Fruit and vegetable pretreatment method for improving quality of fruit and vegetable juice

Abstract

The invention discloses a fruit and vegetable pretreatment method for improving the quality of fruit and vegetable juice. The method comprises the following steps: peeling fruits and vegetables, crushing the peeled fruits and vegetables, carrying out vacuum packaging, and carrying out ultrahigh pressure pretreatment in ultrahigh pressure equipment so as to improve the quality of fruit and vegetable juice; the step of improving the quality of the fruit and vegetable juice comprises at least one of the following steps: 1) improving the Vc content of the fruit and vegetable juice; 2) the polyphenol content of the fruit and vegetable juice is increased; 3) the oxidation resistance of the fruit and vegetable juice is improved; and 4) the protease activity of the fruit and vegetable juice is improved. According to the method, the juice yield of the pulp can be increased, more nutrients, flavors, colors and other substances are dissolved out of the pulp into the fruit juice, the concentration of bioactive substances such as Vc and polyphenol in the fruit juice can be further increased on the basis of original fruit and vegetable juice, and the loss of characteristic flavor substances in the fruit and vegetable juice in the processing process is reduced; the retention rate of characteristic flavor substances is increased, the sensory quality of the fruit and vegetable juice is improved, microorganisms can be effectively killed, and pressure is relieved for subsequent sterilization of the fruit juice.

Description

Technical Field

[0001] The present invention belongs to the technical field of food science and engineering, and particularly relates to a fruit and vegetable pretreatment method for improving the quality of fruit and vegetable juices. Background Art

[0002] Fruits and vegetables are rich in various bioactive substances such as Vc, polyphenols, and flavonoids, which can prevent cardiovascular diseases and protect cells from oxidative damage caused by harmful free radicals. However, fresh fruits and vegetables have a short shelf life and serious losses, and are often processed into fruit and vegetable products through juicing, freeze-drying, etc. Among them, fruit and vegetable juices not only maintain the natural aromatic smell and fresh taste of the original fruits and vegetables, but also retain nutrients and active substances, becoming one of the most popular fruit and vegetable products. However, in the current fruit and vegetable juice processing process, there are still problems such as low juice yield, less dissolution of nutrients, flavors, colors, etc. into the juice, and large losses of fruit and vegetable raw materials.

[0003] Juicing is an important process in the fruit and vegetable juice-making process, and its process directly determines the quality of the juice. Subsequent processes such as homogenization, filtration, and sterilization will all reduce the quality of the juice. Therefore, how to improve the juice yield in the juicing process and make more nutrients, flavors, colors, etc. dissolve from the pulp into the juice, so as to effectively improve the quality of the juice, and at the same time achieve the growth of "quantity" and "quality", is an important research direction.

[0004] Currently, the methods for improving the quality of fruit and vegetable juices mainly include heat treatment, enzyme treatment, and non-thermal processing technologies, etc. Traditional heat treatment technologies can effectively kill microorganisms and enzyme activities, but due to the high-temperature effect, it is easy to cause losses of heat-sensitive nutrients (such as vitamin C, polyphenols, etc.) in fruit and vegetable juices, and at the same time, it may cause adverse flavor and color changes. Some studies have tried to improve the quality of fruit and vegetable juices through enzymatic pretreatment technologies, such as adding pectinase or cellulase to promote the destruction of the pulp cell structure and improve the juice yield. However, the enzymatic treatment process is complex, and the temperature and time need to be strictly controlled, and it may affect the natural flavor of fruit and vegetable juices, which is not conducive to consumer acceptance.

[0005] In recent years, non-thermal processing technologies have developed rapidly, especially the ultra-high pressure technology, which uses high hydrostatic pressure to act on fruit and vegetable juices, and can kill microorganisms and extend the shelf life of products at normal or low temperatures. However, in the existing technologies, the method of directly performing ultra-high pressure treatment on fruit and vegetable juices, although it can maintain the nutrients in the juice, has limited effects in improving the juice yield, improving the flavor and color of the juice, etc., and there are still limitations in improving the quality of fruit and vegetable juices. Therefore, how to further improve the juice yield of fruit and vegetable juices, and at the same time explore more efficient and more in line with consumer needs technologies on the basis of maintaining or improving nutrition and flavor, is still an urgent problem to be solved in this field. Summary of the Invention

[0006] The object of the present invention is to provide a pre-treatment method for fruits and vegetables to improve the quality of fruit and vegetable juices. In the present invention, the pulp obtained after crushing fruits and vegetables is subjected to ultra-high pressure pre-treatment. The ultra-high pressure destroys the tissue structure of the pulp, promotes the dissolution of nutrients and active ingredients, increases the aroma components of fruit and vegetable juices, and thus improves the quality of fruit and vegetable juices.

[0007] In a first aspect, the present invention provides a pre-treatment method for fruits and vegetables to increase the juice yield of fruits and vegetables and / or the soluble solid content of fruit and vegetable juices, comprising the following steps:

[0008] Peel and crush the fruits and vegetables, and then place them in a vacuum packaging device in an ultra-high pressure device for ultra-high pressure pre-treatment to increase the juice yield of fruits and vegetables and / or the soluble solid content of fruit and vegetable juices.

[0009] In the above-mentioned pre-treatment method for fruits and vegetables to increase the juice yield of fruits and vegetables and / or the soluble solid content of fruit and vegetable juices, the fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or,

[0010] The diameter of the crushed fruits and vegetables is 10-80 mm; and / or,

[0011] The fruit and vegetable juice is unfiltered fruit and vegetable juice.

