Preparation method of plant extract preservative for low-sugar food

Abstract

The invention relates to a preparation method of a plant extract preservative for low-sugar food, which solves the problem of low-sugar food preservation by compounding lychee seeds and dried orange peel and combining an enzymolysis-ultrahigh pressure synergistic extraction process. Litchi nucleoside in the lychee seeds has a bacteriostatic effect, and hesperidin and limonene in the pericarpium citri reticulatae have antioxidant and color-protecting functions. Active components are released through enzymolysis pretreatment, the biological activity is reserved at low temperature through ultrahigh-pressure extraction, and high efficiency and stability are ensured. The preservative effectively inhibits putrefying bacteria in the low-sugar fruit and vegetable juice, delays browning, keeps the original flavor of the fruit and vegetable juice, and is free of peculiar smell and flavor interference. According to the method, agricultural wastes and by-products are utilized, the cost is reduced, the green production requirement is met, and good economical efficiency and environmental friendliness are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-sugar food preservation, and in particular to a preparation method of a plant extract preservative for low-sugar food. BACKGROUND

[0002] With the increasing demand for healthy diets among consumers, low-sugar food has gradually become the mainstream in the market. However, low-sugar food may face problems such as microbial growth, color browning, and loss of nutritional ingredients during storage and preservation. Traditional preservation methods often rely on synthetic chemicals such as preservatives and antioxidants, which may pose potential risks to health and affect the original flavor and nutritional value of food. Therefore, developing a natural, green, and harmless preservative has become the key to solving the problem of low-sugar food preservation.

[0003] Plant extracts have been widely used in food preservation due to their antibacterial, antioxidant, and color protection functions. As agricultural waste and by-products, litchi seeds and dried orange peel contain active ingredients such as litchi nucleosides, hesperidin, and limonene, which have good antibacterial, antioxidant, and color protection effects. However, existing plant extract preservatives are mostly single-function and have limited application in low-sugar food. Therefore, there is a need for a specialized preservative for low-sugar fruit and vegetable juice that is efficient, natural, and multifunctional. SUMMARY

[0004] To address the above problems, the present application provides a preparation method of a plant extract preservative for low-sugar food. The preservative is prepared by compounding litchi seeds and dried orange peel and using an enzymatic-ultra-high pressure extraction process. It has antibacterial, antioxidant, and color protection functions, effectively extends the shelf life of low-sugar fruit and vegetable juice, maintains the original flavor and nutritional ingredients, and solves the shortcomings of traditional preservation methods.

[0005] To achieve the above purposes, the present application adopts the following technical solutions: A plant extract preservative for low-sugar food is prepared from the following raw materials by weight: 15-25 parts of litchi seeds, 10-17 parts of dried orange peel, 0.1-0.2 parts of a composite enzyme, and 250-420 parts of an ethanol solution with a volume fraction of 60%. The composite enzyme is composed of cell wall-decomposing enzymes and pectin-decomposing enzymes in a mass ratio of 1:1. The amount of the ethanol solution is 1:12 based on the solid-liquid ratio of the mixed raw materials of "litchi seeds + dried orange peel". The composite preservative takes the composite extract of litchi seeds and dried orange peel as the core active ingredient.

[0006] Preferably, the mass ratio of the lychee kernel and the dried tangerine or orange peel is 3:2, the complex extract contains lychee nucleus, hesperidin and limonene, and the complex extract has an antibacterial rate of 85-90% on acetic acid bacteria and yeast in low-sugar food, an inhibition rate of 80-90% on polyphenol oxidase in low-sugar food, and a 7-day retention rate of 75-85% on vitamin C in low-sugar fruit and vegetable juice.

[0007] Preferably, the cell wall-decomposing enzyme is selected from one or more of cellulase, hemicellulase and xylanase; and the pectin-decomposing enzyme is selected from one or more of pectinase, pectin methylesterase and pectolyase.

[0008] Preferably, the total flavonoid content of the preservative is 35-55 mg RE / g, the total polyphenol content is 55-75 mg GAE / g, and the lychee nucleus content is 1.0-1.5%, and the hesperidin content is 1.8-2.2%.

