Preparation method of lotus root and pear compound fruit and vegetable juice and product

Abstract

The invention provides a preparation method of lotus root and pear compound fruit and vegetable juice. According to the method, by limiting the quality requirements of the raw materials and the freshly squeezed juice, the compatibility ratio and the sterilization mode, the flavor synergy of the lotus root juice and the pear juice and the increase of the suspension stability are realized. The soluble solids of the lotus root juice obtained through squeezing are 5.8%-8.7%, the soluble solids of the pear juice obtained through squeezing are 10.9%-13.8%, the Vc content of the lotus root juice obtained through squeezing is 312.10 mg / L to 343.52 mg / L, the Vc content of the pear juice obtained through squeezing is 7.32 mg / L to 14.57 mg / L, and the total phenol content of the pear juice obtained through squeezing is 559.14 mg / L to 590.23 mg / L and 204.79 mg / L to 239.56 mg / L. The ratio of the lotus roots to the pear juice is 1: (0.8-1.2), and carrying out ultra-high pressure sterilization for 5-10 minutes under 500-600 MPa. The compound fruit and vegetable juice does not need to be added with sugar, has the fresh and sweet flavor of fresh lotus roots, and is milky white in color, good in turbidity stability and high in sensory acceptance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of agricultural product processing, and particularly relates to a production method of lotus root and pear compound fruit and vegetable juice. BACKGROUND

[0002] Lotus root is the underground stem of a lotus plant, and the water content is 75%-91%. According to the starch content and eating characteristics, lotus roots can be divided into powder lotus roots and crisp lotus roots, and are mainly used to make stewed or fried dishes. Fresh lotus roots are clear and juicy, but the lotus root juice has obvious astringency due to the high content of polyphenols. Therefore, the astringency is usually eliminated by dilution, gelatin precipitation or cyclodextrin embedding. In addition to the astringency, the lotus root juice is light in sweetness and aroma, so the lotus root juice is usually not used as fresh juice or original juice, and the proportion of lotus root juice in lotus root drinks is low. At present, the lotus root juice is usually processed by enzymatic hydrolysis of starch, cellulose and pectin, and high-temperature sterilization. For example, CN201810172551.4 discloses a preparation method of lotus root juice beverage. The lotus root juice beverage is prepared by adding 2-5 times the mass of color protection liquid to lotus root slices to make pulp, vacuum microwave enzyme inactivation at 60-100 DEG C, starch enzyme hydrolysis at 80-100 DEG C, ultrasonic treatment, enzyme inactivation at 95-100 DEG C, and sterilization at 120-150 DEG C. After the processes of enzyme hydrolysis and filtration, the final product is clear juice. CN200910213555.3 discloses a method for preventing browning of milky white lotus root juice. The lotus root juice is prepared by heat blanching, enzyme hydrolysis and adding a color protection agent. CN201710171931.1 discloses a snow pear lotus root juice beverage and a preparation method thereof. The juice of snow pear and lotus root and rhizome is prepared by beating, filtering and removing the precipitate, and then the juice is mixed with milk and other materials. In the above-mentioned beverages, lotus root is the main raw material, but the proportion of lotus root in the beverage is about 1 / 4-1 / 3 after dilution or mixing. There are also lotus root beverages prepared by extracting lotus root slices or a plurality of raw materials, and the proportion of lotus root in the beverage is lower, such as 95109719.9 natural series lotus root beverage and a preparation method thereof and CN200610000613.0 lotus beverage and a preparation method thereof.

[0003] Pear as a kind of staple fruit, according to the characteristics of fruit, mainly divided into white pear, sand pear, Xinjiang pear, autumn pear, five categories of western pear, different pear in aroma, hardness, fruit shape all exist big difference, in addition to the influence of maturity and other physiological state of fruit, when making juice, there is also the difference of browning, aroma, sweetness. Pear juice often has low acidity and high sweetness, and the difference between different varieties is very large, and due to regional climate growth stage and other factors, the ratio of soluble solids to total acid can reach 20-125. Due to the great difference of pear raw materials and pear juice components, in order to meet the needs of flavor and taste of commercial products, there are 100% pear juice (CN200410090856.9) in pear juice drinks, and a variety of pear composite juice (CN202211716460.5 a mixed pear juice and its production and processing process), as well as the blending type pear juice from pear with mass fraction not more than 50% (96115942.2 fruit type Laiyang pear juice and its processing method). In addition, concentrated juice is also an important product form of pear juice, which is more convenient for the matching and flavor adjustment of drinks.

