阅读说明：本技术 一种新型红心火龙果酸奶及其制备方法 (Novel red-core dragon fruit yoghourt and preparation method thereof ) 是由 詹木秋 于 2021-05-20 设计创作，主要内容包括：本发明公开了一种新型红心火龙果酸奶及其制备方法,包括如下质量百分比的原料：全脂奶粉10-16％、温水70-80％、红心火龙果果浆1-5％、白砂糖5-9％,制备方法如下：S1、制备红心火龙果果浆；S2、调配、均质；S3、杀菌、冷却；S4、接种、发酵；S5、后熟。本发明为了研究红心火龙果酸奶的加工工艺,以感官测定评分为主要参考指标,选取影响红心火龙果酸奶风味的四个主要因素：奶粉和水的比例、果浆的添加量、白砂糖的添加量、发酵时间作为研究对象,进行L-9(3～(4))正交设计试验,通过对红心火龙果酸奶的护色研究,填补对红心火龙果中花青素护色工艺的空白。(The invention discloses a novel red-core dragon fruit yoghourt and a preparation method thereof, wherein the novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 10-16% of whole milk powder, 70-80% of warm water, 1-5% of red-core dragon fruit pulp and 5-9% of white granulated sugar, and the preparation method comprises the following steps: s1, preparing red-core pitaya pulp; s2, blending and homogenizing; s3, sterilizing and cooling; s4, inoculating and fermenting; and S5, after-ripening. In order to research the processing technology of the red-heart pitaya yoghourt, the sensory measurement score is taken as a main reference index, and four main factors influencing the flavor of the red-heart pitaya yoghourt are selected: the ratio of milk powder and water, the addition amount of fruit pulp, the addition amount of white sugar and the fermentation time are used as research objects to carry out L 9 (3 4 ) Orthogonal design test fills the blank of the color-protecting process of anthocyanin in the red-heart pitaya through color-protecting research on the red-heart pitaya yoghourt.)

1. The novel red-core dragon fruit yoghourt is characterized by comprising the following raw materials in percentage by mass: 10-16% of whole milk powder, 70-80% of warm water, 1-5% of red-core dragon fruit pulp and 5-9% of white granulated sugar.

2. The novel red-heart dragon fruit yoghourt as claimed in claim 1, which comprises the following raw materials in percentage by mass: 11-15% of whole milk powder, 73-78% of warm water, 2-4% of red-core dragon fruit pulp and 6-8% of white granulated sugar.

3. The novel red-heart dragon fruit yoghourt as claimed in claim 1, which comprises the following raw materials in percentage by mass: 12.8 percent of whole milk powder, 77.2 percent of warm water, 3 percent of red-core dragon fruit pulp and 7 percent of white granulated sugar.

4. The preparation method of the novel red-heart pitaya yoghourt as claimed in claim 1, which is characterized by comprising the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 2-3min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle at 70-75 ℃ for sterilization for 15-20min, and cooling to 42-45 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90-95 deg.C for 10-15min, and cooling to 42-45 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 10-15min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a constant temperature box at 42-45 deg.C for 4-5 h;

s5, after ripening

And (3) quickly cooling the fermented product to below 20-25 ℃, and then placing the product in a refrigerator at the temperature of 3-4 ℃ for refrigerating and fermenting for 24-28 hours to obtain a finished product.

5. The method for preparing the novel red dragon fruit yoghourt as claimed in claim 4, wherein four main factors influencing the flavor of the red dragon fruit yoghourt are selected according to the result obtained by the single factor test: the ratio of milk powder to water, the addition of fruit pulp, the addition of white granulated sugar and the fermentation time are taken as research objects.

6. The method for preparing the red dragon fruit yoghourt as claimed in claim 4, wherein 10 persons are arranged to carry out sensory scoring on the appearance, the flavor, the texture and the taste of the finished product, and the scoring data is collected and sorted and then analyzed by using software.

7. The preparation method of the novel red-heart pitaya yoghourt as claimed in claim 4, wherein red-heart pitaya pulp which is not subjected to sterilization operation is mixed with a milk powder solution in a certain proportion to obtain a standard product; and measuring absolute values of the colors of the standard product and the fermented red dragon fruit yoghourt sample by using a full-automatic color measurement colorimeter.

