Snow pear and loquat flavored fermented milk and preparation method thereof
阅读说明：本技术 雪梨枇杷风味发酵乳及其制备方法 (Snow pear and loquat flavored fermented milk and preparation method thereof ) 是由 索超 尹小静 薛建岗 庞飞 张海斌 于 2020-03-19 设计创作，主要内容包括：本发明提供了一种雪梨枇杷风味发酵乳及其制备方法。该制备方法包括将雪梨和枇杷煮沸热烫、打浆、超声、酶解、加入羧甲基壳聚糖/活性白土复合物澄清处理后得到混合果汁,再将混合果汁与原料奶、复配稳定剂混合,经过脱气、均质、杀菌、发酵,得到所述雪梨枇杷风味发酵乳,其中,所述复配稳定剂包括琼脂和乙酰化双淀粉己二酸酯,所述基料包括0.5-1％混合果汁,所述雪梨和枇杷的重量比为8:2-6:4。本发明提供了一种雪梨枇杷风味发酵乳,其是由上述制备方法得到的。本发明提供的雪梨枇杷风味发酵乳稳定性高、质构均一、风味口感较佳。(The invention provides fermented milk with snow pear and loquat flavors and a preparation method thereof. The preparation method comprises the steps of boiling snow pears and loquats, blanching, pulping, carrying out ultrasonic treatment and enzymolysis, adding a carboxymethyl chitosan/activated clay compound, carrying out clarification treatment to obtain mixed juice, mixing the mixed juice with raw milk and a compound stabilizer, degassing, homogenizing, sterilizing and fermenting to obtain the snow pear and loquats flavored fermented milk, wherein the compound stabilizer comprises agar and acetylated distarch adipate, the base material comprises 0.5-1% of the mixed juice, and the weight ratio of the snow pears to the loquats is 8:2-6: 4. The invention provides snow pear and loquat flavored fermented milk which is obtained by the preparation method. The snow pear and loquat flavored fermented milk provided by the invention has the advantages of high stability, uniform texture and good flavor and mouthfeel.)
1. A preparation method of fermented milk with snow pear and loquat flavors comprises the following steps:
(1) boiling snow pears and loquats, blanching, adding water, pulping, ultrasonically softening the pulp, and carrying out enzymolysis to obtain snow pear and loquats pulp;
(2) adding carboxymethyl chitosan/activated clay compound into the pulp of the snow pears and the loquats, and obtaining mixed fruit juice after water bath;
(3) adding the mixed fruit juice into raw milk and a compound stabilizer, and stirring to obtain a base material;
(4) degassing the base material, homogenizing, sterilizing and fermenting to obtain the snow pear and loquat flavored fermented milk;
wherein the compound stabilizer comprises agar and acetylated distarch adipate; the base material comprises 0.5-1% of mixed fruit juice by taking the total weight of the base material as 100%; the weight ratio of the snow pears to the loquats is 8:2-6: 4.
2. The preparation method according to claim 1, wherein the weight ratio of the snow pears and the loquats in step (1) is 7: 3.
3. The preparation method according to claim 1, wherein in the step (1), the boiling blanching is performed in a mixed solution of ascorbic acid and citric acid;
preferably, in the mixed solution of the ascorbic acid and the citric acid, the concentration of the ascorbic acid is 0.3-0.7 wt%, and the concentration of the citric acid is 0.4-0.6 wt%;
more preferably, the concentration of the ascorbic acid is 0.3 wt% and the concentration of the citric acid is 0.5 wt%.
4. The preparation method according to claim 1, wherein in the step (1), the enzyme used for the enzymolysis comprises pectinase;
preferably, the temperature of the enzymolysis is 37-50 ℃, and the time of the enzymolysis is 45-120 min;
more preferably, the temperature of the enzymolysis is 45 ℃, and the time of the enzymolysis is 90 min.
