A high-quality lychee juice processing method and product thereof

Abstract

The present invention provides a high-quality lychee juice processing method and product thereof. The content of oxygen and carbon dioxide in lychee juice and the ratio of the two are controlled to inhibit the growth of microorganisms in the lychee juice; the non-uniform distribution of sugar in lychee aril is used to prepare low-sugar lychee juice; proanthocyanidins are extracted from lychee shells and added to lychee juice to inhibit the hydrolysis of collagen and connective tissue by matrix metalloproteinases.

Description

Technical Field

[0001] The invention relates to the technical field of food and beverage, and in particular to a high-quality lychee juice processing method and a product thereof. Background Art

[0002] Lychee is a famous fruit in Lingnan, China. It is known as the "king of fruits" for its beautiful color, fragrance and taste. Its juice is rich in ascorbic acid. Lychee juice retains the fresh lychee flavor and is currently very popular in the market. Although lychee juice is sweet and delicious, it still has the following problems to be solved:

[0003] First, the sugar content of lychee juice is high, which cannot meet the needs of diabetic patients and patients with high blood sugar for low-sugar juice. The current purification and sugar removal process is relatively complicated and costly.

[0004] Secondly, at 2℃~8℃, the shelf life of lychee juice is generally 1 day to 14 days, which is a short storage time. As the storage time increases, the microorganisms in the lychee juice grow and multiply, posing a challenge to food safety. The common method to extend the shelf life of the juice is heat treatment, which inactivates enzymes and microorganisms by heating, thereby extending the shelf life of the juice. However, sterilization causes the loss of some flavor of fresh lychees, and also destroys nutrients such as vitamins.

[0005] Thirdly, during the storage of lychee juice, a large amount of ascorbic acid is decomposed, resulting in a large loss of nutritional value. Currently, antioxidants are often added to reduce the decomposition of ascorbic acid. However, antioxidants are chemical food additives and have certain potential hazards to the human body.

[0006] Finally, in the litchi processing industry, a large amount of litchi shells are produced, which are not effectively treated and seriously pollute the environment.

[0007] Proanthocyanidins are a type of polyphenolic compound with a high content in litchi shells, which can inhibit matrix metalloproteinases and exert anti-aging effects. However, the process of extracting proanthocyanidins from litchi shells is immature and purification is difficult. Currently, litchi shells and the proanthocyanidins in them have not been effectively utilized.

[0008] Therefore, it is necessary to develop a high-quality lychee juice processing method that can effectively utilize lychee shells and make the lychee juice have the characteristics of low sugar and long shelf life. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a method for processing high-quality lychee juice, comprising the following steps:

[0010] S1: After washing the litchi, the litchi shell is removed to obtain the shelled litchi and the litchi shell;

[0011] S2: after shelling, litchi includes aril and litchi core;

[0012] S3: After shelling, the litchi is removed from the pit and the aril is obtained;

[0013] S4: the aril is processed to obtain litchi puree;

[0014] S5: aerating the litchi puree so that the oxygen content in the litchi puree is 3 mg / L to 8 mg / L and the carbon dioxide content is 100 mg / L to 300 mg / L, thereby obtaining aerated litchi puree;

[0015] S6: Packing the aerated lychee puree into packaging containers to obtain lychee juice; the packaging container is an airtight container.

[0016] When the oxygen content in the lychee juice is 3mg / L-8mg / L and the carbon dioxide content is 100mg / L-300mg / L, the aerobic bacteria, mold and butyric acid anaerobic bacteria content are low after the lychee juice is stored, which reduces the risk of microbial corruption of the lychee juice, prolongs the shelf life of the lychee juice, is conducive to the storage and transportation of the lychee juice, and improves food safety. At the same time, the amount of preservatives added to the lychee juice can also be reduced accordingly.

