Holboellia latifolia pericarp enzyme, and preparation process and application thereof

Abstract

The preparation process comprises the following steps: S1, raw material selection and pretreatment: selecting fresh holboellia latifolia pericarp, cleaning the selected holboellia latifolia pericarp, and crushing the cleaned holboellia latifolia pericarp into holboellia latifolia pericarp paste; s2, performing enzymolysis treatment: adding a proper amount of water into the peel paste, adding 2% of cellulase and 2% of pectinase, performing water bath at 50 DEG C for 2 hours, and performing sterilization at 65 DEG C for 30 minutes; s3, fermentation: high-activity saccharomycetes are used as fermentation strains, the addition amount of the high-activity saccharomycetes is 1.5-2.5%, the addition amount of white granulated sugar is 5-25%, the fermentation temperature is 25-45 DEG C, and the fermentation time is 3-7 days; s4, post-treatment: after fermentation is finished, centrifuging for 15 minutes at the speed of 4000 r / min to separate a solution, and storing the obtained solution at low temperature. The method not only can enrich stauntonia latifolia series products, but also can provide data support for preparation of functional enzymes, antioxidant enzymes and the like through yeast fermentation, and has good development value.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to melon peel enzyme, a preparation process and application thereof. Background Art

[0002] As a perennial deciduous vine of the genus Akebia, the family Akebia, the wax gourd is widely distributed in Yunnan, Guizhou and other places in my country. Its fruit is rich in nutrients, has great potential in the fields of food and health, and has a variety of pharmacological properties. However, during the processing and consumption of wax gourd, the purple-red peel, which accounts for about 70% of the total fruit weight, is often discarded in large quantities, which not only causes a huge waste of resources, but also causes environmental pollution problems. In fact, the peel of wax gourd contains a variety of active ingredients such as triterpenoids, phenolic compounds, pectin, etc., and has a high development value.

[0003] At present, enzymes, as products that use microbial fermentation to produce a variety of nutrients, are widely used in the fields of food, daily necessities, and environmental protection. Studies have explored different fruit peel enzymes. For example, Wu Min screened suitable composite bacteria to produce orange peel puerarin composite enzymes with good antioxidant activity; Shang Zhuo et al. found that green mango-papaya mixed peel enzymes have good antioxidant activity; Ren Pingguo et al. used sea buckthorn as raw material and used specific mixed bacteria fermentation to prepare sea buckthorn enzymes with good antioxidant capacity.

[0004] However, there are still many problems with the existing technology. There is a relative lack of research on the enzyme from the peel of the melon, and the optimization of its fermentation process is insufficient. In addition, different fermentation processes will lead to large differences in the composition and performance of the enzyme. The existing research on peel enzyme lacks in-depth exploration of the specific raw material of the melon peel, and has failed to fully tap its potential. At the same time, it is also difficult to ensure the stability and uniformity of product quality. Summary of the invention

[0005] The present invention aims to provide an enzyme of kiwifruit peel, a preparation process and an application thereof, so as to solve the problem of poor quality of the existing enzyme of kiwifruit peel.

[0006] The preparation process of the melon peel enzyme in this scheme comprises the following steps:

[0007] S1 Raw material selection and pretreatment: Select fresh August melon peels, wash them and crush them into peel mud;

[0008] S2 enzymatic treatment: add appropriate amount of water to the peel paste, add 2% of cellulase and pectinase respectively, bathe at 50℃ for 2h, and sterilize at 65℃ for 30min;

[0009] S3 fermentation: using highly active yeast as the fermentation strain, the addition amount of highly active yeast is 1.5% to 2.5%, the addition amount of white sugar is 5% to 25%, the fermentation temperature is 25℃ to 45℃, and the fermentation time is 3d to 7d;

[0010] S4 post-treatment: After the fermentation is completed, the solution is separated by centrifugation at 4000r / min for 15min, and the obtained solution is stored at low temperature.

[0011] Furthermore, the highly active yeast is highly active dry yeast.

[0012] The physicochemical indicators of the melon peel enzyme prepared by the preparation process are: pH value of 4.7, alcohol content of 6.50% vol, soluble solid content of 2.10%, total acid content of 9.60%, total sugar content of 13.58%, protein content of 14.95%, and it contains 17 kinds of organic acids.

