CN106819115A - A kind of pitaya peel stirred yoghurt and preparation method with anti-oxidation efficacy - Google Patents

Abstract

A kind of pitaya peel stirring type yoghurt with anti-oxidation effect of the present invention comprises 63-72 parts by weight of skim reconstituted milk, 5 parts by weight of five bacteria mixed starter, 6-8 parts by weight of sucrose, 15-25 parts by weight of The pitaya skin freeze-dried powder gelatinization paste, 1 weight part of compound sweetener and 1-2 weight part of compound stabilizer are prepared. The present invention also provides a method for preparing the above-mentioned yoghurt. The defatted reconstituted milk is homogenized, sterilized, inoculated, fermented for the first time, added with dragon fruit peel slurry, stirred, sweetener and stabilizer added, fermented for the second time, and packaged , post-ripening and other steps to obtain the stirred yoghurt containing strong antioxidant active functional ingredients such as dragon fruit peel anthocyanins. The yoghurt of the present invention is designed according to synergistic anti-oxidation activity. It has strong and stable anti-oxidation activity and low sugar content. Regular consumption can not only enhance and improve the effect of intestinal flora, but also improve the anti-oxidation of the body and interfere with the decline of body functions. and other beneficial health effects.

Description

A kind of pitaya peel stirred type yoghurt with antioxidant effect and preparation method thereof

technical field

The invention belongs to the field of food science, and relates to yoghurt, in particular to pitaya peel stirred yoghurt with antioxidant effect and a preparation method thereof.

Background technique

Pitaya peel is the waste of dragon fruit processing, which is rich in various nutrients such as anthocyanins. Anthocyanins have strong antioxidant activity, which can intervene in the decline of body functions and benefit the health of the body. However, anthocyanins are easy to be decomposed during thermal processing, microbial fermentation, storage and transportation, and the stability of antioxidant activity is poor. The growth of lactic acid bacteria in the fermentation process of pitaya yogurt is also inhibited by anthocyanins to a certain extent, and the fermentation flavor is poor, so the amount of pitaya yogurt added to pitaya peel is limited.

Contents of the invention

Aiming at the above-mentioned technical problems in the prior art, the invention provides a pitaya peel stirred yoghurt with anti-oxidative effect and a preparation method thereof. The pitaya peel stirred yogurt with an anti-oxidative effect and a preparation method need to be solved The pitaya skin yogurt in the prior art has the technical problems of unstable antioxidant activity and poor yogurt flavor.

The invention provides a pitaya peel stirred yoghurt with antioxidant effect, which is prepared from the following substances in parts by weight:

Skim reconstituted milk 63~72 parts;

5 parts of five bacteria mixed starter;

6-8 parts of sucrose

15-25 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 1-2 parts;

The skim reconstituted milk is composed of skim milk powder and water, and the weight ratio of the skim milk powder to water is 1:6-7;

The five-bacteria mixed starter consists of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus bifidus, and the Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, The ratio of the number of bacteria between Lactobacillus plantarum and Lactobacillus bifidosum is 1:2:1:1:1;

The compound sweetener is composed of xylitol and aspartame, and the weight ratio of xylitol and aspartame is 5:1;

The composite stabilizer is composed of acid-resistant sodium carboxymethylcellulose, xanthan gum, gelatin and ascorbic acid, and the weight ratio of the acid-resistant sodium carboxymethylcellulose, xanthan gum, gelatin and ascorbic acid is 2:2: 1:1;

Described pitaya peel freeze-dried powder gelatinization slurry is prepared through the following steps:

Select the fresh pitaya peel without rot, cut it into slices after washing, add dry ice, the quality of the dry ice is 5-8 times of the quality of pitaya peel, pass through a 180-220 mesh sieve after being pulverized by a food ultrafine pulverizer, and obtain pitaya Pitaya peel freeze-dried powder, mix dragon fruit peel freeze-dried powder with water, the amount of water added is 10-12 times the weight of pitaya peel freeze-dried powder, pass through a 60-80 mesh filter, heat at 80-90°C for 8-12 minutes, After being filled with nitrogen and cooled, the gelatinized pulp of pitaya peel freeze-dried powder is obtained through colloid grinding.