[0012] In the above-mentioned pre-treatment method for fruits and vegetables to increase the juice yield of fruits and vegetables and / or the soluble solid content of fruit and vegetable juices, the ultra-high pressure treatment is carried out at 100-500 MPa for 1-20 min, preferably at 300-500 MPa for 3-5 min, and more preferably at 500 MPa for 3-5 min.

[0013] In a second aspect, the present invention provides a pre-treatment method for fruits and vegetables to improve the quality of fruit and vegetable juices, comprising the following steps:

[0014] Peel and crush the fruits and vegetables, and then place them in a vacuum packaging device in an ultra-high pressure device for ultra-high pressure pre-treatment to improve the quality of fruit and vegetable juices;

[0015] The improvement of the quality of fruit and vegetable juices includes at least one of the following:

[0016] 1) Increase the Vc content of fruit and vegetable juices;

[0017] 2) Increase the polyphenol content of fruit and vegetable juices;

[0018] 3) Increase the antioxidant capacity of fruit and vegetable juices;

[0019] 4) Increase the protease activity of fruit and vegetable juices.

[0020] In the above-mentioned pre-treatment method for fruits and vegetables to improve the quality of fruit and vegetable juices, the fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or,

[0021] The diameter of the crushed fruits and vegetables is 10 to 80 mm; and / or,

[0022] The ultra-high pressure treatment is a pretreatment for 1 to 20 min at 100 to 500 MPa; and / or,

[0023] The fruit and vegetable juice is unfiltered fruit and vegetable juice; and / or,

[0024] The improvement in antioxidant capacity is reflected in the improvement of the ability to scavenge ·DPPH free radicals and / or the improvement of FRAP antioxidant capacity.

[0025] In the above-mentioned fruit and vegetable pretreatment method for improving the quality of fruit and vegetable juice, further preferably, the quality of the fruit and vegetable juice is to increase the Vc content of the fruit and vegetable juice, and the ultra-high pressure treatment is a pretreatment for 3 min at 300 MPa;

[0026] The quality of the fruit and vegetable juice is to increase the total phenol content of the fruit and vegetable juice, and the ultra-high pressure treatment is a pretreatment for 3 min at 500 MPa;

[0027] The quality of the fruit and vegetable juice is to increase the antioxidant capacity of the fruit and vegetable juice, and the ultra-high pressure treatment is a pretreatment for 5 min at 400 to 500 MPa, such as a pretreatment for 5 min at 400 MPa or 500 MPa;

[0028] The quality of the fruit and vegetable juice is to increase the bromelain activity, and the ultra-high pressure treatment is a pretreatment for 5 min at 500 MPa.

[0029] In a third aspect, the present invention provides a fruit and vegetable pretreatment method for increasing the content of aroma components in fruit and vegetable juice, comprising the following steps:

[0030] Peel and crush the fruits and vegetables, and then place them in a vacuum packaging device in an ultra-high pressure device for ultra-high pressure pretreatment to increase the content of aroma components in the fruit and vegetable juice.

[0031] In the above-mentioned fruit and vegetable ultra-high pressure pretreatment method for increasing the content of aroma components in fruit and vegetable juice, the fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or,

[0032] The diameter of the crushed fruits and vegetables is 10 to 80 mm; and / or,

[0033] The fruit and vegetable juice is unfiltered fruit and vegetable juice.

[0034] In the above-mentioned fruit and vegetable ultra-high pressure pretreatment method for increasing the content of aroma components in fruit and vegetable juice, the ultra-high pressure treatment is a pretreatment for 3 to 5 min at 300 to 500 MPa, preferably a pretreatment for 3 min at 400 to 500 MPa, such as a pretreatment for 3 min at 400 MPa or 500 MPa.

[0035] In the above-mentioned ultra-high pressure pretreatment method of fruits and vegetables for increasing the content of aroma components in fruit and vegetable juices, the aroma components include one or more of ester aroma substances, acid aroma substances, ketone aroma substances, aldehyde aroma substances, terpene aroma substances, and phenolic aroma substances; preferably, the ester aroma substances include one or more of methyl 2-methylbutyrate, methyl hexanoate, ethyl n-hexanoate, methyl 3-methylthiopropionate, methyl 4-octenoate, methyl octanoate, cyclohexyl methacrylate, and isooctyl laurate; preferably, the acid aroma substances include octanoic acid; preferably, the ketone aroma substances include β-ionone; preferably, the aldehyde aroma substances include one or more of nonanal and trans-2-decenal; preferably, the terpene aroma substances include one or more of beta-elemene, (±)-β-copaene, (+)-medicarpene, and Δ-cadinene; preferably, the phenolic aroma substances include 2,6-di-tert-butyl.

[0036] In the method described in any of the above, as an example, the fruits and vegetables are pineapples, such as Golden Crown pineapples, but the fruits and vegetables in the method of the present invention are by no means limited to this. This is because, first, fruits and vegetables including pineapples, oranges, apples, carrots, and tomatoes have similar cell structures, and these structures will undergo similar physical changes under ultra-high pressure, thereby destroying the pulp tissue structure through ultra-high pressure and promoting the dissolution of nutrients and active ingredients; second, fruits and vegetables including pineapples, oranges, apples, carrots, and tomatoes all contain pectin, proteins, enzymes, and volatile aroma precursor substances, etc., and these components will undergo similar chemical reactions under ultra-high pressure treatment, thereby improving the quality of fruit and vegetable juices and aroma components through ultra-high pressure; third, the fruits and vegetables all have adaptability to non-thermal processing: ultra-high pressure, as a non-thermal processing technology, can avoid the destruction of flavor and nutritional components by heat treatment, and this advantage applies to all fruits and vegetables; fourth, the fruits and vegetables all have the universality of the aroma precursor conversion path: the widespread existence of glycoside-bound precursors - the aroma precursors of most fruits and vegetables (such as grapes, mangoes, tomatoes) are stored in the form of glycosides (such as monoterpene glycosides). The β-glucosidase released after ultra-high pressure destroys the cells can specifically hydrolyze the glycosidic bond to release free aroma substances (such as geraniol in rose aroma). Oxidative derivatives of carotenoids and fatty acids - high pressure promotes the oxidation of polyunsaturated fatty acids (such as linoleic acid) or carotenoids catalyzed by lipoxygenase to generate aldehydes, ketones and other aroma substances (such as hexenal in tomatoes), and such precursors are widely present in the lipid components of fruits and vegetables.