5. The preparation method according to claim 1, wherein in the carboxymethyl chitosan/activated clay complex, the mass ratio of carboxymethyl chitosan to activated clay is 1:10 to 1:7, preferably 1: 10;
more preferably, the preparation method of the carboxymethyl chitosan/activated clay complex comprises the following steps: adding carboxymethyl chitosan into an acid solution, adding activated clay, and stirring to obtain a carboxymethyl chitosan/activated clay compound, wherein the ratio of the carboxymethyl chitosan to the acid solution is 1:8-1: 6;
further preferably, the acidic solution is an acetic acid solution;
still more preferably, the acetic acid solution has a mass concentration of 1%.
6. The preparation method according to claim 1 or 5, wherein in the step (2), the mass ratio of the snow pear loquat pulp to the carboxymethyl chitosan/activated clay complex is 9:1-7: 1.
7. The preparation method according to claim 1, wherein in the step (3), the base material comprises 0.3-0.9% of compound stabilizer and the balance of raw milk, wherein the total weight of the base material is 100%;
preferably, the base material also comprises 0.3 to 1 per thousand of sweetener, 1 to 2 percent of white granulated sugar and/or 2 to 4 percent of high fructose corn syrup, wherein the total weight of the base material is 100 percent;
more preferably, the sweetener comprises sucralose and/or acesulfame k; more preferably, the mass ratio of the sucralose to the acesulfame is (0.05-1): (0.3-1.2).
8. The production method according to claim 1 or 7, wherein in the step (3), the mass ratio of the acetylated distarch adipate to the agar is (3-6): (0.5-3).
9. The preparation method as claimed in claim 1, wherein, in the step (4), the stirring temperature of the base material is 50-55 ℃, the stirring time is 30-60min, and the stirring speed is 500-800 rpm;
the degassing pressure is 18-20MPa, and the degassing temperature is 60-70 ℃;
the sterilization temperature is 85-93 ℃, and the sterilization time is 280-300 s;
the fermentation temperature is 40-43 ℃, and the fermentation is carried out until the acidity reaches 70-80 DEG T;
preferably, the temperature of the sterilization is 90-93 ℃, and the time of the sterilization is 290-300 s.
10. A snow pear and loquat flavored fermented milk obtained by the production method according to any one of claims 1 to 9.
Technical Field
The invention relates to the technical field of dairy product preparation, and particularly relates to snow pear and loquat flavored fermented milk and a preparation method thereof.
Background
The yoghourt is a milk product which is prepared by taking milk or milk powder as a raw material, adding beneficial bacteria (leavening agent) into the milk (or reconstituted milk) after pasteurization, fermenting, cooling and filling. The yogurt has high nutritive value, is easier to digest and absorb than fresh milk, and can enhance digestion, promote appetite, and enhance intestinal motility and metabolism. Snow pears contain rich vitamins and minerals and have the functions of moistening lung, clearing dryness, relieving cough, reducing phlegm, nourishing blood and promoting granulation, while loquats are rich in fructose, glucose, potassium, calcium and vitamins and also have various efficacies of moistening lung, relieving cough and the like. At present, patent No. CN107744020A discloses a preparation method of loquat yogurt, which comprises adding fruit juice into yogurt after the yogurt fermentation is completed, so that the problem of insufficient nutrient absorption to fruits is easily caused, which is not good for human health, and when adding fruit juice, the fruits are rich in inorganic salts, organic acids and other substances, and when mixing with yogurt or milk, the fermented product is easily subjected to unstable system such as whey precipitation.
Disclosure of Invention
In order to solve the problems, the invention aims to provide fermented milk with snow pear and loquat flavors and a preparation method thereof, wherein the preparation method can obtain clear mixed juice with high juice yield; and by adding the compound stabilizer and controlling the composition of the compound stabilizer and the content of the fruit juice, the snow pear and loquat flavored fermented milk with uniform texture and better flavor and mouthfeel can be obtained.
