Method for extracting natural pigment from pomace

Abstract

The invention discloses a method for extracting a natural pigment from pomace, and belongs to the technical field of natural pigment preparation, the preparation method comprises the following steps: preparing a pure pomace extraction stock solution; preparing an enzymolysis stock solution; fermenting with lactic acid bacteria; and performing spray drying to obtain the natural pigment extracted from the pomace. A pulsed electric field is introduced into a process from enzymolysis to fermentation completion, and enzymolysis, fermentation and sterilization are assisted by changing the electric field intensity of the pulsed electric field, so that the effective content of natural pigments is greatly increased, and the nutritional value of the product is enhanced; meanwhile, pulsed electric field enzymolysis, fermentation and sterilization processes can be completed in the same equipment, so that raw material loss and equipment switching are reduced, and a reference way is provided for utilization of pomace byproducts.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural pigment preparation, and specifically relates to a method for extracting natural pigments from fruit residues. Background Art

[0002] Fruit residues, as the remaining solid substances after squeezing and extracting juice or oil from plant fruits, contain components such as fruit peels, pulp, seeds, and fruit stalks. In particular, fruit residues of berries such as blueberries, grapes, and raspberries contain rich nutritional components such as anthocyanins, dietary fiber, and various vitamins. If these fruit residues are used as fertilizers or directly discarded, it will lead to serious waste of resources. Therefore, exploring how to efficiently convert fruit residue by-products and reduce resource waste has become an urgent problem to be solved in the food industry. For example, Patent CN116676152A discloses a method for utilizing blood orange fruit residues, in which anthocyanins in the fruit residues are extracted by enzymatic hydrolysis and ultrasonic treatment and then fermented into fruit wine. The ultrasonic process lasts for 1 h, and the heat effect during the process raises the temperature of the raw material liquid, degrading anthocyanins and reducing the extraction efficiency; Patent CN114031591A discloses a vacuum ice-melting solvent extraction method for anthocyanins, in which blueberry fruit residues are ice-melted at -30 to -45 °C under a vacuum degree of 0.35 - 1.0 Mpa, and high-content blueberry anthocyanins are obtained through extraction. However, the ice-melting process is difficult to operate, and the vacuum combined with low-temperature process is not suitable for mass production. From the current technology, for the technology of extracting components such as anthocyanins that can be used as natural pigments from fruit residues, there are problems such as large damage of anthocyanins by heat effect and bottlenecks in large-scale production.

[0003] Pulsed electric field technology (PEF) is an innovative food processing method that uses short-term high-intensity electric pulses to temporarily change the permeability of cell membranes, achieving microbial inactivation or promoting certain biochemical processes. This technology relies on the electroporation effect, that is, instantaneous pores are generated on the cell membrane, promoting the exchange of substances inside and outside the cell and resulting in the loss of cell function. PEF has diverse applications in the food industry, including inhibiting microbial growth, assisting in the extraction of natural components, regulating enzyme activity, and improving the sensory quality of foods. The main factors affecting the PEF effect are electric field strength, pulse duration and frequency, and the overall treatment duration. The advantage of PEF lies in its non-thermal treatment characteristics, which helps to maintain the original nutrition and flavor of foods, has a fast processing speed, and has little impact on the environment. Due to its significant potential in extending the shelf life of foods and improving food quality, PEF technology is becoming an important research and application trend in the field of food science. Summary of the Invention

[0004] Object of the Invention: In order to overcome the deficiencies in the prior art, the present invention provides a method for extracting natural pigments from fruit residues, which uses pulsed electric field technology to assist enzymatic hydrolysis, fermentation, and sterilization in the preparation process of natural pigment extraction, improving the extraction efficiency.

[0005] Technical solution: To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for extracting natural pigments from fruit residues, comprising the following steps:

[0007] S1: Preparation of fruit residue extraction stock solution: Collect fruit residues, wash and dry them, add an ethanol solution of 50%-60% and grind, where the fruit residue:ethanol solution = 1:1-3 (m:m). After grinding, rotate and evaporate to remove ethanol to obtain the fruit residue extraction stock solution;

[0008] S2: Preparation of enzymolysis stock solution: Add cellulase to the fruit residue extraction stock solution obtained in S1, connect to a low-intensity pulsed electric field to assist enzymolysis, and after enzymolysis, adjust to a high-voltage pulsed electric field to inactivate the enzyme and sterilize to obtain the enzymolysis stock solution;

[0009] S3: Lactic acid bacteria fermentation: Inoculate a lactic acid bacteria fermenting agent into the enzymolysis stock solution obtained in S2 for fermentation, and adjust the pulsed electric field to a sublethal intensity for treatment 2-3 times during the process. After fermentation, adjust to a high-voltage pulsed electric field for sterilization to obtain the fermentation broth;

[0010] S4 Spray drying: Spray dry the fermentation broth obtained in S3 to obtain the natural pigment.

