A kind of preparation method of pineapple juice

Abstract

The present invention provides a method for preparing pineapple juice. First, a deaminase is used to convert adenosine to inosine, improving the juice flavor. Simultaneously, the concentration and enzyme treatment steps are combined into one, increasing the efficiency of pineapple juice preparation. Second, methanol is used to extract pineapple peel polyphenols, enhancing the antioxidant properties of each polyphenol unit. Chromatographic purification of pineapple peel polysaccharides also enhances the antioxidant properties of each polysaccharide unit, effectively utilizing the pineapple peel and increasing the added value and utilization rate of plant resources.

Description

Technical Field

[0001] The present invention relates to the technical field of food and beverages, and in particular to a method for preparing pineapple juice. Background Art

[0002] Pineapple, also known as pineapple, is a tropical fruit widely cultivated in tropical coastal areas of southern and southeastern my country. It is one of the four famous fruits of Lingnan and is rich in nutrients such as dietary fiber, sugars, phenolic compounds, protein, vitamins, and minerals. In recent years, pineapple juice has become popular among consumers due to its nutritional value, freshness, convenience, and unique flavor. However, current methods for preparing pineapple juice still have the following problems:

[0003] First, to facilitate storage and transportation, a concentration step is usually added to reduce the volume of pineapple juice. To increase juice yield, an enzymatic hydrolysis step is usually added to hydrolyze pectin. The additional processing steps increase production costs and time.

[0004] Secondly, pineapple peels have a hard trough, generating a significant amount of peel waste during the production and processing of pineapple juice. However, pineapple peels contain numerous substances beneficial to human health, such as proteases, cellulose, polyphenols, and polysaccharides. Current research on pineapple peel residue focuses primarily on extracting industrial raw materials, such as proteases and separating cellulose and hemicellulose; and fermentation, primarily on producing alcohol and developing acetic acid beverages. However, the active substances in the peel, such as polyphenols and polysaccharides, are not effectively utilized, resulting in waste of resources and environmental pollution.

[0005] Therefore, it is necessary to develop a pineapple juice preparation method that can effectively utilize pineapple peel and has a two-in-one concentration and enzymatic hydrolysis process, so as to increase the added value and utilization rate of plant resources and improve production efficiency. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a method for preparing pineapple juice, comprising the following steps:

[0007] Step S1: After washing the pineapple, separate the pineapple pulp A and the pineapple peel B;

[0008] Step S2: homogenizing the pineapple pulp A to obtain pineapple pulp C;

[0009] Step S3: centrifuging the pineapple puree C to obtain a precipitate D and a supernatant E;

[0010] Step S4: Supernatant E is subjected to FRACTOGEL EMD TMAE anion chromatography, and flow-through F is collected to remove organic acids; kojic acid is added to flow-through F to replace the organic acids with kojic acid to obtain juice G; deaminase is added to juice G, and juice G is concentrated simultaneously under the same concentration conditions as the deaminase reaction conditions; after the enzyme reaction and concentration are completed simultaneously, juice H is obtained;

[0011] Step S5: After homogenizing the pineapple peel B, extracting it with methanol at 60° C. to 80° C. for 5 to 8 hours, and centrifuging it at 5,000×g to 10,000×g for 15 to 25 minutes to obtain a precipitate I and a supernatant J. The precipitate I is the primary extract of peel polysaccharides, and the supernatant J is the primary extract of peel polyphenols;

[0012] Step S6: The supernatant J is precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorized with activated carbon. 95% to 100% ethanol by volume is added to adjust the ethanol concentration in the solution to 80% to 90% by volume. The solution is precipitated at 4° C. to 8° C. for 2 to 4 days, and then centrifuged at 5,000×g to 10,000×g for 15 to 25 minutes to obtain a precipitate K and a supernatant. Purified water is used as a dialyzate, and the supernatant is ultrafiltered to remove impurities such as methanol, ethanol, trichloroacetic acid, and n-butanol to obtain a solution L. Solution L is a refined product of peel polyphenols.