In order to achieve the purpose, the invention provides a preparation method of fermented milk with snow pear and loquat flavors, which comprises the following steps:
(1) boiling snow pears and loquats, blanching, adding water, pulping, ultrasonically softening the pulp, and carrying out enzymolysis to obtain snow pear and loquats pulp;
(2) adding carboxymethyl chitosan/activated clay compound into the pulp of the snow pears and the loquats, and obtaining mixed fruit juice after water bath;
(3) adding the mixed fruit juice into raw milk and a compound stabilizer, and stirring to obtain a base material;
(4) degassing the base material, homogenizing, sterilizing and fermenting to obtain the snow pear and loquat flavored fermented milk;
wherein the compound stabilizer comprises agar and acetylated distarch adipate; the base material comprises 0.5-1% of mixed fruit juice by taking the total weight of the base material as 100%; the weight ratio of the snow pears to the loquats is 8:2-6: 4.
In the above preparation method, the content of the mixed juice in the base is calculated as pure juice containing no water.
In the above preparation method, controlling the amount of loquat as an acidic fruit can improve the stability of the fermented milk product. In the step (1), the weight ratio of the snow pears to the loquats is preferably 7: 3.
In the preparation method, the mixed fruit juice is mainly prepared by adopting a physical hot water wall breaking method to accelerate the dissolution speed of the fruit juice, and then the dissolved snow pear and loquat fruit juice is clarified by adding the carboxymethyl chitosan/activated clay compound, so that the obtained mixed fruit juice has no peculiar smell, is clarified and has high juice yield.
In the specific embodiment of the invention, in the step (1), the snow pears and loquats can be further subjected to the treatment of cleaning, peeling, splitting and stoning before boiling and blanching.
In the above preparation method, preferably, in the step (1), the boiling blanching is performed in a mixed solution of ascorbic acid and citric acid, which can function to adjust the pH.
According to a specific embodiment of the present invention, in the mixed solution of ascorbic acid and citric acid, the concentration of ascorbic acid may be controlled to be 0.3 to 0.7 wt% (preferably 0.3 wt%), and the concentration of citric acid may be controlled to be 0.4 to 0.6 wt% (preferably 0.5 wt%).
According to the specific embodiment of the invention, the ultrasonic treatment can uniformly mix the pulp and improve the juice yield of the snow pears and loquats. In the step (1), the power of the ultrasound may be controlled to be 800W, and correspondingly, the time of the ultrasound may be controlled to be 120 min.
According to the specific embodiment of the invention, the juice yield can be improved and resources can be saved by carrying out enzymolysis on the pomace of the snow pears and the loquats obtained by pulping. In the step (1), after ultrasonic softening, the operation of separating the obtained normal juice from the pomace, carrying out enzymolysis on the pomace and then mixing the pomace with the normal juice to obtain the snow pear loquat pulp can be further included. The enzyme for enzymolysis can include pectinase, the enzymolysis temperature can be controlled at 37-50 deg.C (preferably 45 deg.C), and the enzymolysis time can be controlled at 45-120min (preferably 90 min).
In the preparation method, the carboxymethyl chitosan/activated clay compound is used as a natural flocculant to clarify the dissolved mixed juice of snow pears and loquats. Preferably, in the carboxymethyl chitosan/activated clay complex, the mass ratio of carboxymethyl chitosan to activated clay is 1:10 to 1:7 (more preferably 1: 10).
According to a specific embodiment of the present invention, the method for preparing the carboxymethyl chitosan/activated clay composite may include: adding carboxymethyl chitosan into the acid solution, adding activated clay, and stirring to obtain a carboxymethyl chitosan/activated clay compound, wherein the ratio of the carboxymethyl chitosan to the acid solution is 1:8-1: 6. In some embodiments, the acidic solution may be an acetic acid solution, and the mass concentration of the acetic acid solution is preferably 1%; the stirring temperature can be controlled to 60 ℃, and correspondingly, the stirring time can be controlled to 6 h.