[0011] In the above steps, the enzyme activity of cellulase in S2 is 10,000 U / g, and the addition amount is 0.01 wt% - 0.2 wt% of the fruit residue extraction stock solution;

[0012] In S3, the lactic acid bacteria fermenting agent is a mixture of one or two of Lactobacillus rhamnosus and Lactobacillus plantarum, the initial strain activity is 10 log CFU / g, and the inoculation amount is 1 wt% of the enzymolysis stock solution; the fermentation temperature is 36°C and the time is 3 d;

[0013] The parameters of the low-intensity pulsed electric field are: electric field strength 5-12 kV / cm, pulse frequency 400-500 Hz, pulse width 4-6 μs, and residence time 10-20 min.

[0014] The parameters of the sublethal pulsed electric field are: electric field strength 1-5 kV / cm, pulse frequency 1-10 Hz, pulse width 50-100 μs, and number of pulses 5-8.

[0015] The parameters of the high-voltage pulsed electric field are: electric field strength 25-50 kV / cm, pulse frequency 30-40 kHz, pulse width 4-6 μs, and residence time 20-30 min.

[0016] In S4, the inlet air temperature of the spray drying is 150°C - 200°C, the outlet air temperature is 80°C - 100°C, and the feed liquid flow rate is 3% - 5%.

[0017] Beneficial effects: The method for extracting natural pigments from fruit residues in the present invention has the following beneficial effects compared with the prior art:

[0018] 1) The present invention introduces pulsed electric field-assisted enzymatic hydrolysis, enzyme inactivation, fermentation, and sterilization processes. Most of the dietary fiber in fruit residues is insoluble dietary fiber, which needs to be enzymatically hydrolyzed by cellulase into reducing sugars to be utilized by lactic acid bacteria. The enzymatic hydrolysis effect is affected by many factors such as enzyme activity, enzymatic hydrolysis temperature, and enzymatic hydrolysis time. Research shows that low-intensity pulsed electric field treatment can induce enzyme molecule polarization, improve the activity of cellulase, and has a positive promoting effect on enzymatic hydrolysis. Using low-intensity pulsed electric field to stimulate enzyme molecules can accelerate the enzymatic hydrolysis progress; sub-lethal pulsed electric field can change the cell membrane permeability and metabolic ability of probiotics, and induce the production of more active substances during the fermentation process; high-voltage pulsed electric field, as a non-thermal sterilization technology, also has the effect of enzyme inactivation, and can kill microorganisms with little heat effect generated. The present invention adjusts the pulsed electric field intensity to greatly improve the effects of enzymatic hydrolysis, enzyme inactivation, fermentation, and sterilization processes with one technology.

[0019] 2) The present invention reduces production losses and equipment switching. From the enzymatic hydrolysis of fruit residues to the fermentation and sterilization stage, it can be completed in one device, reducing equipment switching, reducing the possible microbial contamination during equipment switching and the residual losses in different devices, and improving the product yield.

[0020] 3) The product of the present invention has high effective content and nutritional value. The natural pigment prepared by the combined process of pulsed electric field-fermentation enriches more anthocyanin coloring active ingredients in the product compared with the simple fermentation process. At the same time, the high-voltage pulsed electric field has little heat effect during sterilization, is friendly to heat-sensitive components. During sterilization, the lactic acid bacteria cells rupture and the contents dissolve, including various postbiotics such as proteins, polysaccharides, and organic acids, improving the nutritional value of the product and expanding other uses besides the coloring function. Specific embodiments

[0021] The following further illustrates the present invention with specific embodiments.

