阅读说明：本技术 一种新鲜枸杞果汁的制备方法 (Preparation method of fresh medlar juice ) 是由 欧泉 柳雅珍 卢顺姬 于 2020-06-11 设计创作，主要内容包括：本发明公开了一种澄清枸杞子果汁的制备方法,它包括如下步骤：1)取新鲜枸杞子果,除杂,清洗,杀菌,再清洗,干燥,打浆,得枸杞汁；2)取步骤1)枸杞汁,加果胶酶酶解,离心,取上清液过滤,即得。本发明一种澄清枸杞子果汁的制备方法,充分保留了枸杞子的主要功能及营养成分,且能除去其中的重金属有害成分,并使有益成分均匀分布于果汁中,利于直接被人体吸收,大大提高其治疗保健价值的利用水平,为枸杞子的综合开发利用开辟新道路。(The invention discloses a preparation method of clear wolfberry fruit juice, which comprises the following steps: 1) taking fresh wolfberry fruits, removing impurities, cleaning, sterilizing, cleaning again, drying and pulping to obtain wolfberry juice; 2) and (3) adding pectinase into the medlar juice obtained in the step 1) for enzymolysis, centrifuging, and filtering supernatant to obtain the medlar. The preparation method of the clear medlar juice fully maintains the main functions and nutritional ingredients of medlar, can remove heavy metal harmful ingredients in the medlar, uniformly distributes beneficial ingredients in the juice, is beneficial to being directly absorbed by human bodies, greatly improves the utilization level of the treatment and health care values of the medlar, and opens up a new way for the comprehensive development and utilization of the medlar.)

1. A preparation method of clear medlar juice is characterized by comprising the following steps: it comprises the following steps:

1) taking fresh wolfberry fruits, removing impurities, cleaning, sterilizing, cleaning again, drying and pulping to obtain wolfberry juice;

2) and (3) adding pectinase into the medlar juice obtained in the step 1) for enzymolysis, centrifuging, and filtering supernatant to obtain the medlar.

2. The method of claim 1, wherein: the step 1) of impurity removal is to remove fruit stalks, impurities, plant diseases and insect pests and mildewed fruits.

3. The method of claim 1, wherein: the sterilization in the step 1) is to sterilize the surfaces of the wolfberry fruits by using chlorine dioxide with the pH value of 3.0-5.0 and the concentration of 6-10 ppm for 3-5 minutes at 25 ℃, preferably, to sterilize the surfaces of the wolfberry fruits by using chlorine dioxide with the pH value of 5.0 and the concentration of 8ppm for 5 minutes at 25 ℃.

4. The method of claim 1, wherein: the cleaning in the step 1) is cleaning with purified water, and the re-cleaning is rinsing with ultra-filtration sterile clear water.

5. The method of claim 1, wherein: the drying in the step 1) is to drain the surface moisture of the wolfberry fruits.

6. The method of claim 1, wherein: the volume mass ratio of the medlar juice to the pectinase in the step 2) is 100 ml: 0.1 to 0.4 g.

7. The method of claim 1, wherein: the volume mass ratio of the medlar juice to the pectinase in the step 2) is 100 ml: 0.2 g.

8. The method of claim 1, wherein: and 2) carrying out enzymolysis at the pH value of 4.0-5.0 and the temperature of 40-50 ℃ for 2-4 hours, preferably, carrying out enzymolysis at the pH value of 4.5 and the temperature of 40 ℃ for 2 hours.

9. The method of claim 1, wherein: and 2) centrifuging for 3-8 minutes at a rotating speed of 3000-5000 rpm, preferably at a rotating speed of 4500 rpm, wherein the centrifuging time is 5 minutes.

10. The method of claim 1, wherein: step 2), the filtration is ceramic membrane filtration; the ceramic membrane filtration parameters are that the ceramic membrane aperture is 100-200 nm, the transmembrane pressure is 1.0bar, the feeding temperature is 30-40 ℃, and preferably, the ceramic membrane aperture is 200nm, the transmembrane pressure is 1.0bar, and the feeding temperature is 40 ℃.

Technical Field

The invention particularly relates to a preparation method of clear wolfberry fruit juice.

