Method for inhibiting polyphenol oxidase in fruit and vegetable products

Abstract

The invention discloses a method for inhibiting polyphenol oxidase in fruit and vegetable products. The method for inhibiting polyphenol oxidase in the fruit and vegetable product comprises the following step: treating an intermediate product or a finished product of the fruit and vegetable product by using dihydroquercetin so as to inhibit the activity of polyphenol oxidase. The natural component dihydroquercetin is adopted as a natural inhibitor, the PPO enzyme activity of fruit and vegetable products can be inhibited, sensory and flavor deterioration caused by enzymatic browning is relieved, the acceptability of consumers is greatly improved, and waste of precious food resources and economic losses of production links such as storage, transportation and processing are expected to be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of food science and engineering, and in particular relates to a method for inhibiting polyphenol oxidase in fruit and vegetable products. Background Art

[0002] Polyphenol oxidase (PPO), also known as tyrosinase, is a type of enzyme that catalyzes the oxidation of phenolic substances and is widely found in animals, plants, and microorganisms. During the storage, transportation, and processing of fresh fruits and vegetables and their products, PPO mediates enzymatic browning reactions, catalyzing phenolic substances to produce highly reactive quinones, which then undergo condensation reactions with sugars, amino acids, etc. to form dark, difficult-to-degrade substances, resulting in deterioration of the product's color, taste, and other sensory qualities, reduced nutritional value, and ultimately a significant decline in consumer acceptance, resulting in huge amounts of food resource waste and economic losses worldwide each year. Seeking effective inhibition of PPO enzyme activity has always been a research focus in the field of food processing.

[0003] At present, synthetic anti-browning agents such as sodium metabisulfite, EDTA and sodium isoascorbate are widely used to inhibit enzymatic browning, but the use of synthetic food additives still has certain safety risks. Nowadays, with the progress of economy and society and the awakening of health awareness, people are more inclined to eat organic raw materials from natural sources because of their high safety and green environmental protection. It is reported that many natural extracts have inhibitory effects on PPO, such as rice bran extract, green tea extract and roselle extract. However, due to the unclear composition of their specific chemical components, unclear inhibition mechanism, and large differences between different raw material batches, it is difficult to achieve commercial-scale application. In fact, some natural phytochemicals play a vital role in this process.

[0004] Therefore, finding an efficient, safe, and mechanism-clear natural PPO inhibitor is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for inhibiting polyphenol oxidase in fruit and vegetable products. The present invention can significantly reduce the PPO enzyme activity by treating the intermediate products or finished products of fruit and vegetable products with dihydroquercetin (Taxifolin), thereby effectively inhibiting the occurrence of enzymatic browning and maintaining product quality.

[0006] To achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention protects a method for inhibiting polyphenol oxidase in fruit and vegetable products, comprising the following steps: treating an intermediate product or a finished product of the fruit and vegetable product with dihydroquercetin to inhibit the activity of polyphenol oxidase in the fruit and vegetable product.

[0007] In the above method, the method is as follows A1) or A2): A1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; A2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

[0008] In a second aspect, the present invention protects a method for inhibiting browning of fruit and vegetable products, comprising the following steps: treating an intermediate product or a finished product of a fruit and vegetable product with dihydroquercetin to inhibit browning of the fruit and vegetable product.

[0009] In the above method, the method is as follows B1) or B2): B1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; B2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

[0010] Based on the technical solutions of the first and second aspects above, by adding dihydroquercetin, dihydroquercetin binds to PPO in fruit and vegetable products and inhibits its activity, thereby effectively inhibiting its enzymatic browning; Furthermore, the fruit and vegetable juice is apple juice, pear juice or peach juice; The fruit and vegetable puree is apple puree, pear puree or purple potato puree; The fruit and vegetable sauce is applesauce, avocado sauce or strawberry sauce; The canned fruits and vegetables are canned apples, canned pears or canned yellow peaches.

[0011] In at least one embodiment of the present invention, the mass percentage of the fruit and vegetable components in the fruit and vegetable product is 100%; The concentration of dihydroquercetin in the fruit and vegetable product is preferably 10 -3 ~10 mg / mL, more preferably 10 -2 ~10 - 1 mg / mL, such as 0.02 mg / mL.

[0012] In one embodiment of the present invention, the fruit and vegetable product is 100% pear juice, and the concentration of dihydroquercetin in the pear juice is 10-30 mg / L, preferably 20 mg / L.