[0022] Example 1

[0023] A method for extracting natural pigments from fruit residues, comprising the following steps:

[0024] S1 Preparation of fruit residue extraction stock solution: Collect fruit residues, wash them, dry them at 50 °C, add 60% ethanol solution and grind for 3 h, fruit residue:ethanol solution = 1:3 (m:m). After grinding, rotate and evaporate to remove ethanol to obtain the fruit residue extraction stock solution;

[0025] Preparation of the S2 enzymolysis stock solution: Add 0.01% of cellulase with an activity of 10,000 U / g to the fruit residue extraction stock solution obtained in S1, apply a low-intensity pulsed electric field of 5 kV / cm, 400 Hz, and 4 μs for 10 min to assist enzymolysis, then continue enzymolysis for 2 h. After that, adjust to a high-voltage pulsed electric field of 30 kV / cm, 30 kHz, and 4 μs to inactivate the enzyme and sterilize for 20 min to obtain the enzymolysis stock solution;

[0026] S3 Lactobacillus fermentation: Inoculate the mixed starter of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis stock solution obtained in S2 at an inoculation amount of 1%, ferment at 36 °C for 3 d, and adjust the pulsed electric field to a sublethal intensity treatment of 1 kV / cm, 1 Hz, 50 μs, and 6 pulse numbers at 24 h and 48 h respectively during the process. After fermentation, adjust to a high-voltage pulsed electric field of 30 kV / cm, 30 kHz, and 4 μs to sterilize for 20 min to obtain the fermentation broth;

[0027] S4 Spray drying: Spray dry the fermentation broth obtained in S3, with an inlet air temperature of 150 °C, an outlet air temperature of 80 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0028] Example 2

[0029] A method for extracting natural pigments from fruit residues, comprising the following steps:

[0030] S1 Preparation of the fruit residue extraction stock solution: Collect the fruit residues, wash them, dry them at 50 °C, add a 55% ethanol solution and grind for 3 h, with the ratio of fruit residue to ethanol solution being 1:2 (m:m). After grinding, rotate and evaporate to remove ethanol to obtain the fruit residue extraction stock solution;

[0031] S2 Preparation of the enzymolysis stock solution: Add 0.1% of cellulase with an activity of 10,000 U / g to the fruit residue extraction stock solution obtained in S1, apply a low-intensity pulsed electric field of 8 kV / cm, 450 Hz, and 5 μs for 10 min to assist enzymolysis, then continue enzymolysis for 2 h. After that, adjust to a high-voltage pulsed electric field of 35 kV / cm, 35 kHz, and 5 μs to inactivate the enzyme and sterilize for 25 min to obtain the enzymolysis stock solution;

[0032] S3 Lactobacillus fermentation: Inoculate the mixed starter of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis stock solution obtained in S2 at an inoculation amount of 1%, ferment at 36 °C for 3 d, and adjust the pulsed electric field to a sublethal intensity treatment of 3 kV / cm, 5 Hz, 70 μs, and 8 pulse numbers at 24 h and 48 h respectively during the process. After fermentation, adjust to a high-voltage pulsed electric field of 35 kV / cm, 35 kHz, and 5 μs to sterilize for 25 min to obtain the fermentation broth;

[0033] S4 Spray drying: Spray dry the fermentation broth obtained in S3, with an inlet air temperature of 160 °C, an outlet air temperature of 90 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0034] Example 3

[0035] A method for extracting natural pigments from fruit residues, comprising the following steps:

[0036] S1 Preparation of fruit residue extraction stock solution: Collect fruit residues, wash them, dry them at 50 °C, add 50% ethanol solution and grind for 3 h, fruit residue:ethanol solution = 1:1 (m:m). After grinding, rotate and evaporate to remove ethanol to obtain the fruit residue extraction stock solution;

[0037] S2 Preparation of enzymolysis stock solution: Add 0.2% cellulase of 10,000 U / g to the fruit residue extraction stock solution obtained in S1, apply low-intensity pulsed electric field with 12 kV / cm, 500 Hz, 6 μs to assist enzymolysis for 20 min, then continue enzymolysis for 2 h. After completion, adjust to high-voltage pulsed electric field of 40 kV / cm, 40 kHz, 6 μs to inactivate the enzyme and sterilize for 30 min to obtain the enzymolysis stock solution;

[0038] S3 Lactobacillus fermentation: Inoculate the mixed starter of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis stock solution obtained in S2 at an inoculation amount of 1%, ferment at 36 °C for 3 d, and adjust the pulsed electric field to sub-lethal intensity treatment of 5 kV / cm, 10 Hz, 100 μs, 8 pulse numbers at 24 h and 48 h respectively during the process. After fermentation, adjust to high-voltage pulsed electric field of 40 kV / cm, 40 kHz, 6 μs to sterilize for 30 min to obtain the fermentation broth;

[0039] S4 Spray drying: Spray dry the fermentation broth obtained in S3, with an inlet air temperature of 180 °C, an outlet air temperature of 90 °C, and a feed liquid flow rate of 4% to obtain the natural pigment.