In the above preparation method, preferably, in the step (2), the mass ratio of the snow pear loquat pulp to the carboxymethyl chitosan/activated clay complex is 9:1-7: 1.
In the above preparation method, preferably, in the step (2), the temperature of the water bath is 35 ℃ and the time of the water bath is 15 min.
In the preparation method, preferably, in the step (3), the base material comprises 0.3-0.9% of compound stabilizer and the balance of raw milk, based on 100% of the total weight of the base material.
In the preparation method, the acetylated distarch adipate and the agar are added into the base material as a compound stabilizer, so that the system stability of the fermented milk product can be improved. Preferably, in the step (3), the mass ratio of the acetylated distarch adipate to the agar is (3-6): (0.5-3).
In the above preparation method, preferably, in the step (3), the base material further comprises 0.3 to 1% o of sweetener based on 100% of the total weight of the base material; more preferably, the sweetener comprises sucralose and/or acesulfame k; further preferably, the mass ratio of the sucralose to the acesulfame is (0.05-1): (0.3-1.2).
In the above preparation method, preferably, in the step (3), the base further comprises 1-2% of sugar, based on 100% of the total weight of the base; more preferably, the sugar comprises white sugar.
In the preparation method, in the step (3), high fructose corn syrup can be added into the base material to serve as a substitute for white granulated sugar, so that the sweetness taste is compensated, and the burden of sucrose is reduced. Preferably, the base stock comprises 2-4% of the high fructose corn syrup, based on 100% of the total weight of the base stock.
According to the embodiment of the invention, the raw milk is fresh milk meeting the raw milk acquisition standard GB6914 of China, and can be the combination of more than two of whole milk, skim milk or partially skim milk. In particular embodiments, the milk may be fresh milk, or a reconstituted product made by reconstituting milk powder, condensed milk, or whey protein.
In the above preparation method, preferably, in the step (4), the stirring temperature of the base material is 50-55 ℃, the stirring time is 30-60min, and the stirring speed is 500-800 rpm.
In the above production method, preferably, in the step (4), the pressure of the degassing is 18 to 20MPa, and the temperature of the degassing is 60 to 70 ℃.
In the above preparation method, preferably, in the step (4), the sterilization temperature is 85-93 ℃, and the sterilization time is 280-300 s; more preferably, the temperature of the sterilization is 90-93 ℃, and the time of the sterilization is 290-300 s.
In the above production method, preferably, in the step (4), the fermentation temperature is 40 to 43 ℃, and the fermentation is performed until the acidity reaches 70 to 80 ° T.
In the preparation method, preferably, in the step (4), the fermentation agent used for fermentation is 0.001-0.002% by weight of the total weight of the base material.
According to a specific embodiment of the present invention, the leavening agent may employ one or a combination of probiotics, preferably one or a combination of two or more of streptococcus thermophilus, lactobacillus bulgaricus, bifidobacterium lactis and lactobacillus rhamnosus.
The raw materials adopted in the preparation method provided by the invention can be obtained commercially, and all the raw materials meet the requirements of relevant quality standards. The sanitation index, physical and chemical index and the like of the snow pear loquat flavored fermented milk provided by the invention also meet the regulations of relevant quality standards.
According to a specific embodiment of the invention, the packaging form of the fermented milk product with snow pear and loquat flavor prepared by the invention can adopt the packaging form of the common yogurt in the market at present, such as: glass bottle packaging, cup packaging, and the like.
According to the embodiments of the present invention, the processes not specifically mentioned in the preparation method of the present invention, such as compounding, degassing, homogenizing, sterilizing, and the like, and the equipment used therein, can be any conventional equipment in the art.
The invention also provides fermented milk with snow pear and loquat flavors, which is obtained by the preparation method.