[0013] In a third aspect, the present invention protects a method for maintaining the quality of fruit and vegetable products, comprising the following steps: treating an intermediate product or a finished product of the fruit and vegetable products with dihydroquercetin to maintain the quality of the fruit and vegetable products.

[0014] In the above method, the method is as follows C1) or C2): C1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; C2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min; Said qualities are colour and / or degree of browning.

[0015] In a fourth aspect, the present invention protects a method for maintaining or increasing the total phenol content in fruit and vegetable products, comprising the following steps: treating an intermediate product or a finished product of the fruit and vegetable product with dihydroquercetin to maintain or increase the total phenol content in the fruit and vegetable product.

[0016] In the above method, the method is as follows D1) or D2): D1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; D2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

[0017] Specifically, the total phenol content is the total phenol content tested by the Folin-Ciocalteu method.

[0018] Based on the technical solutions of the third and fourth aspects above, by adding dihydroquercetin, the quality of fruit and vegetable products can be maintained, and the total phenol content in the fruit and vegetable products can be maintained or increased.

[0019] In one embodiment of the present invention, the fruit and vegetable product is 100% apple juice, and the concentration of the dihydroquercetin in the apple juice is 20 mg / L.

[0020] Furthermore, in the above method, the fresh-cut fruits and vegetables may be fresh-cut eggplant, fresh-cut water chestnut or fresh-cut lotus root.

[0021] In another embodiment of the present invention, the fruit and vegetable product is fresh-cut eggplant; specifically, every 100 g of the intermediate product of the fruit and vegetable product is immersed in 500 mL of the aqueous solution of dihydroquercetin; the mass concentration of the aqueous solution of dihydroquercetin is 0.2%; and the immersion time is 10 min.

[0022] Through immersion, dihydroquercetin can combine with PPO in the surface of fruits and vegetables and inhibit its activity, thereby effectively inhibiting enzymatic browning and maintaining the quality of related products.

[0023] In any of the above methods, it can be understood that the intermediate product of the fruit and vegetable product is a general term for products in the process of production from fruit and vegetable raw materials to fruit and vegetable products, but before becoming the final product, such as fruit and vegetable slices used to prepare dried fruits and vegetables or fresh-cut fruits and vegetables; the finished product of the fruit and vegetable product is the product after the fruit and vegetable product is processed. In an embodiment of the present invention, the intermediate product of the fruit and vegetable product is an eggplant slice with a thickness of 0.5 cm. It can be understood that when the product is dried fruits and vegetables, the method further includes the step of drying the fruit and vegetable slices after the processing is completed.

[0024] In a fifth aspect, the present invention protects the use of dihydroquercetin in any one of the following P1)-P6): P1) inhibit polyphenol oxidase activity; P2) inhibit polyphenol oxidase-mediated enzymatic browning; P3) Inhibit the activity of polyphenol oxidase in fruits and vegetables or fruit and vegetable products; P4) Inhibit browning of fruits and vegetables or fruit and vegetable products; P5) Maintain the quality of fruits, vegetables or fruit and vegetable products; P6) Maintain or increase the total phenolic content of fruits, vegetables or fruit and vegetable products.

[0025] In the above applications, in P1)-P2), the inhibition is manifested as blocking the catalytic oxidation of the substrate by polyphenol oxidase, and the substrate is L-dopamine; In P3)-P6), the fruit and vegetable products are fresh-cut fruits and vegetables, fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruits and vegetables; P5), the quality is color and / or browning degree.

[0026] In the present invention, the dihydroquercetin may be a pure dihydroquercetin, or may be a mixture or a crude extract containing dihydroquercetin.

[0027] The present invention has the following beneficial effects: The dihydroquercetin in the present invention is a natural ingredient commonly found in food. It belongs to the vitamin P family and is commonly found in citrus fruits, grapes, onions, green tea, wine and many other foods. It is naturally derived, green and safe, and even has multiple health and physiological functions for the human body. In April 2021, it was officially approved by the National Health Commission as a new food raw material. The dihydroquercetin in the present invention can be added to food to improve the nutritional value of the food.

[0028] The present invention can significantly reduce the PPO enzyme activity in fruit and vegetable products through the simple operation of adding dihydroquercetin to the products, thereby effectively inhibiting the occurrence of enzymatic browning, retaining the original fresh quality of the products as much as possible, and even making them have better color quality and higher nutritional value.