[0004] Lotus root and pear are both traditional fruits and vegetables with a long history in China. Considering the characteristics of lotus root and pear juice and their functions, it is not difficult to think of making drinks by combining the two. However, due to the diversity of raw materials, it is still necessary to determine the suitability of raw materials and combine feasible processes to achieve stable production of high-quality products through a large number of tests. In addition, both lotus root and pear can be eaten raw or cooked, so it is worth considering how to evaluate the nutritional value under different processing methods. With the increasing demand for food health and freshness without added sugar, avoiding or reducing the use of refined sugar and additives through the combination of different fruit and vegetable juices has become an important method. However, whether the flavor synergy can be achieved and the characteristics of the combined fruit and vegetable juice can be reflected still face many challenges. In addition, new non-thermal processing has significant advantages in preserving the nutritional components and improving the flavor of fresh fruit and vegetable juice, and is increasingly widely used. Therefore, how to better apply new processing technologies, improve the nutritional and flavor characteristics of the combined juice, and enhance the quality stability is a problem that needs to be solved by technical personnel in this field. SUMMARY

[0005] The purpose of the present application is to provide a method for making lotus root and pear combined fruit and vegetable juice. This method limits the quality characteristics of raw materials, juicing methods, compounding ratios, and processes to achieve flavor and nutritional synergy of lotus root juice and pear juice, improve quality stability, and avoid excessive energy consumption, natural nutrient loss, and health risks caused by excessive processes and external additions.

[0006] To achieve the above purpose, the present application adopts the following steps:

[0007] 1) Wash lotus root and pear separately and press to make juice;

[0008] 2) mixing the lotus root juice and the pear juice obtained in step 1) at a mass ratio of 1:(0.8-1.2);

[0009] 3) vacuum degassing the fruit and vegetable compound juice obtained in step 2) and then sealing the fruit and vegetable compound juice after being packaged by a flexible material;

[0010] 5) subjecting the fruit and vegetable compound juice obtained in step 3) to ultra-high pressure sterilization at 15-30 DEG C and 500-600 MPa for 5-10 min.

[0011] One of the purposes of the present application is to determine the physicochemical quality indexes of lotus root and pear for preparing compound fruit and vegetable juice. The lotus root juice yield is 77%-82%, the starch content is 0.5%-4.8%, and the polyphenol oxidase activity is 5.5-6.8 U / g FW; the pear juice yield is 78%-86%, and the polyphenol oxidase activity is 0.75-0.82 U / g FW. The soluble solids of the lotus root juice and the pear juice are 5.8-8.7% and 10.9-13.8% respectively, the Vc content is 312.10-343.52 mg / L and 7.32-14.57 mg / L respectively, the total phenol content is 559.14-590.23 mg / L and 204.79-239.56 mg / L respectively, and the overall acceptance score of sensory evaluation is 2.1-3.7. The selected lotus root has the characteristics of high freshness and water content, low starch content, and high perception of sweet and clean flavor, and the pear juice has the characteristics of moderate sweetness and aroma and is not easy to brown.

[0012] The second purpose of the present application is to shield the astringency of lotus root juice by taking the lotus root clean flavor as a feature. The fresh lotus root juice has its unique sweet and clean flavor, but the perception is low, and the lotus root juice has powder feeling and astringency due to the presence of starch and polyphenol, and the sensory acceptance is low. The fresh pear juice is too sweet, and lacks flavor level and richness. The two form a compound fruit and vegetable juice with coordinated flavor, sweet and clean characteristics, and the aroma intensity is 3.6-4.5 points according to the overall acceptance score of sensory evaluation, and the acceptance is greatly improved, and the compound fruit and vegetable juice is highly praised.