[0037] In the method described in any of the above, the crushing can be carried out in various forms such as shearing and impact, including but not limited to chopping, smashing, crushing, etc. As an example, the crushing method is cutting.

[0038] The morphology of the crushed fruits and vegetables can be in the form of blocks, slices, strips, dices or any other irregular forms.

[0039] The diameter of the crushed fruits and vegetables is 10 - 80 mm. It should be noted that although the size of the fruits and vegetables is described by the diameter in the present invention, this does not mean that the shape of the fruits and vegetables can only be spherical. In the present invention, the diameter can also be the equivalent diameter under other shapes. As an example, the size of the crushed fruits and vegetables is a 1 cm × 2 cm × 2 cm cube, but it can be understood that based on the same principle above, the size of the crushed fruits and vegetables in the present invention is by no means limited to this, and the purpose of the present invention can be achieved as long as the diameter or equivalent diameter is within the above range.

[0040] The vacuum packaging can adopt any packaging method that can form a vacuum, such as placing it in a vacuum bag and evacuating the air.

[0041] The fruit and vegetable juice is unfiltered fruit and vegetable juice, that is, the fruit and vegetable juice containing substances such as fruit residues without any separation after juicing.

[0042] Fourthly, the present invention provides a method for preparing fruit and vegetable juice, including the fruit and vegetable pretreatment method described in any one of the above. Specifically, it includes the following steps: 1) Pretreat the fruits and vegetables by using the fruit and vegetable pretreatment method described in any one of the above; 2) Juice the pretreated fruits and vegetables without filtration to obtain the fruit and vegetable juice. Specifically, the juicing is carried out in a screw juicer. Exemplarily, the fruit and vegetable is pineapple, and the juicing time is 2 - 4 min.

[0043] The present invention has the following beneficial effects:

[0044] (1) The fruit and vegetable pretreatment method adopted in the present invention crushes the pulp through ultra-high pressure pretreatment, which can not only improve the juice yield of the pulp, dissolve more nutrients, flavors, colors and other substances from the pulp into the juice, effectively maintain the product quality, further increase the concentration of bioactive substances such as Vc and polyphenols in the juice on the basis of the original fruit and vegetable juice, but also effectively kill microorganisms through ultra-high pressure treatment, reducing the pressure for subsequent sterilization of the juice.

[0045] (2) The fruit and vegetable pretreatment method adopted in the present invention crushes the pulp through ultra-high pressure pretreatment, which can further reduce the loss of characteristic flavor substances in the fruit and vegetable juice during the processing, improve the retention rate of characteristic flavor substances, and improve the sensory quality of the fruit and vegetable juice. Description of the Drawings

[0046] Figure 1 shows the influence of the quality of pineapple juice under different ultra-high pressure pretreatment conditions in Example 2 (A: Vc content; B: total phenol content; C: ability to scavenge DPPH free radicals; D: FRAP antioxidant ability; E: bromelain activity). Detailed Embodiments

[0047] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements, and do not constitute any limitation to the present invention in any way.

[0048] The methods used in the following embodiments, 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 embodiments, unless otherwise specified, can all be obtained from commercial channels.

[0049] The pineapples in the following embodiments were purchased from Beijing Wumart Duodian Supermarket, produced by Goodfarmer. The pineapple variety is Golden Diamond Pineapple, produced in the Philippines, with a weight of about 1.4 kg, a height of about 20 cm, and a diameter of about 12 cm.

[0050] The ultra-high pressure equipment used in the following embodiments is Beijing Suyuan Zhongtian Technology Co., Ltd., model: HHP-600.

[0051] Example 1. Physicochemical indexes (juice yield, pH, TSS, total color difference ΔE) of pineapple juice under different ultra-high pressure pretreatment conditions

[0052] The following treatment groups were set under different ultra-high pressure pretreatment conditions:

[0053] Treatment 1A, control group

[0054] Peel 1.4 kg of Golden Diamond pineapples, cut them into 1 cm×2 cm×2 cm cubes, put them into a vacuum bag, weigh them, and the mass is m 0 ; put them into a screw juicer, juice for about 3 minutes without filtration to obtain pineapple juice, weigh it, and the mass is m 1 ; put it into a 50 mL PET bottle;

[0055] Treatment 1B, 100 MPa - 3 min

[0056] Peel 1.4 kg of Golden Diamond pineapples, cut them into 1 cm×2 cm×2 cm cubes, put them into a vacuum bag, weigh them, and the mass is m 0 ; treat the obtained system at 100 MPa for 3 minutes; after the treatment, put it into a screw juicer, juice for about 3 minutes without filtration to obtain pineapple juice, weigh it, and the mass is m 1 ; put it into a 50 mL PET bottle;

[0057] Treatment 1C, 100 MPa - 5 min

[0058] Peel 1.4 kg of pineapple, cut it into cubes of 1 cm × 2 cm × 2 cm, pack them into a vacuum bag, and weigh it. The mass is m 0 ; The obtained system is treated at 100 MPa for 5 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, and weigh it. The mass is m 1 ; Pack it into a 50 mL PET bottle;