The invention has the beneficial effects that:
1. in the process of preparing the snow pear and loquat mixed juice, the hot water wall breaking method is combined with the carboxymethyl chitosan/activated clay compound for clarification treatment, compared with the conventional method for preparing the juice by enzymatic hydrolysis, the preparation method provided by the invention avoids the influence of peculiar smell substances on the flavor of the juice, can accelerate the dissolution speed of the juice, and obtains the mixed juice with high clarity, high juice yield and no peculiar smell; the mixed fruit juice is added to enable the product to have natural and soft fragrance and lasting fragrance, and endow the yoghourt product with fine and smooth mouthfeel with moderate sweet and sour taste.
2. According to the preparation method provided by the invention, in the process of preparing the fermented milk, the compound stabilizer comprising the acetylated distarch adipate and the agar is added, and the addition amount of the snow pear and loquat juice is controlled, so that the stability of the product can be improved, the problem of whey precipitation is avoided, and the flavor and the taste of the product are effectively improved.
3. According to the preparation method provided by the invention, the obtained snow pear and loquat flavored fermented milk is rich in flavor, harmonious in fragrance and better in taste by controlling the sterilization conditions.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The embodiment provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats in a weight ratio of 7:3, cleaning, peeling, splitting and digging kernels for later use.
(2) Boiling fructus Pyri and fructus Eriobotryae with mixed solution containing 0.3 wt% ascorbic acid and 0.5 wt% citric acid (at 100 deg.C) for 90s, adding water, pulping, and softening the pulp with ultrasonic power of 800W for 120min to obtain natural juice and fruit residue.
(3) Adding pectinase 0.2 wt% of the fruit residue into the fruit residue, performing enzymolysis in 45 deg.C water bath for 90min, and mixing with the raw juice to obtain pulp.
(4) Weighing 0.5g of carboxymethyl chitosan, adding 4ml of 1% acetic acid solution, stirring into paste, adding 5g of activated clay, stirring for 6 hours in a constant-temperature water bath kettle at 60 ℃, filtering, and drying to obtain the carboxymethyl chitosan/activated clay compound.
(5) Adding 0.3g carboxymethyl chitosan/activated clay compound into 2.7g pulp of fructus Pyri and fructus Eriobotryae, and standing in 35 deg.C water bath for 15min to obtain mixed juice with high juice yield, high clarity and no foreign odor.
2. Preparing fermented milk:
(1) preparing materials: mixing 946.15g of fresh non-defatted milk, 15g of white granulated sugar, 30g of high fructose corn syrup, 3.5g of compound stabilizer (composed of acetylated distarch adipate 3g and agar 0.5 g), 0.35g of sweetener (sucralose 0.05g and acesulfame potassium 0.3g) and 5g of mixed fruit juice (without water), and stirring at 55 ℃ for 25min to obtain a base material;
(2) degassing the base material at 65 deg.C under 18MPa, homogenizing under 30/180bar pressure, and sterilizing at 90 deg.C for 290 s;
(3) cooling the sterilized base material to 40-43 deg.C, adding 0.02g of leaven (including Streptococcus thermophilus and Lactobacillus bulgaricus 0.01g each), feeding into a fermentation tank filled with nitrogen gas via an aseptic filtering device, fermenting at 43 deg.C, and stopping fermentation when acidity reaches 70-75 deg.T;
(4) filling: filling and sealing are carried out in closed sterile filling equipment, nitrogen is filled in the filling machine, and the filled yoghourt is refrigerated at 6 ℃ and is cooked to obtain the snow pear and loquat flavored fermented milk.