[0029] The present invention uses the natural ingredient dihydroquercetin to inhibit the PPO enzyme activity of fruit and vegetable products to reduce the sensory and flavor deterioration caused by enzymatic browning, which can greatly improve consumer acceptance and is expected to reduce the waste of precious food resources and economic losses in production links such as storage, transportation and processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The PPO enzyme activity at different dihydroquercetin concentrations in Example 1.

[0031] Figure 2 This is the molecular docking result of dihydroquercetin and PPO in Example 1.

[0032] Figure 3 The inhibitory effect of dihydroquercetin on PPO enzymatic browning in Example 1 (the first column is the untreated control group, and the second column is the experimental group).

[0033] Figure 4 The effect of adding dihydroquercetin on the appearance of pear juice in Example 2 (from left to right are control 2D, treatment 2A, treatment 2B and treatment 2C, and the amount of dihydroquercetin added is 0, 10, 20 and 30 mg / L, respectively).

[0034] Figure 5 This is the inhibitory effect of adding dihydroquercetin in Example 2 on PPO in pear juice.

[0035] Figure 6 This is the effect of adding dihydroquercetin in Example 3 on maintaining the color parameters of apple juice.

[0036] Figure 7 This is the effect of adding dihydroquercetin in Example 3 on reducing the browning degree of apple juice.

[0037] Figure 8 This is the effect of adding dihydroquercetin in Example 3 on maintaining the total phenolic content of apple juice.

[0038] Fig. 9 The effect of adding dihydroquercetin on the color preservation of fresh-cut yam slices in Example 3 (the upper row is the control sample, and the lower row is the sample after being immersed in the dihydroquercetin solution).

[0039] Fig.10 The effect of adding dihydroquercetin on maintaining the color of fresh-cut eggplant slices in Example 3 (the left column is the control sample, and the right column is the sample after being immersed in the dihydroquercetin solution). DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0041] The methods used in the following examples, unless otherwise specified, are all conventional methods, carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0042] The dihydroquercetin in the following examples was purchased from Shanghai Yuanye Biotechnology Co., Ltd. with product number S31601.

[0043] Example 1: Experimental study on the inhibition of PPO by dihydroquercetin (1) PPO inhibition experiment Inhibitor stock solutions of 1.25-2.5 mol / L were prepared in PBS buffer (0.05 mol / L, pH=6.8). Subsequently, 0.2 mL of PPO stock solution (0.5 mg / mL, 0.05 mol / L PBS buffer, pH=6.8) was mixed with different volumes of inhibitor stock solutions and made up to 5.0 mL with PBS buffer in a 10 mL centrifuge tube, where the final concentration of PPO was 20 μg / mL and the final concentration of inhibitor was 0-600 μmol / L, which were 0, 5, 10, 25, 50, 150, 300 and 600 μmol / L, respectively.

[0044] The enzyme mixture (mixed solution of PPO and inhibitor prepared above) was placed in a constant temperature water bath at 25°C for 30 minutes. The absorbance of the system of 50 μL of the mixed reaction solution and 200 μL of L-DOPA solution (50 mmol / L, PBS) was monitored at 475 nm using a fully automatic multifunctional microplate reader. The change in absorbance per unit time was the enzyme activity. The PPO sample without inhibitor was used as a blank control.

[0045] The relative residual activity of the sample was calculated by the following formula: RA=A / A0×100%; Where A0 is the PPO activity of the blank control sample, and A is the PPO activity of the experimental sample.

[0046] The curve is drawn with the concentration of dihydroquercetin at different concentrations as the horizontal axis and the relative residual activity of the sample corresponding to the concentration as the vertical axis. Figure 1 .Depend on Figure 1 It can be seen that dihydroquercetin can effectively inhibit PPO enzyme activity and show a dose-dependency, and its half-inhibitory concentration is about 300 μM, which indicates that dihydroquercetin has a high efficiency inhibitory ability on PPO.

[0047] (2) Molecular docking Semi-flexible molecular docking of PPO (PDB ID: 2Y9X) and dihydroquercetin was performed based on the commercial software AutoDock-Vina. The grid parameters were set to 102Å×104Å×104Å, and the center coordinates were x=-29.359, y=-2.937, and z=-107.333. The experimental results are shown in Figure 2 shown.