[0013] The functional substance indicators of the August melon peel enzyme are: total phenol content is 1.16 mg / mL, total triterpenoid content is 0.29 mg / mL, total flavonoid content is 1.49 mg / mL, and SOD enzyme activity is 55.65 U / mL.

[0014] The antioxidant capacity indicators of August melon peel enzyme are: hydroxyl free radical scavenging rate is 69.89%, DPPH free radical scavenging rate is 90.87%, and ABTS free radical scavenging rate is 96.58%.

[0015] The microbial index of August melon peel enzyme is: the total colony count is 5×10 3 CFU, yeast count is 3×10 3 CFU, mold and E. coli counts were both 0 CFU.

[0016] Application of melon peel enzyme in the preparation of food and health products.

[0017] The working principle and beneficial effects of this scheme: turning waste into treasure, converting discarded August melon peels into high-value enzyme products, improving resource utilization and reducing environmental pollution. The enzyme prepared by this scheme has excellent antioxidant properties, with a hydroxyl radical scavenging rate of 69.89%, a DPPH radical scavenging rate of 90.87%, and an ABTS radical scavenging rate of 96.58%; it is rich in 17 kinds of organic acids, total phenols 1.16mg / mL, total triterpenes 0.29mg / mL, total flavonoids 1.49mg / mL, SOD enzyme activity 55.65U / mL and other nutrients, and contains 377 kinds of flavor substances, and has broad application prospects in the fields of food and health products. Therefore, the present invention can not only enrich the August melon series of products, but also provide data support for the preparation of functional enzymes, antioxidant enzymes, etc. by yeast fermentation, and has good development value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a single factor experiment for fermentation of different strains;

[0019] Figure 2 Single factor experiment results;

[0020] Figure 3 response surface interaction analysis contour plots;

[0021] Figure 4 3D plots of response surface interaction analysis;

[0022] Figure 5 For organic acid type analysis;

[0023] Figure 6 This paper is an analysis of the flavor substances in the peel of August melon. DETAILED DESCRIPTION

[0024] The following is a further detailed description through specific implementation methods:

[0025] Example:

[0026] Raw material preparation: Purchase fresh, moderately mature wax gourds from the wax gourd planting base in Zunyi, Guizhou. Carefully separate the peels, rinse with clean water to remove surface dust, impurities and residual pesticides, drain the water and use a food processor to crush the peels into puree.

[0027] Enzymatic hydrolysis: Weigh the peel paste and place it in a container. Add an appropriate amount of water to cover the peel paste, stir evenly, add 2% of cellulase and pectinase, and stir well to make the enzymes and peel paste evenly contact. Put the container in a 50℃ water bath and perform the enzymatic hydrolysis reaction for 2 hours. After the enzymatic hydrolysis is completed, quickly transfer the mixture to a 65℃ environment for sterilization for 30 minutes.

[0028] Fermentation process: Activate the highly active dry yeast of Angel Yeast Co., Ltd. according to the conventional method. Inoculate the activated yeast into the sterilized peel paste mixture; add white sugar at the same time. After stirring evenly, divide the mixture into sterilized fermentation tanks, seal them and place them in a constant temperature box at 30℃ for 5 days, and observe the fermentation status regularly during the period.

[0029] Separation and storage: After fermentation is completed, transfer the fermentation liquid to a centrifuge tube, put it into a centrifuge, set the speed to 4000r / min, and centrifuge for 15 minutes. Collect the supernatant after centrifugation, which is the finished product of August melon peel enzyme. Transfer the finished product to a sterile, sealed container and store it in a low temperature environment (such as 4℃ refrigerator) to delay the degradation of enzyme quality.

[0030] Yeast selection

[0031] Weigh appropriate amounts of equal amounts of August melon peels, perform natural fermentation (NF), fermentation with BV818, RW, SY and ADY strains, determine the hydroxyl radical scavenging rate, compare the effects of natural fermentation (NF) and four yeast strains on fermentation, and determine the best yeast fermentation strain, such as Figure 1 shown.

[0032] Single factor experiment: Using the enzyme free radical scavenging rate as the evaluation index, the optimal fermentation conditions of the enzyme were determined by setting the strain amount to 1%-3% (·%, 1.5%, 2%, 2.5%, 3%), the sugar dosage to 10%-50% (10%, 20%, 30%, 40%, 50%), the fermentation temperature to 20℃-40℃ (20℃, 25℃, 30℃, 35℃, 40℃) and the fermentation time to 3d-7d (3d, 4d, 5d, 6d, 7d). The results are as follows: Figure 2 shown.