Background

Fructus Lycii is dried mature fruit of Lycium barbarum L. of Solanaceae. Collected in summer and autumn when the fruit is ripe. It is sweet in taste, neutral in nature, and has the effects of nourishing liver and kidney, replenishing vital essence and improving eyesight. Can be used for treating asthenia, soreness of waist and knees, vertigo, auditory sensation, sexual impotence, spermatorrhea, internal heat, diabetes, blood deficiency, yellowish complexion, and blurred vision. Wolfberry fruit is a medicine-food dual-purpose Chinese medicine approved by the national ministry of health, has a long history of homology of medicine and food, is listed as a top-grade product in the Shen nong herbal classic, and is called as 'long-time taking, light weight, no aging, cold and summer heat resistance'. Modern research shows that: the medlar mainly contains medlar polysaccharide, betaine, various amino acids, vitamins and other chemical components; has the pharmacological effects of reducing blood sugar, reducing blood fat, lowering blood pressure, enhancing immunity, resisting oxidation, aging, fatigue and tumor, etc. Therefore, the medlar has various health care effects and rich resources, is mainly produced in places such as Ningxia, Gansu, inner Mongolia and the like in China, and is cultivated in many places at home and abroad. Therefore, the medlar is a medicinal and edible traditional Chinese medicine with good development prospect. However, the fresh wolfberry fruit has high moisture and sugar content, is easy to be damaged by worms and mildewed when being stored, and is rotted and deteriorated after being picked for several days to lose commodity value.

The instant traditional Chinese medicine decoction pieces are novel decoction pieces, are provided by professor Zhao Rong Hua in the third forum for traditional Chinese medicine inheritance innovation in 7 months in 2015, and are affirmed by experts and scholars of traditional Chinese medicine processing and widely publicized and reported by media. The instant traditional Chinese medicine decoction pieces are used for prevention and health care, rehabilitation and recuperation, and can be eaten after being opened after being processed and packaged. The health-care tea has reliable curative effect and good taste, is convenient to carry and take, can meet the requirements of people on health preservation and health care at any time and any place, and just can meet the increasing requirements of the current market on health products. The method is also a development hotspot and a new direction of modern medicinal and edible Chinese medicaments. The medlar juice is generated in the development of the instant traditional Chinese medicine decoction pieces, and has the functions of tonifying the kidney, producing sperm and strengthening the body; enhancing immunity, inhibiting cancer cell diffusion, and treating chronic hepatitis; nourishing liver, improving eyesight, caring skin, etc. The processing technology of the medlar juice is various, and the concentration reduction technology is mostly adopted at present, so that the prepared products with the color, the flavor and the soluble solid content of the original fruit pulp cannot retain the main functions and the nutrient components of the medlar to the maximum extent, and the full development and the utilization of the health care value of the medlar are directly hindered.

Disclosure of Invention

In order to solve the problems, the invention provides a preparation method of clear wolfberry fruit juice, which comprises the following steps:

1) taking fresh wolfberry fruits, removing impurities, cleaning, sterilizing, cleaning again, drying and pulping to obtain wolfberry juice;

2) and (3) adding pectinase into the medlar juice obtained in the step 1) for enzymolysis, centrifuging, and filtering supernatant to obtain the medlar.

Further, the impurity removal in the step 1) is to remove fruit stalks, impurities, plant diseases and insect pests and mildewed fruits.

Further, the sterilization in the step 1) is to sterilize the surfaces of the wolfberry fruits by using chlorine dioxide with the pH value of 3.0-5.0 and the concentration of 6-10 ppm for 3-5 minutes at the temperature of 25 ℃.

Further, the sterilization is to sterilize the surface of the wolfberry fruit with chlorine dioxide with pH value of 5.0 and concentration of 8ppm for 5 minutes at 25 ℃.

Further, the cleaning in the step 1) is cleaning with purified water, and the re-cleaning is rinsing with ultrafiltration sterile clear water.

Further, the drying in the step 1) is to drain the moisture on the surface of the wolfberry fruits.

Further, the volume-to-mass ratio of the medlar juice in the step 2) to the pectinase is 100 ml: 0.1 to 0.4 g.

Further, the volume-to-mass ratio of the medlar juice in the step 2) to the pectinase is 100 ml: 0.2 g.