[0048] like Figure 2 As shown, dihydroquercetin can directly bind to the active center of PPO and form hydrogen bonds with amino acid residues closely related to the catalytic function, such as His 85, His 244 and His 263, which indicates that dihydroquercetin may effectively block the catalytic oxidation of substrates by PPO through competitive inhibition.

[0049] (3) Anti-browning test 50 μL of enzyme solution (0.1 mg / mL) and enzyme reaction solution (containing 0.1 mg / mL PPO and 100 μM dihydroquercetin) were mixed with 200 μL of L-DOPA solution (50 mmol / L, PBS) in a 96-well transparent ELISA plate, placed in a dark environment, and observed after 6 hours. Figure 3 shown.

[0050] like Figure 3 As shown, PPO catalyzes L-DOPA to generate a large amount of black products, and the presence of dihydroquercetin can effectively inhibit PPO-mediated enzymatic browning, ultimately greatly reducing the generation of black products.

[0051] Example 2: Effect of dihydroquercetin addition on pear juice appearance and PPO enzyme activity In order to study the effects of different concentrations of dihydroquercetin on the appearance and PPO activity of pear juice, the following treatment groups and control groups were set up: Treatment 2A, 10 mg / L dihydroquercetin + pear juice (1) Peel and cut 2 kg of snow pear into pieces, put them into a juicer, and squeeze the juice for about 3 min. Then filter the juice with 4 layers of gauze to obtain the pear juice. (2) Add 10 mg of dihydroquercetin (10 mg / L) to 1 L of pear juice.

[0052] Treatment 2B, 20 mg / L dihydroquercetin + pear juice (1) Peel and cut 2 kg of snow pear into pieces, put them into a juicer, and squeeze the juice for about 3 min. Then filter the juice with 4 layers of gauze to obtain the pear juice. (2) Add 20 mg of dihydroquercetin (20 mg / L) to 1 L of pear juice.

[0053] Treatment 2C, 30 mg / L dihydroquercetin + pear juice (1) Peel and cut 2 kg of snow pear into pieces, put them into a juicer, and squeeze the juice for about 3 min. Then filter the juice with 4 layers of gauze to obtain the pear juice. (2) Add 30 mg of dihydroquercetin (30 mg / L) to 1 L of pear juice.

[0054] Control 2D, pear juice 2 kg of snow pear was peeled and cut into pieces, put into a juicer, and the juice was squeezed for about 3 min and filtered through 4 layers of gauze to obtain the filtrate to obtain pear juice.

[0055] The treated samples were vortexed for 30 s, and after being fully mixed, they were photographed and observed together with the control group in a camera box.

[0056] The appearance of the pear juice obtained after juicing in each treatment group is shown in Figure 4 .

[0057] Depend on Figure 4 It can be seen that after juicing, the originally clear pear juice becomes turbid and reddish due to large-scale exposure to oxygen. After adding dihydroquercetin, the pear juice becomes significantly clearer. When the addition amount is 10 mg / L, the pear juice is no longer turbid but still reddish and yellowish. When the addition amount reaches 20 mg / L, the yellowness of the pear juice becomes lighter. This shows that the addition of dihydroquercetin can effectively inhibit the enzymatic browning of pear juice.

[0058] The treated samples and the control group were placed in an ice bath for 30 min. 1.0 mL of juice (each treated sample and the control group) was taken and mixed with 2.0 mL of 0.05 M catechol (0.05 M PBS buffer, pH = 6.8) solution, and the absorbance change within 1 min of the reaction was immediately measured at 420 nm at room temperature (25 ± 1 ° C). Each sample was measured three times and the average value was taken.

[0059] PPO enzyme activity ( ∆OD / min): The change in absorbance of the entire enzymatic reaction system within a reaction time of 1 min, that is, ∆OD . Relative residual enzyme activity (%) = enzyme activity of treated samples / enzyme activity of untreated blank samples × 100%.

[0060] PPO enzyme activity at different dihydroquercetin addition levels Figure 5 .

[0061] Depend on Figure 5 It can be seen that dihydroquercetin has an inhibitory effect on PPO. With the increase of the addition amount, the residual enzyme activity of PPO decreased to 85.16%, 42.98% and 47.58% respectively. This shows that the presence of dihydroquercetin reduces the activity of PPO in pear juice, thereby effectively inhibiting the enzymatic browning of pear juice, making the pear juice more refreshing and bright, and easier to be accepted by consumers.