[0033] Response surface experimental design: Box-Behnken optimization was used in Design Expert 13 software to conduct multiple regression analysis on the test results, and the relationship between the four factors of yeast dosage, sugar dosage, temperature, and time and the response value (hydroxyl radical scavenging rate) was examined. Based on the single-factor experiment, the appropriate range of the independent variable was obtained, and a response surface experiment with four factors and three levels was designed. The response surface experimental factor and level coding are shown in Table 1.

[0034] Table 1 Factors and level coding of response surface experiment

[0035] Table 1 Response surface test factors and horizontal coding

[0036] Horizontal Encoding Bacteria dosage % (g) Sugar dosage %(g) Temperature(℃) Time (d) -1 1.5 20 25 4 0 2.0 30 30 5 1 2.5 40 35 6

[0037] Specific physical and chemical indicators known in the scheme are tested: pH determination: using a pH meter. Alcohol content determination: using a refractometer. Soluble solids: using a digital sugar meter. Total acid determination: refer to the research method of Zhu Nana et al. Determination of organic acid: refer to the research method of Zhan Nan, Li Miao et al. Determination of total sugar: using the phenol-sulfuric acid method, with slight modifications to the method of Liu Zhiming et al. Determination of protein: using the Coomassie Brilliant Blue method, with slight modifications to the method of Zheng Bin et al.

[0038] Functional substance detection Determination of total phenols: Folin phenol method was used for determination, with slight modifications made to the method of Ning Zhixue, Meng Qi, etc. Determination of total triterpenes: Analysis of total triterpenoid content was slightly modified by the method of Dai Tiantian, etc. Determination of total flavonoids: Analysis of total flavonoid content was performed by referring to the method of Hu Hongkai, etc.

[0039] Antioxidant index detection

[0040] Determination of hydroxyl radical scavenging rate The hydroxyl radical scavenging rate was determined by referring to Wei Jianmin's method. 1438 Vc was used as the positive control. Calculation was performed according to formula (1):

[0041]

[0042] Where: A1: absorbance of sample and reagent; A2: absorbance of sample solution itself, with deionized water replacing hydrogen peroxide; A0: absorbance of sample replaced by deionized water.

[0043] 1.2.7.2 Determination of DPPH The determination of DPPH was carried out according to the method of Wei Jianmin. Vc was used as the positive control. Calculation was performed according to formula (2):

[0044]

[0045] Where: A1: absorbance of 1 mL sample + 2 mL DPPH-ethanol solution; A2: absorbance of 1 mL sample + 2 mL ethanol solution; A0: absorbance of 1 mL ethanol + 2 mL DPPH-ethanol solution.

[0046] 1.2.7.3 Determination of ABTS The determination of ABTS was carried out according to the method of Wei Jianmin. Vc was used as the positive control. Calculation was performed according to formula (3):

[0047]

[0048] Where: A1: absorbance of 0.5mL sample + 4mL ABTS; A2: absorbance of 0.5mL sample + 4mL methanol solution; A0: absorbance of 0.5mL methanol + 4mL ABTS.

[0049] Microbiological index detection Determination of total colony count: refer to "GB 4789.2-2022 National Food Safety Standard Food Microbiology Test Determination of Total Colony Count" to determine the colony count. Determination of Escherichia coli: refer to "GB 4789.3-2016 National Food Safety Standard Food Microbiology Test Coliform Count" to determine the colony count. Determination of yeast (mold): refer to "GB 4789.15-2016 National Food Safety Standard Food Microbiology Test Mold and Yeast Count" to determine the colony count.

[0050] Determination of flavor substances: Samples were taken out from a -80 °C refrigerator (fresh samples were used by default unless otherwise specified) and ground with liquid nitrogen. The samples were vortexed and mixed evenly. About 500 mg (1 mL of liquid) of each sample was weighed into a headspace bottle. Saturated NaCl solution and 20 μL (10 μg / mL) of internal standard solution were added respectively. Fully automatic headspace solid phase microextraction (HS-SPME) was used to extract the samples for GC-MS analysis.

