A method for preparing Momordica grosvenori concentrated juice

Abstract

The present invention discloses a preparation method of Momordica grosvenori concentrated juice, belonging to the technical field of food processing, which comprises the following steps: S1: The freshly picked Momordica grosvenori is ripened using wheat bran as a ripening medium; S2: The ripened Momordica grosvenori is soaked in hot water containing calcium chloride and then washed with clean water; S3: The processed Momordica grosvenori is crushed by pressing and then subjected to freeze-thaw treatment; S4: Hot water extraction is carried out, and after extraction is completed, a crude extract of Momordica grosvenori is obtained by filtration; S5: The crude extract is treated with immobilized enzyme and coarsely filtered; S6: Filtration is carried out using an ultrafiltration membrane, and the filtrate is subjected to vacuum concentration; S7: After concentration, high-temperature sterilization is carried out to obtain Momordica grosvenori concentrated juice. The present invention uses wheat bran as a ripening medium, and by utilizing calcium chloride and enzymatic hydrolysis, it can promote the yellow ripening of Momordica grosvenori, reduce the bitter taste in the concentrated juice, and retain the flavor of Momordica grosvenori.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and specifically relates to a method for preparing Siraitia grosvenorii concentrated juice. Background Art

[0002] Siraitia grosvenorii is a plant fruit with both medicinal and edible properties, containing rich sweet components and various pharmacological active substances, and is widely used in the food, medicine, and health product industries. The main sweet components in Siraitia grosvenorii are a class of saponins with cucurbitane triterpene mogrosol as the aglycone. Among these saponins, there are sweet saponins and saponins without taste or with bitterness. The number of glucose groups in sweet saponins and bitter saponins is different. During the ripening process of Siraitia grosvenorii, bitter saponins will be converted into sweet saponins. If the ripening degree of Siraitia grosvenorii is insufficient, it will lead to a high content of bitter glycosides in the processed products of Siraitia grosvenorii, with a serious bitter and astringent taste and poor taste. In addition, Siraitia grosvenorii contains a large amount of polyphenolic substances, and the large presence of phenolic acid compounds will also make the processed products of Siraitia grosvenorii have a bitter and astringent taste.

[0003] To reduce the content of bitter glycosides in Siraitia grosvenorii, usually freshly picked Siraitia grosvenorii will be stored for 7 - 10 days before being processed to complete the after-ripening of Siraitia grosvenorii. Using this method, the storage time is relatively long. During storage, the respiratory action of Siraitia grosvenorii will produce moisture and release heat, easily forming a high-temperature and high-humidity environment, resulting in mildew and spoilage of Siraitia grosvenorii, which is not conducive to the processing and production of Siraitia grosvenorii. Patent CN114271416A discloses a method for accelerating the ripening of Siraitia grosvenorii, using exogenous reagents such as adenosine triphosphate, methionine solution, jasmonic acid, and / or methyl jasmonate solution for ripening treatment, which can shorten the saccharification time. However, the Siraitia grosvenorii ripened by chemical reagents has insufficient fruity aroma, which will affect the flavor of Siraitia grosvenorii concentrated juice. Patent CN114886099A discloses a peeled cake-shaped dried Siraitia grosvenorii and its preparation method. Spraying a dilute ethanol solution of rice bran oil fatty acid on the surface of fresh Siraitia grosvenorii, and at the same time controlling the stacking height, temperature, and relative humidity in the warehouse, ventilating regularly, and standing for 6 - 7 days can promote the yellow ripening of Siraitia grosvenorii. However, in this method, the stacking environment has a high humidity, which is prone to bacterial growth and is not conducive to the storage of Siraitia grosvenorii.