Example 2
The embodiment provides a preparation method of fermented milk with pear and loquat flavors, which comprises two processes of fruit juice preparation and fermented milk preparation:
1. the preparation method of the fruit juice comprises the following steps: by the same preparation method as in example 1, a mixed juice was obtained;
2. the preparation of the yoghourt comprises the following steps:
(1) preparing materials: mixing 935.65g fresh milk, 15g white granulated sugar, 30g high fructose corn syrup, 9g compound stabilizer (composed of acetylated distarch adipate 6g and agar 3g), 0.35g sweetener (sucralose 0.05g and acesulfame potassium 0.3g) and 10g mixed fruit juice (without water), and stirring at 55 deg.C for 25min to obtain base material;
(2) degassing the base material at 65 deg.C under 18MPa, homogenizing under 30/180bar pressure, and sterilizing at 93 deg.C for 300 s;
(3) cooling the sterilized base material to 40-43 deg.C, adding 0.02g of leaven (including Streptococcus thermophilus and Lactobacillus bulgaricus 0.01g each), filtering with sterile filter device, introducing into a fermentation tank filled with nitrogen gas, fermenting at 43 deg.C, and stopping fermentation when acidity reaches 70-75 deg.T;
(4) filling: filling and sealing are carried out in closed sterile filling equipment, nitrogen is filled in the filling machine, and the filled yoghourt is refrigerated at 6 ℃ and is cooked to obtain the snow pear and loquat flavored fermented milk.
Example 3
This example provides a method for preparing fermented milk with pear and loquat flavors, wherein the method for preparing fruit juice is the same as that of example 1, and the fermented milk preparation comprises the following steps:
(1) preparing materials: the base composition and the specific operation were the same as in example 1;
(2) degassing the base material at 55 deg.C under 18MPa, homogenizing under 30/180bar pressure, and sterilizing at 85 deg.C for 280 s;
(3) cooling the sterilized base material to 40-43 deg.C, adding leaven (same as in example 1), fermenting at 43 deg.C in a fermenter filled with nitrogen gas via sterile filtering device, and stopping fermentation when acidity reaches 70-75 deg.C T;
(4) filling: filling and sealing are carried out in closed sterile filling equipment, nitrogen is filled in the filling machine, and the filled yoghourt is refrigerated at 6 ℃ and is cooked to obtain the snow pear and loquat flavored fermented milk.
Comparative example 1
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats, respectively cleaning, peeling, splitting, digging cores, pre-boiling and pulping to obtain snow pear pulp and loquats pulp.
(2) Mixing the snow pear pulp and the loquat pulp uniformly according to the weight ratio of 7:3, heating to 50 ℃, adding pectinase which is 0.5 percent of the total weight of the snow pear pulp and the loquat pulp, performing enzymolysis for 1h at 55 ℃, and filtering in a filter to obtain mixed fruit juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 946.65g fresh milk, 15g white granulated sugar, 30g high fructose corn syrup, 3g stabilizer (acetylated distarch adipate 3g), 0.35g sweetener (sucralose 0.05g, acesulfame potassium 0.3g), 5g mixed fruit juice (without water), stirring at 55 deg.C for 25min to obtain base material;
the rest of the procedure was the same as in example 1.
Comparative example 2
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats, respectively cleaning, peeling, splitting, digging cores, pre-boiling and pulping to obtain snow pear pulp and loquats pulp.
(2) Mixing the snow pear pulp and the loquat pulp uniformly according to the weight ratio of 7:3, heating to 50 ℃, adding pectinase which is 0.5 percent of the total weight of the snow pear pulp and the loquat pulp, performing enzymolysis for 1h at 50 ℃, and filtering in a filter to obtain mixed fruit juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 946.65g fresh milk, 15g white sugar, 30g high fructose corn syrup, 3g stabilizer (i.e. agar 3g), 0.35g sweetener (sucralose 0.05g, acesulfame potassium 0.3g), 5g mixed fruit juice (without water), stirring at 55 deg.C for 25min to obtain base material;
the rest of the procedure was the same as in example 1.
Comparative example 3
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats, respectively cleaning, peeling, splitting, digging cores, pre-boiling and pulping to obtain snow pear pulp and loquats pulp.