Further, the above-mentioned dragon fruit peel stirred yoghurt with antioxidant effect is prepared from the following substances by weight:

63 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

25 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 2 parts.

Further, the above-mentioned dragon fruit peel stirred yoghurt with antioxidant effect is prepared from the following substances by weight:

72 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

15 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 1 part.

Further, the above-mentioned dragon fruit peel stirred yoghurt with antioxidant effect is prepared from the following substances by weight:

68 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

20 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 2 parts.

The present invention also provides a method for preparing the above-mentioned dragon fruit peel stirred yoghurt with anti-oxidation effect, comprising the following steps:

1) Weighing skimmed reconstituted milk, five bacteria mixed starter, sucrose, dragon fruit peel freeze-dried powder gelatinization slurry, compound sweetener, compound stabilizer according to parts by weight;

2) Mix and stir the reconstituted milk and sucrose evenly to obtain the premixed fermentation broth;

3) Heat the premixed fermentation broth obtained in step 2) to 55~60°C, first control the homogenization pressure to 30~35MPa for the first homogenization for 12~18min, and then control the homogenization pressure to 20~25MPa for the second Sub-homogenization 8~10min;

4) Sterilize the premixed fermentation broth obtained in step 3) at 80-85°C for 5-10 minutes;

5) Inoculate the five-bacteria mixed starter into the premixed fermentation broth cooled to 40-45°C in 4);

6) Control the fermentation temperature to 40-43°C and ferment for 5-6 hours to obtain a primary fermentation liquid;

7) After the primary fermentation, the pitaya peel freeze-dried powder gelatinization slurry, compound sweetener, and compound stabilizer are added to the primary fermentation liquid under a sterile environment, and mixed and stirred evenly;

8) Control the fermentation temperature at 37-39° C., and ferment for 3-4 hours to obtain a secondary fermentation liquid;

9) After the fermentation is completed, it is rapidly cooled to below 18°C, and stirred, and canned below 10°C;

10) Store the stirred fermented milk after subpackaging in step 9) at 2-4°C for 24 hours to obtain a dragon fruit peel stirred yogurt with antioxidant effect.

In order to maintain the activity of anthocyanins in the pitaya peel, the invention adopts freeze-drying to prepare the pitaya peel powder, and prepares the pitaya peel freeze-dried powder gelatinization liquid under the condition of filling nitrogen. The present invention adopts secondary fermentation in order to reduce the destruction of pitaya peel anthocyanins in the fermentation process, reduce the inhibitory effect of anthocyanins on the growth of lactic acid bacteria and improve the activity of lactic acid bacteria. Through one fermentation, the sucrose is converted into lactic acid, which reduces the sugar content and increases the acidity and the activity of lactic acid bacteria. After the second fermentation, the activity and acidity of lactic acid bacteria are higher, which is beneficial to the transformation of carbohydrates and proteins in pitaya peel, and the fermentation temperature is lowered and the fermentation time is controlled to prevent the loss of antioxidant activity caused by excessive anthocyanin hydrolysis.

The stirred nutritional yoghurt containing pitaya peel components prepared by the present invention has a high procyanidin content and high antioxidant activity due to the optimized formula according to the synergistic antioxidant effect evaluation and the use of secondary fermentation technology. The average value of the proanthocyanidin content reaches 0.1%. The average scavenging rate of oxidative activity DPPH and ABTS reaches 90% and 92% respectively, the average Q value of synergistic antioxidant effect is greater than 1.5, and the reduction rate of antioxidant activity within 15 days (4°C storage environment) is less than 15%. However, among the commercially available yogurt products, there are few products containing anthocyanins and stable antioxidant activity during the shelf life.