[0004] To reduce the content of phenolic acid substances in Siraitia grosvenorii concentrated juice, multiple fine processing methods are usually adopted during the processing. For example, the processing method of Siraitia grosvenorii concentrated juice disclosed in Patent CN114271416A. The Siraitia grosvenorii concentrated juice obtained through operations such as centrifugal filtration, cross-flow filtration by a ceramic membrane complete set of equipment, decolorization and desalination by ion exchange resin, and removal of phenolic acids by a macroporous adsorption resin column although removes the bitter and astringent taste, but will reduce the particle size of non-volatile matrix in Siraitia grosvenorii concentrated juice, weaken its slow-release effect on volatile compounds, resulting in the loss of the aroma of Siraitia grosvenorii concentrated juice during processing and storage, and losing the original fruity aroma of Siraitia grosvenorii. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for preparing Momordica grosvenori concentrated juice. Using wheat bran as a ripening medium and utilizing calcium chloride and enzymatic hydrolysis, it can promote the yellow ripening of Momordica grosvenori, reduce the bitter taste in the concentrated juice, and retain the flavor of Momordica grosvenori.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing Momordica grosvenori concentrated juice, comprising the following steps:

[0008] S1: Freshly picked Momordica grosvenori is ripened using wheat bran as a ripening medium;

[0009] S2: The ripened Momordica grosvenori is soaked in hot water containing calcium chloride, and then washed with clean water;

[0010] S3: The processed Momordica grosvenori is crushed by pressing, and then freeze-thaw treatment is carried out;

[0011] S4: Hot water extraction is carried out, and after extraction is completed, a crude Momordica grosvenori extract is obtained by filtration;

[0012] S5: The crude extract is treated with immobilized enzyme;

[0013] S6: Filtration is carried out using an ultrafiltration membrane, and the filtrate is subjected to vacuum concentration;

[0014] S7: After concentration, high-temperature sterilization is carried out to obtain Momordica grosvenori concentrated juice.

[0015] As a further improvement of the above solution, the treatment method in S1 is: Momordica grosvenori is evenly embedded in wheat bran, and the thickness of the wheat bran on the outer layer of Momordica grosvenori is controlled at 3 - 5 cm, and the yellow-ripened Momordica grosvenori is taken out after embedding for 4 - 7 days. Wheat bran is a by-product of wheat flour processing, with low water content and a granular structure, which can reduce the accumulation of water generated by the respiration of Momordica grosvenori on the fruit surface, provide a warm and dry after-ripening environment, and wheat bran contains various volatile components, such as aldehydes, ketones, esters, etc., which can promote the after-ripening process of Momordica grosvenori.

[0016] As a further improvement of the above solution, the content of calcium chloride in S2 is 0.2 - 0.4 g / L, the soaking temperature is 60 - 80 °C, and the soaking time is 3 - 5 min. Calcium chloride is a food additive that can make soluble pectin coagulate into gel-like insoluble calcium pectate, maintaining the crispness and hardness of fruit and vegetable processed products. Under heating conditions, the cells on the surface of Momordica grosvenori peel open, which can promote the penetration of calcium chloride. Under the action of calcium ions, organic acids or phenolic substances in Momordica grosvenori peel will form insoluble substances, thereby reducing the concentration of phenolic acid substances in Momordica grosvenori concentrated juice and reducing the bitter taste.

[0017] As a further improvement of the above solution, the freeze-thaw treatment process in S3 is as follows: freeze Momordica grosvenori at a low temperature to -20°C, thaw it at room temperature, and then freeze it again. Repeat this process 3 - 5 times. During the processing of Momordica grosvenori, in order to reduce the bitter taste, it is necessary to avoid damaging the seed kernels of Momordica grosvenori as much as possible during the processing. However, the connection between the seed kernels and the fruit pulp in Momordica grosvenori is very tight, which increases the extraction difficulty. The freeze-thaw treatment can destroy the cell wall structure in Momordica grosvenori and promote the separation of the seed kernels from the fruit pulp.

[0018] As a further improvement of the above solution, the hot water extraction method in S4 is as follows: add Momordica grosvenori materials and 5 - 10 times of purified water to the extraction container, heat and stir, the heating temperature is 40 - 60°C, and the extraction time is 30 - 50 min. Using hot water extraction can save costs and improve the solubility of mogrosides and other substances, thus improving the extraction efficiency.