Further, the pH value of the enzymolysis in the step 2) is 4.0-5.0, the temperature is 40-50 ℃, the time is 2-4 hours,

further, the pH value of the enzymolysis is 4.5, the temperature is 40 ℃, and the time is 2 hours.

Further, the centrifugation time in the step 2) is 3-8 minutes, the rotating speed is 3000-5000 r/min, preferably, the centrifugation time is 5 minutes, and the rotating speed is 4500 r/min.

Further, the filtration in the step 2) is ceramic membrane filtration; the ceramic membrane filtration parameters are that the aperture of the ceramic membrane is 100-200 nm, the transmembrane pressure is 1.0bar, the feeding temperature is 30-40 ℃,

furthermore, the ceramic membrane filtration parameters are ceramic membrane aperture 200nm, transmembrane pressure 1.0bar and feeding temperature 40 ℃.

The preparation method of the clear medlar juice fully maintains the main functions and nutritional ingredients of medlar, can remove heavy metal harmful ingredients in the medlar, uniformly distributes beneficial ingredients in the juice, is beneficial to being directly absorbed by human bodies, greatly improves the utilization level of the treatment and health care values of the medlar, and opens up a new way for the comprehensive development and utilization of the medlar.

Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Drawings

FIG. 1 Effect of pore size on Membrane flux

FIG. 2 Effect of transmembrane pressure on Membrane flux

FIG. 3 Effect of feed temperature on Membrane flux

Detailed Description

Example 1 preparation of a wolfberry fruit juice according to the invention

1) Taking fresh and mature medlar fruits, removing fruit stalks, impurities, plant diseases and insect pests and mildewed fruits, cleaning the fruits by drinking water for one time, cleaning the fruits by using purified water, placing the cleaned fruits in chlorine dioxide with the pH value of 5.0 and the concentration of 8ppm, carrying out surface sterilization for 5 minutes at the temperature of 25 ℃, washing the fruits by using ultrafiltration sterile clear water, draining the fruits, conveying the fruits into a whole-process closed aseptic production workshop, and preparing the fresh medlar fruits into fine and homogeneous medlar juice by using pulping equipment.

2) Taking medlar juice, adding 0.2% of pectinase, mixing uniformly, treating for 2 hours at 40 ℃ with the pH value of 4.5, centrifuging for 5 minutes at 4500 r/min, taking supernate, and performing membrane filtration treatment (process parameters: 200nm ceramic membrane, transmembrane pressure of 1.0bar, feeding temperature of 40 deg.C), aseptically packaging the filtrate, and sealing with cover.

The advantageous effects of the present invention are described below by way of test examples.

Experimental example 1 screening experiment study of fructus Lycii juice

1. Research on sterilization process of chlorine dioxide on surface of wolfberry fruit

1.1 Single factor test

In the chlorine dioxide disinfection method, factors influencing the disinfection effect mainly comprise the concentration of chlorine dioxide solution, the disinfection time, the disinfection temperature and the pH value. In order to screen out the disinfection process of the chlorine dioxide solution on the surface of the wolfberry fruit, the invention aims to perform single factor investigation on the 4 influencing factors, measure the sterilization efficiency under each factor condition and screen out the key influencing factors influencing the disinfection effect.

1.1.1 chlorine dioxide solution concentration

Taking fresh and mature wolfberry fruits, removing fruit stalks, impurities, plant diseases and insect pests and mildewed fruits, cleaning the fruits by drinking water for one time, cleaning the fruits by using purified water, placing the fruits into chlorine dioxide solution with the pH value of 5.0 and the concentration of 6, 8, 10 and 12ppm respectively, performing surface sterilization for 5 minutes at the temperature of 25 ℃, washing the fruits by using ultrafiltration sterile clear water and draining, taking wolfberry fruits treated by the chlorine dioxide solution and wolfberry fruits (control) just washed by using water, placing the wolfberry fruits and the wolfberry fruits into sterile bags filled with 100mL broth culture media respectively, sealing the bags, rubbing the bags forcibly for 2 minutes to ensure that all parts of the wolfberry fruits are fully rubbed, then spreading the bags on the TSA culture media, culturing the bags at the temperature of 37 ℃ for 24 hours, counting bacterial colonies and calculating the sterilization efficiency.