The present invention converts sucrose into lactic acid through the first fermentation, and the highly active lactic acid bacteria in the second fermentation can decompose the carbohydrates and proteins in the pitaya peel to improve the absorption and utilization rate of the body, and reduce the sugar content of the finished product of the present invention (less than 1%) ). The compound sweetener with low calorie is added in the invention to adjust the sweet-acid ratio of the finished product, so that the finished product is sweet and sour, and the lower calorie is beneficial to health.

The present invention is a stirring type yoghurt with anti-oxidation effect containing pitaya peel anthocyanins and other functional components, utilizes pitaya peel anthocyanins and yogurt's own antioxidant components to form a composite antioxidant system, and optimizes the combination of anthocyanins and yoghurt according to synergy evaluation. The ratio of yogurt fermentation liquid improves the stability of the antioxidant activity of the finished product, and adopts methods such as preparation of freeze-dried dragon fruit peel powder and secondary fermentation to reduce the loss of antioxidant activity of anthocyanins during processing, storage and transportation, and obtains The finished product is a stirred yogurt with good antioxidant activity and stability, low sugar content and other health benefits.

Compared with the prior art, the technical progress of the present invention is remarkable. The yoghurt prepared by the present invention is designed according to the synergistic anti-oxidation activity. The anti-oxidation activity is strong and stable, and the sugar content is low. Regular consumption can not only enhance and improve the effect of intestinal flora, but also improve the anti-oxidation of the body and interfere with the function of the body. Healthy effects such as aging, and suitable for special populations such as diabetes to drink.

detailed description

The present invention is illustrated by the following examples, but the present invention is not limited.

In each embodiment of the present invention:

The raw material sweeteners xylitol, aspartame and stabilizer gelatin, xanthan gum, acid-resistant sodium hydroxymethylcellulose, ascorbic acid, etc. used in each embodiment of the present invention all meet the GB2760-2014 hygienic standard for the use of food additives ;

The dragon fruit used in the actual case of the present invention, sucrose is commercially available;

The fermented strains adopted in the present invention are conventional fermented strains used in the preparation of yoghurt in the prior art.

Determination method of total sugar in the present invention: Determination by acid hydrolysis method in GB/T 5009.8-2008.

Determination method of proanthocyanidins of the present invention: adopt iron salt catalytic colorimetric method determination in "Technical Specifications for Inspection and Evaluation of Health Food", the specific steps are as follows:

(1) Preparation of standard curve: Dissolve 10.0 mg of proanthocyanidin standard substance in 10 mL of methanol, draw 0, 0.10, 0.25, 0.50, 1.00, 1.50 mL of the solution into a 10 mL volumetric flask, add methanol to the mark, shake uniform. Take 1 mL each into a test tube, add 6 mL of n-butanol-hydrochloric acid solution and 0.2 mL of ferric ammonium sulfate solution, mix thoroughly, place in a boiling water bath and heat precisely under reflux for 40 min, immediately put in ice water to cool, and then heat for 15 min before placing The absorbance was measured at a wavelength of 546 nm, and the color was stable within 1 h. A standard curve was made with the concentration of proanthocyanidins as the abscissa and the absorbance as the ordinate. The regression equation of the standard curve is obtained: Y=19.026X-0.0245, R ² =0.9895, X is the proanthocyanidin concentration (mg/mL), and Y is the absorbance.

(2) Determination of sample proanthocyanidins: Take a certain amount of sample and centrifuge at 3000rpm for 10min, take 1 mL of the supernatant in a test tube, add 6 mL of n-butanol-hydrochloric acid solution and 0.2 mL of ferric ammonium sulfate solution, mix thoroughly Heat evenly in a boiling water bath under reflux for 40 min, then immediately cool in ice water, and after heating for another 15 min, measure the absorbance at a wavelength of 546 nm. Calculate the content of proanthocyanidins in the sample solution according to the standard curve.