[0059] Treatment 1D, 300 MPa - 3 min

[0060] Peel 1.4 kg of pineapple, cut it into cubes of 1 cm × 2 cm × 2 cm, pack them into a vacuum bag, and weigh it. The mass is m 0 ; The obtained system is treated at 300 MPa for 3 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, and weigh it. The mass is m 1 ; Pack it into a 50 mL PET bottle;

[0061] Treatment 1E, 300 MPa - 5 min

[0062] Peel 1.4 kg of pineapple, cut it into cubes of 1 cm × 2 cm × 2 cm, pack them into a vacuum bag, and weigh it. The mass is m 0 ; The obtained system is treated at 300 MPa for 5 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, and weigh it. The mass is m 1 ; Pack it into a 50 mL PET bottle;

[0063] Treatment 1F, 400 MPa - 3 min

[0064] Peel 1.4 kg of pineapple, cut it into cubes of 1 cm × 2 cm × 2 cm, pack them into a vacuum bag, and weigh it. The mass is m 0 ; The obtained system is treated at 400 MPa for 3 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, and weigh it. The mass is m 1 ; Pack it into a 50 mL PET bottle;

[0065] Treatment 1G, 400 MPa - 5 min

[0066] Peel 1.4 kg of pineapple, cut it into cubes of 1 cm × 2 cm × 2 cm, pack them into a vacuum bag, and weigh it. The mass is m 0 ; The obtained system is treated at 400 MPa for 5 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, and weigh it. The mass is m 1 ; Pack it into a 50 mL PET bottle;

[0067] Treatment 1H, 500 MPa - 3 min

[0068] Peel 1.4 kg of golden pineapple, cut it into 1 cm × 2 cm × 2 cm cubes, pack them into a vacuum bag, weigh it, and the mass is m 0 ; The obtained system is treated at 500 MPa for 3 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, weigh it, and the mass is m 1 ; Pack it into a 50 mL PET bottle;

[0069] Treatment 1I, 500 MPa - 5 min

[0070] Peel 1.4 kg of golden pineapple, cut it into 1 cm × 2 cm × 2 cm cubes, pack them into a vacuum bag, weigh it, and the mass is m 0 ; The obtained system is treated at 500 MPa for 5 min; After the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, weigh it, and the mass is m 1 ; Pack it into a 50 mL PET bottle;

[0071] Test or calculate the physical and chemical indexes of the pineapple juice in the above different treatment groups. The test methods or calculation formulas are as follows:

[0072] Juice yield:

[0073]

[0074] pH: Use a pH meter. First, calibrate the pH meter and clean the electrode with distilled water. Immerse the electrode in the pineapple juice and record the pH value after the reading is stable. After completion, ensure that the instrument is cleaned to keep it clean.

[0075] Total soluble solids (TSS): Use an Abbe refractometer and calibrate the refractometer with distilled water. During the calibration process, adjust the eyepiece of the refractometer to ensure that the reading is at zero. Drop the prepared pineapple juice sample into the sample chamber of the Abbe refractometer, ensure that the surface of the sample is flat and fills the sample chamber. Gently close the sample chamber to ensure that there are no bubbles and observe the scale of the refractometer. Observe the scale of the refractometer through the eyepiece and record the refractive index at this time expressed in °Brix.

[0076] Total color difference ΔE: Use a color difference meter. At room temperature, use a standard white board as the standard, and set the parameters as: RSIN - specular reflection, area is 0.375 inches. Measure the L * , a * , b * values. Among them: L * represents brightness, a * > 0, represents the degree of redness, a* <0 represents the degree of greenness; b * >0 represents the degree of yellowness, b * <0 represents the degree of blueness. Calculate ΔE through the following formula:

[0077]

[0078] In the formula: ΔE—total color difference; L * —brightness value of the sample after treatment; L 0 * —brightness value of the sample before treatment; a * —red value of the sample after treatment; a 0 * —red value of the sample before treatment; b * —yellow value of the sample after treatment; b 0 * —yellow value of the sample before treatment.

[0079] The physical and chemical indexes (juice yield, pH, TSS, total color difference ΔE) of pineapple juice in each treatment group under different ultra-high pressure pretreatment conditions are shown in Table 1.

[0080] Table 1. Physical and chemical indexes (juice yield, pH, TSS, total color difference ΔE) of pineapple juice in Example 1 under different ultra-high pressure pretreatment conditions

[0081]

[0082]

[0083] Note: Data in the same row (column) marked with different upper (lower) case letters indicate significant differences (p<0.05).

[0084] It can be seen from Table 1 that:

[0085] Compared with the control group, the juice yield of pineapple chunks pretreated with ultra-high pressure of 100-500 MPa is higher, preferably 300-500 MPa, more preferably 400-500 MPa, and the juice yield is the highest when pretreated with ultra-high pressure at 500 MPa for 5 min;

[0086] Compared with the control group, the content of soluble solids (TSS) in the pineapple juice obtained by juicing after ultra-high pressure pretreatment of 100-500 MPa is higher, preferably pretreated at 500 MPa for 3 min;

[0087] Compared with the control group, the total color difference, L * value and b * value of the pineapple juice obtained by juicing after ultra-high pressure pretreatment of 100-500 MPa change little. Generally speaking, with the increase of pressure and the prolongation of pressure holding time, ΔE *gradually increased, indicating that the color change was significant after high-pressure treatment under different conditions, probably because high pressure promoted the release of pigments in the pulp cells; when the pressure was 100 Mpa and the holding time was 3 min, ΔE * was the smallest, and the color change was the smallest; when the pressure was 500 Mpa and the holding time was 5 min, ΔE * was the largest, and the color change was the most obvious. Generally speaking, with the increase of pressure and the extension of holding time, the b * value gradually decreased, the pulp gradually turned yellow, and the change was obvious; with the extension of holding time, the L * value gradually decreased, and the brightness of the juice gradually decreased, but the overall change was not significant. When the pressure was 500 Mpa, the L * value was lower than that of other treatment groups, and the brightness of the juice decreased, corresponding to the b value.