The experimental results in table 1 show that the higher the concentration of chlorine dioxide solution, the better the sterilization effect, when the concentration is 8ppm, the sterilization rate can reach 99.8%, and when the concentration is increased, the sterilization effect is not affected, so 8ppm is set as the optimal sterilization concentration of chlorine dioxide.

TABLE 1 Effect of chlorine dioxide solution concentration on germicidal effectiveness

1.1.2 Sterilization time

Taking fresh and mature wolfberry fruits, removing fruit stalks, impurities, plant diseases and insect pests and mildewed fruits, cleaning the fruits by drinking water for one time, cleaning the fruits by using purified water, placing the fruits into a chlorine dioxide solution with the pH value of 5.0 and the concentration of 8ppm, carrying out surface sterilization for 3, 5, 7 and 9 minutes at the temperature of 25 ℃, washing the fruits by using ultrafiltration sterile clear water and draining, taking the wolfberry fruits treated by the chlorine dioxide solution for different times and the wolfberry fruits (control) just washed by water, respectively placing the wolfberry fruits and the wolfberry fruits into sterile bags filled with 100mL broth culture media, sealing the bags, rubbing the bags for 2 minutes with force to ensure that all parts of the wolfberry fruits are fully rubbed, then paving the bags on the TSA culture media, culturing the bags for 24 hours at the temperature of 37 ℃, counting bacterial colonies and calculating the sterilization efficiency.

The experimental results in table 2 show that the longer the sterilization time is, the better the sterilization effect is, but the sterilization time is longer than 5min, and then the sterilization time is prolonged, so that the sterilization effect is not influenced, and the sterilization rate can reach 99.6% when the sterilization time is 5min, so that the optimal sterilization time can be selected to be 5 min.

TABLE 2 Effect of Sterilization time on the Sterilization Effect

1.1.3 pH value

Taking fresh and mature wolfberry fruits, removing fruit stalks, impurities, plant diseases and insect pests and mildewed fruits, cleaning the fruits with drinking water for one time, cleaning the fruits with purified water, placing the fruits into chlorine dioxide solution with the pH value of 4.0, 5.0, 6.0 and 7.0 and the concentration of 8ppm, performing surface sterilization for 5 minutes at the temperature of 25 ℃, washing the fruits with ultrafiltration sterile clear water and draining the fruits, respectively putting the wolfberry fruits treated by the chlorine dioxide solution and the wolfberry fruits (control) just washed by water into sterile bags filled with 100mL broth culture medium, sealing the bags, forcibly rubbing the fruits for 2 minutes to ensure that all parts of the wolfberry fruits are fully rubbed, then paving flat plates on the TSA culture medium, culturing the fruits for 24 hours at the temperature of 37 ℃, counting bacterial colonies and calculating the sterilization efficiency.

The experimental results in table 3 show that the sterilization efficiency is higher as the pH value is increased, the sterilization rate reaches the maximum value (99.3%) when the pH value is 5.0, and the sterilization efficiency is in a downward trend when the pH value is greater than 5.0, so that the optimal sterilization pH value of 5.0 is selected.

TABLE 3 influence of pH on the germicidal efficacy

1.1.4 Sterilization temperature

Taking fresh and mature wolfberry fruits, removing fruit stalks, impurities, plant diseases and insect pests and mildewed fruits, cleaning the fruits by drinking water for one time, cleaning the fruits by using purified water, placing the cleaned fruits into chlorine dioxide solution with the pH value of 5.0 and the concentration of 8ppm respectively, performing surface sterilization for 5 minutes at the temperature of 20, 25, 30 and 35 ℃, washing the fruits by using ultrafiltration sterile clear water and draining, taking wolfberry fruits treated by the chlorine dioxide solution and wolfberry fruits (control) just cleaned by using water, respectively placing the wolfberry fruits and the wolfberry fruits into sterile bags filled with 100mL broth culture media, sealing the bags, rubbing the bags forcibly for 2 minutes to ensure that all parts of the wolfberry fruits are fully rubbed, then spreading the bags on the TSA culture media, culturing the bags at the temperature of 37 ℃ for 24 hours, counting bacterial colonies and calculating the sterilization efficiency.