8. The preparation method of the novel red-heart pitaya yoghourt as claimed in claim 1, wherein the total color difference delta E value between a sample and a standard substance is calculated during color protection measurement of the red-heart pitaya yoghourt; the formula for Δ E is as follows:

Technical Field

The invention relates to the technical field of yogurt, and particularly relates to novel red-core pitaya yogurt and a preparation method thereof.

Background

Pitaya belongs to the family Cactaceae, genus trigonostema (also known as genus Petasites), and is a typical tropical and subtropical plant. Dragon fruits are currently widely grown in asian countries, such as malaysia, vietnam, thailand, philippines and china. In recent years, pitaya, an economically important fruit crop, has been widely grown in the south and southwest of china. The pulp can be divided into red skin white pulp dragon fruit, yellow skin white pulp dragon fruit and red skin red dragon fruit according to the color of the pulp, wherein the red skin white core and the red skin red core are preferred.

With the arousal of health consciousness of consumers, the consumers pay attention to not only taste enjoyment but also food efficacy, and foods with functionality and health care are more and more favored by the consumers. The dragon fruit gradually enters the visual field of people with unique appearance and rich nutrition. The dragon fruit contains a plurality of nutrients: polysaccharide, protein, mineral substances, dietary fiber, vitamins and the like, wherein the content of the protein is 2-3 times of that of the fruits such as mango and pineapple; VB₂The content of the extract is 20-30 times of that of sweet orange and peach. It is worth mentioning that the pitaya contains less vegetable albumin of common fruits, the albumin is a substance with viscosity and colloid, and the albumin can remove acidic substances generated by cell metabolism in vivo, can wrap heavy metal ions in human bodies, prevents intestinal tracts from absorbing and poisoning heavy metals, plays a role in detoxification, and prevents stomach walls from being damaged.

Compared with red-peel white-core pitaya, the red-peel white-core pitaya has higher nutritional value, and water-soluble fiber and VB of the red-peel white-core pitaya₃、VB₅、VB₉The contents of potassium, calcium, magnesium and the like are more than those of the red skin and the white heart. Besides the nutrients of the white-heart pitaya, the red-heart pitaya also contains a large amount of phenolic compounds with antioxidant activity, such as anthocyanin, flavone, phenolic acid and the like, wherein the antioxidant capacity of the anthocyanin is higher than that of the flavone and the phenolic acid. The pulp of the red heart pitaya contains up to (19.14 +/-0.52) mg/kg of anthocyanin, and the anthocyanin can protect a human body from being invaded by free radicals, and the capability of removing the free radicals is 50 times of that of vitamin E and 20 times of that of vitamin C. Meanwhile, the anthocyanin can also enhance the liver function, regulate blood fat, resist aging and the like.

Nowadays, the red-heart dragon fruits in China are mainly sold in the fresh market, and the deep processing of the red-heart dragon fruits is researched but rarely applied. The advantages of the red-heart pitaya described above can be obtained, and the red-heart pitaya has an extremely high commercial economic value. Therefore, the deep research on the red-heart pitaya not only can endow the red-heart pitaya with higher nutrition and more functionality, but also can expand the deep processing application channel of the red-heart pitaya, solve the problem of the sales volume of the red-heart pitaya and help farmers increase the income.

The yunchun tea (2019) takes pomegranate and red-core pitaya as raw materials to obtain the compound beverage with proper sour and sweet taste and unique flavor. Test results show that the optimal process formula comprises 6:4 of pomegranate and red dragon fruit juice, 40% of juice, 1.0% of citric acid and 6% of white granulated sugar.

Jam

The huyanting and the like (2019) take sweet osmanthus and red pitaya as raw materials, and the compound jam with deep purple sauce, bright color, soft and fine taste and good texture is prepared under the conditions that the proportion of sweet osmanthus juice to red pitaya juice is 1:6, the addition amount of white granulated sugar is 8%, the addition amount of konjac flour is 2.5% and the addition amount of citric acid is 0.2%.

Preserved fruit

The aged navy (2019) takes red-core pitaya as a raw material, and a sour, sweet, delicious, healthy and green preserved fruit is prepared by applying orthogonal design and sensory evaluation. Test results show that the optimal technological parameters are that the sugar content of the sugar solution is 6.6%, the sugar boiling temperature is 70 ℃, and the sugar boiling time is 2 hours.

Fruit wine

Zhanglun et al (2019) use pineapple and red-core dragon fruit as raw materials to develop a fruit wine with attractive color, coordinated composite fragrance and moderate sour-sweet taste. Experiments show that the optimal process conditions are that the ratio of the dragon fruit to the pineapple is 1:1, the fermentation temperature is 18-20 ℃, the yeast inoculation amount is 300mg/L, and the dosage of the pectinase is 200 mg/L.