The antioxidant activity DPPH and ABTS free radical scavenging rate determination method of the present invention is based on literature (Serpen A, Gökmen V, Fogliano V. Total Antioxidant Capacities of Raw and Cooked Meats[J]. Meat Science, 2012, 90: 60-65) Method determination.

The determination steps of DPPH clearance rate are as follows:

(1) Configuration of DPPH stock solution: Accurately weigh 20mg of DPPH, dilute to 250mL volumetric flask with absolute ethanol, and store in the dark.

(2) Sample measurement: After the sample was centrifuged at 3000 rpm for 10 min, 100 μL of the supernatant was taken, and 4.9 mL of DPPH stock solution was added to measure its absorbance at 517 nm.

DPPH clearance rate (%) = (A _blank - A _sample ) / A _sample × 100%

In the formula: A _sample is the absorbance value of the sample tube;

A _blank is the absorbance value of the blank group;

ABTS (2, 2-azinobis-( 3-ethylbenzothiazoline - 6-sulphonic acid)) free radical scavenging ability assay steps are as follows:

(1) Preparation of 7mmol/L ABTS free radical and 140mmol/L K2S2O8 preparation: Take 0.48g ABTS and dilute to 100ml brown volumetric flask with distilled water. Accurately weigh 0.3784g K2S2O8 and dilute it with distilled water to a 100ml brown volumetric flask. Mix 100mL of 7 mmol/L ABTS and 1.76ml of 140mmol/L potassium persulfate, and let stand overnight at room temperature in the dark to form an ABTS free radical stock solution. This stock solution is stable at room temperature and protected from light. Before use, dilute with absolute ethanol to make a working solution. It is required that when 1mL of absolute ethanol is added to 4mL of working solution, its absorbance at room temperature at 734nm wavelength is 0.7±0.02.

(2) Sample determination: Take 0.35ml of sample solutions of different concentrations, add 1.4mL of ABTS working solution, use 1.75ml of absolute ethanol as a blank, mix for 10s, and keep it at room temperature for 20min in the dark, and at 734nm wavelength Measure the absorbance. The experiment was repeated 3 times. Calculate the inhibition rate (%) of the sample. Calculated as follows:

ABTS clearance rate (%) = (A _blank - A _sample ) / A _sample × 100%

In the formula: A _sample is the absorbance value of the sample tube;

A _blank is the absorbance value of the blank group;

Antioxidant synergistic evaluation method of the present invention: according to literature (Vares M, Álvarez Rocha L, Lópezrivadulla M, et al. Sequelae-free survival in a case of potentially fatal methanol poisoning using CVVHDF as dialysis technique].[J]. Medicina Intensiva, 2012 , 36(5):379-380.), by using the Q value (Q = d1/Dx1 + d2/Dx2) to calculate and compare their antioxidant properties. (In the formula, d1 and d2 are respectively the concentration when reaching the predetermined reaction, Dx1 and Dx2 are respectively the concentration when reaching the reaction alone; Q>1.15 is synergistic, Q<0.85 is antagonistic, 0.85≤Q≤1.15 is relative additive.)

Example 1

A pitaya peel stirred yoghurt with synergistic antioxidant effect and a preparation method thereof, the fermented liquid used is calculated in parts by weight, and the composition and content of the raw materials and the secondary fermentation conditions are as follows:

63 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

Primary fermentation (42°C) 5 hours

After one fermentation, add:

25 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 2 parts;

Secondary fermentation (38°C) 4 hours

The five-bacteria mixed starter is calculated according to the ratio of the number of bacteria, and is composed of Lactobacillus bulgaricus: Streptococcus thermophilus: Lactobacillus acidophilus: Lactobacillus plantarum: Lactobacillus bifidus 1:2:1:1:1 ;

The compound sugar is calculated by weight ratio and is formed by compounding xylitol: aspartame at 5:1;