Table 4 the experimental results show that the temperature has no significant effect on the sterilizing effect of chlorine dioxide, and the optimum temperature is 25 ℃ in order to preserve the nutrients and original flavor of the fruit to the maximum extent.

By combining the analysis of the experimental results in the table 1-4, the optimal process for screening out the chlorine dioxide to sterilize the surfaces of the medlar comprises the following steps: chlorine dioxide with concentration of 8ppm is subjected to surface sterilization for 5 minutes under the conditions that the pH value is 5.0 and the temperature is 25 ℃.

1.2 Process for sterilizing fructus Lycii surface by optimized chlorine dioxide

From the above single-factor test results, it is known that the concentration of chlorine dioxide solution, sterilization time and pH value have significant influence on sterilization efficiency, while the influence of sterilization temperature is not significantly negligible, so the present invention uses the concentration (A, ppm) of chlorine dioxide, sterilization time (B, min) and pH value (C) as independent variable factors for further investigation. And (3) performing a 3-factor 3 level test by taking the sterilization efficiency as an evaluation index, and optimizing an optimal process. The experimental results are shown in tables 4-5.

TABLE 4 factor level table

TABLE 5 visual analysis of the results

From the analysis of the results in tables 4 and 5, it can be seen that the order of the importance of the factors affecting the chlorine dioxide sterilization effect is: the concentration of chlorine dioxide is more than the sterilization time and more than the pH value, and the concentration of chlorine dioxide has obvious influence on the sterilization effect. The optimal process combination capable of screening out chlorine dioxide sterilization through comprehensive result analysis is A₃B₃C₂I.e. chlorine dioxide sterilizing the surface of the fruit of Chinese wolfberryThe optimal process comprises the following steps: sterilizing at 25 deg.C and pH of 5.0 for 5min to obtain the final product with chlorine dioxide concentration of 8 ppm.

Tests prove that the sterilizing effect is as high as 99.6% under the process condition.

2. Study on clarification process of Chinese wolfberry fruit juice

Pectin contained in the medlar juice has high viscosity, so that the sedimentation of solid particles is hindered, and the juice is turbid. Pectinase hydrolyzes pectin so that the solids precipitate more readily, thereby clarifying the juice. Factors influencing the clarity of the medlar juice include the addition amount of pectinase, enzymolysis temperature, enzymolysis time and pH value. In order to screen out the clarification process of the medlar juice, the invention takes the light transmittance of the juice as an evaluation index, and performs single factor investigation on the 4 influencing factors to screen out the optimal parameters of the medlar juice clarification process.

2.1 adding pectase into the juice, adding pectase of different amount, mixing, treating at 40 deg.C for 4 hr with pH of 4.5, and measuring light transmittance of fructus Lycii juice.

Table 6 the results of the experiments show that: the higher the adding amount of the pectinase, the better the clarity of the wolfberry fruit juice, but the influence effect is very little when the adding amount exceeds 0.2 percent, so the optimal adding amount of the pectinase is selected to be 0.2 percent.

TABLE 6 Effect of pectinase addition on juice clarification

2.2 enzymolysis temperature adding 0.2% pectase into the fruit juice, mixing, pH 4.5, treating at different temperatures for 4 hr, and measuring light transmittance of fructus Lycii juice.

Table 7 the experimental results show that: the activity of the pectinase is improved to a great extent when the enzymolysis temperature is increased, and the light transmittance is obviously increased along with the increase of the enzymolysis temperature at 35-40 ℃; reaching an extreme value at about 40 ℃, and then, with the increase of the enzymolysis temperature, the light transmittance of the medlar juice begins to slowly decrease, which shows that the activity of pectinase is inhibited by the overhigh temperature, so that the enzymolysis temperature is determined to be 40 ℃.

TABLE 7 Effect of enzymolysis temperature on juice clarification

2.3 enzymolysis time

Adding 0.2% pectase into the fruit juice, mixing, treating at 40 deg.C for different time with pH of 4.5, and measuring light transmittance of fructus Lycii juice.