Fruit vinegar

The Xianda fruit wine is clear and transparent, moderate in sour and sweet and harmonious in flavor and is obtained by combining the pomelo kernels and the red-core dragon fruits (2019) through response surface tests and sensory evaluation. Experiments show that the optimal process parameters are that the initial alcoholic strength is 7.24%, the fermentation temperature is 35.48 ℃, and the inoculation amount of fruit vinegar bacteria is 572.4 mg/L.

The yoghourt is more and more popular with consumers due to the characteristics of nutrition and health care, and the market is continuously exploring to add more taste and functional substances to the yoghourt along with the change of the concept of the consumers. The red heart pitaya contains rich water-soluble fiber, vitamin B3, vitamin B5, vitamin B9, potassium, calcium, magnesium and the like, and also contains a large amount of phenolic compounds with antioxidant activity, such as anthocyanin, flavonoid, phenolic acid and the like, and is very beneficial to human bodies.

The health care function of the yoghourt is as follows:

has anticancer effect

After a series of metabolic reactions, harmful bacteria in the intestinal bacteria can release carcinogenic factors such as phenols, indole, nitrous acid, nitrosamine and the like to the intestinal tract, so that the organism cancerates. The lactobacillus in the yoghourt can prevent harmful bacteria from releasing carcinogenic substances to human bodies, and can enhance the activity of system macrophages, kill cancerating cells in time and prevent the diffusion of tumor cells, so the yoghourt has a certain effect of inhibiting cancers.

Reduction of lactose intolerance

Lactose intolerance is determined by genetic genes, and lactase activity in such populations is low, resulting in inefficient absorption of nutrients from dairy products. The fermented yoghourt can decompose lactose into lactic acid, so people suffering from lactose intolerance can eat milk, and adverse phenomena such as abdominal distension, qi abundance, diarrhea and the like are reduced.

Maintaining balance of intestinal flora

Intestinal bacteria exist in small intestine and consist of beneficial bacteria and harmful bacteria. The pathogenic factors generated by metabolism can be discharged into intestinal tracts by the harmful bacteria, so that the human body can be ill. Beneficial bacteria can effectively inhibit the activity and reproduction of harmful bacteria, so the balance of the flora in the intestinal tract has great significance to the health of human bodies. When some people take or inject antibiotics, beneficial bacteria in the bodies of the people can be attacked or killed by the antibiotics to cause dysbacteriosis, so that the people can increase the number of the beneficial bacteria in the bodies by eating the yoghourt, regulate the number of the beneficial bacteria in the bodies to reach a normal level and maintain the balance of the flora in intestinal tracts.

Reducing cholesterol

Cardiovascular disease is called the "first killer of health", where the highest mortality rate is coronary heart disease, and studies have shown that the occurrence of coronary heart disease is inversely proportional to the amount of cholesterol in the blood vessels. The yoghurt can obviously reduce the content of cholesterol in serum by 16 percent, and the cholesterol is reduced mainly through two aspects. On the one hand, enzymes contained in lactic acid bacteria promote the production of substances reacting with cholesterol in the human body, and then are discharged out of the body through the excretory system, thereby reducing the cholesterol content in blood vessels. On the other hand, the lactobacillus can be adhered to the mucous membrane of the inner wall of the intestinal tract, so that the absorption of the human body to cholesterol is reduced.

Based on the description of the nutritional value and the health care function of the red-heart pitaya, the great edible value and the medical value of the red-heart pitaya can be seen, so that the red-heart pitaya has great potential and development space in the fields of health care food and medicines. At present, many researches on red-heart pitaya exist, but the color and the antioxidant function of the red-heart pitaya are mainly determined by anthocyanin contained in the red-heart pitaya, and the anthocyanin is extremely unstable, so that the deep processing of the red-heart pitaya is limited to a certain extent. At present, the red-heart pitaya products on the market are few, and only a small amount of fruit juice, fruit wine and fruit vinegar exist.

Disclosure of Invention

The invention aims to provide novel red-heart pitaya yoghourt and a preparation method thereof, and fills the blank of a process for protecting the color of anthocyanin in red-heart pitaya through the color protection research of the red-heart pitaya yoghourt so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 10-16% of whole milk powder, 70-80% of warm water, 1-5% of red-core dragon fruit pulp and 5-9% of white granulated sugar.