[0013] Step S7: combining precipitate I and precipitate K, dissolving them in purified water, precipitating them with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorizing them with activated carbon to obtain solution M; loading solution M onto DEAE-52 chromatography medium, washing, and first eluting with a 0.1 mol / L to 0.2 mol / L sodium chloride solution; then eluting with a 0.2 mol / L to 0.4 mol / L sodium chloride solution, collecting the eluted product, and the eluted product having a weight-average molecular weight of 1900 kDa to 3100 kDa; using purified water as a dialysate, ultrafiltrating the eluted product to remove sodium chloride, and obtaining a refined product of peel polysaccharide;

[0014] Step S8: adding the refined polyphenol product and the refined polysaccharide product of the peel to the juice H to obtain juice N;

[0015] Step S9: The juice N is sterilized and packaged to produce pineapple juice.

[0016] In step S3, the pineapple puree contains a large amount of insoluble matter, which is pre-treated by centrifugation to remove suspended solids to avoid clogging of the chromatography medium during the chromatography process.

[0017] The sugars and cations in pineapple puree cannot bind to anionic chromatography media. Organic acids, however, carry a negative charge in solution and are adsorbed by the media, thereby being removed. Gallic acid imparts flavor to pineapple juice, but excessive gallic acid in pineapple can lead to a poor flavor. This invention utilizes anionic chromatography technology to rationally control the gallic acid content in juice, resulting in a more optimal flavor.

[0018] Kojic acid is a food additive. It is used to replace the removed organic acids, increase the acidity and inhibit the growth of microorganisms. Kojic acid is also an inhibitor of polyphenol oxidase, which improves the antioxidant properties of fruit juice.

[0019] Pineapple juice contains adenosine, but its ability to impart flavor is poor. Inosinic acid (IMP), an important flavoring substance in food, can be converted from adenosine. The present invention uses deaminase to convert adenosine into inosinic acid, enhancing the flavor of the juice.

[0020] The present invention combines the concentration step and the enzyme treatment step into one, thereby improving the efficiency of pineapple juice production. The parameters of the concentration step can meet the optimal conditions for the enzyme. The optimal conditions for deaminase are a temperature of 50°C to 75°C and a pH of 3.0 to 5.0.

[0021] As a preferred embodiment, in the concentration step, the concentration temperature is 50° C. to 75° C.; the pH range is 3.0 to 5.0; the concentration time is 30 minutes to 180 minutes; and the vacuum degree is 0.5 bar to 1.0 bar.

[0022] Using methanol to extract pineapple peel polyphenols can increase the scavenging rate of ABTS free radicals per unit polyphenol and improve the antioxidant properties of polyphenols.

[0023] Solution M is loaded onto a DEAE-52 chromatography medium. After washing, it is first eluted with a 0.1-0.2 mol / L sodium chloride solution to remove polyphenols with poor antioxidant properties. Elution is then performed with a 0.2-0.4 mol / L sodium chloride solution, and the eluate is collected to obtain a refined polysaccharide with a weight-average molecular weight of 1900 kDa to 3100 kDa. This step-by-step elution method can purify and separate polysaccharides with a weight-average molecular weight of 1900 kDa to 3100 kDa, increase the scavenging rate of ABTS free radicals per unit polyphenol, and enhance the antioxidant properties of the polyphenols.

[0024] As a preferred embodiment, in step S7, the refined polysaccharide product is further purified by Sephadex G-100 column chromatography, and the second peak at OD490nm absorption is collected. This can further improve the homogeneity of the polysaccharide, increase the scavenging rate of ABTS free radicals per unit polyphenol, and enhance the antioxidant properties of the polyphenol.

[0025] Through the above technical solutions, the present invention produces the following technical effects:

[0026] (1) Through the action of deaminase, adenosine is converted into inosine, thereby improving the flavor of the juice.

[0027] (2) The concentration step and the enzyme treatment step are combined into one, thereby improving the preparation efficiency of pineapple juice.