[0062] Example 3: Effect of dihydroquercetin on apple juice quality and total phenol content In order to study the effects of different concentrations of dihydroquercetin on apple juice quality and total phenolic content, the following treatment groups and control groups were set up: Processing 3A, dihydroquercetin + apple juice (1) Peel and cut 2 kg of Gala apples into pieces, put them into a juicer, and squeeze the juice for about 3 min. Then filter the juice with 4 layers of gauze to obtain apple juice. (2) Add 20 mg of dihydroquercetin to 1 L of apple juice.

[0063] Control 3B, apple juice Peel and cut 2 kg of Gala apples into pieces, put them into a juicer, squeeze the juice for about 3 minutes, and filter it with 4 layers of gauze to obtain apple juice.

[0064] The color, browning degree and total phenol content of the apple juice obtained by squeezing the above-mentioned treatment 3A and control 3B were tested: 1) Color parameters: Use a colorimeter, with a standard white board as the standard at room temperature, and set the parameters to: RSIN-specular reflection, area 0.375 inches. Measure in this mode L *、 a*、 b * value. Among them: L * indicates brightness, a *>0, indicating the degree of redness, a *<0, indicating green degree; b *>0, indicating the degree of yellowness, b *<0, indicating the degree of blue.

[0065] Comparison of color parameters of apple juice with dihydroquercetin and control group Figure 6 Obviously, although apple juice L *and b *The value has not changed significantly, but a The * value was significantly reduced, which means that the red color of apple juice with added dihydroquercetin was lighter and the enzymatic browning was effectively inhibited.

[0066] 2) Browning degree BD: Using the spectrophotometric method, the juice was diluted with an equal volume of acetone, centrifuged at 1500 rpm for 10 minutes in a refrigerated centrifuge, and then passed through a 0.45 μm nitrocellulose membrane. The absorbance was measured at 420 nm using a UV spectrophotometer at 25±2°C. The absorbance value was taken as the browning degree BD. The browning degree of apple juice added with dihydroquercetin and the control group is as follows Figure 7 As shown. Figure 7 It can be seen that the browning degree of apple juice added with dihydroquercetin is significantly lower.

[0067] 3) Total phenol content: Folin-Ciocalteu method, preparation of extract: take 10 mL of juice, add 20 mL of anhydrous methanol, extract at 4°C for 30 min, centrifuge at 10000×g, 4°C for 10 min, and take the supernatant for use. Dilute Folin phenol reagent 10 times with ultrapure water at 1:9 (v:v), dilute 0.1 mL of extract to 0.5 mL and mix with 2 mL of diluted Folin phenol reagent, then add 0.8 mL of 7.5% Na2CO3 solution, react at room temperature in the dark for 1 h, measure the absorbance at 765 nm with a spectrophotometer, and the total phenol content is expressed as mg gallic acid per 100 g sample. Preparation of gallic acid standard curve: prepare gallic acid standard solutions with concentrations of 10, 20, 40, 60, 80, and 100 μg / mL, respectively. 0.4 mL of gallic acid solution of different concentrations was mixed with 2 mL of 10-fold diluted Folin phenol reagent, and then 0.8 mL of 7.5% Na2CO3 solution was added. The mixture was reacted at room temperature in the dark for 1 h, and the absorbance at 765 nm was measured by a spectrophotometer.

[0068] Total phenolic content of apple juice supplemented with dihydroquercetin and the control group Figure 8 As shown. Figure 8 It can be seen that dihydroquercetin can effectively maintain the total phenolic content of apple juice by inhibiting PPO activity, and even increase it, thereby improving the nutritional value of apple juice.

[0069] Example 4: Effect of dihydroquercetin on the quality of fresh-cut fruits and vegetables Fresh-cut yam / eggplant: Wash and peel (eggplant is not peeled) and slice into 0.5 cm thick slices. Soak in 0.2% dihydroquercetin solution, with a material-liquid ratio of about 1:5 (i.e. 100 g of material is soaked in 500 mL of solution). Take out and drain after 10 min. The sample soaked in water is used as a blank control. Then take photos of the samples immediately.