Further, 11-15% of whole milk powder, 73-78% of warm water, 2-4% of red-core dragon fruit pulp and 6-8% of white granulated sugar.

Further, 12.8% of whole milk powder, 77.2% of warm water, 3% of red-core dragon fruit pulp and 7% of white granulated sugar.

The health care efficacy of the red-heart pitaya is as follows:

whitening, intestine moistening and defecation promoting effects

The production of melanin in a human body needs the participation of tyrosinase, and the VC rich in the red-heart pitaya can prevent the activation of the tyrosinase, thereby achieving the whitening effect. In addition, the red-heart pitaya also has a large amount of water-soluble dietary fibers, can accelerate the speed of excrement discharged out of the body through an excretion system, and has the effect of relaxing the bowels.

Reduce the pathogenic rate

According to epidemiological findings, many human diseases are caused by the attack of free radicals on human proteins, esters and deoxynucleic acids. The anthocyanin contained in the red heart pitaya has strong capability of eliminating free radicals, and the incidence rate can be reduced by eating the phenolic compound food with antioxidant activity.

Toxin expelling effect

The red heart pitaya contains plant albumin which is less in other fruits, can encapsulate heavy ions such as lead, mercury, chromium and the like taken in a human body, is discharged out of the body along with excrement, avoids poisoning of the human body, and can prevent stomach walls from being damaged.

Protecting cardiovascular function

If the food provides more saturated fatty acid, the biosynthesis of cholesterol is promoted, and the food has great threat to the heart and blood health of human bodies. The red heart dragon fruit seeds contain abundant unsaturated fatty acids, mainly comprising linoleic acid, oleic acid and palmitic acid, wherein the linoleic acid can reduce and eliminate the accumulation of cholesterol in blood vessels, can increase the elasticity and toughness of the blood vessels and plays a role in protecting the health of heart blood.

Promote hematopoiesis

Iron is an important mineral substance of human body, is a main component of hemoglobin, and can cause anemia once iron deficiency occurs in the body and hemoglobin cannot be normally synthesized. The red-core pitaya is rich in iron elements, and the VC contained in the red-core pitaya can convert ferric ions into ferrous ions of ferrous ions, so that hematopoiesis of a human body is promoted.

Current utilization status of red-heart pitaya

The novel nutritional health-care red-heart pitaya yoghourt developed by the experiment can meet the market demand and has important research significance and wide market prospect.

The invention provides another technical scheme that: a preparation method of novel red-core pitaya yoghourt comprises the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 2-3min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle at 70-75 ℃ for sterilization for 15-20min, and cooling to 42-45 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90-95 deg.C for 10-15min, and cooling to 42-45 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 10-15min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a constant temperature box at 42-45 deg.C for 4-5 h;

s5, after ripening

And (3) quickly cooling the fermented product to below 20-25 ℃, and then placing the product in a refrigerator at the temperature of 3-4 ℃ for refrigerating and fermenting for 24-28 hours to obtain a finished product.

Further, according to the result obtained by the single-factor test, four main factors influencing the flavor of the red-heart dragon fruit yoghourt are selected: the ratio of milk powder to water, the addition of fruit pulp, the addition of white granulated sugar and the fermentation time are taken as research objects.

Furthermore, 10 persons were arranged to perform sensory scoring on the finished product in terms of appearance, flavor, texture and taste, and the scoring data was collected and collated and analyzed using software.

Further, mixing red-heart pitaya pulp which is not subjected to sterilization operation with the milk powder solution in a certain ratio to obtain a standard product; and measuring absolute values of the colors of the standard product and the fermented red dragon fruit yoghourt sample by using a full-automatic color measurement colorimeter.

Compared with the prior art, the invention has the beneficial effects that: in order to research the processing technology of the red-heart pitaya yoghourt, the sensory measurement score is taken as a main reference index, and four main factors influencing the flavor of the red-heart pitaya yoghourt are selected: the ratio of milk powder and water, the addition amount of fruit pulp, the addition amount of white sugar and the fermentation time are used as research objects to carry out L₉(3⁴) Orthogonal design experiment, the experiment results in: the ratio of milk powder to water is 1:6, the adding amount of the red-core pitaya pulp is 3%, the adding amount of the white granulated sugar is 7%, and the fermentation time is 4 hours, so that the prepared red-core pitaya yoghourt is pink in color, sour, sweet, tasty, smooth in taste and fine and smooth in tissue. Meanwhile, four oxidants of ascorbic acid (VC), tannic acid, citric acid and tea polyphenol are taken as color fixative, and blank group color difference delta E and sensory evaluation of red-heart dragon fruit yoghourt are taken as evaluation standards, so that the optimal color fixative composition is obtained as follows: 0.08 percent of ascorbic acid and 0.01 percent of citric acid, and fills the blank of the process for protecting the color of anthocyanin in the red-heart pitaya through the color protection research of the red-heart pitaya yoghourt.