[0019] Polyphenols can be divided into polyphenol monomers, polyphenol oligomers or polymers. Among them, polyphenol monomers are mainly phenolic acids such as gallic acid, ferulic acid, caffeic acid, chlorogenic acid and ellagic acid, as well as flavonoid compounds. During the processing and storage of fruit juice, polyphenols and proteins will polymerize with each other through hydrophobic, hydrogen bond and other interaction forces in the solution system to form turbidity, causing fruit juice turbidity and flavor changes. Phenolic acids will cause sour, bitter and astringent tastes, affecting the quality and taste of fruit juice.

[0020] As a further improvement of the above solution, the immobilized enzyme in S5 uses macroporous adsorption resin as the carrier, the immobilized enzyme is tyrosinase, and peroxidase is used as the cross-linking agent. Macroporous adsorption resin is a kind of artificial synthetic polymer with a porous three-dimensional structure. It has good stability and can adsorb enzymes through intermolecular forces such as van der Waals force, electrostatic attraction and hydrogen bond to achieve enzyme immobilization. Tyrosinase is an enzyme that can catalyze the oxidation of phenolic substances, which can catalyze the hydroxylation of monophenol compounds to o-diphenols and then oxidize these o-diphenols to the corresponding o-quinones. In the oxidation reaction, oxygen molecules are reduced to water or other oxides. Peroxidase is an oxidoreductase that can not only decompose oxides into water and oxygen, but also oxidize the phenols on tyrosine residues to form dityrosine and oligotyrosine cross-links, playing the role of a cross-linking agent.

[0021] As a further improvement of the above solution, in S6, a ultrafiltration membrane with a molecular weight cut-off of 100,000 - 300,000 Daltons is used for filtration, and the ultrafiltration pressure is 0.2 - 0.3 MPa.

[0022] As a further improvement of the above solution, the vacuum concentration conditions in S6 are a vacuum degree of -0.08 MPa to -0.1 MPa and a temperature of 30 - 40°C until the concentration reaches 55 - 65 Brix.

[0023] As a further improvement of the above solution, the high-temperature sterilization method in S7 is as follows: Place the concentrated solution under the condition of 80 - 85 °C and heat it for 15 - 30 min to obtain the finished Momordica grosvenori concentrated juice.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) Using wheat bran as the ripening medium, the water absorption and heat preservation performance of wheat bran provides a warm and dry environment for the after-ripening of Momordica grosvenori, promoting its internal metabolic processes, including saccharification. Volatile substances in wheat bran, such as phenethyl alcohol, furfural, ethyl acetate, and phenols, affect the enzyme activity in Momordica grosvenori, thereby promoting the glycosylation of mogrosides and reducing the content of bitter glycosides, reducing the bitter taste from the source.

[0026] (2) Using calcium chloride to reduce the solubility of phenolic acids by reacting with phenolic acid substances or through chelation, thereby reducing the concentration of phenolic acid compounds in the Momordica grosvenori peel in the concentrated juice, and further reducing the entry of phenolic acids in the Momordica grosvenori peel into the juice to increase the bitter taste.

[0027] (3) Using immobilized enzymes to enzymatically hydrolyze the crude extract of Momordica grosvenori. Tyrosinase can oxidize phenolic acids into corresponding quinone compounds, and quinone compounds can combine with proteins to form macromolecular polymers. Then, through filtration and precipitation, the removal of phenolic acids can be achieved, and the original flavor of the juice can be better retained compared with fine processing methods such as centrifugation and fine filtration. Detailed implementation manners

[0028] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below in conjunction with embodiments. The description in this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention.

[0029] Example 1

[0030] This example provides a preparation method for Momordica grosvenori concentrated juice, including the following steps:

[0031] S1: Uniformly embed the freshly picked Momordica grosvenori in wheat bran, and control the thickness of the wheat bran on the outer layer of Momordica grosvenori to be about 3 cm. Take out the yellow-ripened Momordica grosvenori after embedding for 7 days. After inspection, more than 80% of the surface of fresh Momordica grosvenori has turned into mung bean yellow, about 60% has turned yellow, the characteristic fruit fragrance of Momordica grosvenori is obvious, and calculated based on the fresh Momordica grosvenori stored in the warehouse, the bad fruit rate is 0.72%.