[0028] (3) Use methanol to extract pineapple peel polyphenols to improve the antioxidant properties of each polyphenol.

[0029] (4) Purify pineapple peel polysaccharides by chromatography to improve the antioxidant properties of each unit polysaccharide.

[0030] (5) Effectively utilize pineapple peels to increase the added value and utilization rate of plant resources. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, 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.

[0032] Specific research process:

[0033] 1. Study on the extraction of polyphenols from pineapple peel

[0034] 1.1 Sample preparation test method

[0035] Preparation of Test Sample 1: 10 g of pineapple peel was homogenized and extracted with purified water at 60°C for 5 hours. The extract was centrifuged at 5000 g for 15 minutes. The supernatant was precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins. The extract was then decolorized with activated carbon and centrifuged at 5000 g for 15 minutes. The supernatant was removed and 95% ethanol was added to a concentration of 80%. The extract was then precipitated at 4°C for 2 days and centrifuged again at 5000 g for 15 minutes. The supernatant was removed and the polyphenol concentration was adjusted to 2 g / L to prepare Test Sample 1.

[0036] Preparation of Test Sample 2: 10 g of pineapple peel was homogenized and extracted with ethyl acetate at 60°C for 5 hours. The extract was centrifuged at 5000 g for 15 minutes. The supernatant was precipitated with trichloroacetic acid-n-butanol solution to remove impurity proteins. The extract was then decolorized with activated carbon and centrifuged at 5000 g for 15 minutes. The supernatant was removed and 95% ethanol was added to a concentration of 80%. The extract was then precipitated at 4°C for 2 days and centrifuged again at 5000 g for 15 minutes. The supernatant was removed and the polyphenol concentration was adjusted to 2 g / L to prepare Test Sample 2.

[0037] Preparation of Test Sample 3: 10 g of pineapple peel was homogenized and extracted with methanol at 60°C for 5 hours. The extract was centrifuged at 5000 g for 15 minutes. The supernatant was precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins. The extract was then decolorized with activated carbon and centrifuged at 5000 g for 15 minutes. The supernatant was removed and 95% ethanol was added to a concentration of 80%. The extract was then precipitated at 4°C for 2 days and centrifuged at 5000 g for 15 minutes. The supernatant was removed and the polyphenol concentration was adjusted to 2 g / L to prepare Test Sample 3.

[0038] Preparation of Test Sample 4: 10 g of pineapple pulp was homogenized and extracted with methanol at 60°C for 5 hours. The pulp was centrifuged at 5000 g for 15 minutes, and the supernatant was precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins. The pulp was then decolorized with activated carbon and centrifuged at 5000 g for 15 minutes. The supernatant was removed, 95% ethanol was added to a concentration of 80%, and the pulp was precipitated at 4°C for 2 days. The pulp was then centrifuged at 5000 g for 15 minutes. The supernatant was removed and the polyphenol concentration was adjusted to 2 g / L to prepare Test Sample 4.

[0039] 1.2 Detection method

[0040] The antioxidant capacity of polyphenols was evaluated using the 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical scavenging rate, following the method of Miller NJ (1996). The ABTS free radical scavenging principle utilizes the redox reaction ability of the ABTS molecule to evaluate the free radical scavenging ability of antioxidants. When ABTS free radicals excite electrons to a high-energy state, they emit blue fluorescence. However, when a free radical-scavenging antioxidant interacts with ABTS, a chemical reaction occurs, trapping electrons and reducing them to inactive ABTS molecules, thereby weakening or eliminating the blue fluorescence. The stronger the free radical scavenging ability of the antioxidant, the faster the ABTS reduction rate, which is reflected in a greater decrease in fluorescence intensity.

[0041] According to the phenolic compound detection method of F Shahidi (1995), the mass percentage content of o-dihydroxyphenol compounds in total phenols was determined.

[0042] 1.3 Test results and analysis

[0043] The test results of ABTS free radical scavenging rate and mass percentage of ortho / para dihydroxyphenol compounds in total phenols are shown in the table below.