[0017] In addition, carbon dioxide can bind to the active site of ascorbic acid oxidase, inhibiting the oxidation of ascorbic acid by oxidase, thereby improving the ascorbic acid retention rate of litchi juice during storage.

[0018] Litchi pulp contains respiratory enzymes that break down sugars into pyruvate; in the presence of oxygen, the respiratory enzymes continue to break down pyruvate into carbon dioxide and water. That is, sugars and acids are enzymatically degraded into carbon dioxide and water during the aerobic respiration of litchi pulp. In addition, the formation of the high-energy compound adenosine triphosphate in the aerobic respiration pathway is beneficial to improving the quality of juice. In the anaerobic respiration pathway, pyruvate breaks down into odorous compounds such as ethanol, lactic acid, and acetaldehyde, forming only a small amount of adenosine triphosphate, which can cause the quality of the juice to deteriorate during storage. However, the aerobic respiration in litchi juice is very weak. The technical solution of the present application appropriately increases the oxygen content in litchi juice, which helps the spontaneous aerobic respiration of litchi juice during storage, increases the adenosine triphosphate content of litchi juice, and improves the quality of juice.

[0019] Preferably, the gas charged into the litchi pulp in step S5 is a mixed gas, the mixed gas contains 10% to 15% oxygen, 50% to 60% carbon dioxide, and the remainder is nitrogen or an inert gas, and the ratio is a volume ratio.

[0020] Preferably, after the aerated lychee puree is packaged into the packaging container in step S6, the empty space in the packaging container is filled with the mixed gas and maintained at a constant pressure, wherein the constant pressure is greater than 1 standard atmospheric pressure.

[0021] Preferably, after the aerated lychee pulp is dispensed into the packaging container in step S6, the empty space in the packaging container is filled with a mixed gas and maintained at a constant pressure; the mixed gas contains 10% to 15% oxygen, 50% to 60% carbon dioxide, and the remainder is nitrogen or an inert gas. By controlling the ratio of the mixed gas components, the content and ratio of oxygen and carbon dioxide in the lychee pulp can be more effectively controlled. By increasing the mixed gas pressure in the packaging container, the content of oxygen and carbon dioxide in the lychee juice is kept stable.

[0022] According to the need for gas replacement, preferably, the airtight packaging container can selectively allow oxygen in the air to pass through.

[0023] According to the need for gas replacement, preferably, the airtight packaging container can selectively pass carbon dioxide in the air.

[0024] Preferably, the processing in step S4 includes pressing.

[0025] Preferably, the processing in step S4 includes homogenization.

[0026] Preferably, the processing in step S4 includes filtration.

[0027] Preferably, the processing in step S4 includes sterilization.

[0028] Litchi shell is rich in lychee flavor substances such as polyphenols and spices, including flavonoid derivatives such as flavanoids, flavonoids, flavonols, etc., especially anthocyanins.

[0029] Preferably, the litchi shell extract is prepared from the litchi shell obtained in step S1, and the preparation steps are as follows:

[0030] S11: crushing and homogenizing the litchi shell, mixing the crushed product with an ethanol solution with a volume concentration of 55% to 95% at a mass ratio of 1:10 to 1:15, reacting at 50° C. to 60° C. for 2 to 4 hours, and centrifuging to separate the supernatant and the precipitate;

[0031] S12: mixing the precipitate with an ethanol solution having a volume concentration of 55% to 95% in a mass ratio of 1:10 to 1:15, reacting at 50° C. to 60° C. for 2 to 4 hours, and centrifuging to separate the supernatant and the precipitate;

[0032] S13: combining the supernatants, removing ethanol from the supernatants, and making the volume concentration of ethanol in the supernatants not higher than 10%; purifying the supernatants using XDA-7 resin at 2°C to 25°C, with a supernatant flow rate of 150 cm / hour to 200 cm / hour; using 55% to 60% by volume ethanol as an eluent, with an elution flow rate of 100 cm / hour to 120 cm / hour; collecting the eluted product;

[0033] S14: the eluted product is processed to obtain a litchi shell extract;

[0034] S15: The litchi shell extract is mixed with the litchi puree obtained in step S4.