(2) Mixing the snow pear pulp and the loquat pulp uniformly according to the weight ratio of 7:3, heating to 50 ℃, adding pectinase which is 0.5 percent of the total weight of the snow pear pulp and the loquat pulp, performing enzymolysis for 1h at 50 ℃, and filtering in a filter to obtain mixed fruit juice.
2. Preparing fermented milk:
(1) preparing materials: the base material with the same formulation as in example 1 was stirred at 55 ℃ for 25 min;
(2) degassing the base material at 65 deg.C under 18MPa, homogenizing under 30/180bar pressure, and sterilizing at 100 deg.C for 300 s;
(3) cooling sterilized base material to 40-43 deg.C, adding 0.02g of leaven (including Streptococcus thermophilus and Lactobacillus bulgaricus 0.01g each), fermenting at 43 deg.C in a fermenter filled with nitrogen gas via sterile filtering device, and stopping fermentation when acidity reaches 70-75 deg.T;
(4) filling: filling and sealing are carried out in closed sterile filling equipment, nitrogen is filled in the filling machine, and the filled yoghourt is refrigerated at 6 ℃ and is cooked to obtain the snow pear and loquat flavored fermented milk.
Comparative example 4
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats, respectively cleaning, peeling, splitting, digging cores, pre-boiling and pulping to obtain snow pear pulp and loquats pulp.
(2) Mixing the snow pear pulp and the loquat pulp uniformly according to the weight ratio of 7:3, heating to 50 ℃, adding pectinase which is 0.5 percent of the total weight of the snow pear pulp and the loquat pulp, performing enzymolysis for 1h at 50 ℃, and filtering in a filter to obtain mixed fruit juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 936.25g fresh milk, 15g white granulated sugar, 30g high fructose corn syrup, 3.4g compound stabilizer (namely 3g acetylated distarch adipate, 0.4g agar), 0.35g sweetener (0.05 g sucralose, 0.3g acesulfame potassium) and 15g mixed fruit juice (without water), and stirring at 55 ℃ for 25min to obtain a base material;
the rest of the procedure was the same as in example 1.
Comparative example 5
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice:
(1) selecting fresh snow pears and loquats, respectively cleaning, peeling, splitting, digging cores, pre-boiling and pulping to obtain snow pear pulp and loquats pulp.
(2) Mixing the snow pear pulp and the loquat pulp uniformly according to the weight ratio of 7:3, heating to 50 ℃, adding pectinase which is 0.5 percent of the total weight of the snow pear pulp and the loquat pulp, performing enzymolysis for 1h at 50 ℃, and filtering in a filter to obtain mixed fruit juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 931.25g fresh milk, 15g white granulated sugar, 30g high fructose corn syrup, 3.4g compound stabilizer (namely 3g acetylated distarch adipate, 0.4g agar), 0.35g sweetener (0.05 g sucralose, 0.3g acesulfame potassium) and 20g mixed fruit juice (without water), and stirring at 55 ℃ for 25min to obtain a base material;
the rest of the procedure was the same as in example 1.
Comparative example 6
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice: the procedure and operating parameters were the same as in example 1 to obtain a blended juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 931.25g fresh milk, 15g white sugar, 30g high fructose syrup, 3.4g pectin, 0.35g sweetener (0.05 g sucralose and 0.3g acesulfame potassium) and 20g mixed fruit juice (containing no water), and stirring at 55 deg.C for 25min to obtain base material;
the rest of the procedure was the same as in example 1.
Comparative example 7
The comparative example provides a preparation method of snow pear and loquat flavored fermented milk, which comprises two processes of preparing fruit juice and fermented milk, and specifically comprises the following steps:
1. preparing fruit juice: the procedure and operating parameters were the same as in example 1 to obtain a blended juice.