The composite stabilizer, calculated by weight ratio, is composed of acid-resistant sodium carboxymethylcellulose: xanthan gum: gelatin: ascorbic acid in a ratio of 2:2:1:1;

The above-mentioned pitaya peel freeze-dried powder gelatinization slurry is prepared through the following steps:

Choose fresh dragon fruit peel without rot, wash it and cut it into 1cm small square pieces, add dry ice according to the quality of 1:5-8, pass through a food ultrafine pulverizer and sieve (200 mesh) to get dragon fruit peel freeze-dried powder, 4 Store below ℃ until use. Take the above-mentioned dragon fruit peel powder and mix it with water, the weight ratio of material to liquid is 1:12, pass through a 60-80 mesh filter, heat at 85°C for 10 minutes (filled with nitrogen), cool down, and then go through colloid grinding to obtain freeze-dried dragon fruit peel powder paste;

Skim milk powder and water are compounded at a weight ratio of 1:6 to make reconstituted milk.

The preparation steps are as follows:

(1) According to the parts by weight, mix and stir the reconstituted milk and sucrose evenly to obtain the premixed fermentation liquid;

(2) Heat the premixed fermentation broth obtained in step (1) to 55~60°C, first control the homogenization pressure to 30~35MPa for the first homogenization for 12~18min, and then control the homogenization pressure to 20~25MPa for Homogenizing for the second time for 8~10 minutes;

(3) Sterilize the premixed fermentation broth obtained in step (2) at 80-85°C for 5-10 minutes;

(4) Quickly inoculate the five-bacteria mixed starter into the premixed fermentation broth cooled to 40-45°C in (3) according to the parts by weight;

(5) Control the fermentation temperature at 40-43°C and ferment for 5 hours to obtain a primary fermentation broth;

(6) After the primary fermentation, according to the parts by weight, the pitaya peel freeze-dried powder gelatinization slurry, compound sweetener, and compound stabilizer are added to the primary fermentation liquid in a sterile environment, and mixed and stirred evenly;

(7) Control the fermentation temperature at 37-39°C and ferment for 4 hours to obtain the secondary fermentation liquid;

(8) After the fermentation is completed, it is rapidly cooled to below 18°C, and stirred, and canned below 10°C;

(9) Store the stirred fermented milk subpackaged in step (8) at 2-4°C for 24 hours to obtain a dragon fruit peel stirred yogurt with synergistic antioxidant effect.

Utilize above-mentioned steps to contain pitaya peel antioxidant stirring type yogurt obtained, its total sugar content is 0.95% after testing; Its proanthocyanidin is 125.2mg/100mL; Its antioxidant activity DPPH scavenging rate is 92%, ABTS scavenging rate is 95.3%, Synergy Q value is 1.92; tested according to GB/T12465-90, its acidity is 82°T; lactic acid bacteria content is 1.5×10 ⁸ CFU/g; Escherichia coli ≤3MPN/mL, pathogenic bacteria: not detected, meets GB/T4789.1~4789.3-2003 food hygiene standards.

Example 2

A pitaya peel stirred yoghurt with synergistic antioxidant effect and a preparation method thereof, the fermented liquid used is calculated in parts by weight, and the composition and content of the raw materials and the secondary fermentation conditions are as follows:

68 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

Primary fermentation (42°C) 5.5 hours

Add after one fermentation:

20 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 2 parts;

Secondary fermentation (38°C) for 3.5 hours

The five-bacteria mixed starter is calculated according to the ratio of the number of bacteria, and is composed of Lactobacillus bulgaricus: Streptococcus thermophilus: Lactobacillus acidophilus: Lactobacillus plantarum: Lactobacillus bifidus 1:2:1:1:1 ;

The compound sugar is calculated by weight ratio and is formed by compounding xylitol: aspartame at 5:1;

The composite stabilizer, calculated by weight ratio, is composed of acid-resistant sodium carboxymethylcellulose: xanthan gum: gelatin: ascorbic acid in a ratio of 2:2:1:1;

