase; 10 g of skimmed milk powder, 0.25 g of guar gum, 15 g of sucrose and 64.75 g of deionized water were taken and heated and stirred at 60°C to completely dissolve them to obtain an aqueous phase; then the oil phase was slowly added to the uniformly mixed aqueous phase while stirring, and the oil phase and the aqueous phase were fully mixed with a stirrer at a speed of 800 rpm for 10 minutes. The mixture was sheared at a speed of 15000 rpm for 3 minutes to obtain a crude emulsion. During the emulsification process, the water bath temperature was maintained at about 60°C. The crude emulsion was pasteurized at 80°C for 10 minutes, and then homogenized three times under high pressure homogenization conditions with a primary pressure of 15 MPa and a secondary pressure of 5 MPa to obtain a final emulsion. The emulsion was immediately cooled to 4°C and aged at this temperature for 6 hours.

[0077] (2) placing the aged emulsion obtained in step (2) into an ice cream machine and freezing and whipping it at -18°C for 20 minutes, then placing the frozen and whipped sample at -18°C for hardening for 24 hours, and finally obtaining an ice cream product and storing it at -18°C.

[0078] By using the detection method described in Example 1, ice cream with an overrun of about 79% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by laser confocal microscopy. Figure 3 It was found that there was a small amount of fat aggregate on the bubble surface, and the attachment area was smaller than that of Example 1 and Example 2. The anti-melting property of the ice cream was observed and it was found that when stored at 20°C, the first drop of the sample was dripped for 15 minutes, and the melting rate of the sample was 80% at 60 minutes. The product did not have good anti-melting properties.

[0079] Comparative Example 2

[0080] (1) 10 g of coconut oil (CO) was heated and stirred at 60° C. to completely melt the oil phase; 10 g of skimmed milk powder, 0.25 g of guar gum, 15 g of sucrose and 64.75 g of deionized water were heated and stirred at 60° C. to completely dissolve the oil phase to obtain a water phase; the oil phase was then slowly added to the uniformly mixed water phase while stirring, the oil phase and the water phase were fully mixed at a speed of 800 rpm for 10 min with a stirrer, the mixture was high-speed sheared at a speed of 15000 rpm for 3 min to obtain a coarse emulsion, the water bath temperature was maintained at about 60° C. during the emulsification process, the coarse emulsion was pasteurized at 80° C. for 10 min, and then homogenized three times in a secondary high-pressure homogenizer with a primary pressure of 15 MPa and a secondary pressure of 5 MPa to obtain a fine emulsion, and the fine emulsion was immediately cooled to 4° C. and aged at this temperature for 6 h.

[0081] (2) placing the aged emulsion obtained in step (2) into an ice cream machine and freezing and whipping it at -18°C for 20 minutes, then placing the frozen and whipped sample at -18°C for hardening for 24 hours, and finally obtaining an ice cream product and storing it at -18°C.

[0082] By using the detection method described in Example 1, ice cream with an overrun of about 72% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by collecting fluorescence images using laser confocal microscopy. Figure 5 It was found that there were small fat aggregates on the bubble surface, the attachment area was also small, the protein adsorption area was large, and the melting point of coconut oil was lower than that of coconut oil diglyceride, indicating that the fat crystal network formation effect and strength on the bubble surface were worse than those in Example 1. The anti-melting properties of the ice cream were observed and found that when stored at 20°C, the first drop of the sample was dripped for 15 minutes, and the melting rate of the sample was 80% at 60 minutes, which was close to complete melting, and the product had poor anti-melting properties.

[0083] Comparative Example 3

[0084] Refer to the steps and conditions of Comparative Example 2, except that the oil phase of step 2 uses palm kernel stearin (PKST).

[0085] By using the detection method described in Example 1, ice cream with an expansion ratio of about 77% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by collecting fluorescence images using laser confocal microscopy. Figure 5 It was found that small fat aggregates were attached to the surface of the bubbles, the attachment area was also small, the protein adsorption area was large, and the melting point of palm kernel oil stearin was lower than that of palm kernel oil stearin-derived diglyceride, indicating that the fat crystal network formation effect and strength on the bubble surface were worse than those in Example 2. The anti-melting properties of the ice cream were observed and it was found that when stored at 20°C, the time for the first drop of the sample to drip was 7 minutes, and the melting rate of the sample was 79% at 60 minutes, and the product had poor anti-melting properties.

[0086] Comparative Example 4

[0087] Refer to the steps and conditions of Comparative Example 1, except that anhydrous milk fat (AMF) is used as the oil phase in step 2.