2. Preparing fermented milk:
(1) preparing materials: mixing 929.15g fresh milk, 15g white granulated sugar, 30g high fructose corn syrup, 5.5g compound stabilizer (i.e. acetylated distarch adipate 2g, agar 3.5g), 0.35g sweetener (sucralose 0.05g, acesulfame potassium 0.3g) and 20g mixed fruit juice (without water), and stirring at 55 deg.C for 25min to obtain base material;
the rest of the procedure was the same as in example 1.
Test example 1
Sensory evaluation was performed on the fermented milk with snow pear and loquat flavor prepared in examples 1 to 3 and comparative examples 1 to 7 in terms of taste and flavor. The items of the main evaluation include: texture (whey separation, viscosity, fineness, texture, etc.), color, flavor, taste, and ice crystal morphology. The number of the test subjects was 30, and the yogurt products of examples 1 to 3 and comparative examples 1 to 7 were subjected to sensory evaluation. Sensory scoring criteria are shown in table 1, and the results of the experimental recordings are summarized in table 2.
TABLE 1
TABLE 2
As can be seen from the results in Table 2, the flavored fermented milks of examples 1 and 2 have good texture, mouthfeel and flavor, no whey precipitation, strong characteristic flavor, harmonious aroma, fine mouthfeel, moderate sweetness and sourness and uniform taste.
Comparing examples 1-3 with comparative examples 1-7, it can be seen that the following factors can affect the sensory evaluation of the product:
1. the preparation method of the mixed fruit juice comprises the following steps: the mixed juice of comparative examples 1-5 was clarified without the addition of carboxymethyl chitosan/activated clay complex during the preparation process, and the products of comparative examples 1-5 had whey precipitated. This is because the juice obtained without clarification contains certain fiber substances, which can cause texture change of the fermented yoghurt and result in whey precipitation.
2. The compound stabilizer comprises the following components: comparing comparative example 1 (stabilizer containing only acetylated distarch adipate), comparative example 2 (stabilizer containing only agar), and comparative example 6 (stabilizer being conventional pectin), with example 1-2 (using a composite stabilizer containing acetylated distarch adipate and agar), it can be seen that the products of comparative examples 1-2 and 6 show whey precipitation, and are inferior in both characteristic flavor and aroma of the products. Therefore, when the compound stabilizer which simultaneously comprises the acetylated distarch adipate and the agar is added into the product, the product has uniform texture and better flavor and fragrance.
3. The compound stabilizer comprises the following components in percentage by weight: in comparative example 7, although the compound stabilizer contained agar and acetylated distarch adipate, the ratio of acetylated distarch adipate to agar was not (3-6): (0.5-3). At the moment, the product also has a whey precipitation state, and the taste of the product is influenced, so that the product has rough taste and uneven flavor. Therefore, the proportion of the acetylated distarch adipate to the agar is controlled within a proper proportion range, so that the stability, the flavor and the mouthfeel of the product can be effectively improved.
4. Adding amount of fruit juice: the fruit juice content in the products of comparative example 4, comparative example 5, comparative example 6 and comparative example 7 is higher than that in examples 1-2, so that the inorganic salt content of the fruit juice in the products is high, the texture state of the products is influenced, and the whey precipitation occurs. It is thus seen that a fermented milk product with a stable texture can be obtained by controlling the amount of juice added to the product within a suitable range.
5. And (3) sterilization conditions: example 3 and comparative example 3 differ from example 1 and example 2 in the sterilization temperature. Compared with examples 1-2, the products of example 3 and comparative example 3 have weak characteristic flavor and insufficiently coordinated aroma, but the product of example 3 reaches the factory standards, while the product of comparative example 3 does not reach the factory standards. Therefore, the characteristic flavor and aroma of the product can be influenced by the sterilization conditions, and when the sterilization temperature is controlled to be 90-93 ℃ and the sterilization time is controlled to be 290-300s, the fermented milk with the snow pear and loquat flavor, which is rich in characteristic flavor and harmonious in aroma, can be obtained.