[0040] Example 4

[0041] Adjust the starter in S3 of Example 1 to a single-strain starter of Lactobacillus rhamnosus.

[0042] Other steps are the same as those in Example 1 to obtain the natural pigment.

[0043] Example 5

[0044] Adjust the starter in S3 of Example 1 to a single-strain starter of Lactobacillus plantarum.

[0045] Other steps are the same as those in Example 1 to obtain the natural pigment.

[0046] Comparative Example 1

[0047] A method for extracting natural pigments from fruit residues, comprising the following steps:

[0048] Preparation of the original extract from fruit residue: Collect the fruit residue, wash it, dry it at 50 °C, add 60% ethanol solution and grind for 3 h with a fruit residue:ethanol solution ratio of 1:3 (m:m). After grinding, remove ethanol by rotary evaporation to obtain the original extract from fruit residue;

[0049] Preparation of the enzymolysis original solution: Add 0.01% cellulase with an activity of 10,000 U / g to the original extract from fruit residue obtained in S1 and enzymolyze for 2 h. After that, use a high-voltage pulsed electric field with 30 kV / cm, 30 kHz, and 4 μs to inactivate the enzyme and sterilize for 20 min to obtain the enzymolysis original solution;

[0050] Lactic acid bacteria fermentation: Inoculate the mixed fermentation agent of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis original solution obtained in S2 at an inoculation amount of 1%, and ferment at 36 °C for 3 d. During the fermentation, adjust the pulsed electric field to a sublethal intensity of 1 kV / cm, 1 Hz, 50 μs, and 6 pulses at 24 h and 48 h respectively. After fermentation, adjust it to a high-voltage pulsed electric field of 30 kV / cm, 30 kHz, and 4 μs to sterilize for 20 min to obtain the fermentation broth;

[0051] Spray drying: Spray dry the fermentation broth obtained in S3 at an inlet air temperature of 150 °C, an outlet air temperature of 80 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0052] Comparative Example 2

[0053] A method for extracting natural pigment from fruit residue, comprising the following steps:

[0054] Preparation of the original extract from fruit residue: Collect the fruit residue, wash it, dry it at 50 °C, add 60% ethanol solution and grind for 3 h with a fruit residue:ethanol solution ratio of 1:3 (m:m). After grinding, remove ethanol by rotary evaporation to obtain the original extract from fruit residue;

[0055] Preparation of the enzymolysis original solution: Add 0.01% cellulase with an activity of 10,000 U / g to the original extract from fruit residue obtained in S1, apply a low-intensity pulsed electric field of 5 kV / cm, 400 Hz, and 4 μs to assist enzymolysis for 10 min, then continue enzymolysis for 2 h. After that, adjust it to a high-voltage pulsed electric field of 30 kV / cm, 30 kHz, and 4 μs to inactivate the enzyme and sterilize for 20 min to obtain the enzymolysis original solution;

[0056] Lactic acid bacteria fermentation: Inoculate the mixed fermentation agent of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis original solution obtained in S2 at an inoculation amount of 1%, and ferment at 36 °C for 3 d. After fermentation, adjust it to a high-voltage pulsed electric field of 30 kV / cm, 30 kHz, and 4 μs to sterilize for 20 min to obtain the fermentation broth;

[0057] S4 Spray drying: Spray dry the fermentation broth obtained in S3 at an inlet air temperature of 150 °C, an outlet air temperature of 80 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0058] Comparative Example 3

[0059] A method for extracting natural pigment from fruit pomace, comprising the following steps:

[0060] S1 Preparation of fruit pomace extraction stock solution: Collect fruit pomace, wash it, dry it at 50 °C, add 60% ethanol solution and grind for 3 h, fruit pomace:ethanol solution = 1:3 (m:m). After grinding, rotary evaporate to remove ethanol to obtain the fruit pomace extraction stock solution;