[0035] Preferably, in step S15, the volume ratio of the lychee shell extract to the lychee puree is 1:200 to 1:100. At this ratio, the lychee puree can effectively inhibit the hydrolysis of collagen and connective tissue by matrix metalloproteinases.

[0036] Preferably, the processing in step S14 is to reduce the ethanol content of the eluted product so that the volume ratio of ethanol in the eluted product is not higher than 10%.

[0037] Preferably, the processing in step S14 is filtration.

[0038] XDA-7 is provided by Xi'an Lanxiao Technology Co., Ltd., with a particle size of 20 to 60 mesh and a pore size between 100 and 1000 nm. It has stable physical and chemical properties and can absorb solvents and swell in water and organic solvents, but is insoluble in water, acids, alkali solutions and organic solvents. It has good thermal stability and can be used below 150°C.

[0039] XDA-7 resin has a large pore size, a porous network structure, and a strong adsorption capacity. It can adsorb more proanthocyanidins per unit resin. XDA-7 resin has a weak polarity. Under the combined effects of van der Waals forces, hydrogen bonds, porous structures, and molecular similarity attraction, XDA-7 resin selectively adsorbs proanthocyanidins. After purification by XDA-7 resin, the purity of proanthocyanidins in litchi shell extract is relatively high. XDA-7 resin has good desorption capacity, which improves the yield of proanthocyanidins in the preparation process of litchi shell extract. After resin screening, the applicant found that XDA-7 resin had the best effect among more than ten kinds of resins, so XDA-7 resin was selected for purification.

[0040] When the supernatant is purified by XDA-7 resin, when the volume concentration of ethanol in the supernatant is not higher than 10%, the adsorption capacity of proanthocyanidins by the unit XDA-7 resin can be increased; when the supernatant flow rate is 150 cm / hour to 200 cm / hour, the adsorption rate of proanthocyanidins by the resin can be increased, and the proanthocyanidin content in the flow-through liquid can be reduced; when 55% to 60% ethanol is used as the eluent and the elution flow rate is 100 cm / hour to 120 cm / hour, the desorption rate of the resin and the proanthocyanidins can be increased, and the proanthocyanidin yield can be increased.

[0041] The applicant has conducted a large number of experimental studies and found that the sugar content in the litchi aril gradually decreases from the area directly below the litchi shell to the core, showing a non-uniform distribution. The sugar content is higher in the peripheral part of the aril, and the content of disaccharides and oligosaccharides is higher; the monosaccharide content is relatively higher in the inner part of the aril close to the core.

[0042] Preferably, the aril in step S2 is divided into a peripheral part and an inner core part, and the inner core part is processed according to steps S3 to S6 to prepare low-sugar lychee juice, which can meet the needs of consumers with low sugar requirements.

[0043] Preferably, terpene glycosides are added to the low-sugar lychee juice in step S4, wherein the terpene glycosides are natural glycosides extracted and prepared from monk fruit. Terpene glycosides are natural compounds with low calories and high sweetness. While improving the sweetness of lychee juice, they can meet consumers' requirements for low sugar and low calories.

[0044] Preferably, the thickness of the peripheral portion of the aril is 1 mm to 3 mm.

[0045] Preferably, the peripheral part of the aril is processed according to steps S4 to S6 to prepare high-sweetness lychee juice, which can meet the needs of consumers with higher requirements for sweetness.

[0046] Through the above technical solutions, the present invention produces the following technical effects:

[0047] (1) By controlling the content of oxygen and carbon dioxide in litchi juice and the ratio of the two, the growth of microorganisms in the litchi juice is inhibited and the shelf life of the litchi juice is extended.