Drawings

FIG. 1 is a line graph showing the effect of the ratio of milk powder and water on the finished product;

FIG. 2 is a line graph showing the effect of the amount of pulp added on the finished product;

FIG. 3 is a line graph showing the effect of the amount of sweetener of the present invention on the final product;

FIG. 4 is a line graph showing the effect of fermentation time on the final product according to the present invention;

FIG. 5 is a line graph of the effect of tea polyphenols on the delta E value of red heart dragon fruit yogurt of the present invention;

FIG. 6 is a line graph of the effect of tea polyphenols on sensory evaluation of red heart dragon fruit yogurt of the present invention;

FIG. 7 is a line graph of the effect of tannic acid on Δ E values of red heart dragon fruit yogurt of the present invention;

FIG. 8 is a line graph of the effect of tannic acid on sensory evaluation of red heart pitaya yogurt of the present invention;

FIG. 9 is a line graph of the effect of citric acid of the present invention on the Δ E value of red heart dragon fruit yogurt;

FIG. 10 is a line graph of the effect of citric acid of the present invention on the sensory evaluation of red heart pitaya yogurt;

FIG. 11 is a line graph of the effect of VC of the present invention on the Δ E value of red-heart pitaya yogurt;

fig. 12 is a line graph of the effect of VC of the invention on sensory evaluation of red heart pitaya yogurt.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

A novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 10% of whole milk powder, 80% of warm water, 1% of red-core pitaya pulp and 9% of white granulated sugar.

A preparation method of novel red-core pitaya yoghourt comprises the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 2min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle, sterilizing at 70 ℃ for 15min, and cooling to 42 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90 deg.C for 10min, and cooling to 42 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 10min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a constant temperature box at 42 deg.C for 4 hr;

s5, after ripening

And (3) quickly cooling the fermented product to below 20 ℃, and then placing the product in a refrigerator at 4 ℃ for refrigerating and fermenting for 24 hours to obtain a finished product.

Example 2

A novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 10% of whole milk powder, 80% of warm water, 5% of red-core pitaya pulp and 5% of white granulated sugar.

A preparation method of novel red-core pitaya yoghourt comprises the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 2min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle, sterilizing at 75 ℃ for 18min, and cooling to 42 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90 deg.C for 12 min, and cooling to 45 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 15min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a 42 deg.C constant temperature oven for 4 hr;

s5, after ripening

And (3) quickly cooling the fermented product to below 20 ℃, and then placing the product in a refrigerator at 3 ℃ for refrigerating and fermenting for 26 hours to obtain a finished product.

Example 3

A novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 12.8 percent of whole milk powder, 77.2 percent of warm water, 3 percent of red-core dragon fruit pulp and 7 percent of white granulated sugar.

A preparation method of novel red-core pitaya yoghourt comprises the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 3min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle, sterilizing at 70 ℃ for 15min, and cooling to 42 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90 deg.C for 10min, and cooling to 42 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 10min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a constant temperature box at 45 deg.C for 5 hr;

s5, after ripening

And (3) quickly cooling the fermented product to below 22 ℃, and then placing the product in a refrigerator at 3 ℃ for refrigerating and fermenting for 28 hours to obtain a finished product.

Example 4

A novel red-core dragon fruit yoghourt comprises the following raw materials in percentage by mass: 16% of whole milk powder, 70% of warm water, 5% of red-core pitaya pulp and 9% of white granulated sugar.