[0070] like Fig. 9 As shown in the figure, the upper row of samples are slices of iron stick yam soaked in water. It can be found that the color brightness and whiteness of the samples are significantly higher than those of the samples soaked in inhibitor solution in the lower row (brightness value L * Significantly decreased from 85.22 to 72.33).

[0071] like Fig.10 As shown in the figure, the sample on the left is the eggplant slices soaked in water. It can be found that the sample has a significant browning, and the color brightness and whiteness are significantly lower than the sample on the right after being soaked in the inhibitor solution (brightness value L *Significantly increased from 52.09 to 72.16).

[0072] It can be seen from the above results that, for fresh-cut fruits and vegetables, the dihydroquercetin impregnation method of the present invention is suitable for fresh-cut eggplants, and how to optimize the treatment of iron stick yam with dihydroquercetin needs further study.

[0073] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for inhibiting polyphenol oxidase in fruit and vegetable products, characterized in that: The method comprises the following steps: treating the intermediate product or finished product of the fruit and vegetable product with dihydroquercetin to inhibit the activity of polyphenol oxidase in the fruit and vegetable product.

2. The method for inhibiting polyphenol oxidase in fruit and vegetable products according to claim 1, characterized in that: The method is as follows A1) or A2): A1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01 to 100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; A2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

3. A method for inhibiting browning of fruit and vegetable products, characterized in that: The method comprises the following steps: treating the intermediate product or the finished product of the fruit and vegetable product with dihydroquercetin to inhibit the browning of the fruit and vegetable product.

4. The method for inhibiting browning of fruit and vegetable products according to claim 3, characterized in that: The method is as follows B1) or B2): B1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; B2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

5. A method for maintaining the quality of fruit and vegetable products, characterized in that: The method comprises the following steps: treating the intermediate product or finished product of the fruit and vegetable product with dihydroquercetin to maintain the quality of the fruit and vegetable product.

6. The method for maintaining the quality of fruit and vegetable products according to claim 5, characterized in that: The method is as follows C1) or C2): C1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; C2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min; Said qualities are colour and / or degree of browning.

7. A method for maintaining or increasing the total phenol content in fruit and vegetable products, characterized in that: The method comprises the following steps: treating the intermediate product or finished product of the fruit and vegetable product with dihydroquercetin to maintain or increase the total phenol content in the fruit and vegetable product.

8. The method for maintaining the quality of fruit and vegetable products according to claim 7, characterized in that: The method is as follows D1) or D2): D1) The treatment comprises: adding dihydroquercetin to the finished fruit and vegetable product; The fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, fruit and vegetable sauce or canned fruit and vegetable; The mass percentage of the fruit and vegetable components in the fruit and vegetable product is 0.01-100%; The concentration of dihydroquercetin in the fruit and vegetable product is 10 -7 ~10 mg / mL; D2) The treatment comprises: immersing the intermediate product of the fruit and vegetable product in an aqueous solution of dihydroquercetin, and taking it out after the immersion is completed to prepare the fruit and vegetable product; The fruit and vegetable products are dried fruits and vegetables or fresh-cut fruits and vegetables, preferably fresh-cut eggplant; Every 10 to 500 g of the intermediate product of the fruit and vegetable preparation is immersed in 500 mL of the aqueous solution of dihydroquercetin; The mass concentration of the aqueous solution of dihydroquercetin is 0.005% to 0.2%; The immersion time is 0.5 to 60 min.

9. Use of dihydroquercetin in any one of the following P1)-P6): P1) inhibit polyphenol oxidase activity; P2) inhibit polyphenol oxidase-mediated enzymatic browning; P3) Inhibit the activity of polyphenol oxidase in fruits and vegetables or fruit and vegetable products; P4) Inhibit browning of fruits and vegetables or fruit and vegetable products; P5) Maintain the quality of fruits, vegetables or fruit and vegetable products; P6) Maintain or increase the total phenolic content of fruits, vegetables or fruit and vegetable products.

10. The use according to claim 9, characterized in that: In P1)-P2), the inhibition is manifested as blocking the catalytic oxidation of the substrate by polyphenol oxidase, and the substrate is L-dopamine; In P3)-P6), the fruit and vegetable products are fruit and vegetable juice, fruit and vegetable puree, dried fruit and vegetable, fruit and vegetable sauce, canned fruit and vegetable or fresh-cut fruit and vegetable; P5), the quality is color and / or browning degree.

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