The above-mentioned pitaya peel freeze-dried powder gelatinization slurry is prepared through the following steps:

Choose fresh dragon fruit peel without rot, wash it and cut it into 1cm small square pieces, add dry ice according to the quality of 1:5-8, pass through a food ultrafine pulverizer and sieve (200 mesh) to get dragon fruit peel freeze-dried powder, 4 Store below ℃ until use. Take the above-mentioned dragon fruit peel powder and mix it with water, the weight ratio of material to liquid is 1:12, pass through a 60-80 mesh filter, heat at 85°C for 10 minutes (filled with nitrogen), cool down, and then go through colloid grinding to obtain freeze-dried dragon fruit peel powder paste;

Skim milk powder and water are compounded at a weight ratio of 1:6 to make reconstituted milk.

The preparation steps are as follows:

(1) According to the parts by weight, mix and stir the reconstituted milk and sucrose evenly to obtain the premixed fermentation broth;

(2) Heat the premixed fermentation broth obtained in step (1) to 55~60°C, first control the homogenization pressure to 30~35MPa for the first homogenization for 12~18min, and then control the homogenization pressure to 20~25MPa for Homogenizing for the second time for 8~10 minutes;

(3) Sterilize the premixed fermentation broth obtained in step (2) at 80-85°C for 5-10 minutes;

(4) Quickly inoculate the five-bacteria mixed starter into the premixed fermentation broth cooled to 40-45°C in (3) according to the parts by weight;

(5) Control the fermentation temperature at 41-43°C and ferment for 5.5 hours to obtain a primary fermentation liquid;

(6) After the primary fermentation, according to the parts by weight, the pitaya peel freeze-dried powder gelatinization slurry, compound sweetener, and compound stabilizer are added to the primary fermentation liquid in a sterile environment, and mixed and stirred evenly;

(7) Control the fermentation temperature at 37-39°C and ferment for 3.5 hours to obtain the secondary fermentation liquid;

(8) After the fermentation is completed, it is rapidly cooled to below 18°C, and stirred, and canned below 10°C;

(9) Store the stirred fermented milk subpackaged in step (8) at 2-4°C for 24 hours to obtain a dragon fruit peel stirred yogurt with synergistic antioxidant effect.

Utilize above-mentioned steps to contain pitaya peel antioxidant stirring type yogurt obtained, its total sugar content is 0.89% after testing; Its proanthocyanidin is 115.2mg/100mL; Its antioxidant activity DPPH scavenging rate is 90.5%, ABTS scavenging rate is 92.8%, Synergy Q value is 1.7; tested according to GB/T12465-90, its acidity is 85°T; lactic acid bacteria content is 1.7×10 ⁸ CFU/g; Escherichia coli ≤3MPN/mL, pathogenic bacteria: not detected, meets GB/T4789.1~4789.3-2003 food hygiene standards.

Example 3

A pitaya peel stirred yoghurt with synergistic antioxidant effect and a preparation method thereof, the fermented liquid used is calculated in parts by weight, and the composition and content of the raw materials and the secondary fermentation conditions are as follows:

72 parts of skimmed reconstituted milk;

5 parts of five bacteria mixed starter;

3 parts cane sugar

Primary fermentation (42°C) 6 hours

After one fermentation, add:

15 parts of pitaya peel freeze-dried powder gelatinization slurry;

1 part compound sweetener;

Composite stabilizer 1 part;

Secondary fermentation (38°C) for 3 hours

The five-bacteria mixed starter is calculated according to the ratio of the number of bacteria, and is composed of Lactobacillus bulgaricus: Streptococcus thermophilus: Lactobacillus acidophilus: Lactobacillus plantarum: Lactobacillus bifidus 1:2:1:1:1 ;

The compound sugar is calculated by weight ratio and is formed by compounding xylitol: aspartame at 5:1;