[0088] By using the detection method described in Example 1, ice cream with an overrun of about 79% can be obtained by freezing and whipping. The distribution of fat and protein on the surface of ice cream bubbles is observed by collecting fluorescence images using laser confocal microscopy. Figure 5It was found that the fat attached to the bubble surface was spherical and the degree of fat aggregation was the lowest, indicating that the fat crystal network formed on the bubble surface could not effectively maintain the stability of the product structure. The anti-melting properties of ice cream were observed and it was found that when stored at 20°C, the first drop of the sample was leaked in 8 minutes, and the melting rate of the sample was 81% at 60 minutes. The product under this ratio has weak anti-melting ability.

[0089] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a nutritional anti-melting ice cream with increased agglomeration degree of fat part, characterized in that: The following steps are involved: (1) Raw material preparation: vegetable oil and glycerol are used as raw materials to react with lipase and water to prepare diglyceride. After the reaction, the mixture is centrifuged and the upper layer is taken to obtain a crude diglyceride product. The crude diglyceride product is purified by molecular distillation to obtain mixed fatty acid monoglycerides and diglycerides respectively. (2) Preparation of O / W emulsion: Heat and stir the diglyceride to completely melt it to obtain an oil phase; heat and stir the dairy product, stabilizer, sweetener and water to obtain a water phase; The oil phase is added to the water phase while stirring, premixed with a stirrer, and then sheared and emulsified to obtain a crude emulsion; The crude emulsion is pasteurized and then homogenized to obtain the final emulsion; finally, it is cooled and aged; (3) Preparation of ice cream: freeze-whipping the aged O / W emulsion sample obtained in step (2), and then hardening it at low temperature to finally obtain the nutritious anti-melting ice cream with increased agglomeration degree of the fat part; The catalytic enzyme in the reaction in step (1) is phospholipase A1, and the amount of the catalytic enzyme added is 2-6% of the total mass of glycerol and vegetable oil; the amount of water added is 6-10% of the total mass of glycerol and vegetable oil; the molar ratio of glycerol to vegetable oil is 10:1-20:1; The diglyceride in step (2) is coconut oil diglyceride or palm kernel oil stearin diglyceride; The stabilizer in step (2) is guar gum, and the added amount is 0.0~0.3wt%.

2. The method for preparing the nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that: In step (1), the vegetable oil is at least one of coconut oil and palm kernel oil stearin.

3. The method for preparing the nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that: The water in step (1) is deionized water; the reaction temperature in step (1) is 30-50°C, and the reaction time is 3 h.

4. The method for preparing a nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that ； In step (1), the mixture is centrifuged at a speed of 8000-12000 rpm for 8-12 min; In step (1), the crude diglyceride product is purified by molecular distillation at a distillation temperature of 140-180°C.

5. The method for preparing the nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that: In step (2), the diglyceride is added in an amount of 8-16 wt %, the dairy product is skimmed milk powder, the added amount is 8-16 wt %, the sweetener is sucrose, the added amount is 15-16 wt %, and the water is deionized water, the added amount is 51.7-69 wt %.

6. The method for preparing a nutritional anti-melting ice cream with increased agglomeration degree of fat part according to claim 1, characterized in that ； The step (2) of adding the oil phase to the water phase while stirring means that the oil phase is first preheated to 50-80°C, the water phase is preheated to the same temperature, and the oil phase is added to the water phase while stirring; the premixing means that the mixture is premixed with a stirrer at a speed of 500-1000 rpm for 8-12 minutes; The shear rate of the shear emulsification in step (2) is 8000-15000 rpm, the processing time is 2-5 min, and the temperature of the mixture of the water phase and the oil phase is maintained at 50-80°C during the process.

7. The method for preparing a nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that ； The pasteurization temperature in step (2) is 60-80°C and the processing time is 8-12 minutes; The homogenization treatment in step (2) refers to two-stage high-pressure homogenization, with a first-stage homogenization pressure of 15-20 MPa, a second-stage homogenization pressure of 4-6 MPa, and homogenization 2-3 times; The aging temperature in step (2) is 0-5°C and the time is 4-10h.

8. The method for preparing the nutritional anti-melting ice cream with increased agglomeration degree of the fat part according to claim 1, characterized in that: The freezing and whipping temperature in step (3) is -6 to -20°C and the time is 10 to 30 minutes; The hardening temperature in step (3) is -16 to -22°C and the hardening time is 24 to 48 hours.

9. A nutritional anti-melting ice cream with increased agglomeration degree of the fat part prepared by the method according to any one of claims 1 to 8.

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