[0009] Preferably, the preparation method of the plant extract preservative for low-sugar food comprises the following steps: S1, crushing lychee kernels to 60-100 mesh, cutting dried tangerine or orange peel into shreds, and mixing to obtain mixed raw materials; S2, adding a complex enzyme to the obtained mixed raw materials, adjusting the pH of the system to 3.5-4.5, and enzymatically hydrolyzing at 40-50℃ for 1.0-2.0 h to obtain an enzymatic hydrolysate; S3, adding an ethanol solution to the enzymatic hydrolysate, placing the mixed system in an ultrahigh-pressure device, and extracting at a pressure of 280-320 MPa and a temperature of 30-40℃ for 15-25 min to obtain an extract; S4, filtering the obtained extract with a 0.20-0.25 μm microporous filter membrane, and vacuum concentrating at a temperature of 50-60℃ and a vacuum degree of -0.08--0.10 MPa to a solid content of 22-33% to obtain the plant extract preservative for low-sugar food.

[0010] Preferably, the pH value of the preservative is 4.0-5.0, the density is 1.0-1.2 g / mL, and after being stored at 4℃ in the dark for 6 months, the DPPH free radical scavenging rate of the preservative decreases by 5-15%.

[0011] Preferably, the addition amount of the preservative in low-sugar food is 0.3-0.5%; after addition, the shelf life of solid low-sugar food is extended to 10-15 days, the shelf life of liquid low-sugar food is extended to 13-20 days, and there is no odor or spoilage phenomenon in low-sugar food during the shelf life, the hardness of solid low-sugar food increases by 15-20%, and the color difference ΔE of liquid low-sugar food is 1.0-3.0.

[0012] Preferably, the low-sugar food has been pretreated before the addition of the preservative, wherein the low-sugar dairy product, low-sugar beverage is pasteurized or ultra-high temperature instant sterilized, and the low-sugar baked food is cooled to room temperature.

[0013] The beneficial effects of the present application are: The plant extract preservative for low-sugar food prepared by the present application has excellent bacteriostatic, antioxidant and color protection properties, can effectively prolong the shelf life of low-sugar food, and maintain the original flavor and nutritional ingredients. The preservative has a bacteriostatic rate of more than 90% on common spoilage bacteria such as acetic acid bacteria and yeast, and an inhibition rate of more than 85% on polyphenol oxidase (PPO) in fruit and vegetable juice, effectively preventing browning of fruit and vegetable juice. The active ingredients in the preservative are efficiently released through the enzyme hydrolysis-ultra-high pressure extraction process, maintaining their biological activity and helping to delay the degradation of vitamin C, with a retention rate of more than 80% within 7 days. The preservative is suitable for low-sugar food and has no flavor interference, can maintain the original taste of fruit and vegetable juice, and meets the preservation needs during long-term storage and transportation. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate embodiments of the present application, and are used to explain the present application, and do not constitute a limitation on the present application.

[0015] Figure 1 The figure is a comparison chart of total polyphenol content and DPPH free radical scavenging rate of different samples of the present application; Figure 2 The figure is a comparison chart of 7-day vitamin C retention rate and browning inhibition rate of different samples of the present application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0017] Example 1 The preparation method of the plant extract preservative for low-sugar food in this embodiment 1 is prepared from the following raw materials by weight: 20 parts of litchi seeds, 13 parts of dried tangerine or orange peel, 0.17 parts of composite enzyme: cellulase and pectinase, and 400 parts of 60% ethanol solution by volume fraction; The preparation method of the plant extract preservative for low-sugar food in this embodiment is as follows: S1, grind the litchi seeds to 80 mesh, cut the dried tangerine or orange peel into silk, and mix them evenly in a 500 mL beaker to obtain the mixed raw materials; S2, add composite enzyme to the mixed raw materials, add 2 times the mass of deionized water to the mass of the mixed raw materials, adjust the pH of the system to 4.0 with a 10% citric acid solution, transfer to a constant-temperature water bath, and enzymatically hydrolyze at 45°C for 1.5 h with magnetic stirring to obtain an enzymatic hydrolysate; S3, transfer the enzymatic hydrolysate to an ultrahigh-pressure reaction kettle, add a 60% ethanol aqueous solution, seal the reaction kettle, and place it in an ultrahigh-pressure device, set the pressure to 300 MPa and the temperature to 35°C, and keep the pressure for 20 min, then remove the extraction liquid after pressure relief; S4, filter the extraction liquid under reduced pressure with a 0.22 μm microporous filter membrane, collect the filtrate, and place the filtrate in a rotary evaporator under the conditions of a temperature of 50°C and a vacuum degree of -0.08 MPa to reduce the pressure and concentrate to a solid content of 25-30% to obtain a brown-yellow transparent plant extract preservative for low-sugar food.