[0048] (2) Making full use of litchi shell to extract proanthocyanidins, obtaining litchi shell extract with high proanthocyanidin content, and mixing it with litchi juice can not only improve the flavor of litchi juice, but also use proanthocyanidins to inhibit the hydrolysis of collagen and connective tissue by matrix metalloproteinases, thus having anti-aging effects.

[0049] (3) Taking advantage of the uneven distribution of sugar in litchi aril, high-sugar litchi juice and low-sugar litchi juice were prepared to meet the needs of different groups of people. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the applicant first explains the specific research process of the present invention, and then conducts process verification and comparative analysis through specific embodiments and comparative examples.

[0051] Specific research process:

[0052] 1. Effect of aeration of lychee juice on microorganisms

[0053] 1.1 Sample preparation test method

[0054] The outer surface of the litchi was cleaned and disinfected with a 150 ppm effective chlorine solution to inactivate microorganisms; the litchi shell and core were removed, and the juice was squeezed from the aril; at 4°C, a mixed gas (containing 10% oxygen, 60% carbon dioxide, and 30% nitrogen, the ratio being by volume) was charged into the juice to make the oxygen and carbon dioxide concentrations in the original juice as shown in Table 1, and the juice was hermetically sealed and stored at 4°C for 8 weeks.

[0055] 1.2 Detection Method

[0056] Taking mold as a representative of aerobic bacteria and butyric acid anaerobic bacteria as a representative of anaerobic bacteria, samples were taken after storage to detect the content of mold and butyric acid anaerobic bacteria in the juice. The detection methods are all existing technologies and will not be repeated here.

[0057] Ascorbic acid is easily oxidized and deteriorated. The applicant uses the ascorbic acid retention rate as an indicator of the antioxidant performance of juice. Samples are taken to detect the ascorbic acid content in the juice before and after storage, and the ascorbic acid retention rate is calculated. The retention rate calculation method is: ascorbic acid content in the juice after storage / ascorbic acid content in the juice before storage × 100%. The ascorbic acid content detection method belongs to the prior art and will not be repeated here.

[0058] 1.3 Test results and analysis

[0059] It can be seen from Tables 1 and 2 that increasing the oxygen content in litchi juice can promote the growth of mold and inhibit the growth of butyric acid anaerobic bacteria. Increasing the carbon dioxide content in litchi juice can inhibit the growth of mold and promote the growth of butyric acid anaerobic bacteria. When the oxygen content in the juice is 3mg / L~8mg / L and the carbon dioxide content is 100mg / L~300mg / L, the content of mold and butyric acid anaerobic bacteria is low after the juice is stored for 8 weeks, which is conducive to the preservation of litchi juice.

[0060] The lower concentration of oxygen in litchi juice is not enough to cause the growth and reproduction of aerobic bacteria, but it can inhibit the growth and reproduction of anaerobic bacteria; the higher concentration of carbon dioxide in litchi juice can inhibit the growth and reproduction of aerobic bacteria. The lower concentration of oxygen and the higher concentration of carbon dioxide work synergistically to inhibit the growth and reproduction of anaerobic and aerobic bacteria, thereby reducing the risk of microbial corruption of litchi juice and extending the shelf life of litchi juice.

[0061] Table 1 Fungal content in juice (CFU / ml)

[0062]

[0063] Table 2 Butyric acid anaerobic bacteria content in juice (CFU / ml)

[0064]

[0065] As shown in Table 3, increasing the oxygen content in litchi juice to 8 mg / L is not enough to significantly reduce the ascorbic acid retention rate; increasing the carbon dioxide content in litchi juice to 100 mg / L significantly increases the ascorbic acid retention rate. Therefore, the oxidation of ascorbic acid can be prevented by dissolving carbon dioxide in the juice. Carbon dioxide replaces oxygen in the juice, reducing the oxidation of oxygen on ascorbic acid; in addition, carbon dioxide can be adsorbed on the active site of ascorbic acid oxidase, inhibiting the oxidation of ascorbic acid by oxidase, thereby increasing the ascorbic acid retention rate in litchi juice.