[0044] Polyphenols extracted using methanol showed the highest ABTS free radical scavenging rate, followed by ethyl acetate, and the lowest by purified water. The order of polarity, from highest to lowest, was purified water, methanol, and ethyl acetate. Polyphenols extracted using highly polar water and less polar ethyl acetate showed poor ABTS free radical scavenging rates. Polyphenols extracted using methanol, which has a moderate polarity, showed a higher ABTS free radical scavenging rate, demonstrating superior antioxidant activity.

[0045] Further analysis of the test samples revealed that the content of ortho- and para-dihydroxyphenolic compounds in the peel extract (Test Sample 3) was significantly higher than that in the pulp extract (Test Sample 4). This characteristic contributes to the stronger antioxidant properties of the polyphenolic compounds in the peel extract compared to those in the pulp extract. Based on the same principle, when methanol was used for extraction, the content of ortho- and para-dihydroxyphenolic compounds in Test Sample 3 was significantly higher than in Test Samples 1 and 2, thereby enhancing the antioxidant properties of the polyphenolic compounds per unit.

[0046] Table 1 Polyphenol extraction test results

[0047]

[0048] 2. Purification of polysaccharide primary extract using DEAE-52 chromatography medium

[0049] 2.1 Sample preparation test method

[0050] 10 g of pineapple peel was homogenized and extracted with methanol at 60°C for 5 hours. The precipitate was then centrifuged at 5000 g for 15 minutes to obtain the primary polysaccharide extract. The primary polysaccharide extract was dissolved in purified water and precipitated with trichloroacetic acid n-butanol solution to remove protein impurities. The solution was then decolorized with activated carbon to obtain solution M. Solution M was loaded onto DEAE-52 chromatography medium. After washing, the solution was first eluted with 0.1 mol / L NaCl solution to obtain test sample 1; then with 0.2 mol / L NaCl solution to obtain test sample 2; then with 0.4 mol / L NaCl solution to obtain test sample 3; and finally, with 0.8 mol / L NaCl solution to obtain test sample 4.

[0051] 2.2 Detection method

[0052] The polysaccharide content of samples 1 to 4 was adjusted to 5 g / L, and the antioxidant capacity of the polysaccharides was evaluated using the scavenging rate of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radicals. The assay method was consistent with the previous study.

[0053] High performance liquid chromatography (HPLC) was used to determine the weight average molecular weight of test samples 1 to 4, calculate PDI, and analyze the molecular weight distribution of polysaccharides. The high performance liquid chromatograph was an Agilent 1100 series, equipped with a refractive index detector and a TSK-GelG3000 chromatographic column (7.8×300 mm, Tokyo Tosoh Co., Ltd.). At 25°C, a flow rate of 0.8 ml / min was used. The column was calibrated with standard dextran to establish a standard curve. PDI, or molecular weight distribution index, is a parameter that describes the width of the molecular weight distribution of a polymer. It is usually defined as the ratio of the weight average molecular weight (Mw) to the average molecular weight (Mn), that is, PDI = Mw / Mn. If PDI is close to 1, it means that the molecular weight distribution is narrow and the molecular weights are close; if Mw / Mn is far from 1, it means that the molecular weight distribution is wide and the molecular weight difference is large.

[0054] 2.3 Test results and analysis

[0055] The test results are shown in the table below.

[0056] When 0.4 mol / L sodium chloride was used as the eluent, the purified polysaccharide had the highest scavenging rate for ABTS free radicals, followed by 0.2 mol / L sodium chloride, then 0.8 mol / L sodium chloride, and the worst was 0.1 mol / L sodium chloride.

[0057] Further testing of the test samples revealed that the polysaccharide molecular weight in test sample 1 was the lowest, and the polysaccharide molecular weight in test sample 4 was the highest, and the antioxidant effects of the two were relatively poor; the weight-average molecular weight of the polysaccharides in test samples 2 and 3 was 1900kDa~3100kDa, and their antioxidant effects were stronger.

