Method for clarifying pomegranate juice by adopting compound polysaccharide clarifying agent and application

Abstract

The invention discloses a clarification method of pomegranate juice. The clarification method comprises the steps of raw material pretreatment, compound polysaccharide clarifying agent treatment, light transmittance measurement and the like. The compound polysaccharide clarifying agent is adopted to clarify the pomegranate juice, the clarification treatment can effectively reduce mixing substances in the pomegranate juice, the light transmittance and the storage stability of the juice are improved, the juice is clear and transparent, the appearance quality is enhanced, and consumers are attracted. Besides, compared with a traditional natural clarification method, the pomegranate juice clarified by the compound polysaccharide clarifying agent is higher in oxidation resistance, anthocyanin content, protein content and total phenol content, which indicates that the polysaccharide clarifying agent not only effectively improves the color and appearance of the product, but also better preserves the nutritional ingredients of the pomegranate juice.

Description

Technical Field

[0001] The invention relates to a method for clarifying pomegranate juice by using a composite polysaccharide clarifier and application thereof, belonging to the technical field of food processing. Background Art

[0002] As a member of the Punicaceae family, pomegranate (Punica L.) has a variety of health functions, such as antioxidant, anti-cancer, anti-inflammatory, vision improvement and beauty properties. Therefore, pomegranate juice is favored by consumers as a high-quality beverage and has great market potential at home and abroad. Although pomegranate is rich in nutrients, its juice contains a large amount of macromolecular substances such as pectin, tannins, cellulose, starch, tannins, protein complexes, etc., which are prone to color changes and turbidity during processing, storage and sales. Therefore, before preparing pomegranate juice products, clarification treatment is required. Fresh juice will become turbid immediately after the initial squeezing, mainly due to the suspension of pectin particles in the cell wall. During storage, the turbidity of the juice is mainly formed by mist, which is mainly affected by the interaction between polyphenols and fogging active proteins. At present, in the large-scale processing of apple juice, pear juice, blueberry juice, cherry juice, cranberry juice, grape juice and other juices, clarification technologies such as adding pectinase, xanthan gum, chitosan, diatomaceous earth, etc. are often used to solve the problems of pectin degradation and the generation of precipitation and mist. Clarification is a basic process to prevent turbidity in fresh pomegranate juice during processing and storage. However, the current deep-processing of pomegranate products and their scale of production are far behind other fruits, especially the clarification of pomegranate juice has not been completely solved. In order to improve the quality of pomegranate juice products in my country, this study used a composite polysaccharide clarifier to clarify pomegranate juice and screened the best clarification process, aiming to provide technical support and reference for my country's pomegranate juice industry. Summary of the invention

[0003] The present invention aims to develop a pomegranate juice clarification method to achieve the best clarification effect. After clarification under the process conditions, the light transmittance of the pomegranate juice is 82.357%, and the anthocyanin content is 176.337 mg / L. The antioxidant capacity, anthocyanin content, protein content and total phenol content of the pomegranate juice are improved, the product color is improved, and the pomegranate juice is given a bright red juice color.

[0004] To achieve the above object, the technical solution adopted in the present invention is: A pomegranate juice clarification technology specifically comprises the following steps: (1) Raw material pretreatment: Select fresh pomegranates that are free of pests and diseases as raw materials to ensure their high quality. After careful cleaning to remove impurities and residues on the surface, the pomegranate juice is finally crushed and squeezed to obtain the pomegranate juice.

[0005] (2) Preparation of composite polysaccharide clarifier: Chitosan and sodium alginate are prepared into 1%~2% (w / v) clarifier solutions respectively. Chitosan needs to be dissolved in 1%~2% acetic acid solution, and sodium alginate is dissolved in distilled water in a certain proportion. The two types of clarifiers are then diluted in proportion to prepare clarification solvents with a concentration of 0.05~0.1g / L. When in use, the chitosan and sodium alginate solutions are mixed in a volume ratio of 1:1~1:1.5 to prepare the composite polysaccharide clarifier.