[0061] S2 Preparation of enzymolysis stock solution: Add 0.01% of 10,000 U / g cellulase to the fruit pomace extraction stock solution obtained in S1, apply low-intensity pulsed electric field assistance for enzymolysis at 5 kV / cm, 400 Hz, 4 μs for 10 min, then continue enzymolysis for 2 h, and after completion, perform pasteurization at 90 °C for 20 min to obtain the enzymolysis stock solution;

[0062] S3 Lactic acid bacteria fermentation: Inoculate the mixed starter culture of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis stock solution obtained in S2 at an inoculation amount of 1%, ferment at 36 °C for 3 d, and adjust the pulsed electric field to a sublethal intensity treatment of 1 kV / cm, 1 Hz, 50 μs, 6 pulse numbers at 24 h and 48 h respectively during the process. After fermentation, perform pasteurization at 90 °C for 20 min to obtain the fermentation broth;

[0063] S4 Spray drying: Spray dry the fermentation broth obtained in S3 at an inlet air temperature of 150 °C, an outlet air temperature of 80 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0064] Comparative Example 4

[0065] A method for extracting natural pigment from fruit pomace: comprising the following steps:

[0066] S1 Preparation of fruit pomace extraction stock solution: Collect fruit pomace, wash it, dry it at 50 °C, add 60% ethanol solution and grind for 3 h, fruit pomace:ethanol solution = 1:3 (m:m). After grinding, rotary evaporate to remove ethanol to obtain the fruit pomace extraction stock solution;

[0067] S2 Preparation of enzymolysis stock solution: Add 0.01% of 10,000 U / g cellulase to the fruit pomace extraction stock solution obtained in S1 and enzymolyze for 2 h. After completion, perform pasteurization at 90 °C for 20 min to obtain the enzymolysis stock solution;

[0068] S3 Lactic acid bacteria fermentation: Inoculate the mixed starter culture of Lactobacillus rhamnosus and Lactobacillus plantarum into the enzymolysis stock solution obtained in S2 at an inoculation amount of 1%, ferment at 36 °C for 3 d, and after fermentation, perform pasteurization at 90 °C for 20 min to obtain the fermentation broth;

[0069] S4 Spray drying: Spray dry the fermentation broth obtained in S3 at an inlet air temperature of 150 °C, an outlet air temperature of 80 °C, and a feed liquid flow rate of 3% to obtain the natural pigment.

[0070] Table 1 Increase rate of soluble solids content before and after enzymatic hydrolysis

[0071]

[0072] As can be seen from Table 1, the soluble solids in the examples with low-intensity electric field-assisted enzymatic hydrolysis (Examples 1, 2, 3, 4, 5, Comparative Examples 2, 3) are significantly increased compared to the examples without electric field assistance (Comparative Examples 1, 4). Under the action of low-intensity pulsed electric field, the non-covalent bonds maintaining the enzyme protein molecular structure change under the electric field, resulting in the refolding of enzyme molecules, making more aromatic amino acid residues such as tryptophan exposed. This makes the structure of the enzyme more ordered and flexible, thus making it easier to interact with the substrate, ultimately leading to an increase in enzyme activity.

[0073] Determination of anthocyanin content: The total anthocyanin content was determined by the pH differential method. The product was dissolved in methanol containing 0.1% hydrochloric acid to prepare a solution with a concentration of 1 mg / mL. Subsequently, the solution was diluted with buffer solutions with pH values of 1.0 and 4.5 at a ratio of 1:100 and equilibrated at 37 °C for 60 min. After equilibration, the absorbance was measured at 518 nm using an ultraviolet spectrophotometer, and the absorbance at 700 nm was used as the calibration reference. The total anthocyanin calculation formula:

[0074]

[0075] Among them, ε is the molar extinction coefficient, 26900 L / (mol*cm); L is the optical path, 1 cm; MW is the relative molecular mass of cyanidin anthocyanin, 449.2 g / mol; DF is the dilution factor; V is the total volume, L; M is the sample mass, g. The anthocyanin content of the natural pigments obtained in the above examples and comparative examples is shown in Table 2:

[0076] Table 2 Anthocyanin content of natural pigments

[0077]