[0066] Table 3 Ascorbic acid retention rate (%)

[0067]

[0068]

[0069] 2. Research on extraction of litchi shell

[0070] 2.1 Sample preparation test method:

[0071] Extraction Example Preparation Method:

[0072] S1: The litchi shell is crushed and homogenized, and the crushed product is mixed with an ethanol solution having a volume concentration of 95% at a mass ratio of 1:10, reacted at 50° C. for 2 hours, and centrifuged to separate the supernatant and the precipitate.

[0073] S2: Repeat the precipitation in step S1 once according to step S1.

[0074] S3: Combine the supernatants, remove ethanol, and make the volume concentration of ethanol in the supernatant 5%; use XDA-7 resin to purify and concentrate the supernatant at 25°C, with a supernatant flow rate of 150 cm / hour; use 60% ethanol as eluent, with an elution flow rate of 100 cm / hour. After elution, obtain the extraction sample.

[0075] Preparation method of control example:

[0076] S1: The litchi shell is crushed and homogenized, and the crushed product is mixed with an ethanol solution having a volume concentration of 95% at a mass ratio of 1:10, reacted at 50° C. for 2 hours, and centrifuged to separate the supernatant and the precipitate.

[0077] S2: Repeat the precipitation in step S1 once according to step S1.

[0078] S3: Combine the supernatants and remove ethanol to make the volume concentration of ethanol in the supernatant 60%, and concentrate the sample to make the sample volume consistent with the final volume of the extraction example; obtain a control sample.

[0079] 2.2 Detection methods

[0080] Inhibitory rate method of matrix metalloproteinases:

[0081] Matrix metalloproteinases, which contain zinc ions in their center, can catalyze the degradation of skin connective tissue proteins. Under the influence of inflammation, ultraviolet rays, etc., matrix metalloproteinases are released from neutrophils or macrophages, catalyzing the degradation of skin connective tissue proteins and accelerating human skin aging. Matrix metalloproteinases can be used to evaluate the degree of skin aging.

[0082] Clostridium histolyticum collagenase (strain number ATCC19401) was used as an indicator protease for matrix metalloproteinases, and fluorescent chromium-labeled gelatin was used as a culture medium. The sample was mixed with gelatin culture medium (the mixing ratio is shown in Table 4), and the inhibitory effect of litchi shell extract on matrix metalloproteinases was studied on gelatin culture medium. The incubation time was 60 minutes, the incubation temperature was 20°C, and the substrate hydrolysis degree was monitored by 393nm fluorescence (excitation wavelength was 328nm). At the same time, gelatin culture medium without the addition of Clostridium histolyticum collagenase was used as a positive control, and the matrix metalloproteinase inhibition rate was calculated as sample test result / positive control test result × 100%.

[0083] The method for detecting the purity of proanthocyanidins is a prior art and will not be described in detail here.

[0084] 2.3 Test results and analysis

[0085] The purity of proanthocyanidins in the extraction example is significantly higher than that in the control example, indicating that the purity of proanthocyanidins in the lychee shell extract is improved by using the chromatography purification process of the present invention. Due to the improved purity of proanthocyanidins, the lychee shell extract effectively inhibits the hydrolysis of collagen by matrix metalloproteinases.

[0086] Table 4 Matrix metalloproteinase inhibition rate (%)

[0087]

[0088] 3. Sugar distribution study

[0089] 3.1 Sample preparation test method

[0090] The lychee shell was removed, and the lychee aril was divided into the outer 1 / 5, the middle 3 / 5, and the inner 1 / 5 according to thickness from the outside to the inside. The aril of the above three parts of 96 lychees of different varieties, batches, and sources were respectively taken for total sugar content testing. According to different varieties and sources of lychees, the thickness of the outer 1 / 5 of the aril ranged from 1mm to 3mm.