[0088] In summary, the present invention treats the pulp under different ultra-high pressure conditions to strengthen the mass transfer process of the pulp juice and active ingredients, and improve the juice yield of the pulp and the content of soluble solids in the pulp. This is because ultra-high pressure treatment can strengthen the disintegration of the pulp cell tissue, enhance the cell permeability, accelerate the diffusion mass transfer and dissolution of the juice and active components in the pulp cells, and then strengthen the subsequent juice extraction process of the pulp.

[0089] Example 2. Influence of different ultra-high pressure pretreatment conditions on the quality of pineapple juice (Vc content; total phenol content; DPPH free radical scavenging ability; FRAP antioxidant ability; bromelain activity)

[0090] Set up treatment groups under the following different ultra-high pressure pretreatment conditions:

[0091] Treatment 2A, control group

[0092] Peel 1.4 kg of golden pineapple, cut it into 1 cm × 2 cm × 2 cm cubes, put it into a vacuum bag; put it into a screw juicer, juice for about 3 min, without filtration, obtain pineapple juice, and put it into a 50 mL PET bottle;

[0093] Treatment 2B, 100 MPa - 3 min

[0094] Peel 1.4 kg of golden pineapple, cut it into 1 cm × 2 cm × 2 cm cubes, put it into a vacuum bag; the obtained system is treated at 100 MPa for 3 min; after the treatment, put it into a screw juicer, juice for about 3 min, without filtration, obtain pineapple juice, and put it into a 50 mL PET bottle;

[0095] Treatment 2C, 100 MPa - 5 min

[0096] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 100 MPa for 5 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0097] Treatment 2D, 300 MPa - 3 min

[0098] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 300 MPa for 3 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0099] Treatment 2E, 300 MPa - 5 min

[0100] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 300 MPa for 5 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0101] Treatment 2F, 400 MPa - 3 min

[0102] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 400 MPa for 3 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0103] Treatment 2G, 400 MPa - 5 min

[0104] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 400 MPa for 5 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0105] Treatment 2H, 500 MPa - 3 min

[0106] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm × 2 cm × 2 cm cubes, and pack them into a vacuum bag; the obtained system is treated at 500 MPa for 3 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0107] Treatment 2I, 500 MPa - 5 min

[0108] Peel 1.4 kg of golden diamond pineapples, cut them into cubes of 1 cm × 2 cm × 2 cm, and pack them into vacuum bags; the obtained system is treated at 500 MPa for 5 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles.

[0109] Test the quality of the pineapple juice in the above different treatment groups. The test methods are as follows:

[0110] Vc content: 《GB 5009.86-2016》;

[0111] Total phenol content: Folin-Ciocalteu method. Preparation of the extract: Take 0.7 mL of pineapple juice, add 6.3 mL of pure water, centrifuge at 12000 rpm and 4 °C for 10 min, and take the supernatant for standby. Dilute the Folin-Ciocalteu reagent 10 times with ultrapure water according to 1:9 (v:v). After diluting 0.1 mL of the extract to 0.5 mL and mixing it with 2 mL of the diluted Folin-Ciocalteu reagent, react in the dark at room temperature for 1 h, then add 1.8 mL of 7.5% Na 2 CO 3 solution, react in the dark at room temperature for 15 min, measure the absorbance at 765 nm with a spectrophotometer, and the total phenol content is expressed as the number of mg of pyrogallic acid equivalent per 100 g of the sample. Preparation of the gallic acid standard curve: Prepare gallic acid standard solutions with concentrations of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.08 mg / mL respectively. After mixing 0.4 mL of gallic acid solutions with different concentrations with 2 mL of the Folin-Ciocalteu reagent diluted 10 times respectively, react in the dark at room temperature for 1 h, then add 1.8 mL of 7.5% Na 2 CO 3 solution, react in the dark at room temperature for 15 min, and measure the absorbance at 765 nm with a spectrophotometer. Draw the standard curve: y = 11.891x + 0.0225 (R 2 = 0.9995);

[0112] DPPH radical scavenging ability: Take 0.7 mL of pineapple juice, add 6.3 mL of pure water, centrifuge at 12,000 rpm and 4 °C for 10 min, and take the supernatant for use. Add 100 μL of the above sample extract to 4 mL of DPPH solution (0.14 mM), place it in the dark at room temperature for 45 min, and then measure the absorbance at 517 nm. Use 100 μL of methanol added to 4 mL of DPPH solution as a control. Preparation of Trolox standard curve: Prepare Trolox standard solutions with concentrations of 100, 200, 400, 600, 800, and 1000 μM using methanol. Take 100 μL of each and react with 4 mL of DPPH solution in the dark at room temperature for 45 min, measure the absorbance at 517 nm, and plot the standard curve: y = -0.6551x + 1.5478 (R 2 = 0.9978);