[0058] Therefore, the eluent is preferably 0.2 mol / L to 0.4 mol / L sodium chloride. Under this condition, the weight-average molecular weight of the purified polysaccharide is 1900 kDa to 3100 kDa, the scavenging rate of ABTS free radicals is high, and it has a good antioxidant effect, which can improve the antioxidant performance of unit polysaccharide.

[0059] Table 2 DEAE-52 chromatography medium purification test results

[0060]

[0061] 3. Purification of polysaccharides using Sephadex G-100 column

[0062] 3.1 Sample preparation test method

[0063] Preparation of experimental sample 1: Take 10g of pineapple peel, homogenize it, extract it with methanol at 60℃ for 5 hours, and centrifuge it at 5000g for 15 minutes to obtain a precipitate, which is the primary polysaccharide extract. The primary polysaccharide extract is dissolved in purified water, precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorized with activated carbon to obtain solution M. Solution M is loaded onto DEAE-52 chromatography medium, washed, and first eluted with 0.2mol / L NaCl solution; then, eluted with 0.4mol / L NaCl solution to obtain the refined polysaccharide. The refined polysaccharide is purified by Sephadex G-100 column (2.6×60cm), and three OD490nm absorption peaks are obtained in chronological order. Samples of the first peak, the second peak, and the third peak are collected respectively.

[0064] 3.2 Detection method

[0065] The polysaccharide content of the first, second, and third peak samples was adjusted to 5 g / L, and the antioxidant capacity of the polysaccharides was evaluated by scavenging 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radicals. The assay method was consistent with the previous study.

[0066] High-performance liquid chromatography (HPLC) was used to determine the weight-average molecular weight of the first, second, and third peak samples, calculate the PDI, and analyze the polysaccharide molecular weight distribution. The determination method was consistent with the previous study.

[0067] 3.3 Test results and analysis

[0068] The test results are shown in the table below.

[0069] The scavenging rate of ABTS free radicals by the polysaccharide in the second peak was the highest, followed by that in the first peak, and the third peak was the worst.

[0070] Further testing of the test samples revealed that the molecular weight of the polysaccharide in peak 1 was the lowest, and the molecular weight of the polysaccharide in peak 3 was the highest, and the antioxidant effects of the two were relatively poor; the weight-average molecular weight of the polysaccharide in peak 2 was 3100 kDa, and the PDI was 1.1, and its antioxidant effect was the strongest.

[0071] Therefore, the second peak was collected after purification by Sephadex G-100 column. Under this condition, the weight-average molecular weight of the polysaccharide was 3100 kDa, the PDI was 1.1, the antioxidant performance of the unit polysaccharide was high, the scavenging rate of ABTS free radicals was high, and it had a good antioxidant effect.

[0072] Table 3 Sephadex G-100 column purification test results

[0073]

[0074] Example 1

[0075] S1: After washing the pineapple, separate the pineapple pulp A and the pineapple peel B;

[0076] S2: homogenizing pineapple pulp A to obtain pineapple pulp C;

[0077] S3: centrifuge pineapple puree C to obtain precipitate D and supernatant E;

[0078] S4: Supernatant E is subjected to FRACTOGEL EMD TMAE anion chromatography to collect flow-through F; kojic acid is added to flow-through F to adjust the pH of the juice to 3.0, thereby obtaining juice G; deaminase is added to juice G to achieve a deaminase concentration of 1% by mass in juice G; juice G is simultaneously concentrated at a temperature of 50°C, a pH of 3.0, a concentration time of 30 minutes, and a vacuum of 0.5 bar; upon simultaneous completion of the enzyme reaction and concentration, juice H is obtained;

[0079] S5: After homogenizing pineapple peel B, extract it with methanol at 60°C for 5 hours and centrifuge it at 5000×g for 15 minutes to obtain precipitate I and supernatant J. Precipitate I is the primary extract of peel polysaccharides; supernatant J is the primary extract of peel polyphenols.