[0018] Example 2: The preparation method of the plant extract preservative for low-sugar food in this example 2 is as follows: Litchi seeds 16.5 parts, dried tangerine or orange peel 16.5 parts, composite enzyme: cellulase and pectinase 0.17 parts, 60% ethanol solution by volume 400 parts; The preparation method of the plant extract preservative for low-sugar food in this example is the same as that in example 1.

[0019] Comparative Example 1: To explore the effect of composite enzyme on the performance of the preservative, the preservative in this comparative example 1 is prepared from the following raw materials by weight: Litchi seeds 20 parts, dried tangerine or orange peel 13 parts, composite enzyme: cellulase and pectinase 0 parts, 60% ethanol solution by volume 400 parts; The preparation method of the preservative in this comparative example is the same as that in example 1.

[0020] Comparative Example 2: To explore the effect of the extraction method on the performance of the preservative, the preservative in this comparative example 2 is prepared from the following raw materials by weight: Litchi seeds 20 parts, dried tangerine or orange peel 13 parts, composite enzyme: cellulase and pectinase 0.17 parts, 60% ethanol solution by volume 400 parts; The preparation method of the preservative in this comparative example is the same as that in example 1, and the ultrahigh-pressure reaction kettle is replaced with a constant-temperature water bath, and the extraction is carried out at 60°C with magnetic stirring at 400 rpm for 2 h.

[0021] Comparative Example 3: To explore the effect of using a single raw material on the performance of the preservative, the preservative in this comparative example 2 is prepared from the following raw materials by weight: Litchi kernel 33 parts, dried tangerine or orange peel 0 parts, complex enzyme: cellulase and pectinase 0.17 parts, 60% ethanol solution 400 parts by volume; The preparation method of the preservative in the present comparative example is the same as that in Example 1.

[0022] Comparative Example 4: To explore the effect of using a single raw material on the performance of the preservative, the preservative of Comparative Example 2 is prepared from the following raw materials by weight: Litchi kernel 0 parts, dried tangerine or orange peel 33 parts, complex enzyme: cellulase and pectinase 0.17 parts, 60% ethanol solution 400 parts by volume; The preparation method of the preservative in the present comparative example is the same as that in Example 1.

[0023] Performance test 1. Antioxidant performance test (1) Standard curve drawing: accurately weigh 0.01 g of gallic acid standard, dissolve and dilute to 100 mL with distilled water to prepare a standard stock solution with a concentration of 100 μg / mL; respectively take 0, 0.2, 0.4, 0.6, 0.8, 1.0 mL of the standard stock solution into a 10 mL volumetric flask, add 0.5 mL of Folin-Ciocalteu reagent, shake well, and stand for 3 min, then add 2 mL of 10% sodium carbonate solution, dilute to the mark with distilled water, shake well, and react at 25°C in the dark for 60 min; with the blank solution as the reference, the absorbance is measured at 765 nm wavelength, and the standard curve is drawn with the gallic acid concentration as the abscissa and the absorbance as the ordinate.

[0024] (2) Sample determination: accurately weigh 0.05 g of the preservative sample, dissolve and dilute to 50 mL with 60% ethanol aqueous solution, shake well, filter, take 0.5 mL of the filtrate, and operate according to the standard curve drawing procedure, measure the absorbance, and calculate the total polyphenol content according to the standard curve.