[0113] FRAP antioxidant ability: Take 0.7 mL of pineapple juice, add 6.3 mL of pure water, centrifuge at 12,000 rpm and 4 °C for 10 min, and take the supernatant for use. Take 100 μL of the sample (using distilled water as a blank control) and add it to 4 mL of TPTZ working solution, react at 37 °C for 10 min, and then measure the absorbance at 593 nm. Preparation of Trolox standard curve: Prepare Trolox standard solutions with concentrations of 0.06, 0.1, 0.2, 0.4, 0.6, and 0.8 mmol / L using anhydrous methanol. Take 100 μL of each and react with 4 mL of TPTZ working solution in the dark at 37 °C for 10 min, measure the absorbance at 593 nm, and plot the standard curve: y = 1.0861x + 1.0222 (R 2 = 0.993);

[0114] Bromelain Activity: (1) Take 2 mL of pineapple juice, mix it with 2 mL of 80% ethanol solution, shake well, and let it stand for 15 min. Centrifuge at 6000 rpm and 4 °C for 10 min, remove the supernatant, and retain the precipitate. Dissolve the precipitate with 2 mL of 0.2 mol / L phosphate buffer at pH = 7. Solution Preparation: ① Preparation of Substrate Solution: Weigh 0.6 g of casein, add it to 80 mL of 0.05 mol / L sodium dihydrogen phosphate solution, heat to dissolve, and after cooling, adjust the pH value of the solution to the range of 5 to 8 with appropriate acid or base and make up the volume to 100 mL with water. ② Preparation of Trichloroacetic Acid Solution: Mix 1.8 g of trichloroacetic acid, 2.99 g of anhydrous sodium acetate, and 1.9 mL of glacial acetic acid, and stir until completely dissolved. ③ Preparation of Tyrosine Standard Solution: First, weigh 0.1 g of tyrosine, dissolve it with 1 mol / L HCl solution and make up the volume to 100 mL. Then, take 5 mL from this solution and further make up the volume to 100 mL with 0.1 mol / L HCl solution. ④ Dilution of Folin-Ciocalteu Reagent: Take 5 mL of the stock solution and add 45 mL of ultrapure water to make the total volume reach 50 mL, thus achieving a 10-fold dilution. ⑤ Preparation of 7.5% Sodium Carbonate Solution: Take 42.4 g of sodium carbonate, dissolve it with ultrapure water and make up the volume to 100 mL. Determination of Standard Solution: Mix 0.5 mL of tyrosine standard solution with 2.5 mL of sodium carbonate solution and 0.5 mL of Folin-Ciocalteu reagent, shake well, and after reacting in the dark at room temperature for 20 min, measure the absorbance at 680 nm. Determination of Enzyme Activity: First, preheat the substrate solution and enzyme extract in a 40 °C constant temperature water bath for 5 min. Take 0.4 mL of enzyme extract and mix it with 2 mL of substrate solution, react at 40 °C for 10 min, then add 2 mL of trichloroacetic acid to terminate the reaction, let it stand for 10 min, and then centrifuge at 10000 rmp and 4 °C for 10 min with a high-speed refrigerated centrifuge. Take 0.5 mL of the supernatant, mix it with 2.5 mL of sodium carbonate solution and 0.5 mL of Folin-Ciocalteu reagent, shake well, and after reacting in the dark at room temperature for 20 min, measure the absorbance at 680 nm. The blank control is to add trichloroacetic acid first and then the substrate solution. Processing of Measurement Results: Taking the enzyme amount that can hydrolyze casein to produce 1 μg of tyrosine per 1 mL of pineapple juice in 1 min as 1 enzyme activity unit, expressed in U / mL, the activity (X) of bromelain in the sample is calculated according to the formula;

[0115]

[0116] In the formula:

[0117] X — The activity of bromelain, unit is U / g;

[0118] A — The absorbance of the sample to be measured at 680 nm wavelength;

[0119] A 0—— Absorbance value at 680 nm of the blank

[0120] A n —— Absorbance value at 680 nm of the standard solution

[0121] C n —— Value of the concentration of the tyrosine standard solution. Unit: microgram per milliliter (μg / mL)

[0122] W —— Value of the sample volume taken for the test, unit: milliliter (mL)

[0123] 10 —— Value of the reaction time, unit: minute (min)

[0124] 4.4 —— Value of the total volume of the determination, unit: milliliter (mL)

[0125] N —— Dilution factor of the sample

[0126] The quality of pineapple juice in each treatment group under different ultra-high pressure pretreatment conditions is shown in Figure 1

[0127] It can be seen from Figure 1A that compared with the Vc content of the control group (0 min) (22.575 mg / 100 g), the Vc content in the pineapple juice obtained by juicing after ultra-high pressure pretreatment at 100 - 500 MPa has increased to varying degrees, and the Vc content is the highest (23.15 mg / 100 g) under the treatment conditions of 300 MPa / 3 min. Higher pressure treatment will instead activate the activity of vitamin C oxidase, resulting in Vc degradation

[0128] It can be seen from Figure 1B that compared with the total phenol content of the control group (0 min) (650.769 g GAE / mL), the total phenol content in the pineapple juice obtained by juicing after ultra-high pressure pretreatment at 100 - 500 MPa has increased to varying degrees, and the total phenol content is the highest (722.85 g GAE / mL) under the treatment conditions of 500 MPa / 3 min

[0129] It can be seen from Figure 1C that compared with the relative reduction percentage of DPPH scavenging ability of the control group (0 min) (18.73%), the relative reduction percentage of the scavenging ability in the pineapple juice obtained by juicing after ultra-high pressure pretreatment at 100 - 500 MPa has increased to varying degrees, and the relative reduction percentage of DPPH scavenging ability is the highest (22.49%) under the treatment conditions of 400 MPa / 5 min

[0130] It can be seen from Figure 1DIt can be seen that, compared with the relative total reduction percentage of FRAP in the control group (0 min) (83.08%), the relative total reduction percentage of FRAP in the pineapple juice obtained by juicing after ultra-high pressure pretreatment at 100 - 500 MPa all increased to varying degrees, and the relative total reduction percentage of FRAP was the highest (101.05%) under the treatment condition of 500 MPa / 5 min.