[0078] As can be seen from Table 2, the effects of pulsed electric field-assisted enzymatic hydrolysis, fermentation, and sterilization on the natural pigment anthocyanin are significantly enhanced. Compared with the products without pulsed electric field treatment (Comparative Example 4), the anthocyanin contents of the products treated with pulsed electric fields of different intensities (Examples 1, 2, and 3) are increased by 65.7%, 111.4%, and 99.7%, respectively. The increase in anthocyanin content between Examples 2 and 3 is reduced because, in the pulsed electric field-assisted enzymatic hydrolysis stage, due to the relatively high electric field intensity, proteins aggregate and denature due to hydrophobic interactions and disulfide bond cross-linking, reducing the cellulase activity; secondly, the sub-lethal electric field intensity is too high, and the inhibitory effect on the growth of lactic acid bacteria is greater than the promoting effect, affecting the metabolism. Comparative Example 1 shows the significant promoting effect of electric field-assisted enzymatic hydrolysis on anthocyanin content, mainly by promoting the metabolism of cellulose by cellulase into glucose, providing raw material nutrients for probiotic fermentation, and indirectly enhancing the development and metabolism of probiotics; Comparative Example 2 shows the promoting effect of sub-lethal pulsed electric field on probiotic fermentation, by changing the cell permeability of probiotics, inducing cell proliferation and performance improvement, and enhancing the metabolic capacity; Comparative Example 3 shows the protective effect of pulsed electric field non-thermal sterilization on the natural pigment anthocyanin. The destructive effect of heat sterilization at 90°C on anthocyanin is significant, and the anthocyanin content is reduced by 28.3% compared with Example 1.

[0079] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for extracting natural pigments from pomace, characterized in that: The following steps are involved: S1: Preparation of pomace extraction stock solution: collecting pomace, washing and drying, adding ethanol solution to grind, and removing ethanol after grinding to obtain pomace extraction stock solution; S2: Preparation of enzymatic hydrolysis stock solution: adding cellulase to the pomace extraction stock solution obtained in S1, connecting to a low-intensity pulsed electric field to assist enzymatic hydrolysis, and after the enzymatic hydrolysis is completed, adjusting to a high-voltage pulsed electric field to inactivate the enzyme and sterilize, to obtain an enzymatic hydrolysis stock solution; S3: Lactic acid bacteria fermentation: inoculating the lactic acid bacteria starter into the enzymatic hydrolyzed stock solution obtained in S2 for fermentation, adjusting the pulsed electric field to a sublethal intensity treatment during the fermentation, and adjusting to a high-voltage pulsed electric field for sterilization after the fermentation is completed to obtain a fermentation liquid; S4 spray drying: spray drying the fermentation liquid obtained in S3 to obtain the natural pigment.

2. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The mass ratio of pomace to ethanol solution in S1 is 1:1-3.

3. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The cellulase activity in S2 is 10,000 U / g, and the added amount is 0.01 wt% to 0.2 wt% of the pomace extract.

4. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The initial bacterial activity of the lactic acid bacteria starter in S3 was 10 log CFU / g, and the inoculation amount was 1 wt% of the enzymatic hydrolysis stock solution.

5. The method for extracting natural pigments from pomace according to claim 1 or 4, characterized in that: The lactic acid bacteria fermentation agent is one of Lactobacillus rhamnosus and Lactobacillus plantarum or a mixture of both.

6. The method for extracting natural pigments from pomace according to claim 1 or 4, characterized in that: The fermentation temperature in S3 was 36°C and the fermentation time was 3 days.

7. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The parameters of the low-intensity pulse electric field are electric field intensity of 5-12 kV / cm, pulse frequency of 400-500 Hz, pulse width of 4-6 μs, and dwell time of 10-20 min.

8. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The sublethal pulse electric field parameters are electric field intensity 1-5 kV / cm, pulse frequency 1-10 Hz, pulse width 50-100 μs, and pulse number 5-8.

9. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The parameters of the high-voltage pulse electric field are electric field intensity of 25-50 kV / cm, pulse frequency of 30-40 kHz, pulse width of 4-6 μs, and dwell time of 20-30 min.

10. The method for extracting natural pigments from pomace according to claim 1, characterized in that: The inlet air temperature of the spray drying in S4 is 150°C-200°C, the outlet air temperature is 80°C-100°C, and the feed liquid flow rate is 3%-5%.

Images