[0051] Data processing

[0052] Excel 2019, WPS Office2021, Design Expert 13, and GraphPad Prism 8 software were used for graphing and data processing, and SPSS26 software was used for significance analysis. Each group of experiments was performed in parallel three times, and the results were expressed as mean ± standard deviation.

[0053] Results and Analysis

[0054] The choice of fermentation method depends on Figure 1 It can be seen that under the condition of certain levels of other factors, taking hydroxyl radical scavenging rate as the evaluation index, compared with natural fermentation (NF) and fermentation by other four yeasts, SY and BV818 had the lowest hydroxyl radical scavenging rates, while natural fermentation and RW had higher rates, and the high-activity yeast had the highest rate of 71.86%. Therefore, high-activity yeast was selected as the fermentation strain for enzyme fermentation.

[0055] Response surface experiment analysis Based on the results of single factor experiment, the amount of bacteria (A), sugar amount (B), temperature (C), and time (D) were selected as independent variables, and the hydroxyl radical scavenging rate was used as the response value. The Box-Behnken response surface experiment with three levels and four factors was carried out.

[0056] Table 2 Response surface analysis of level 3 factors

[0057] Table 2 Experimental analysis of the response surface of horizontal 3 factors

[0058] Group Yeast dosage Sugar dosage temperature time Hydroxyl free radical scavenging rate / % 1 0 0 0 0 68.72 2 0 -1 0 1 57.29 3 1 0 -1 0 52.13 4 0 -1 1 0 57.30 5 0 1 1 0 50.30 6 1 0 0 1 52.63 7 1 -1 0 0 51.44 8 2 0 -1 -1 52.69 9 -1 0 -1 0 59.69 10 2 1 -1 0 53.26 11 -1 0 0 1 59.68 12 0 0 0 0 69.40 13 0 1 0 1 52.80 14 0 0 0 0 67.32 15 0 0 1 1 54.91 16 1 0 1 0 53.34 17 0 0 0 0 69.54 18 0 0 1 -1 55.63 19 -1 -1 0 0 60.36 20 1 1 0 0 63.45 21 0 0 0 0 71.40 22 -1 0 1 0 60.43 23 -1 0 0 -1 58.37 24 0 -1 0 -1 56.76 25 0 1 0 -1 50.82 26 0 -1 -1 0 59.19 27 1 0 0 -1 51.56 28 -1 1 0 0 53.50 29 0 0 -1 1 56.88

[0059] Box-Behnken was used to perform quadratic multivariate regression fitting analysis on the test results. From Table 2, the quadratic regression equation of the influence of various factors (yeast dosage, sugar dosage, temperature, time) on the hydroxyl radical scavenging rate can be obtained:

[0060] Y=69.28-2.29A-1.53B-0.1692C+0.6967D+4.72AB+0.1175AC-0.06AD-0.2925BC+0.3625BD-1.23CD-5.66A 2 -6.94B 2 -7.03C 2 -7.73D 2 .

[0061] Table 3 Response surface regression equation analysis

[0062] Table 3 Response surface regression equation analysis

[0063] Sources of variance sum of squares Degrees of Freedom Mean Square F-number P-value Significance Model 985.20 14 70.31 9.26 <0.0001 ** A 62.93 1 62.93 8.28 0.0122 * B 27.94 1 27.94 3.67 0.0759 C 0.3434 1 0.3434 0.0452 0.8348 D 5.82 1 5.82 0.7661 0.3962 AB 89.02 1 89.02 11.71 0.0041 ** AC 0.0552 1 0.0552 0.0037 0.9333 AD 0.0144 1 0.0144 0.0019 0.9659 BC 0.3422 1 0.3422 0.0450 0.8350 BD 0.5256 1 0.5256 0.0691 0.7964 CD 6.03 1 6.03 0.7928 0.3884 <![CDATA[A 2 ]]> 207.93 1 207.93 27.35 0.0001 ** <![CDATA[B 2 ]]> 312.23 1 312.23 41.07 <0.0001 ** <![CDATA[C 2 ]]> 320.39 1 320.39 42.14 <0.0001 ** <![CDATA[D 2 ]]> 387.76 1 387.76 51.00 <0.0001 ** Residual 106.44 14 7.60 Lack of Fit 97.70 10 9.77 4.48 0.0808 Not significant Net Error 8.73 4 2.18 Total deviation 1091.64 28 <![CDATA[R 2 ]]> 0.9025 <![CDATA[R adj ]]> 0.8050 CV% 4.76

[0064] Note: **.P<0.01, extremely significant difference; *.P<0.05, significant difference.