Table 8 the results of the experiments show that: the light transmittance of the medlar juice is gradually improved along with the increase of the enzymolysis time, the light transmittance rises quickly within 1.0-2.0 h, and the medlar juice tends to be gentle when the enzymolysis time exceeds 2.0h, which indicates that the enzymolysis effect reaches balance at the moment, and the clarification effect is not continued, so that the optimal enzymolysis time is determined to be 2.0 h.

TABLE 8 Effect of enzymolysis time on juice clarification

2.4pH value

Adding 0.2% pectase into the fruit juice, mixing, treating at 40 deg.C under different pH value environment, and measuring light transmittance of fructus Lycii juice.

Table 9 the experimental results show that: when the pH value is 4.5, the light transmittance of the medlar juice reaches a peak value, obviously shows that the light transmittance is also reduced along with the increasing or decreasing of the pH value at the two ends of the peak value, the activity of the pectinase is inhibited, and the enzymatic reaction tends to be smooth. Therefore, the optimum pH value of the pectinase is determined to be 4.5.

TABLE 9 Effect of pH on juice clarification

3. Study on ceramic membrane filtration sterilization process of wolfberry fruit juice

The heat treatment of the medlar juice can damage the nutrient components and the flavor of the medlar juice, and in order to furthest preserve the flavor and the nutrient components of the medlar juice, the medlar juice is sterilized and filled by adopting an inorganic ceramic membrane filtration method. And (3) screening optimal parameter conditions for three major influencing factors of the aperture of the inorganic ceramic membrane, the feeding temperature and the transmembrane pressure by taking the membrane flux, the content of active ingredients (lycium barbarum polysaccharide and betaine) of the wolfberry fruit juice before and after filtration, the total heavy metal content and the sterilization effect as evaluation indexes.

3.1 index measurement method

Calculating the membrane flux: j is V/(a × t)

Where J is the membrane flux, J (L/m)²H); v is permeate volume, L; a is the effective area of the film, m²(ii) a t is the time required to obtain a certain volume of permeate, h.

② the determination method of the nutritional ingredients of the medlar juice:

the method for measuring the lycium barbarum polysaccharide and the betaine refers to a method for measuring the lycium barbarum polysaccharide and the betaine in 'Chinese pharmacopoeia' 2015 edition and page P249 of the first part.

Heavy metals and harmful elements are measured by an atomic absorption spectrophotometry or an inductively coupled plasma mass spectrometry according to 2321 in the fourth proceedings of the 'Chinese pharmacopoeia' 2015 edition).

③ the method for measuring the degerming effect:

determination of the total number of colonies: measuring according to GB 4789.2-2010 food safety national standard food microbiology test colony total number determination;

determination of coliform group: measuring according to GBT 4789.32-2002 Rapid detection of coliform bacteria in food hygiene microbiology;

3.2 screening of Membrane pore size

The size of the membrane aperture is an important influence factor influencing the sterilization effect of the medlar juice, the loss of active ingredients and the removal effect of heavy metals and harmful elements. Centrifuging the juice treated by the '2 medlar juice clarification process' for 5 minutes by using a centrifuge 4500 r/min, taking supernatant, filtering medlar juice by respectively selecting inorganic ceramic membranes with the pore diameters of 100nm, 200nm and 400nm, measuring the change condition of membrane flux in 30 minutes, measuring the contents of medlar polysaccharide, betaine and heavy metal elements in the medlar juice filtered by different pore diameters, and measuring the sterilization effect of the medlar juice filtered by different pore diameters.

The experimental results of fig. 1 show that: at the beginning of filtration, the larger the pore size, the larger the membrane flux; in the first 10min, the membrane flux of the 3 membranes is reduced, the larger the pore diameter is, the more violent the flux attenuation is, because fine particles in the medlar juice are filled in the pore diameter of the membranes along with the filtration, the more serious the membrane pollution is caused, and the smaller the pore diameter is, because the membrane resistance is larger, the flux is smaller, and the flux attenuation is relatively smaller; after 10min, the flux of the three membranes is stable, and the flux of the membrane with the pore diameter of 200nm is maximum, so that the optimal pore diameter of the ceramic membrane is determined to be 200 nm.