[0091] 3.2 Total sugar content determination method

[0092] Take 1g of aril and homogenize it with 5mL of distilled water, then centrifuge it in a 50℃ water bath for 30min, add 5mL of distilled water and repeat the extraction once, combine the supernatant and make it up to 50mL for testing. Use 3,5-dinitrosalicylic acid (DNS) to determine the total sugar content. Glucose is dried at 105℃ for 2h and prepared into a 1mg / mL solution as a standard curve to calculate the sugar content.

[0093] 3.3 Test results and analysis

[0094] The results of the measurement of total sugar content of 96 different varieties, batches and sources of litchi showed that the total sugar content of the outer 1 / 5 of the litchi aril was significantly higher than that of the other middle and inner parts. When processing litchi juice, different parts can be separated to prepare juice with different sugar contents to meet the needs of different groups of people.

[0095] Table 5 Total sugar content in different parts, n = 96

[0096] project External 1 / 5 Central 3 / 5 Internal 1 / 5 all Total sugar content (mass ratio) 25.6％±5.3％ 15.7％±4.4％ 12.2％±6.1％ 17.3±4.5％

[0097] Example 1

[0098] S1: After washing the litchi, peel the litchi shell to obtain the shelled litchi and litchi shell. The litchi shell is crushed and homogenized, and the crushed material is mixed with a 55% ethanol solution at a mass ratio of 1:10, reacted at 50°C for 2 hours, and the supernatant and precipitate are separated by centrifugation; the precipitate is mixed with a 55% ethanol solution at a mass ratio of 1:10, reacted at 50°C for 2 hours, and the supernatant and precipitate are separated by centrifugation. The supernatants are combined, and the ethanol in the supernatant is removed by reduced pressure evaporation to make the volume concentration of ethanol in the supernatant 2%. At 2°C, the supernatant is purified using XDA-7 resin at a supernatant flow rate of 150 cm / hour; 55% ethanol by volume is used as an eluent at an elution flow rate of 100 cm / hour, and the eluted product is collected and filtered to obtain a litchi shell extract.

[0099] S2: After shelling, the lychees include arils and lychee seeds; the arils are divided into a peripheral part and an inner core part, the thickness of the peripheral part is 1 mm, and the arils of the peripheral part are processed according to steps S4 to S6 to prepare high-sweet lychee juice.

[0100] S3: After shelling, the litchi is removed from the pit and the inner core of the aril is obtained;

[0101] S4: the inner core of the aril is squeezed to obtain litchi puree; the litchi shell extract of step S1 is mixed with the litchi puree in a volume ratio of 1:200.

[0102] S5: Filling the litchi puree with a mixed gas, wherein the mixed gas contains 10% oxygen, 50% carbon dioxide, and 40% nitrogen, and the ratio is a volume ratio, so that the oxygen content in the litchi puree is 3 mg / L and the carbon dioxide content is 100 mg / L, thereby obtaining aerated litchi puree.

[0103] S6: Packing the aerated lychee puree into airtight packaging containers, and filling the empty space in the packaging containers with the mixed gas in step S5 to obtain lychee juice.

[0104] Example 2

[0105] S1: After washing the litchi, peel the litchi shell to obtain the shelled litchi and litchi shell. The litchi shell is crushed and homogenized, and the crushed material is mixed with a 75% ethanol solution at a mass ratio of 1:12, reacted at 55°C for 3 hours, and the supernatant and precipitate are separated by centrifugation; the precipitate is mixed with a 75% ethanol solution at a mass ratio of 1:12, reacted at 55°C for 3 hours, and the supernatant and precipitate are separated by centrifugation. The supernatant is combined, and the ethanol in the supernatant is removed to make the volume concentration of ethanol in the supernatant 5%. At 15°C, the supernatant is purified using XDA-7 resin at a supernatant flow rate of 180 cm / hour; 58% ethanol is used as an eluent at an elution flow rate of 110 cm / hour, and the eluted product is collected. The ethanol content of the eluted product is reduced to make the volume concentration of ethanol in the eluted product 7%, and the litchi shell extract is obtained.