[0065] The quadratic multiple regression model was subjected to variance analysis. As shown in Table 3, the regression model was highly significant (F = 9.26, P < 0.0001), and the difference in the lack of fit term was not significant (P = 4.48 > 0.05), indicating that the regression equation had a good fit to the experiment. The coefficient of determination R2 was 0.9025, and the adjusted coefficient of determination R2adj was 0.8050, indicating that the model had a good fit and predictability to the actual experimental method, and was suitable for the fermentation process of the fruit peel enzyme in August melon. The process coefficient of variation was 4.76%, which can be used to explain that the response value of 80.50% of the model was small, which may be affected by accidental errors, indicating that the model can be used as a reference for predicting and analyzing the fermentation process conditions of the fruit peel in August melon. The P value shows that the linear term A, the interaction term AB, and the quadratic terms A2, B2, C2, and D2 have extremely significant effects on the scavenging rate of hydroxyl radicals (P < 0.01). By comparing the various factors, it can be seen that A>B>D>C, that is, the amount of yeast>the amount of sugar>the time>the temperature. In summary, it shows that the optimization test results obtained by the multivariate regression equation model are highly reliable, and the model can be used to analyze and predict the scavenging rate of hydroxyl radicals of August melon peel enzyme.

[0066] Depend on Figure 3 and Figure 4 It can be seen that the response surface contour map and the response surface three-dimensional map can intuitively reflect the mutual influence between each single factor. When a single factor takes the zero level, the influence of another or two single factors on other factors and the scavenging rate of hydroxyl radicals can be seen. The response surface contour map shows that the two single factors also influence each other, and the response surface three-dimensional map shows the influence of the two factors on the scavenging rate of hydroxyl radicals. The color of the response surface map can be used to see the significance of the influence of a certain factor on the test result (Y). The change of the color of the surface of the map from blue to red can show the influence on the test result (Y). In addition, the steepness of the curve surface and the density of the contour lines can be used to explain the influence of the factor on the test results. The greater the steepness, the denser the contour lines, and the greater the influence. The significance of the interaction between the two factors can be reflected by the shape of the contour lines. When the contour lines are circular, it means that the interaction between the two factors is not significant. When the contour lines are elliptical, it means that the interaction between the two factors is significant.

[0067] The response surface shows that the effects of yeast dosage (A), sugar dosage (B), temperature (C) and time (D) on the hydroxyl radical scavenging rate (Y) all show a trend of increasing first and then decreasing. By observing the shape of the contour lines, the interaction between yeast dosage and sugar dosage (AB) is significant (P<0.05), and the surface of yeast dosage (A) is steeper than that of sugar dosage (B), and the contour lines are denser, indicating that the effect on the response value (Y) is more significant; while the effects of other factors on the response value are relatively small, which is consistent with the results of ANOVA.

[0068] Physical and chemical composition analysis

[0069] Table 4 Physicochemical analysis of enzymes from August melon peel

[0070] Table 4 Physicochemical analysis of melon peel enzymes in August

[0071] Components Alcohol content / % Soluble solids / % pH Total acid / % Total sugar / % protein / % August melon peel pulp 0 1.4±0.20 6.5±0.1 3.1±0.12 23.45±0.15 20.13±0.43 August melon peel enzyme 6.5±0.20 2.10±0.30 4.7±0.1 9.26±0.24 13.58±0.04 14.95±0.07

[0072] The analysis of the physical and chemical components of the August melon peel enzyme is shown in Table 4. Compared with the control group, the alcohol content in the August melon peel enzyme increased by 6.50%, the soluble solid content increased by 0.70%, the pH changed to 4.7, the total acid content increased by 6.16%, the total sugar content decreased by 9.87%, and the protein content decreased by 5.18%, indicating that the yeast in the enzyme used the added sugar and the original sugar in the peel to carry out alcohol fermentation and reproduced in large quantities, resulting in changes in various substances.