[0032] S2: Put the intact yellow-ripened Momordica grosvenori into hot water containing 0.2 g / L of calcium chloride, keep the water temperature at about 80 °C, soak for 5 min, and then rinse 2 times with clean water to remove the residual calcium chloride solution on the surface.

[0033] S3: Press and crush the Momordica grosvenori fruits after the treatment in S2, taking care not to damage the seeds and kernels. Freeze the crushed Momordica grosvenori materials at about -20°C, thaw them at room temperature, and then freeze them again. Repeat this process three times.

[0034] S4: Add purified water approximately five times the weight of the materials after freeze-thaw treatment, heat and stir. The heating temperature is 60°C, and the extraction time is 30 minutes. After extraction, filter to obtain the crude extract.

[0035] S5: Treat the crude extract with macroporous adsorption resin immobilized enzyme. Add the immobilized enzyme to the crude extract. The addition ratio of the immobilized enzyme is 10 g of immobilized enzyme per liter of crude extract. Carry out enzymatic hydrolysis at 30°C for 1.5 hours, and then perform rough filtration to obtain the extracted solution after enzymatic hydrolysis.

[0036] S6: Filter the extracted solution treated in step S5 using a 100,000 Dalton ultrafiltration membrane. The ultrafiltration pressure is 0.3 MPa. The filtrate is concentrated in vacuo using an internal circulation decompression concentrator. The vacuum degree is -0.08 MPa, and the temperature is 40°C until the concentration reaches 55 Brix.

[0037] S7: Heat the concentrated solution at 80°C for 30 minutes to obtain concentrated Momordica grosvenori juice.

[0038] Example 2

[0039] This example provides a method for preparing concentrated Momordica grosvenori juice, including the following steps:

[0040] S1: Uniformly embed the freshly picked Momordica grosvenori fruits in wheat bran. Control the thickness of the wheat bran on the outer layer of the Momordica grosvenori fruits to be about 5 cm. After embedding for 4 days, take out the yellow-ripened Momordica grosvenori fruits. After inspection, more than 75% of the surface of the fresh Momordica grosvenori fruits has turned into mung bean yellow, about 55% has turned yellow, and the characteristic fruit fragrance of Momordica grosvenori is obvious. Based on the fresh Momordica grosvenori fruits stored in the warehouse, the bad fruit rate is 0.64%.

[0041] S2: Soak the intact yellow-ripened Momordica grosvenori fruits in hot water containing 0.4 g / L of calcium chloride. Keep the water temperature at about 60°C and soak for 5 minutes. Then rinse with clean water four times to remove the residual calcium chloride solution on the surface.

[0042] S3: Press and crush the Momordica grosvenori fruits after the treatment in S2, taking care not to damage the seeds and kernels. Freeze the crushed Momordica grosvenori materials at about -20°C, thaw them at room temperature, and then freeze them again. Repeat this process five times.

[0043] S4: Add purified water ten times the weight of the materials after freeze-thaw treatment, heat and stir. The heating temperature is 40°C, and the extraction time is 50 minutes. After extraction, filter to obtain the crude extract.

[0044] S5: Treat the crude extract with macroporous adsorption resin immobilized enzyme. Place the immobilized enzyme and the crude extract in a closed fluidized tank. The addition ratio of the immobilized enzyme is 15 g of immobilized enzyme per liter of crude extract. Pressurize to 100 MPa, at a temperature of 30 °C, enzymatically hydrolyze for 20 min, and then perform rough filtration to obtain the enzymatically hydrolyzed extract;

[0045] S6: Filter the extract treated in step S5 using a 300,000 Dalton ultrafiltration membrane. The ultrafiltration pressure is 0.2 MPa. The filtrate is vacuum concentrated using an internal circulation decompression concentrator. The vacuum degree is -0.1 MPa, and the temperature is 30 °C until the concentration reaches 65 Brix;

[0046] S7: Heat the concentrated liquid at 85 °C for 15 min to obtain Siraitia grosvenorii concentrated juice.