TABLE 10 Effect of different pore sizes on active ingredients and heavy metal harmful elements of Lycium barbarum juice

Table 10 the experimental results show that: the filter membrane with aperture of 100nm can cause partial loss of active ingredients of the medlar juice, and the filter membrane with aperture of more than 200nm can hardly cause partial loss of the active ingredients of the medlar juice; in addition, the effect of removing heavy metals with 3 pores has the priority of 100nm to 200nm to 400nm, and all meet the requirement of medicinal limit standard. The wolfberry fruit juice filtered by the ceramic filter membrane with the diameter of 200nm can not only maximally preserve the active ingredients and the flavor of the original fruit juice, but also effectively reduce the content of heavy metals in the fruit juice and avoid the harm to the human body, so that the optimal ceramic membrane pore diameter is determined to be 200 nm.

Table 11 the results of the experiments show: the ceramic membrane with the aperture of 100nm has the best sterilization effect, namely 200nm times, and the worst is 400 nm. The total number of colonies obtained by 200nm sterilization is 11.39CFU/mL, coliform groups are not detected, and the total number of colonies is far lower than (GB19297-2003) hygienic standards of fruit and vegetable juice beverages. The fruit juice filtered by the 400nm ceramic filter membrane still contains higher total number of bacterial colonies, and the number of coliform groups exceeds the standard. Therefore, the optimal pore diameter of the ceramic membrane is determined to be 200 nm.

TABLE 11 Membrane Sterilization Effect for different pore sizes

Comprehensively analyzing the influence results of different apertures on membrane flux, active ingredients of the medlar juice, harmful elements of heavy metals and sterilization effect, and finally determining that a ceramic membrane with an aperture of 200nm is used in the process.

3.3 transmembrane pressure screening

Centrifuging the juice treated by the "2 fructus Lycii juice clarifying process" for 5min at 4500 rpm, collecting supernatant, filtering fructus Lycii juice with selected ceramic membrane with pore diameter of 200nm under pressure of 0.5, 1.0, 1.5bar, and measuring membrane flux change in 30 min.

FIG. 2 shows the results of the experiment: when the filtration of the ceramic membrane with the aperture of 200nm is started, the larger the transmembrane pressure is, the larger the membrane flux is; in the first 10min, the membrane flux of 3 membranes all dropped, and the flux decay was instead greater for greater transmembrane pressures. After 10min, the membrane flux of 3 kinds of transmembrane pressures tends to be stable, and the membrane flux of the transmembrane pressure of 1.0bar is maximum and stable. The optimal transmembrane pressure was determined to be 1.0 bar.

3.4 screening of the feed temperature

Centrifuging the juice treated by the '2 fructus Lycii juice clarifying process' for 5min at 4500 rpm, collecting supernatant, filtering with selected ceramic membrane with pore diameter of 200nm under transmembrane pressure of 1.0bar and material liquid temperature of 30, 40, and 50 deg.C respectively, and measuring the membrane flux change for 30 min.

FIG. 3 shows the results of the experiment: when the filtration of the ceramic membrane with the pore diameter of 200nm is started, the higher the feeding temperature is, the higher the membrane flux is; in the first 10min, the membrane flux decreased at all 3 temperatures, and the flux decay was instead greater for higher feed temperatures. After 10min, the membrane flux at the feed temperature of 40 ℃ is maximum and stable after the membrane flux at 3 feed temperatures all tend to be stable. The optimum feed temperature was determined to be 40 ℃.

The best process for filtering the medlar juice by the ceramic membrane is obtained by integrating all the experimental results as follows: the transmembrane pressure of the ceramic membrane with the aperture of 200nm is 1.0bar, and the feeding temperature is 40 ℃.

The process parameters are verified by 3 times of experiments, and the results are consistent with the experimental results, so that the process is stable and feasible, and can be used for filtering, sterilizing and filling the medlar juice.

In conclusion, the preparation method of the clear wolfberry fruit juice fully maintains the main functions and nutritional ingredients of wolfberry fruit, can remove the heavy metal harmful ingredients in the wolfberry fruit, uniformly distributes the beneficial ingredients in the juice, is beneficial to being directly absorbed by human bodies, and greatly improves the utilization level of the treatment and health care values of the juice. The wolfberry fruit juice prepared by the method has rich nutrition and high health care value, and is easy to popularize and apply in the market.