[0131] It can be Figure 1E seen that, compared with the bromelain activity in the control group (0 min) (626.382 U / g), the bromelain activity in the pineapple juice obtained by juicing after ultra-high pressure pretreatment at 100 - 500 MPa all increased to varying degrees, and the bromelain activity was the highest (810.57 U / g) under the treatment condition of 500 MPa / 5 min.

[0132] In summary, in the present invention, by treating the pulp under different ultra-high pressure conditions, the Vc content, total phenol content, antioxidant capacity, and bromelain activity of the obtained pineapple juice are all improved. This is because through ultra-high pressure treatment in the present invention, the mass transfer process between the pulp juice and active ingredients can be strengthened, promoting the dissolution of physiological active substances such as Vc and polyphenols in the pulp, and improving the quality of the fruit and vegetable juice.

[0133] Example 3. Influence of aroma components of pineapple juice under different ultra-high pressure pretreatment conditions

[0134] Set up the treatment groups under the following different ultra-high pressure pretreatment conditions:

[0135] Treatment 3A, control group

[0136] Peel 1.4 kg of golden pineapple, cut it into 1 cm×2 cm×2 cm cubes, pack them into a vacuum bag; put them into a screw juicer, juice for about 3 min without filtration, obtain pineapple juice, and pack it into 50 mL PET bottles;

[0137] Treatment 3B, 400 MPa - 3 min

[0138] Peel 1.4 kg of golden pineapple, cut it into 1 cm×2 cm×2 cm cubes, pack them into a vacuum bag; treat the obtained system at 400 MPa for 5 min; after the treatment, put it into a screw juicer, juice for about 3 min without filtration, obtain pineapple juice, and pack it into 50 mL PET bottles;

[0139] Treatment 3C, 500 MPa - 3 min

[0140] Peel 1.4 kg of golden diamond pineapples, cut them into 1 cm×2 cm×2 cm cubes, and pack them into vacuum bags; the obtained system is processed at 500 MPa for 3 min; after the treatment, put it into a screw juicer and juice for about 3 min without filtration to obtain pineapple juice, which is packed into 50 mL PET bottles;

[0141] Test the aroma components of the pineapple juice in the above different treatment groups. The test method is as follows:

[0142] Adopt headspace solid-phase microextraction-gas chromatography-mass spectrometry technology. Before sampling, the PDMS solid-phase microextraction head is aged in the gas chromatograph injection port for 60 min, and the aging temperature is 250 °C. Take 6.0 g of pineapple juice and 1 g of NaCl into a 20 mL headspace vial, add 2-methyl-3-heptanone 28 2 L at 400 mg / L to the sample as an internal standard, and seal it. Perform solid-phase microextraction at 50 °C (solid-phase microextraction fiber: DVB / CAR / PDMS (LabTech)), with a shaking time of 10 min, an adsorption time of 40 min, and desorption at 250 °C for 3 min before testing. Gas chromatography-mass spectrometry analysis method: The instrument model is GC-MS 7890B-5977B (Agilent, American); the injector model is PAL RTC Autosampler (CTC Analytics AG, Switzerland); the column is DB-5ms (Agilent, J&W Scientific, 30 m * 0.25 mm * 0.25 μm). The column temperature is programmed, with an initial temperature of 60 °C, then rising to 120 °C at a rate of 4 °C / min, then rising to 200 °C at a rate of 6 °C / min, and holding for 5 min; the injection port temperature is 250 °C, using splitless injection, with a carrier gas of He and a flow rate of 1.0 mL / min. The extraction head is desorbed in the injection port at 250 °C for 2 min. Mass spectrometry conditions: Electron impact ionization source (EI); detector voltage 350 V; ion source temperature 230 °C; interface temperature 250 °C, electron energy 70 eV; scanning mass range 35 - 335 amu.

[0143] The aroma components of the pineapple juice in each treatment group under different ultra-high pressure pretreatment conditions are shown in Table 2.

[0144] Table 2. Influence of aroma components of pineapple juice under different ultra-high pressure pretreatment conditions

[0145]

[0146]

[0147] It can be seen from Table 2 that:

[0148] Compared with the control group, the contents of various aroma substances were basically increased. Among them, the relative contents of ester components in the pineapple juice obtained by juicing the pineapple pulp treated at 400 MPa / 3 min and 500 MPa / 3 min were 55.62% and 70.86% respectively, and the 500 MPa / 3 min treatment group was significantly higher than the control group (50.95%); the relative contents of ketone substances treated at 400 MPa / 3 min and 500 MPa / 3 min were 2.98% and 3.52% respectively, significantly higher than the control group (1.60%); the relative contents of aldehyde substances treated at 400 MPa / 3 min and 500 MPa / 3 min were 1.50% and 1.56% respectively, which were twice that of the control group; the relative contents of terpene substances treated at 400 MPa / 3 min and 500 MPa / 3 min were 2.75% and 2.80% respectively, both greater than the relative content of terpene substances in the control group; for phenolic substances, the relative contents treated at 400 MPa / 3 min and 500 MPa / 3 min were 0.24% and 0.23% respectively, higher than the control group (0.12%).