A preparation method of novel red-core pitaya yoghourt comprises the following steps:

s1, preparing red-core pitaya pulp

Selecting red-core pitaya without spots and pathological changes, cleaning to remove dust and impurities, peeling and dicing, then putting the pulp into a wall breaking machine to break the wall for 2min, filtering, adding a color fixative, putting into a constant-temperature water bath kettle, sterilizing at 75 ℃ for 20min, and cooling to 45 ℃;

s2, blending and homogenizing

Preparing whole milk powder, warm water and white granulated sugar into emulsion according to a certain proportion, and then carrying out homogenization treatment;

s3, sterilizing and cooling

Sterilizing at 90 deg.C for 15min, and cooling to 45 deg.C;

s4, inoculation and fermentation

Inoculating in a certain proportion under aseptic condition, stirring for 10min to ensure uniform dissolution of strains, and fermenting the inoculated semi-finished product in a constant temperature box at 45 deg.C for 5 hr;

s5, after ripening

And (3) quickly cooling the fermented product to below 25 ℃, and then placing the product in a refrigerator at 4 ℃ for refrigerating and fermenting for 28 hours to obtain a finished product.

According to the result obtained by the single-factor test, four main factors influencing the flavor of the red-heart dragon fruit yoghourt are selected: the ratio of milk powder and water, the addition amount of fruit pulp, the addition amount of white sugar and the fermentation time are used as research objects to carry out L₉(3⁴) Orthogonal design test, the orthogonal test factors and the horizontal design of the red dragon fruit yoghourt are shown in table 5, and the orthogonal test design of the red dragon fruit yoghourt is shown in table 1.

TABLE 1 orthogonal test factors and horizontal design of red-heart pitaya yogurt

TABLE 2 orthogonal test design for red-heart pitaya yogurt

10 persons are arranged to perform sensory scoring on the four aspects of appearance, flavor, texture and taste of the product, and the scoring data is collected and sorted and then analyzed by using software. Sensory evaluation criteria are shown in table 3.

TABLE 3 sensory evaluation table of red-heart dragon fruit yoghourt

Mixing red-heart pitaya pulp which is not subjected to sterilization operation with a milk powder solution in a certain ratio to obtain a standard product; and measuring absolute values of the colors of the standard sample and the fermented red dragon fruit yoghourt sample by using a full-automatic color measurement colorimeter, namely L, a and b. Calculating the total color difference delta E value of the sample and the standard; the total color difference delta E value is used as an evaluation index of the color protection effect, and the smaller the delta E value is, the smaller the color difference between the sample and the standard is, the better the color protection effect is. Δ E is calculated as follows:

(1) acidity determination of red-heart pitaya yoghourt

The acidity of the red-heart dragon fruit yoghourt is measured according to a phenolphthalein indicator method in GB5009.239-2016 (national food safety standard food acidity measurement).

(2) Determination of red-heart dragon fruit yoghourt protein content

The content of the red-heart dragon fruit yoghourt protein is determined according to the Kjeldahl method in GB 5009.5-2016 (determination of protein in national food safety standard).

(3) Determination of red-heart dragon fruit yoghourt lactic acid bacteria

The number of the red-heart dragon fruit yoghourt lactobacillus is determined according to the method of a lactobacillus culture medium in GB 4789.35-2016 (food safety national standard food microbiology inspection lactobacillus inspection).

1. Effect of milk powder and Water ratio on the finished product

As can be seen from figure 1, when the ratio of the milk powder to the water is 1: 4-1: 6, the sensory score shows an ascending trend along with the increase of the ratio of the milk powder; when the ratio of the milk powder to the water is 1:6, the yoghourt has smooth mouthfeel, fine and smooth texture, better curd and no whey separation; when the ratio of the milk powder to the water is 1: 6-1: 8, sensory score shows a descending trend, and the yogurt has more whey separated out and obvious layering, so that the ratio of the milk powder to the water is 1: the mouthfeel is optimal when the tea is 6 days.

2. Effect of the amount of pulp added on the finished product

As can be seen from fig. 2, as the addition amount of the fruit pulp increases, the sensory score of the yogurt increases first and then decreases, and when the addition amount of the fruit pulp is 3%, the sensory score reaches the maximum value, and the yogurt is pink in color, fine and smooth, sour, sweet and delicious, and has the faint scent of pitaya; when the adding amount of the fruit pulp is more than 3%, the color of the yoghourt is darker, the gelling effect is poor, more whey is separated out, layering occurs, and the taste is poor. Therefore, the optimum amount of pulp to be added is 3%.

3. Influence of the addition amount of white granulated sugar on the finished product

As can be seen from FIG. 3, the sensory score of the white granulated sugar is increased between 7% and 8%; with the increase of white granulated sugar, after 8%, the sweet taste is too heavy, the sweet-sour ratio is not appropriate, and the sensory score shows a descending trend, so that the addition amount of the white granulated sugar is 8%, and the flavor is optimal.