[0025] Table 1 Total polyphenol content data table of different samples 2. DPPH free radical scavenging rate test Accurately weigh 0.0025 g of DPPH reagent, dissolve and dilute to 50 mL with anhydrous ethanol to prepare a DPPH solution with a concentration of 0.1 mmol / L, and store in the dark at low temperature. Dilute the preservative sample with distilled water to a concentration of 0.1 mg / mL; take 2 mL of the sample solution into a test tube, add 2 mL of the DPPH solution, shake well, and react in the dark for 30 min; use 2 mL of anhydrous ethanol + 2 mL of distilled water as a blank control, and measure the absorbance at a wavelength of 517 nm; at the same time, measure the absorbance of 2 mL of the DPPH solution + 2 mL of distilled water, and calculate the DPPH free radical scavenging rate.

[0026] Table 2 DPPH free radical scavenging rate data table of different samples 3. Antimicrobial performance test Inoculate E. coli (ATCC 25922) in nutrient broth medium, shake culture at 37°C for 18 h, dilute with sterile physiological saline to a bacterial concentration of 10 10 CFU / mL; dilute the preservative sample with sterile physiological saline to a concentration of 0.5 mg / mL, filter sterilize through a 0.22 μm sterile filter; mix 1 mL of the sample solution with 1 mL of the bacterial suspension, and incubate at 37°C for 24 h; at the same time, set sterile physiological saline + bacterial suspension as a positive control, and sample solution + sterile physiological saline as a negative control; after incubation, take 0.1 mL of the mixture and spread on nutrient agar medium, and incubate at 37°C for 24 h; count the number of colonies, and calculate the antibacterial rate.

[0027] Table 3 E. coli antibacterial rate data table of different samples 4. Vitamin C retention rate test Add the preservative to low-sugar orange juice with a sugar content of 6 g / 100 mL at a mass fraction of 0.4%, mix well, and then store in sterile brown bottles at 4°C; accurately weigh 0.01 g of vitamin C standard, dissolve in 1% oxalic acid solution, and dilute to 100 mL to prepare a standard stock solution with a concentration of 100 μg / mL; take 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 mL of the standard stock solution into 10 mL volumetric flasks, and dilute to the mark with 1% oxalic acid solution; use HPLC method for determination, with a C18 chromatographic column (250 mm × 4.6 mm, 5 μm), a mobile phase of 0.1% phosphoric acid aqueous solution, a flow rate of 1.0 mL / min, a detection wavelength of 245 nm, and a column temperature of 30°C; plot a standard curve with the concentration of vitamin C as the abscissa and the peak area as the ordinate.

[0028] Take 2 mL of low-sugar orange juice sample, add 2 mL of 1% oxalic acid solution, shake well, centrifuge at 8000 rpm for 10 min, take the supernatant through 0.22 μm filter membrane, and determine the peak area of vitamin C according to the standard curve chromatographic conditions. Calculate the content of vitamin C according to the standard curve.

[0029] Table 4 7-day vitamin C retention rate data table of samples without sample 5, browning inhibition rate The preservative is added to the low-sugar apple juice with a sugar content of 5 g / 100 mL at a mass fraction of 0.4%, and then evenly mixed and stored in transparent glass bottles at 25°C in the dark. The low-sugar apple juice without the addition of preservative is set as the control group. At 0 days and 7 days of storage, the L (brightness), a (red-green color), and b (yellow-blue color) values of the samples are measured using a colorimeter, and the color difference ΔE is calculated. The color difference calculation formula is: The calculation formula of browning inhibition rate is: Table 5 browning inhibition rate data table of different samples Based on the above test data, it can be concluded that: (1) The total polyphenol content, antibacterial rate, etc. of Example 1 and Example 2 are all decreased, indicating that the best synergistic effect is achieved when litchi kernels and dried tangerine or orange peel are compounded at a ratio of 3:2, and litchi kernels and dried tangerine or orange peel interact more fully. (2) The total polyphenol extraction rate of Comparative Example 1 is about 20% lower than that of Example 1, which proves that the compound enzyme can effectively destroy the cell wall of litchi kernels and the pectin layer of dried tangerine or orange peel, promote the release of active ingredients, and is the key step to improve the extraction efficiency; (3) The performance indicators of Comparative Example 2 are all significantly reduced compared with Example 1, indicating that the physical action of ultra-high pressure can accelerate solvent penetration and avoid the degradation of active ingredients caused by high temperature, and the extraction effect is better than that of traditional methods; (4) The antibacterial rate and browning inhibition rate of Comparative Examples 3 and 4 are lower than those of Example 1, indicating that the compounding of litchi kernels and dried tangerine or orange peel can achieve the complementary functions of "bacteriostasis + antioxidant + color protection", which is better than single raw material.