[0149] In summary, by treating the pulp under different ultra-high pressure conditions in the present invention, the aroma substances of the obtained pineapple juice are also improved. This is because the present invention can strengthen the mass transfer process of the pulp juice and active ingredients through ultra-high pressure treatment, promote the dissolution of aroma substances in the pulp, and increase the content of aroma components in the fruit and vegetable juice.

[0150] The above has described the present invention in detail. For those skilled in the art, without departing from the purpose and scope of the present invention, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In summary, according to the principle of the present invention, this application intends to include any changes, uses or improvements to the present invention, including changes made by using conventional techniques known in the art that are outside the scope disclosed in this application.

Claims

1. A method for pretreating fruits and vegetables for increasing the juice yield of fruits and vegetables and / or the soluble solids content of fruit and vegetable juice, characterized in that: The steps include: The fruits and vegetables are peeled and crushed, then vacuum packed and placed in an ultra-high pressure device for ultra-high pressure pretreatment to increase the juice yield of the fruits and vegetables and / or the soluble solids in the fruit and vegetable juice.

2. The method for pretreating fruits and vegetables for increasing the juice yield of fruits and vegetables and / or the soluble solids content of fruit and vegetable juice according to claim 1, characterized in that: The fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or, The diameter of the crushed fruits and vegetables is 10 to 80 mm; and / or, The fruit and vegetable juice is unfiltered fruit and vegetable juice.

3. The method for pretreating fruits and vegetables for increasing the juice yield of fruits and vegetables and / or the soluble solids content of fruit and vegetable juice according to any one of claims 1 to 2, characterized in that: The ultra-high pressure treatment is pre-treated at 100-500 MPa for 1-20 min, preferably at 300-500 MPa for 3-5 min, and more preferably at 500 MPa for 3-5 min.

4. A method for pre-treating fruits and vegetables for improving the quality of fruit and vegetable juice, characterized in that: The steps include: Peel the fruits and vegetables, crush them, and then vacuum pack them and place them in an ultra-high pressure device for ultra-high pressure pretreatment to improve the quality of the fruit and vegetable juice; Improving the quality of fruit and vegetable juice includes at least one of the following: 1) Increase the vitamin C content of fruit and vegetable juice; 2) Increase the polyphenol content of fruit and vegetable juice; 3) Improve the antioxidant capacity of fruit and vegetable juice; 4) Improve the activity of protease in fruit and vegetable juice.

5. The method for pre-treating fruits and vegetables for improving the quality of fruit and vegetable juice according to claim 4, characterized in that: The fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or, The diameter of the crushed fruits and vegetables is 10 to 80 mm; and / or, The ultra-high pressure treatment is pre-treatment at 100-500 MPa for 1-20 min; and / or, The fruit and vegetable juice is unfiltered fruit and vegetable juice; and / or, The improvement of the antioxidant capacity is reflected in the improvement of the ability to scavenge DPPH free radicals and / or the improvement of the FRAP antioxidant capacity.

6. The method for pre-treating fruits and vegetables for improving the quality of fruit and vegetable juice according to claim 5, characterized in that: The quality of the fruit and vegetable juice is to increase the vitamin C content of the fruit and vegetable juice, and the ultra-high pressure treatment is pre-treatment at 300 MPa for 3 minutes; The fruit and vegetable juice quality is to increase the total phenol content of the fruit and vegetable juice, and the ultra-high pressure treatment is pre-treatment at 500 MPa for 3 minutes; The quality of the fruit and vegetable juice is to improve the antioxidant capacity of the fruit and vegetable juice, and the ultra-high pressure treatment is pre-treated at 400-500 MPa for 5 minutes; The quality of the fruit and vegetable juice is improved by increasing the activity of bromelain, and the ultra-high pressure treatment is pre-treated at 500 MPa for 5 minutes.

7. A method for pretreating fruits and vegetables for increasing the content of aroma components in fruit and vegetable juice, characterized in that: The steps include: The fruits and vegetables are peeled and crushed, then vacuum packed and placed in an ultra-high pressure device for ultra-high pressure pretreatment to increase the content of aroma components in the fruit and vegetable juice.

8. The method for ultra-high pressure pretreatment of fruits and vegetables for increasing the content of aroma components in fruit and vegetable juice according to claim 7, characterized in that: The fruits and vegetables include pineapple, orange, apple, carrot or tomato; and / or, The diameter of the crushed fruits and vegetables is 10 to 80 mm; and / or, The fruit and vegetable juice is unfiltered fruit and vegetable juice.

9. The method for pre-treating fruits and vegetables for increasing the content of aroma components in fruit and vegetable juice according to claim 7, characterized in that: The ultra-high pressure treatment is pre-treatment at 300-500 MPa for 3-5 min, preferably pre-treatment at 400-500 MPa for 3 min; and / or, The aroma components include one or more of ester aroma substances, acid aroma substances, ketone aroma substances, aldehyde aroma substances, terpene aroma substances, and phenol aroma substances; preferably, the ester aroma substances include one or more of methyl 2-methylbutyrate, methyl hexanoate, ethyl hexanoate, methyl 3-methylthiopropionate, methyl 4-octenoate, methyl octanoate, cyclohexyl methacrylate, and isooctyl laurate; preferably, the acid aroma substances include octanoic acid; preferably, the ketone aroma substances include β-ionone; preferably, the aldehyde aroma substances include one or more of nonanal and trans-2-decenal; preferably, the terpene aroma substances include one or more of Beta-elemene, (±)-Β-copaene, (+)-cloverene, and Δ-cadinene; preferably, the phenol aroma substances include 2,6-di-tert-butyl.

10. A method for preparing fruit and vegetable juice, characterized in that: The method comprises the fruit and vegetable pretreatment method according to any one of claims 1 to 9.

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