[0080] S6: Supernatant J was precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins, then decolorized with activated carbon, and 95% ethanol was added to bring the ethanol concentration in the solution to 80%. The solution was precipitated at 4°C for 2 days and then centrifuged at 5000×g for 15 minutes to obtain precipitate K and supernatant. Purified water was used as the dialyzate, and the supernatant was ultrafiltered to remove impurities such as methanol, ethanol, trichloroacetic acid, and n-butanol to obtain solution L. The main component of precipitate K is polysaccharide; solution L is a refined product of peel polyphenols.

[0081] S7: Combine precipitate I and precipitate K, dissolve in purified water, precipitate with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorize with activated carbon to obtain solution M; load solution M onto DEAE-52 chromatography medium, wash, and first elute with 0.1 mol / L sodium chloride solution; then elute with 0.2 mol / L sodium chloride solution, purify the eluted product with Sephadex G-100 column, and collect the second peak at OD490nm absorption peak; the second peak is the refined product of peel polysaccharide;

[0082] S8: adding the refined polyphenol product and the refined polysaccharide product of the peel to juice H to increase the polyphenol content of juice H by 1 g / L and the polysaccharide content by 3 g / L, thereby obtaining juice N;

[0083] S9: Juice N is sterilized at 100°C for 1 minute and packaged to make pineapple juice.

[0084] Example 2

[0085] S1: After washing the pineapple, separate the pineapple pulp A and the pineapple peel B;

[0086] S2: homogenizing pineapple pulp A to obtain pineapple pulp C;

[0087] S3: centrifuge pineapple puree C to obtain precipitate D and supernatant E;

[0088] S4: Supernatant E is subjected to FRACTOGEL EMD TMAE anion chromatography to collect flow-through F; kojic acid is added to flow-through F to adjust the pH of the juice to 4.0, thereby obtaining juice G; deaminase is added to juice G to achieve a deaminase concentration of 1% by mass in juice G; juice G is simultaneously concentrated at a temperature of 60°C, a pH of 4.0, a concentration time of 100 minutes, and a vacuum of 0.8 bar; after simultaneous completion of the enzyme reaction and concentration, juice H is obtained;

[0089] S5: After homogenizing pineapple peel B, extract it with methanol at 70°C for 6 hours and centrifuge it at 7000×g for 20 minutes to obtain precipitate I and supernatant J. Precipitate I is the primary extract of peel polysaccharides; supernatant J is the primary extract of peel polyphenols.

[0090] S6: Supernatant J was precipitated with trichloroacetic acid and n-butanol solution to remove impurity proteins, and then decolorized with activated carbon. 98% ethanol was added to bring the ethanol concentration in the solution to 85% by volume. The solution was precipitated at 6°C for 3 days and then centrifuged at 7000×g for 20 minutes to obtain precipitate K and supernatant. Purified water was used as the dialysate, and the supernatant was ultrafiltered to remove impurities such as methanol, ethanol, trichloroacetic acid, and n-butanol to obtain solution L. The main component of precipitate K was polysaccharide; solution L was a refined product of peel polyphenols.

[0091] S7: Precipitate I and Precipitate K are combined, dissolved in purified water, precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorized with activated carbon to obtain solution M; solution M is loaded onto DEAE-52 chromatography medium, washed, and first eluted with 0.15 mol / L sodium chloride solution; then eluted with 0.3 mol / L sodium chloride solution, and the eluted product is purified by Sephadex G-100 column, and the second peak at OD490 nm absorption peak is collected; the second peak is the refined polysaccharide;

[0092] S8: adding the refined polyphenol product and the refined polysaccharide product of the peel to juice H to increase the polyphenol content of juice H by 2 g / L and the polysaccharide content by 5 g / L, thereby obtaining juice N;

[0093] S9: Juice N is sterilized at 100°C for 1 minute and packaged to make pineapple juice.