The composite stabilizer, calculated by weight ratio, is composed of acid-resistant sodium carboxymethylcellulose: xanthan gum: gelatin: ascorbic acid in a ratio of 2:2:1:1;

The above-mentioned pitaya peel freeze-dried powder gelatinization slurry is prepared through the following steps:

Choose fresh dragon fruit peel without rot, wash it and cut it into 1cm small square pieces, add dry ice according to the quality of 1:5-8, pass through a food ultrafine pulverizer and sieve (200 mesh) to get dragon fruit peel freeze-dried powder, 4 Store below ℃ until use. Take the above dragon fruit peel powder and mix it with water, the weight ratio of material to liquid is 1:10, pass through a 60-80 mesh filter, heat at 85°C for 10 minutes (filled with nitrogen), cool down, and then go through colloidal grinding to obtain freeze-dried dragon fruit peel powder paste;

Skim milk powder and water are compounded at a weight ratio of 1:7 to make reconstituted milk.

The preparation steps are as follows:

(1) According to the parts by weight, mix and stir the reconstituted milk and sucrose evenly to obtain the premixed fermentation broth;

(2) Heat the premixed fermentation broth obtained in step (1) to 55~60°C, first control the homogenization pressure to 30~35MPa for the first homogenization for 12~18min, and then control the homogenization pressure to 20~25MPa for Homogenizing for the second time for 8~10 minutes;

(3) Sterilize the premixed fermentation broth obtained in step (2) at 80-85°C for 5-10 minutes;

(4) Quickly inoculate the five-bacteria mixed starter into the premixed fermentation broth cooled to 40-45°C in (3) according to the parts by weight;

(5) Control the fermentation temperature at 41-43°C and ferment for 6 hours to obtain a primary fermentation broth;

(6) After the primary fermentation, according to the parts by weight, the pitaya peel freeze-dried powder gelatinization slurry, compound sweetener, and compound stabilizer are added to the primary fermentation liquid in a sterile environment, and mixed and stirred evenly;

(7) Control the fermentation temperature at 37-39°C and ferment for 3 hours to obtain the secondary fermentation liquid;

(8) After the fermentation is completed, it is rapidly cooled to below 18°C, and stirred, and canned below 10°C;

(9) Store the stirred fermented milk subpackaged in step (8) at 2-4°C for 24 hours to obtain a dragon fruit peel stirred yogurt with synergistic antioxidant effect.

Utilize above-mentioned steps to contain pitaya skin anti-oxidation stirring type yoghurt obtained, its total sugar content is 0.81% after testing; Its proanthocyanidin is 0.961mg/100mL; Its antioxidant activity DPPH scavenging rate is 88.7%, ABTS scavenging rate is 89.2%, Synergy Q value is 1.9; tested according to GB/T12465-90, its acidity is 85°T; lactic acid bacteria content is 2.1×10 ⁸ CFU/g; Escherichia coli ≤ 3MPN/mL, pathogenic bacteria: not detected, meets GB/T4789.1~4789.3-2003 food hygiene standards.

The above content is only a basic description of the concept of the present invention, and any equivalent transformation made according to the technical solution of the present invention shall fall within the scope of protection of the present invention.

Claims (5)