[0006] (3) Clarification of pomegranate juice: Add 3-10% of the prepared complex polysaccharide clarifier and 0.1%-0.3% of CaCl2 to the pomegranate juice, mix the clarifier and pomegranate juice thoroughly, and ensure that the clarifier is evenly dispersed in the juice.

[0007] (4) Reaction and clarification: Place the mixed pomegranate juice treated in step 3 in a constant temperature water bath at 30°C to 40°C and react for 30 to 40 minutes under this condition. During this process, the polysaccharide clarifier will react with the impurities in the juice and form a precipitate. After the reaction is completed, the precipitate will gradually settle to the bottom, making the juice clear and transparent, that is, the pomegranate juice with the best clarification effect is obtained.

[0008] The present invention further discloses the use of the pomegranate juice prepared by the method in improving the light transmittance of the pomegranate juice, and improving the antioxidant capacity, anthocyanin content, protein content and total phenol content of the pomegranate juice. The experimental results show that the pomegranate juice clarified by the composite polysaccharide is superior to the naturally clarified pomegranate juice in terms of light transmittance, antioxidant capacity, anthocyanin content, protein content, total phenol content and soluble solid content. The pomegranate juice clarified by the composite polysaccharide has a brighter color, a richer red color, and is closer to the original color of the pomegranate. The composite polysaccharide clarification method can effectively improve the quality of the pomegranate juice, making it clearer and more transparent, with a better taste, and retaining more nutrients.

[0009] The main tests for the pomegranate juice prepared by the present invention include: (1) Determination of light transmittance: The light transmittance was determined by spectrophotometry with distilled water as the reference solution. The light transmittance of pomegranate juice was measured at 720 nm and the result was expressed in %.

[0010] (2) Antioxidant activity assay (DPPH): refer to (Xiao et al. 2020).

[0011] Add 1000 μL of DPPH solution and 800 μL Tris-HCl buffer (pH 7.4) to the test tube. Then add 200 μL of sample solution and mix quickly. Store the solution at room temperature for 30 minutes. Record the absorbance of the solution at 517 nm. Use a mixed solution containing 1200 μL ethanol and 800 μL TrisHCl buffer (pH 7.4) as a blank. The DPPH free radical scavenging rate (%) is obtained by the following formula: DPPH free radical scavenging rate (%) = (A 1 – A 2 ）´ 100 / A 1 Where: A1: absorbance of the solution with ethanol added instead of the test sample; A2: absorbance of the test sample solution.

[0012] (3) Anthocyanin determination: Anthocyanin was determined by the pH differential method (Chen D et al., 2013).

[0013] Prepare pH 1.0 buffer (0.2mol / L KCL:0.2mol / L HCl=25:67 (V / V)) and pH 4.5 buffer (1mol / L NaAc:1mol / LHCl:H2O=100:60:90 (V / V / V)), take two 10mL test tubes, add 0.5mL of pomegranate juice to each, dilute to 5mL with pH 1.0 and pH 4.5 buffers respectively, and keep in dark for 1h. Measure the absorbance value A at 520nm and 700nm respectively, and calculate the anthocyanin content according to the following formula, and the result is calculated as cyanidin-3-glucoside: Anthocyanin content (mg / L) = DA ´ Mw ´ DF ´ 1000 / e ´ 1 Where: ∆A = pH1.0(A520nm-A700nm) – pH4.5(A520nm-A700nm); Mw: cyanidin-3-glucoside as standard (449.2); ε: molar extinction coefficient of cyanidin-3-glucoside 26900; DF: sample dilution factor; 1 is the optical path length of the cuvette.

[0014] (4) Protein determination: The Coomassie Brilliant Blue-G250 method was used to detect the soluble protein content (Cao et al., 2007).

[0015] (5) Determination of total phenols: The total phenols were determined by the Folin phenol method (Ren et al., 2015).