[0073] Analysis of organic acid components of enzyme from August melon peel Figure 5 It can be seen that compared with the control group, the sashikimic acid, quinic acid, lactic acid, malic acid, succinic acid, etc. in the enzyme increased due to fermentation, among which quinic acid increased the most, while salicylic acid decreased a lot after fermentation, indicating that fermentation increased the types and contents of organic acids. The increase of organic acids can effectively inhibit the growth and reproduction of miscellaneous bacteria and increase the flavor of the enzyme.

[0074] Functional substance analysis

[0075] Table 5 Analysis of functional substances in August melon peel enzyme

[0076] Table 5 Analysis of functional substances of melon peel enzyme in August

[0077] Group Total phenols (mg / mL) Total triterpenes (mg / mL) Total flavonoids (mg / mL) SOD enzyme activity (U / mL) August melon peel pulp 0.47±0.08 0.52±0.03 0.25±0.30 22.12±11.13 August melon peel fermented liquid 1.16±0.04 0.29±0.05 1.49±0.20 55.65±12.10

[0078] The analysis of functional substances in August melon peel enzyme is shown in Table 5. Compared with the control group, the total phenol content in August melon peel enzyme increased by 0.69 mg / mL, the total triterpenoid content decreased by 0.23 mg / mL, the total flavonoid content increased by 0.14 mg / mL, and the SOD enzyme activity increased by 33.53 U / mL, indicating that enzyme fermentation is conducive to the increase of total phenol, total flavonoid and SOD enzyme activity, and the reduction of total triterpenoid may be caused by mass loss. This shows that fermentation into enzyme can promote the increase of functional substances and reduce the loss of other substances to a certain extent. The increase of these substances can make the enzyme have a certain antioxidant capacity and can also have a certain protective effect on the body.

[0079] Antioxidant analysis

[0080] Table 6 Analysis of antioxidant activity of enzymes from August melon peel

[0081] Group <![CDATA[OH - / %]]> DPPH / % ABTS / % August melon peel pulp 29.11±0.13 36.89±0.05 25.41±0.03 August melon peel enzyme 69.89±0.03 90.87±0.02 96.58±0.01

[0082] Table 6 Analysis of antioxidant activity of melon peel enzyme in August

[0083] The antioxidant analysis of the melon peel enzyme is shown in Table 6. Compared with the control group, the hydroxyl radical scavenging rate of the melon peel enzyme increased by 40.78%, the DPPH free radical scavenging rate increased by 53.98%, and the ABTS free radical scavenging rate increased by 71.17%, indicating that after fermentation into enzymes, the scavenging of various free radicals has increased, indicating that the enzyme has good free radical scavenging ability and also has strong scavenging ability for some common free radicals. Strong free radical scavenging ability can protect the body well, thereby reducing the occurrence of various diseases and maintaining good health.

[0084] Microbiological analysis

[0085] Table 7 Analysis of enzyme microorganisms in August melon peel

[0086] Table 7 Microbial analysis of melon peel enzyme in August

[0087] Group Total colony count / CFU Yeast / CFU Mold / CFU E. coli / CFU August melon peel pulp 0 0 0 0 August melon peel enzyme 5×103 3×103 0 0 Standards for Edible Plant Enzymes 102(103) -- ≤20(50) 1(10)

[0088] From the analysis of the microorganisms of the August melon peel enzyme, it can be seen in Table 7 that the enzyme control group was sterilized more thoroughly, thus ensuring that the strains were derived from the inoculated strains. Through the determination of the August melon peel enzyme, the total bacteria content in the enzyme was 5×105, the yeast content was 3×105, and the mold and E. coli content were 0. This shows that the yeast content in the enzyme is the highest, and other bacteria may have entered from the air during the operation. The strain content in the enzyme may be harmful to the body, and appropriate sterilization can be carried out to reduce the strain content and the harm of pathogenic bacteria.

[0089] Flavor analysis

[0090] Analysis of flavor substances in August melon peel enzyme Figure 6 It can be seen that compared with the enzyme control group, the number of various flavor substances in the enzyme was 360 less and the relative content increased by 5.28, indicating that after fermentation into enzymes, some flavor substances in the flavor substances were transformed into other flavor substances through fermentation. As fermentation continued over time, the content of flavor substances increased, indicating that fermentation is conducive to the unification of flavor substances and the accumulation of their content.