[0094] Example 3

[0095] S1: After washing the pineapple, separate the pineapple pulp A and the pineapple peel B;

[0096] S2: homogenizing pineapple pulp A to obtain pineapple pulp C;

[0097] S3: centrifuge pineapple puree C to obtain precipitate D and supernatant E;

[0098] S4: Supernatant E is subjected to FRACTOGEL EMD TMAE anion chromatography to collect flow-through F; kojic acid is added to flow-through F to adjust the pH of the juice to 5.0 to obtain juice G; deaminase is added to juice G to achieve a mass fraction of deaminase in juice G of 1%; juice G is simultaneously concentrated at a temperature of 75°C, a pH range of 5.0, a concentration time of 180 minutes, and a vacuum degree of 0.1 bar; after simultaneous completion of the enzyme reaction and concentration, juice H is obtained;

[0099] S5: After homogenizing pineapple peel B, extract it with methanol at 80°C for 8 hours and centrifuge it at 10,000 × g for 25 minutes to obtain precipitate I and supernatant J. Precipitate I is the primary extract of peel polysaccharides; supernatant J is the primary extract of peel polyphenols.

[0100] S6: Supernatant J was precipitated with trichloroacetic acid and n-butanol solution to remove impurity proteins, and then decolorized with activated carbon. 100% ethanol was added to bring the ethanol concentration in the solution to 90% by volume. The solution was precipitated at 8°C for 4 days and then centrifuged at 10,000 × g for 25 minutes to obtain precipitate K and supernatant. Purified water was used as the dialyzate, and the supernatant was ultrafiltered to remove impurities such as methanol, ethanol, trichloroacetic acid, and n-butanol to obtain solution L. The main component of precipitate K was polysaccharide; solution L was a refined product of peel polyphenols.

[0101] S7: Combine precipitate I and precipitate K, dissolve in purified water, precipitate with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorize with activated carbon to obtain solution M; load solution M onto DEAE-52 chromatography medium, wash, and first elute with 0.2 mol / L sodium chloride solution; then elute with 0.4 mol / L sodium chloride solution, purify the eluted product with Sephadex G-100 column, and collect the second peak at OD490nm absorption peak; the second peak is the refined product of peel polysaccharide;

[0102] S8: adding the refined polyphenol product and the refined polysaccharide product of the peel to juice H to increase the polyphenol content of juice H by 3 g / L and the polysaccharide content by 10 g / L, thereby obtaining juice N;

[0103] S9: Juice N is sterilized at 100°C for 1 minute and packaged to make pineapple juice.

[0104] Comparative Example 1

[0105] The supernatant E was concentrated, sterilized at 100°C for 1 minute, and packaged to produce pineapple juice. The concentration temperature was 50°C, the concentration time was 30 minutes, and the vacuum degree was 0.5 bar.

[0106] Comparative Example 2

[0107] The supernatant E was concentrated, sterilized at 100°C for 1 minute, and packaged to produce pineapple juice. The concentration temperature was 60°C, the concentration time was 100 minutes, and the vacuum degree was 0.8 bar.

[0108] Comparative Example 3

[0109] The supernatant E was concentrated, sterilized at 100°C for 1 minute, and packaged to produce pineapple juice. The concentration temperature was 75°C, the concentration time was 180 minutes, and the vacuum degree was 1.0 bar.

[0110] The antioxidant capacity of the pineapple juices prepared in Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3 was evaluated using the scavenging rate of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS). The assay method was consistent with the previous study.

[0111] The results show that since the embodiment of the present invention adds refined pineapple peel polyphenols and refined polysaccharides, the ABTS free radical scavenging rate is significantly higher than that of the comparative example, and the pineapple juice prepared according to the technical solution of the present invention has stronger antioxidant properties.

[0112] Table 4 ABTS free radical scavenging rate results of Examples and Comparative Examples

[0113] Classification ABTS free radical scavenging rate Example 1 96％ Example 2 98％ Example 3 99％ Comparative Example 1 40％ Comparative Example 2 41％ Comparative Example 3 41％ .