[0016] Accurately weigh 0.005g of gallic acid standard sample, dissolve it in distilled water and dilute to 50mL. The concentration of the standard solution is 0.1mg / mL. Accurately measure 0.1, 0.2, 0.3, 0.4, and 0.5mL of the above standard solution and dilute to 5mL, add 500μL of Folin phenol reagent, shake well, let stand for 5min, add 500μL of 20% sodium carbonate solution, shake and stand in the dark for 1h, measure the absorbance at 765nm, and draw a standard curve with gallic acid content as the horizontal axis. Take 50ul of sample for measurement, and calculate the total phenol content according to the standard curve.

[0017] (6) Soluble solids: Soluble solids were measured at room temperature (25 ± 2 °C) using an Abbe refractometer with distilled water as the blank. The results were expressed in °Brix. Each test was performed three times in parallel and the results were averaged.

[0018] (7) Color determination: The color parameters of pomegranate juice were determined using a fully automatic colorimeter. The L*, a*, and b* values ​​of the samples were measured in the reflectance mode.

[0019] (8) Effect evaluation: The transmittance and anthocyanin content were used as indicators of pomegranate juice clarification effect to evaluate the effect of the clarification technology.

[0020] The present invention mainly solves the problems of low clarification efficiency, poor color and large nutritional loss of pomegranate juice, and focuses on investigating the optimal ratio of a composite polysaccharide clarifier and its influence on the quality of pomegranate juice. The main difficulty lies in how to find a composite polysaccharide clarifier that can effectively clarify pomegranate juice and retain its nutritional components and color to the greatest extent, and determine its optimal ratio.

[0021] (1) The present invention uses a composite polysaccharide clarifier to clarify pomegranate juice. The clarification process can effectively remove the turbidity-causing substances in the pomegranate juice, improve the light transmittance of the pomegranate juice, and enhance the storage stability of the pomegranate juice; make the juice clear and transparent, improve the appearance quality, and attract consumers.

[0022] (2) The use of a composite polysaccharide clarifier to clarify pomegranate juice increased the antioxidant capacity, anthocyanin content, protein content, and total phenol content of the pomegranate juice, improved the product color, and gave the pomegranate juice a bright red color.

[0023] Table 1 is a comparison table of pomegranate juice components clarified by the composite clarifier of the present invention and naturally clarified BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a color comparison chart of the composite clarifier and natural clarification of the present invention; The pictures show pomegranate juice processed by two different methods, namely natural clarification and compound clarification. The pomegranate juice that is naturally clarified (the pomegranate juice is left to stand at 20-25°C for 1-2 hours and centrifuged at 4000-4500 r / min for 5-10 minutes) is turbid red, while the pomegranate juice that is compound clarified is clearer and transparent, and has a layer of brown-purple sediment at the bottom.

[0025] This indicates that the composite clarification method can effectively remove impurities from pomegranate juice, making it clearer, and the precipitate may be formed by the reaction between the composite clarifier and impurities. DETAILED DESCRIPTION

[0026] The present invention is described below by specific embodiments. Unless otherwise specified, the technical means used in the present invention are methods known to those skilled in the art. In addition, the embodiments should be understood as illustrative rather than limiting the scope of the present invention, and the essence and scope of the present invention are limited only by the claims. For those skilled in the art, various changes or modifications to the material composition and dosage in these embodiments, without departing from the essence and scope of the present invention, also belong to the protection scope of the present invention. The raw materials and reagents used in the present invention are all commercially available. Example

[0027] The method for clarifying pomegranate juice comprises the following steps: (1) Raw material pretreatment: Select fresh pomegranates that are free of pests and diseases as raw materials to ensure their high quality. After careful cleaning to remove impurities and residues on the surface, the pomegranate juice is finally crushed and squeezed to obtain the pomegranate juice.

[0028] (2) Preparation of composite polysaccharide clarifier: Chitosan and sodium alginate are prepared into 1% (w / v) clarifier solutions respectively. Chitosan needs to be dissolved in 1% acetic acid solution, and sodium alginate is dissolved in distilled water in a certain proportion. The two types of clarifiers are then diluted in proportion to prepare a clarification solvent with a concentration of 0.05 g / L. When in use, the chitosan and sodium alginate solutions are mixed in a volume ratio of 1:1 to prepare a composite polysaccharide clarifier.