[0106] S2: After shelling, the lychees include arils and lychee pits. The arils are divided into an outer portion and an inner portion, the thickness of the outer portion is 2 mm, and the outer portion of the arils is processed according to steps S4 to S6 to prepare high-sweet lychee juice.

[0107] S3: After shelling, the litchi is removed from the pit and the inner core of the aril is obtained.

[0108] S4: The inner core of the aril is homogenized to obtain litchi puree. The litchi shell extract of step S1 is mixed with litchi puree in a volume ratio of 1:150.

[0109] S5: Filling the litchi puree with a mixed gas, wherein the mixed gas contains 13% oxygen, 55% carbon dioxide, and 32% nitrogen, and the ratio is a volume ratio, so that the oxygen content in the litchi puree is 5 mg / L and the carbon dioxide content is 200 mg / L, thereby obtaining aerated litchi puree.

[0110] S6: Packing the aerated lychee puree into airtight packaging containers, and filling the empty space in the packaging containers with the mixed gas in step S5 to obtain lychee juice.

[0111] Example 3

[0112] S1: After washing the litchi, peel the litchi shell to obtain the shelled litchi and litchi shell. The litchi shell is crushed and homogenized, and the crushed material is mixed with a 95% ethanol solution at a mass ratio of 1:15, reacted at 60°C for 4 hours, and the supernatant and precipitate are separated by centrifugation; the precipitate is mixed with a 95% ethanol solution at a mass ratio of 1:15, reacted at 60°C for 4 hours, and the supernatant and precipitate are separated by centrifugation. The supernatant is combined, and the ethanol in the supernatant is removed to make the volume concentration of ethanol in the supernatant 10%. At 25°C, the supernatant is purified using XDA-7 resin with a supernatant flow rate of 200 cm / hour; 60% ethanol by volume is used as an eluent with an elution flow rate of 120 cm / hour; the eluted product is collected and filtered to obtain a litchi shell extract.

[0113] S2: After shelling, the lychees include arils and lychee pits. The arils are divided into a peripheral part and an inner core part, the thickness of the peripheral part is 3 mm, and the peripheral part of the arils is processed according to steps S4 to S6 to prepare high-sweet lychee juice.

[0114] S3: After shelling, the litchi is removed from the pit and the inner core of the aril is obtained.

[0115] S4: the inner core of the aril is homogenized and filtered to obtain litchi puree; the litchi shell extract of step S1 is mixed with the litchi puree in a volume ratio of 1:100.

[0116] S5: Filling the litchi puree with a mixed gas, wherein the mixed gas contains 15% oxygen, 60% carbon dioxide, and 25% nitrogen, and the ratio is a volume ratio, so that the oxygen content in the litchi puree is 8 mg / L and the carbon dioxide content is 300 mg / L, thereby obtaining aerated litchi puree.

[0117] S6: Packing the aerated lychee puree into airtight packaging containers, and filling the empty space in the packaging containers with the mixed gas in step S5 to obtain lychee juice.

[0118] The comparative example adopts the existing technology, and its main process is as follows:

[0119] S1: washing litchis, peeling litchi shells, and obtaining shelled litchis and litchi shells.

[0120] S2: After shelling, the lychee includes the aril and the lychee seed.

[0121] S3: After shelling, the litchi is removed from the pit and the aril is obtained.

[0122] S4: The aril is squeezed to obtain litchi pulp.

[0123] S5: Packing the lychee pulp into airtight packaging containers to obtain lychee juice.

[0124] According to the above process, three comparative examples of lychee juice were prepared and compared with the examples.