[0091] in conclusion

[0092] In this study, fresh August melon peel was used as raw material, highly active yeast was used as fermentation strain, and hydroxyl radical scavenging rate was used as evaluation index. The optimal fermentation process conditions of August melon peel enzyme were determined by single factor experiment and response surface methodology, and the final product was obtained by optimal process fermentation, and its physicochemical composition, functional substances, antioxidant activity and microbial indexes were determined. The optimal fermentation conditions were: 2.11% of highly active yeast, 29.68% of sugar, 29.93℃ of fermentation temperature, and 5.05d of fermentation time. Under these optimized conditions, the enzyme hydroxyl radical scavenging rate was 69.89%. The physicochemical composition, functional substances, antioxidant activity, microbial composition and flavor substances of the enzyme were determined. The components and antioxidant capacity of the enzyme are as follows: the total acid content increased significantly by 6.16%, the total phenol content increased by 0.69 mg / mL, the total triterpenoid content decreased by 0.23 mg / mL, the total flavonoid content increased by 0.14 mg / mL, the SOD enzyme activity increased by 33.53 U / mL, the hydroxyl radical scavenging rate increased by 40.78%, the DPPH radical scavenging rate increased by 53.98%, and the ABTS radical scavenging rate increased by 71.17%. The free radical scavenging rate increased significantly, the total colony count was 5×103 CFU, among which the yeast content was the largest, reaching 3×103 CFU, and the relative content of various flavor substances in the enzyme increased significantly by 5.28. From the above, it can be seen that after the fermentation process, its physicochemical indicators, functional substances, antioxidant activity, microbial content and relative content of flavor substances have increased significantly, and the quality has been greatly improved. Therefore, this study can not only enrich the wax gourd product series, but also provide data support for the yeast fermentation preparation of functional enzymes, antioxidant enzymes, etc., and has good development value.

[0093] The above is only an embodiment of the present invention, and common knowledge such as structure and characteristics is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. The preparation process of the melon peel enzyme is characterized by: The following steps are involved: S1 Raw material selection and pretreatment: Select fresh August melon peels, wash them and crush them into peel mud; S2 enzymatic treatment: add appropriate amount of water to the peel paste, add 2% of cellulase and pectinase respectively, bathe at 50℃ for 2h, and sterilize at 65℃ for 30min; S3 fermentation: using highly active yeast as the fermentation strain, the addition amount of highly active yeast is 0.5% to 1.5%, the addition amount of white sugar is 5% to 25%, the fermentation temperature is 25℃ to 45℃, and the fermentation time is 3d to 7d; S4 post-treatment: After the fermentation is completed, the solution is separated by centrifugation at 4000r / min for 15min, and the obtained solution is stored at low temperature.

2. The preparation process of the melon peel enzyme according to claim 1, characterized in that: In S3 fermentation, the amount of high-activity yeast added was 2.11%, the amount of sugar was 29.68%, the fermentation temperature was 29.93℃, and the fermentation time was 5.05d.

3. The melon peel enzyme according to claim 2, characterized in that: The physical and chemical indicators of the enzyme are: pH value of 4.7, alcohol content of 6.50% vol, soluble solid content of 2.10%, total acid content of 9.60%, total sugar content of 13.58%, protein content of 14.95%, and contains 17 kinds of organic acids.

4. The melon peel enzyme prepared according to the preparation process of claim 2 is characterized in that: The functional substance indicators of the enzyme are: total phenol content of 1.16 mg / mL, total triterpene content of 0.29 mg / mL, total flavonoid content of 1.49 mg / mL, and SOD enzyme activity of 55.65 U / mL.

5. The melon peel enzyme prepared according to the preparation process of claim 2 is characterized in that: The antioxidant capacity indicators of the enzyme are: hydroxyl radical scavenging rate is 69.89%, DPPH free radical scavenging rate is 90.87%, and ABTS free radical scavenging rate is 96.58%.

6. The melon peel enzyme prepared according to the preparation process of claim 2, characterized in that: The microbial index of the enzyme is: the total colony count is 5×10 3 CFU, yeast count is 3×10 3 CFU, mold and E. coli counts were all 0 CFU.

7. The application of melon peel enzyme is characterized by: Use of the melon peel enzyme according to any one of claims 3 to 6 in the preparation of foods and health products.

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