[0029] (3) Clarification of pomegranate juice: Add 3% of the prepared complex polysaccharide clarifier and 0.1% of CaCl2 to the pomegranate juice, and mix the clarifier and pomegranate juice thoroughly to ensure that the clarifier is evenly dispersed in the juice.

[0030] (4) Reaction and clarification: The mixed pomegranate juice treated in step 4 was placed in a constant temperature water bath at 30°C and reacted for 30 minutes under this condition. During this process, the polysaccharide clarifier reacts with the impurities in the juice and forms a precipitate. After the reaction is completed, the precipitate will gradually settle to the bottom, making the juice clear and transparent, that is, the pomegranate juice with the best clarification effect is obtained. The light transmittance of the pomegranate juice is 81.09%, and the anthocyanin content is 173.56 mg / L. Embodiment 2 The method for clarifying pomegranate juice comprises the steps: (1) Raw material pretreatment: Select fresh pomegranates that are free of pests and diseases as raw materials to ensure their high quality. After careful cleaning to remove impurities and residues on the surface, the pomegranate juice is finally crushed and squeezed to obtain the pomegranate juice.

[0031] (2) Preparation of composite polysaccharide clarifier: Chitosan and sodium alginate are prepared into 1% (w / v) clarifier solutions respectively. Chitosan needs to be dissolved in 1% acetic acid solution, and sodium alginate is dissolved in distilled water in a certain proportion. The two types of clarifiers are then diluted in proportion to prepare a clarification solvent with a concentration of 0.1 g / L. When in use, the chitosan and sodium alginate solutions are mixed in a volume ratio of 1:1 to prepare a composite polysaccharide clarifier.

[0032] (3) Clarification of pomegranate juice: Add 3% of the prepared complex polysaccharide clarifier and 0.1% of CaCl2 to the pomegranate juice, and mix the clarifier and pomegranate juice thoroughly to ensure that the clarifier is evenly dispersed in the juice.

[0033] (4) Reaction and clarification: The mixed pomegranate juice treated in step 4 was placed in a constant temperature water bath at 30°C and reacted for 30 minutes under this condition. During this process, the polysaccharide clarifier will react with the impurities in the juice and form a precipitate. After the reaction is completed, the precipitate will gradually settle to the bottom, making the juice clear and transparent, that is, the pomegranate juice with the best clarification effect is obtained. The light transmittance of the pomegranate juice is 83.587%, and the anthocyanin content is 179.11 mg / L.

Claims

1. A method for clarifying pomegranate juice, characterized in that Proceed as follows: (1) Raw material pretreatment: fresh pomegranates free of pests and diseases are selected as raw materials, and impurities and residues on the surface are removed after careful cleaning, and finally the pomegranate juice is crushed and squeezed to obtain pomegranate juice; (2) Preparation of composite polysaccharide clarifier: chitosan and sodium alginate are respectively prepared into 1%~2% (w / v) clarifier solutions, chitosan is dissolved in 1%~2% acetic acid solution, and sodium alginate is dissolved in distilled water in a certain proportion; the two types of clarifiers are then diluted in proportion to prepare clarification solvents with a concentration of 0.05~0.1g / L, and when used, the chitosan and sodium alginate solutions are mixed in a volume ratio of 1:1~1:1.5 to prepare the composite polysaccharide clarifier; (3) Clarification of pomegranate juice: Add 3-10% of the prepared composite polysaccharide clarifier and 0.1%-0.3% of CaCl2 to the pomegranate juice, and mix the clarifier and the pomegranate juice thoroughly to ensure that the clarifier is evenly dispersed in the juice; (4) Reaction and clarification: The mixed pomegranate juice treated according to step (3) is placed in a constant temperature water bath at 30°C to 40°C for reaction for 30 to 40 minutes. After the reaction is completed, the precipitate will gradually settle to the bottom, making the juice clear and transparent, thereby obtaining pomegranate juice with the best clarification effect.

2. Use of the pomegranate juice prepared by the method of claim 1 in improving the light transmittance of the pomegranate juice, and improving the antioxidant capacity, anthocyanin content, protein content and total phenol content of the pomegranate juice.

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