[0013] The third purpose of the present application is to determine the juicing and sterilization method of lotus root and pear compound juice. The juicing method can effectively remove the crude fiber and reduce the color and flavor changes caused by oxidation. The static ultra-high pressure sterilization technology can make a small amount of starch in the lotus root juice gelatinize or semi-gelatinize at low temperature, and enhance the consistency, taste and turbidity of the compound juice. The turbidity of the fresh lotus root juice and the pear juice decreases by 24.74% and 25.25% respectively after standing for 1 h, and the turbidity of the compound juice after sterilization decreases only by 9%. In addition, the ultra-high pressure sterilization at 15-30 DEG C avoids the color and flavor changes and precipitation caused by high temperature, and better retains the nutrients of fresh fruit and vegetable.

[0014] The fourth object of the present application determines the product characteristics of the new lotus root compound fruit and vegetable juice. The compound fruit and vegetable juice is milky white, the soluble solid content is 8.7-9.2%, the total phenol content is 195.94-223.11 mg / L, the Vc content is 143.65-177.94 mg / L, the overall sensory acceptance score is 3.6-4.5, the taste is soft, and the taste is sweet and delicious.

[0015] The present application maintains the fresh flavor and color of lotus root and pear through the limitation of raw material characteristics, the matching ratio and process control, forms the fruit and vegetable juice matching scheme without adding sugar, essence and pigment, realizes the flavor synergy and the increase of suspension stability, forms the product characteristics of sweet and delicious taste, and improves the nutritional value and health characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Lotus root and pear compound juice prepared by different methods (A: example 1, B-E: comparative examples 1-4)

[0017] Figure 2 Quantitative sensory description (A) and turbidity (B) of lotus root juice, pear juice and lotus root and pear compound juice DETAILED DESCRIPTION

[0018] In order to make the objects and technical solutions of the present application clearer, the following examples are further explained. It should be understood that the examples of the present application are only for illustration but not for limitation of the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0019] Example 1

[0020] 1) Select fresh lotus roots on the market from July to August, wash and cut the lotus roots, and use a screw type extrusion juicer to extract juice to obtain lotus root juice. The juice yield of lotus root juice is 78±2%, the starch content is 0.8±0.2%, the polyphenol oxidase activity is 6.0±0.5 U / g FW; the soluble solid content of lotus root juice is 6.5±0.7%, the Vc content is 325.30±35.2 mg / L, and the overall sensory acceptance score is 2.1-2.9.

[0021] 2) Wash and cut the pear, and use a screw type extrusion juicer to extract juice to obtain pear juice. The juice yield of pear is 83±3%, the starch oxidase activity is 0.79±0.2 U / g FW, the soluble solid content of pear juice is 12.8±1.6%, the Vc content is 10.42±2.67 mg / L, the total phenol content is 221.46±18.92 mg / L, and the flavor sensory intensity score is 2.4-3.7.

[0022] 3) The fruit juice squeezed out in step 1) and step 2) is mixed uniformly at a mass ratio of 1:1, and is packed in 300 mL polypropylene beverage bottles, is vacuum degassed at -0.095 MPa, is sealed, is placed in an ultrahigh pressure treatment device, is retained for 10 min at 25 DEG C and 500 MPa, and a compound fruit and vegetable juice is obtained.

[0023] 4) The lotus root and pear compound fruit and vegetable juice sample in step 3) is subjected to physical and chemical and sensory evaluation, has a soluble solid content of 9.0+ / -0.2%, a pH value of 5.79+ / -0.04, a Vc content of 160.86+ / -8.04 mg / L, a total phenol content of 214.99+ / -7.48 mg / L, a color value L* of 22.94+ / -0.22, a* of -0.23+ / -0.02, b* of 0.62+ / -0.09, no obvious precipitate, and a milky white color. The flavor sensory intensity score is 3.6-4.5.

[0024] Comparative Example 1

[0025] The difference from Example 1 is that the mass ratio of lotus root juice to pear juice in step 3) is 1:0.25.

[0026] Comparative Example 2

[0027] The difference from Example 1 is that the mass ratio of lotus root juice to pear juice in step 3) is 1:4.

[0028] Comparative Example 3

[0029] The difference from Example 1 is that the lotus root and pear are chopped, homogenized using a colloid mill, and filtered using a 120 mesh filter to obtain lotus root juice and pear juice in step 1) and step 2).

[0030] Comparative Example 4

[0031] The difference from Example 1 is that the packing in step 3) is into a glass beverage bottle, and sterilization is performed in a high pressure steam sterilization pot at 121 DEG C for 15 min.