[0125] The total sugar content of the high-sweet lychee juice and lychee juice prepared in Examples 1, 2 and 3, and the lychee juice prepared in Comparative Examples 1, 2 and 3 were measured, and the matrix metalloproteinase inhibition rate, ascorbic acid retention rate, and microbial inhibition were evaluated. The determination and evaluation methods were consistent with those in the previous research process.

[0126] The results show that the matrix metalloproteinase inhibition rate of the lychee juice prepared according to the technical solution of the present invention is significantly higher than that of the control example, and the total sugar content is significantly lower than that of the control example. The total sugar content of the high-sweet lychee juice is significantly increased, which can meet the needs of people with higher sweetness requirements.

[0127] After 8 weeks of storage, the total number of microbial colonies in litchi juice was significantly lower than that in the control group, and the ascorbic acid retention rate was significantly higher than that in the control group.

[0128] Table 6 Comparative analysis of examples and comparative examples

[0129]

[0130]

Claims

1. A method for processing high-quality lychee juice, characterized in that: The following steps are involved: S1: After washing the litchi, the litchi shell is removed to obtain the shelled litchi and the litchi shell; S2: The shelled litchi includes the aril and the litchi core; the aril of the shelled litchi is divided into an outer part and an inner part, and the thickness of the outer part is 1 mm to 3 mm; S3: After shelling, the litchi is removed from the pit and the inner core of the aril is obtained; S4: the inner core of the aril is processed to obtain litchi puree; S5: injecting gas into the litchi puree to make the oxygen content in the litchi puree be 3 mg / L to 8 mg / L and the carbon dioxide content be 100 mg / L to 300 mg / L, thereby obtaining aerated litchi puree; S6: Packing the aerated lychee pulp into a packaging container to obtain low-sugar lychee juice; the packaging container is an airtight container; The litchi shell is crushed and homogenized, the crushed material is mixed with an ethanol solution with a volume concentration of 55% to 95% in a mass ratio of 1:10 to 1:15, the mixture is reacted at 50°C to 60°C for 2 to 4 hours, and the supernatant and the precipitate are separated by centrifugation; the precipitate is mixed with an ethanol solution with a volume concentration of 55% to 95% in a mass ratio of 1:10 to 1:15, the mixture is reacted at 50°C to 60°C for 2 to 4 hours, and the supernatant and the precipitate are separated by centrifugation; the supernatant is combined, and ethanol in the supernatant is removed so that the volume concentration of ethanol in the supernatant is not higher than 10%; the supernatant is purified using XDA-7 resin at a temperature of 2°C to 25°C, and the supernatant flow rate is 150 cm / hour to 200 cm / hour; 55% to 60% ethanol by volume is used as an eluent, and the elution flow rate is 100 cm / hour to 120 cm / hour; collecting and filtering the eluted product to obtain a litchi shell extract; mixing the litchi shell extract with the litchi puree of step S4, with the volume ratio of the litchi shell extract to the litchi puree being 1:200 to 1:

100.

2. The method for processing lychee juice according to claim 1, characterized in that: The gas charged into the litchi puree in step S5 is a mixed gas, which contains 10% to 15% oxygen, 50% to 60% carbon dioxide, and the remainder is nitrogen or an inert gas, and the ratio is a volume ratio.

3. The method for processing lychee juice according to claim 2, characterized in that: After the aerated lychee puree is dispensed into the packaging container in step S6, the empty space in the packaging container is filled with the mixed gas and maintained at a constant pressure.

4. The method for processing lychee juice according to claim 3, characterized in that: The processing in step S4 includes pressing, homogenization, filtration and sterilization.

5. A high-quality lychee juice, characterized in that: The high-quality lychee juice is prepared by the processing method described in claim 1.

6. The method for processing lychee juice according to claim 1, characterized in that: The peripheral part of the aril is processed according to steps S4 to S6 to prepare high-sweetness lychee juice.

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