[0047] Preparation of macroporous adsorption resin immobilized enzyme: Immerse the macroporous adsorption resin in an ethanol solution for 12 h, stir it from time to time to make it swell sufficiently, and then wash it with purified water to obtain the pretreated resin. Weigh the pretreated resin and add it to the tyrosinase solution. The dosage of tyrosinase is 255 U / g of resin. Adsorb for 4 h in a constant temperature oscillation water bath environment at 30 °C and 150 r / min. Then add the peroxidase solution. The dosage of peroxidase is 180 U / g of resin, and continue to react for 3 h. Filter and wash 3 times with buffer solution. After drying the water with filter paper, obtain the immobilized enzyme and store it refrigerated for later use.

[0048] Comparative Example 1

[0049] This comparative example provides a method for preparing Siraitia grosvenorii concentrated juice, which is the same as Example 1, except that wheat bran is not used as the ripening medium. Instead, the Siraitia grosvenorii fruits are placed in a well-ventilated warehouse for about 10 days to allow them to ripen. After inspection, more than 70% of the surface of the fresh Siraitia grosvenorii fruits has turned into mung bean yellow, and about 50% has turned yellow. The characteristic fruit fragrance of Siraitia grosvenorii is obvious. Based on the fresh Siraitia grosvenorii fruits stored in the warehouse, the bad fruit rate is 1.47%.

[0050] Comparative Example 2

[0051] This comparative example provides a method for preparing Siraitia grosvenorii concentrated juice, which is the same as Example 1, except that calcium chloride treatment is not used.

[0052] Comparative Example 3

[0053] This comparative example provides a method for preparing Siraitia grosvenorii concentrated juice. The crude extract is obtained by using the method of S1 - S4 in Example 1. After that, the crude extract is not treated with immobilized enzyme. Instead, it is filtered and clarified, decolorized and desalted with ion exchange resin, chromatographed with macroporous adsorption resin, clarified at low temperature, concentrated and sterilized according to the method disclosed in Patent CN114271416A to obtain Siraitia grosvenorii concentrated juice.

[0054] Comparative Example 4

[0055] In this comparative example, a method for preparing Momordica grosvenori concentrated juice was provided. The crude extract was obtained by the method of S1 - S4 in Example 1, but step S2 was omitted. After that, the crude extract was not treated with immobilized enzyme, but was subjected to filtration and clarification, decolorization and desalting with ion exchange resin, macroporous adsorption resin chromatography, low-temperature clarification, concentration and sterilization according to the method disclosed in Patent CN114271416A to obtain Momordica grosvenori concentrated juice.

[0056] The present invention was detected by the following method:

[0057] 1. The contents of mogrosides and phenolic acids in Momordica grosvenori concentrated juice were determined by high performance liquid chromatography, and the protein content of Momordica grosvenori concentrated juice was determined by BCA method. The determination results are shown in the following table.

[0058] Table 1

[0059]

[0060] 2. According to the provisions of GB / T 16291.2 - 2010, sensory evaluation personnel were screened. After taste sensitivity training, 20 (10 males and 10 females) sensory evaluation personnel were finally selected to form a sensory evaluation group. The Momordica grosvenori concentrated juice prepared in the above Examples 1, 2 and Comparative Examples 1 - 4 was diluted 10 times with pure water and then tasted by the test subjects, and their odor and taste were scored. The specific parameters of sensory evaluation are shown in Table 2. After the sensory evaluation group scored each group, the average value of each group was taken, and the results are shown in Table 3.