[0032] The juice yield of lotus root and pear in the examples and comparative examples is determined according to the following method: the mass of lotus root or pear before juicing is recorded as M0, the juice obtained after juicing is M, and the juice yield is calculated as M / M0x100%.

[0033] The lotus root starch content is determined according to the following method: fresh lotus root is washed, chopped, 100 g is weighed, 300 g of water is added for pulping, the pulp is filtered through a 100 mesh sieve, the filter residue is washed with water for 3 times, the filtrate is left to stand, the supernatant is discarded, 20 mL of water is added to the precipitate, the mixture is stirred, and the mixture is centrifuged at 4000 r for 10 min, the upper suspended matter and clear liquid are removed, the lower precipitate is collected as starch, and the starch is dried in a 60 DEG C oven until the moisture content is about 10% to obtain a powdery lotus root starch.

[0034] The application determines the polyphenol oxidase activity of lotus root and pear, and the specific method is: ① 5g of pre-cooled sample to 4 DEG C is weighed into a mortar, 5.0mL of pre-cooled pH 7.0 disodium hydrogen phosphate-sodium dihydrogen phosphate buffer (0.2mol / L containing 2% PVPP) is added in an ice bath, and the ground sample liquid is loaded into a 10mL centrifuge tube, and centrifuged at 13,200r / min for 10min at 4 DEG C, and the supernatant is obtained as the crude enzyme solution of polyphenol oxidase.

[0035] ② Determination of enzyme activity: 0.02mol / L of catechol solution is prepared as a reaction substrate using pH 7.0 disodium hydrogen phosphate-sodium dihydrogen phosphate buffer (0.05mol / L). 2.8mL of the substrate solution is taken and added to a colorimetric cup after being kept in a 25 DEG C water bath for 10min, 0.2mL of the crude enzyme solution is added to the colorimetric cup, and colorimetry is performed at 420nm, and the absorption value is recorded every 30s after the addition of the enzyme solution. The absorbance value of the reaction system at 420nm is recorded, and the OD 420 value-time curve is drawn, and the absorbance change value per minute ΔOD 420 is calculated according to the initial linear part of the curve. Then, when the absorbance change value per minute of each gram of fresh weight (FW) of fruit and vegetable sample increases by 1, it is 1 PPO activity unit (U), then U=ΔOD 420 ·min -1 ·g -1 FW.

[0036] The application determines the total soluble solids, and the specific determination method is: a Japanese Eto PAL-1 digital hand-held refractometer is used to record the Brix value.

[0037] The application determines the pH value, and the specific method is: a Mettler FE20 pH meter is used to determine the pH value.

[0038] The application determines the Vc content, and the specific method is: GB 5009.86-2016 Determination of Vc in food by 2,6-dichlorophenol indophenol titration method.

[0039] The application determines the total phenol content, and the specific determination method is: 3g of juice is mixed with 30mL of ethanol (concentration of 60%) and centrifuged at 10,000r / min for 10min, 2mL of supernatant is diluted to 10mL with distilled water and mixed. 2mL of sample diluent is mixed with 2.5mL of Folin phenol reagent and 2.5mL of distilled water, and after standing for 3min, 4mL of 7.5g / 100ml Na2CO3 solution is added, and the mixture is placed in the dark at room temperature for 90min. The OD value is measured at 765nm. A standard curve is drawn with 10-100μg / L of gallic acid, and the total phenol content of the sample is calculated.

[0040] The color is measured, and the specific method is: using a CM-700d spectrophotometer to measure and record the brightness value L*, red value a* and yellow value b*.

[0041] The browning degree is measured: 10 mL of juice is centrifuged at 10,000 r / min for 5 min, and the supernatant is collected, and distilled water is used as zero, and the absorbance is measured at 410 nm by using an Epoch full-wavelength enzyme marker.

[0042] The turbidity is measured: using formazin standard solution for calibration, and using SGZ-200I turbidimeter for measurement. After the sample is mixed, the turbidity values after 1 min and 1 h are recorded.