4. Influence of fermentation time on the end product

As can be seen from FIG. 4, when the fermentation time is 4.5 hours, the sensory score reaches the maximum value of 89 minutes, and at the time, the yogurt has the advantages of uniform color, good agglomeration, no delamination, smooth mouthfeel, no bubbles, moderate sour and sweet taste, rich yogurt taste and optimal yogurt mouthfeel. When the fermentation time is longer than 4.5h, the sensory score of the yoghourt is reduced, the taste of the yoghourt is slightly sour, and the yoghourt tastes too sour due to excessive acid production caused by overlong fermentation time. Therefore, the optimal fermentation time of the yoghurt is 4.5 h.

The four single-factor tests are used for screening 3 levels of milk powder and water ratio, red-core dragon fruit pulp addition amount, white granulated sugar addition amount and fermentation time respectively to carry out L treatment₉(3⁴) Orthogonal test, the levels of experimental factors are shown in table 4, and the results are shown in table 5.

TABLE 4 orthogonal experimental factor levels for Red-heart dragon fruit yogurt Process formulas

TABLE 5 results and analysis of orthogonal experiments

As can be seen from the analysis of Table 5, the optimal process ratio of the red-heart pitaya yogurt is A2B2C1D1, namely the ratio of milk powder to water is 1:6, the addition amount of white granulated sugar is 7%, the addition amount of fruit pulp is 3%, and the fermentation time is 4 h. The main and secondary sequences influencing the yoghourt quality by analyzing the extremely poor R value are as follows: c, B, D, A, namely the addition amount of white granulated sugar, the addition amount of fruit pulp, the fermentation time and the proportion of milk powder and water.

1. Color protection effect of tea polyphenol on red-heart dragon fruit yoghourt

The color protection effect of tea polyphenol is firstly increased and then reduced along with the increase of concentration, and because the tea polyphenol is easy to be oxidized to generate substances with strong oxidation performance and new free radicals and is easy to generate the effect opposite to the oxidation resistance of the tea polyphenol, when the addition amount of the tea polyphenol is too much, the color protection is not facilitated. As shown in FIG. 5, when the amount of tea polyphenol added was 0.03%, the value of Δ E was 5.11, and the color-protecting effect was the best.

2. The influence of different tea polyphenols on sense organ

As can be seen from the above, the color-protecting effect of the red-heart pitaya yogurt is the best when the added amount of the tea polyphenol is 0.03%, but as can be seen from fig. 6, the sensory score of the red-heart pitaya yogurt gradually decreases with the increase of the content of the tea polyphenol, and when the content of the tea polyphenol is 0.03%, the sensory score is 60, and the odor of the yogurt is heavy, and the Δ E and the sensory score are combined, so that the tea polyphenol is not considered as the color-protecting agent.

3. Color protection effect of tannic acid on red-heart dragon fruit yoghourt

As can be seen from FIG. 7, with the increase of the addition amount of tannic acid, the total color difference Δ E value tends to decrease first and then increase, the color protection effect is obvious, when the addition amount of tannic acid is 0.08%, the Δ E value is 7.55, the original standard color and luster of the sample are maintained to the maximum extent after the process flows of sterilization, fermentation, after-ripening and the like, and the color change is relatively small.

4. The sensory effect of different tannin addition amounts

From the above, it can be seen that the effect of color protection of the red-heart pitaya yogurt is the best when the addition amount of tannic acid is 0.08%, but as can be seen from fig. 8, the sensory score of the red-heart pitaya yogurt gradually decreases with the increase of the content of tannic acid, and when the content of tannic acid is 0.08%, the sensory score is 55, and at this time, the astringent taste of the yogurt is heavy, and Δ E and the sensory score are combined, so that tannic acid is not considered as the color protection agent.

5. Color protection effect of citric acid on red-heart dragon fruit yoghourt

The addition of citric acid can lower the pH of the solution, and anthocyanin is relatively stable when it exists in the form of red cation under acidic conditions, but when the addition amount of citric acid is too large, the dissolution of anthocyanin is inhibited. As is clear from fig. 9, the color protection effect decreased with the increase in the amount of citric acid added, and when the amount of citric acid added was 0.01%, Δ E was 8.05, and the maximum value was obtained, and the color protection effect was the best at this time.