[0061] Table 2

[0062]

[0063] Table 3

[0064]

[0065]

[0066] As can be seen from Table 2, the Momordica grosvenori concentrated juice prepared in Examples 1-2 had the highest score, above 90 points, indicating that the Momordica grosvenori concentrated juice processed by the present invention performed well in terms of color, taste, smell and texture. In Comparative Example 1, post-ripening treatment was carried out by natural ripening, and the resulting Momordica grosvenori concentrated juice had a relatively light fruity aroma and poor color, which was due to the inconsistent maturity of Momordica grosvenori caused by differences in environmental conditions, affecting the sensory score of the final product. In Comparative Example 2, calcium chloride was not used for treatment, and the removal effect of phenolic acids in the Momordica grosvenori concentrated juice was not as good as that of the examples, and the overall score was relatively low. In Comparative Example 3, fine processing was used to remove the bitterness and astringency in the concentrated juice, but the removal effect was not as good as that with the addition of immobilized enzyme treatment. The resulting Momordica grosvenori concentrated juice had a relatively pure taste, but a large amount of fruity aroma was lost. In Comparative Example 4, neither calcium chloride treatment was used nor fine processing was used to remove the bitterness and astringency in the concentrated juice, so the resulting Momordica grosvenori concentrated juice had a greater bitterness and astringency and a relatively poor overall sensory quality.

[0067] It should be noted that in this article, the terms: including, containing and any other variants are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such a process, method, article or device. Specific examples are used in this article to elaborate on the principle and implementation manner of the technical solution of the present invention. The description of the above examples is only used to help understand the method of the present invention and its core idea. The above is only the preferred implementation manner of the present invention. It should be pointed out that due to the limited nature of written expression and the objectively infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the present invention to other occasions without improvement, should all be regarded as the protection scope of the present invention.

Claims

1. A method for preparing Momordica grosvenori concentrated juice, characterized in that, It includes the following steps: S1: The freshly picked Momordica grosvenori fruits are ripened using wheat bran as a ripening medium; S2: The ripened Momordica grosvenori fruits are soaked in hot water containing calcium chloride and then washed with clean water; S3: They are crushed by pressing and then subjected to freeze-thaw treatment; S4: Hot water extraction is carried out, and after extraction is completed, a crude extract of Momordica grosvenori is obtained by filtration; S5: The crude extract is treated with immobilized enzyme. The immobilized enzyme uses macroporous adsorption resin as a carrier, the immobilized enzyme is tyrosinase, and peroxidase is used as a crosslinking agent; S6: Filtration is carried out using an ultrafiltration membrane, and the filtrate is concentrated under vacuum; S7: After concentration, high-temperature sterilization is carried out to obtain concentrated Momordica grosvenori juice.

2. The preparation method of a Momordica grosvenori concentrated juice according to claim 1, wherein, The treatment method in S1 is: The Momordica grosvenori fruits are evenly embedded in wheat bran, and the thickness of the wheat bran on the outer layer of the Momordica grosvenori fruits is controlled at 3 - 5 cm, and they are taken out after embedding for 4 - 7 days.

3. The preparation method of a Momordica grosvenori concentrated juice according to claim 1, characterized in that, In S2, the content of calcium chloride is 0.2 - 0.4 g / L, the soaking temperature is 60 - 80 °C, and the soaking time is 3 - 5 min.

4. The preparation method of a Momordica grosvenori concentrated juice according to claim 1, characterized in that, The hot water extraction method in S4 is: Purified water 5 - 10 times the amount of Momordica grosvenori materials is added to the extraction container, heated and stirred, the heating temperature is 40 - 60 °C, and the extraction time is 30 - 50 min.

5. The preparation method of a momordica grosvenori concentrated juice according to claim 1, wherein, In S6, filtration is carried out using an ultrafiltration membrane with a molecular weight cut-off of 100,000 - 300,000 Daltons, and the ultrafiltration pressure is 0.2 - 0.3 MPa.

6. The preparation method of Momordica grosvenori concentrated juice according to claim 1, wherein, The vacuum concentration conditions in S6 are a vacuum degree of -0.08 MPa to -0.1 MPa, a temperature of 30 - 40 °C, and concentration to a concentration of 55 - 65 Brix.

7. The preparation method of a Siraitia grosvenorii concentrated juice according to claim 1, characterized in that, The high-temperature sterilization method in S7 is: Heating at 80 - 85 °C for 15 - 30 min.

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