[0043] The sensory description of each embodiment and the comparative example is carried out: the color description is carried out under natural light; the aroma is added to 200 mL of fruit and vegetable juice in a 300 mL diameter 5 cm glass cup, the liquid surface is inclined at 30°, and the smell is smelled at a distance of 3 cm from the cup opening; the taste evaluation is carried out by putting 15 mL of fruit and vegetable juice into the mouth, making it spread in the mouth, and then swallowing after 20 seconds, and then evaluating the memory perception after 1 min; the shape is observed whether there are visible flocculent, spherical and block-shaped objects suspended and settled.

[0044] The quantitative sensory evaluation is carried out: preferably 10 evaluators, the aroma, sweetness, astringency and overall acceptance of each embodiment sample are scored. Five-point intensity scale is used for evaluation, wherein the aroma, sweetness and astringency are the perceived intensity, i.e. 1-not perceived, 2-just perceived, 3-perceived, 4-clearly perceived, 5-perceived very strongly. The overall acceptance is the comprehensive evaluation scale from entry to swallowing, which is 1-completely unacceptable; 2-difficult to accept; 3-acceptable; 4-flavor coordination, like; 5-taste coordination, like very much.

[0045] Table 1 Quality comparison of lotus root and pear composite juice of each embodiment and comparative example

[0046]

[0047] Note: The same row data with different letters indicates that the difference is significant by one-way analysis of variance, P<0.05.

[0048] Table 1 lists the quality indicators of lotus root and pear composite juice of each example and comparative example, and the underlined data does not meet the requirements of the present application. Comparative example 1 has a high lotus root juice ratio and still has a significant astringent taste. Comparative example 2 has a high pear juice content, a high sweet taste, and is closer to pear juice, low Vc and total phenol content, and cannot reflect the flavor characteristics of the composite juice. Comparative example 3 has a significant browning phenomenon, low Vc content and total phenol content, the color changes to yellow-brown, L* and browning degree increase significantly. Comparative example 4 has a color change to red-brown, a*, b* and browning degree all increase significantly, a large amount of precipitate appears, and the flavor changes significantly after sterilization.

[0049] The pictures of lotus root and pear composite juice of each example and comparative example can be directly observed to see the color and precipitate of the sample. Figure 1 The pictures of lotus root and pear composite juice of each example and comparative example can be directly observed to see the color and precipitate of the sample.

[0050] Figure 2 The sensory evaluation and turbidity determination results of lotus root juice, pear juice and their composite juice can be seen. It can be seen that the acceptance of lotus root juice and pear juice alone is low, there are astringent taste, too sweet, low aroma intensity and other problems, and the composite of the two enhances the aroma intensity and taste coordination, and the overall acceptance rises.

[0051] Although the above examples make a detailed description of the present application, it is only a part of the examples of the present application, not all examples, and people can also obtain other examples according to the present examples without creativity, and these examples all belong to the protection scope of the present application.​

Claims

1. A method for preparing a lotus root and pear compound fruit and vegetable juice, characterized in that, Includes the following steps: 1) Fresh lotus root and pear, wash them and then juice them separately; 2) Mix the lotus root juice and pear juice obtained in step 1) at a mass ratio of 1:(0.8-1.2); 3) After degassing the fruit and vegetable juice obtained in step 2) under vacuum at -0.095MPa, seal it in a flexible material package. 4) The compound fruit and vegetable juice obtained in step 3) is subjected to ultra-high pressure sterilization at 500-600MPa for 5-10 minutes.

2. The method according to claim 1, characterized in that, In step 1), the polyphenol oxidase activities of lotus root and pear were 5.5-6.8 U / gFW and 0.75-0.82 U / gFW, respectively; the starch content of lotus root was 0.5%-4.8%, and the juice yield was 77%-82%; the juice yield of pear juice was 78%-86%.

3. The method according to claim 1, characterized in that, In step 2), the lotus root juice has 5.8%-8.7% soluble solids, 312.10-343.52 mg / L vitamin C, pH 6.0-6.2, and 559.14-590.23 mg / L total phenols; the pear juice has 10.9%-13.8% soluble solids, 7.32-14.57 mg / L vitamin C, and 204.79-239.56 mg / L total phenols.

4. A lotus root and pear compound fruit and vegetable juice, characterized in that, The lotus root and pear compound fruit and vegetable juice obtained by the method described in claims 1-6 is milky white, with a soluble solids content of 8.9%-9.2%, a total phenol content of 195.94-223.11 mg / L, and a vitamin C content of 143.65-177.94 mg / L.

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