6. Sensory impact of different citric acid additions

The effect of citric acid on the product is mainly acidity, when the addition amount of citric acid is between 0.006% and 0.014%, the sensory score of the red-heart pitaya yoghourt is between 86 and 90, and the sensory scores of the addition amount gradients are not greatly different. As can be seen from fig. 10, since the color protection effect of the product reaches the maximum value at 0.01%, and the sensory score at this time is 87, the optimum amount of citric acid added was 0.01% in combination with Δ E and the sensory score.

7. Color protection effect of VC on red-heart dragon fruit yoghourt

As can be seen from fig. 11, as the amount of VC added increases, the total color difference Δ E fluctuates within a certain range (7.20 to 9.48), and the Δ E values are small relative to the blank groups to which no color fixative is added, and the color fixative effect is good, and when the amount of VC added is 0.10%, the Δ E value is 7.20, and the color fixative effect is relatively optimal.

8. The influence of different addition amounts of VC on sense

As can be seen from fig. 12, since the sensory score was 85 when the amount of VC added was 0.10%, the optimum amount of VC added was 0.1% in combination with Δ E and the sensory score.

And selecting VC and citric acid to carry out a compound color protection effect experiment according to the results of the color protection effect test and the sensory evaluation test of the four oxidants. And the VC and the citric acid are combined to use to have a synergistic effect, and the decomposition of the VC can be reduced due to the existence of the citric acid, so that the color protection capability of the VC is improved. The results of the color-protecting effect of the composite color-protecting agent on red-heart dragon fruit yogurt are shown in table 6.

TABLE 6 color protecting effect of composite color fixative on red-heart dragon fruit yoghourt

As can be seen from Table 6, the ten groups of compound color fixative have obvious color fixative effects, wherein the color fixative effect of the experimental scheme No. 3 is the best, the total color difference delta E value is 3.05, and the color fixative effect is obvious compared with the color fixative effect of the blank group delta E value of 9.26, so the optimal compound scheme of the red-heart pitaya yoghourt color fixative is 0.08% of ascorbic acid and 0.01% of citric acid.

Evaluation by senseThe optimal combination of the obtained dragon fruit yoghourt is as follows: the ratio of milk powder to water is 1:6, the addition amount of red-core pitaya pulp is 3%, the addition amount of white granulated sugar is 7%, the fermentation temperature is 42 ℃, and the fermentation time is 4 hours. The yogurt prepared under the condition has the following quality indexes: protein content of 3.76g/100g, acidity of 90 ° T, and total number of lactobacillus colonies of 3.2 × 10⁷CFU/mL。

The processing technology of the red-heart pitaya yoghourt is researched by taking milk powder and red-heart pitaya as raw materials, sensory measurement scores are taken as main reference indexes, and four main factors influencing the flavor of the red-heart pitaya yoghourt are selected: the ratio of milk powder and water, the addition amount of fruit pulp, the addition amount of white sugar and the fermentation time are used as research objects to carry out L₉(3⁴) Orthogonal design tests show that the optimal processing technological parameters of the red dragon fruit yoghourt are that the ratio of milk powder to water is 1:6, the addition amount of red dragon fruit pulp is 3%, the addition amount of white granulated sugar is 7%, the fermentation temperature is 42 ℃, and the fermentation time is 4 hours, and under the conditions, the dragon fruit yoghourt has the following quality indexes: protein content of 3.76g/100g, acidity of 90 °, and lactobacillus colony count of 3.2 × 10⁷CFU/mL, the color is uniform pink; the taste is moderate, fine and smooth, and has no bubbles; has the characteristic fragrance and flavor of yoghourt and dragon fruit, and has no peculiar smell.

The color fixative of the red-heart pitaya yoghourt is researched, four oxidants of VC, tannic acid, citric acid and tea polyphenol are selected to carry out a single-factor experiment by taking total color difference delta E and sensory measurement scores as evaluation indexes, the experimental result shows that the sensory scores of the yoghourt are lower and are not in line with the requirements when the tannic acid and the tea polyphenol are in the optimal values, and finally the VC and the citric acid are selected to carry out a compounding experiment to optimize and obtain the composite color fixative with 0.08% of VC and 0.01% of citric acid, so that the color fixative has an obvious color fixative effect because of the synergistic effect of the combination of VC and citric acid, and the decomposition of VC can be reduced due to the existence of the citric acid, thereby improving the color fixative capability of VC.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.