1. a pitaya peel stirring type yoghurt with antioxidant effect is characterized in that it is prepared from the following materials by weight: Skim reconstituted milk 63~72 parts; 5 parts of five bacteria mixed starter; 6-8 parts of sucrose 15-25 parts of pitaya peel freeze-dried powder gelatinization slurry; 1 part compound sweetener; Composite stabilizer 1-2 parts; The skim reconstituted milk is composed of skim milk powder and water, and the weight ratio of the skim milk powder to water is 1:6-7; The five-bacteria mixed starter consists of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus bifidus, and the Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, The ratio of the number of bacteria between Lactobacillus plantarum and Lactobacillus bifidosum is 1:2:1:1:1; The compound sweetener is composed of xylitol and aspartame, and the weight ratio of xylitol and aspartame is 5:1; The composite stabilizer is composed of acid-resistant sodium carboxymethylcellulose, xanthan gum, gelatin and ascorbic acid, and the weight ratio of the acid-resistant sodium carboxymethylcellulose, xanthan gum, gelatin and ascorbic acid is 2:2: 1:1; Described pitaya peel freeze-dried powder gelatinization slurry is prepared through the following steps: Select the fresh pitaya peel without rot, cut it into slices after washing, add dry ice, the quality of the dry ice is 5-8 times of the quality of pitaya peel, pass through a 180-220 mesh sieve after being pulverized by a food ultrafine pulverizer, and obtain pitaya Freeze-dried fruit peel powder, mix the freeze-dried dragon fruit peel powder with water, the amount of water added is 10-12 times the weight of the dragon fruit freeze-dried powder, pass through a 60-80 mesh filter, and fill it with nitrogen at 80-90°C Heating for 8-12 minutes, cooling and then passing through a colloid mill to obtain a gelatinized pulp of pitaya peel freeze-dried powder. 2. a kind of pitaya peel stirring type yoghurt with antioxidant effect as claimed in claim 1 is characterized in that being prepared from by the material of following weight portion: 63 parts of skimmed reconstituted milk; 5 parts of five bacteria mixed starter; 3 parts cane sugar 25 parts of pitaya peel freeze-dried powder gelatinization slurry; 1 part compound sweetener; Composite stabilizer 2 parts. 3. a kind of pitaya peel stirring type yoghurt with antioxidant effect as claimed in claim 1, is characterized in that being prepared from by the material of following weight portion: 72 parts of skimmed reconstituted milk; 5 parts of five bacteria mixed starter; 3 parts cane sugar 15 parts of pitaya peel freeze-dried powder gelatinization slurry; 1 part compound sweetener; Composite stabilizer 1 part. 4. a kind of pitaya peel stirring type yoghurt with antioxidant effect as claimed in claim 1 is characterized in that being prepared from by the material of following weight portion: 68 parts of skimmed reconstituted milk; 5 parts of five bacteria mixed starter; 3 parts cane sugar 20 parts of pitaya peel freeze-dried powder gelatinization slurry; 1 part compound sweetener; Composite stabilizer 2 parts. 5. the preparation method of a kind of pitaya peel stirring type yoghurt with antioxidant effect as claimed in claim 1, is characterized in that comprising the steps: 1) Weigh skimmed reconstituted milk, five-bacteria mixed starter, sucrose, dragon fruit peel freeze-dried powder gelatinization pulp, compound sweetener, and compound stabilizer according to parts by weight; 2) Mix and stir the reconstituted milk and sucrose evenly to obtain the premixed fermentation broth; 3) Heat the premixed fermentation broth obtained in step 2) to 55~60°C, first control the homogenization pressure to 30~35MPa for the first homogenization for 12~18min, and then control the homogenization pressure to 20~25MPa for the second Sub-homogenization 8~10min; 4) Sterilize the premixed fermentation broth obtained in step 3) at 80-85°C for 5-10 minutes; 5) Inoculate the five-bacteria mixed starter into the premixed fermentation broth cooled to 40-45°C in 4); 6) Control the fermentation temperature at 40-43°C and ferment for 5-6 hours to obtain a primary fermentation liquid; 7) After the primary fermentation, add the gelatinized pulp of the freeze-dried pitaya peel powder, compound sweetener, and compound stabilizer to the primary fermentation liquid in a sterile environment, and mix and stir evenly; 8) Control the fermentation temperature at 37-39°C and ferment for 3-4 hours to obtain the secondary fermentation liquid; 9) After the fermentation is finished, cool down rapidly to below 18°C, and stir, and then fill in tanks below 10°C; 10) Store the stirred fermented milk subpackaged in step 9 at 2-4°C for 24 hours to obtain a dragon fruit peel stirred yogurt with antioxidant effect.