Claims

1. A method for preparing pineapple juice, characterized in that, The following steps are involved: Step S1: After washing the pineapple, separate the pineapple pulp A and the pineapple peel B; Step S2: homogenizing the pineapple pulp A to obtain pineapple pulp C; Step S3: centrifuging the pineapple puree C to obtain a precipitate D and a supernatant E; Step S4: Supernatant E is subjected to FRACTOGEL EMD TMAE anion chromatography, and flow-through F is collected to remove organic acids; kojic acid is added to flow-through F to replace the organic acids with kojic acid to obtain juice G; deaminase is added to juice G, and juice G is concentrated simultaneously under the same concentration conditions as the deaminase reaction conditions; after the enzyme reaction and concentration are completed simultaneously, juice H is obtained; Step S5: After homogenizing the pineapple peel B, extracting it with methanol at 60° C. to 80° C. for 5 to 8 hours, and centrifuging it at 5,000×g to 10,000×g for 15 to 25 minutes to obtain a precipitate I and a supernatant J. The precipitate I is the primary extract of peel polysaccharides, and the supernatant J is the primary extract of peel polyphenols; Step S6: The supernatant J is precipitated with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorized with activated carbon. 95% to 100% ethanol by volume is added to adjust the ethanol concentration in the solution to 80% to 90%. The solution is precipitated at 4° C. to 8° C. for 2 to 4 days, and then centrifuged at 5000×g to 10000×g for 15 to 25 minutes to obtain a precipitate K and a supernatant. Purified water is used as a dialyzate, and the supernatant is ultrafiltered to remove impurities such as methanol, ethanol, trichloroacetic acid, and n-butanol to obtain a solution L, which is a refined product of peel polyphenols. Step S7: combining precipitate I and precipitate K, dissolving them in purified water, precipitating them with trichloroacetic acid n-butanol solution to remove impurity proteins, and then decolorizing them with activated carbon to obtain solution M; After loading the solution M onto a DEAE-52 chromatography medium and washing, the solution was first eluted with a 0.1 mol / L to 0.2 mol / L sodium chloride solution; then eluted with a 0.2 mol / L to 0.4 mol / L sodium chloride solution, and the eluted product was collected; the eluted product had a weight-average molecular weight of 1900 kDa to 3100 kDa; purified water was used as a dialysate to ultrafilter the eluted product to remove sodium chloride; the product was then purified on a Sephadex G-100 column, and the second peak at the OD490 nm absorption peak was collected to obtain a refined product of the peel polysaccharide; Step S8: adding the refined polyphenol product and the refined polysaccharide product of the peel to the juice H to obtain juice N; Step S9: The juice N is sterilized and packaged to prepare pineapple juice; the pineapple juice contains peel polyphenols with a mass percentage of ortho- and para-dihydroxyphenol compounds in the total phenols of 30%; the pineapple juice contains peel polysaccharides with a weight-average molecular weight of 3100 kDa and a PDI of 1.

1.

2. The preparation method according to claim 1, characterized in that The deaminase enzyme reaction temperature is 50° C. to 75° C., and the pH value is 3.0 to 5.

0.

3. The preparation method according to claim 1, characterized in that In step S4, the concentration conditions are: concentration temperature 50°C to 75°C; pH value 3.0 to 5.0; concentration time 30 minutes to 180 minutes; vacuum degree 0.5 bar to 1.0 bar.

4. The preparation method according to claim 3, characterized in that In step S9, the sterilization temperature is 100° C. and the sterilization time is 1 minute.

5. The preparation method according to claim 4, characterized in that In step S4, the mass fraction of the deaminase in the juice G is 1%.

6. The preparation method according to claim 5, characterized in that In step S8, after the refined peel polysaccharide is added, the polysaccharide concentration in the juice H increases by 3 g / L to 10 g / L.

7. The preparation method according to claim 6, characterized in that In step S8, after the refined peel polyphenol product is added, the polyphenol concentration in the juice H increases by 1 g / L to 3 g / L.

8. A pineapple juice, characterized in that The pineapple juice is prepared by any one of the methods described in claims 1 to 7.

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