[0030] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low-sugar food plant extract preservative, characterized in that, The preservative is prepared from the following raw materials in parts by weight: The ingredients are: 15-25 parts litchi seeds, 10-17 parts dried tangerine peel, 0.1-0.2 parts compound enzyme, and 250-420 parts 60% ethanol solution. The compound enzyme is composed of cell wall degrading enzyme and pectin degrading enzyme in a mass ratio of 1:

1. The amount of ethanol solution used is such that the material-to-liquid ratio of the litchi seed and dried tangerine peel mixture is 1:

12. The compound preservative has a compound extract of litchi seeds and dried tangerine peel as its core active ingredient.

2. The low-sugar food plant extract preservative according to claim 1, characterized in that, The mass ratio of litchi seed to dried tangerine peel is 3:

2. The compound extract contains litchi glycoside, hesperidin and limonene. The compound extract has an inhibition rate of 85-90% against acetic acid bacteria and yeast in low-sugar foods, an inhibition rate of 80-90% against polyphenol oxidase in low-sugar foods, and a 7-day retention rate of 75-85% for vitamin C in low-sugar fruit and vegetable juices.

3. The low-sugar food plant extract preservative according to claim 1, characterized in that, The cell wall degrading enzyme is selected from one or more of cellulase, hemicellulase, and xylanase; the pectin degrading enzyme is selected from one or more of pectinase, pectin methylesterase, and pectin dissolving enzyme.

4. A low-sugar food plant extract preservative according to claim 1, characterized in that, The preservative contains 35-55 mg RE / g of total flavonoids, 55-75 mg GAE / g of total polyphenols, and 1.0-1.5% litchi glycosides and 1.8-2.2% hesperidin.

5. A method for preparing a plant extract preservative for low-sugar foods, wherein the preservative is as described in any one of claims 1-4, characterized in that, The steps are as follows: S1. Crush the lychee seeds to 60-100 mesh, shred the dried tangerine peel, and mix them together to obtain the mixed ingredients; S2. Add the compound enzyme to the obtained mixed raw materials, adjust the pH of the system to 3.5-4.5, and enzymatically hydrolyze at 40-50℃ for 1.0-2.0 h to obtain the enzymatic hydrolysis product; S3. Add ethanol solution to the enzymatic hydrolysis product, place the mixture in an ultra-high pressure device, and extract for 15-25 min at a pressure of 280-320 MPa and a temperature of 30-40℃ to obtain the extract. S4. Filter the obtained extract through a 0.20-0.25 μm microporous membrane, and then concentrate it under reduced pressure at a temperature of 50-60℃ and a vacuum degree of -0.08--0.10 MPa until the solid content is 22-33% to obtain the low-sugar food plant extract preservative.

6. A low-sugar food plant extract preservative according to claim 1, characterized in that, The preservative has a pH of 4.0-5.0 and a density of 1.0-1.2 g / mL. After being stored at 4°C in the dark for 6 months, its DPPH free radical scavenging rate decreases by 5-15%.

7. A low-sugar food plant extract preservative according to claim 1, characterized in that, The amount of the preservative added to the low-sugar food is 0.3-0.5%; after addition, the shelf life of solid low-sugar food is extended to 10-15 days, and the shelf life of liquid low-sugar food is extended to 13-20 days. During the shelf life, the low-sugar food has no off-odor or spoilage. The hardness of solid low-sugar food increases by 15-20%, and the color difference ΔE of liquid low-sugar food is 1.0-3.

0.

8. A low-sugar food plant extract preservative according to claim 1, characterized in that, The low-sugar foods have been pretreated before the preservative is added. The pretreatment of low-sugar dairy products and low-sugar beverages is pasteurization or ultra-high temperature instantaneous sterilization, and the pretreatment of low-sugar baked goods is cooling to room temperature.

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