A grape pulp preservation process

Abstract

The application discloses a grape pulp storage process, which comprises the following steps: pretreatment, selecting full and unbroken grape clusters, disinfecting after flowing water cleaning, washing out the grape clusters, dehulling, collecting the fruit grains for use; peeling, soaking the fruit grains in 1-3% sodium hydroxide solution for 3-7 min, washing and separating the peel, collecting the pulp for use; cold shock, placing the pulp in 0 DEG C ice water mixture for 25-35 min, and washing out for use; anti-freezing treatment, immersing the pulp in an anti-freezing agent solution for 5-10 min at normal temperature, and washing out for use; color protection, soaking the pulp in 0.5-1.0% citric acid solution for 2-3 min, and washing out for use; precooling, air cooling the pulp to 0-4 DEG C; deep freezing, deep freezing the pulp at-40 DEG C for 30-35 min, vacuum packaging, and freezing at-18 DEG C. The application solves the problems of weight loss and low cost performance of grape pulp in the prior art.

Description

Technical Field

[0001] This invention relates to the field of grape deep processing technology, and in particular to a grape pulp preservation process. Background Technology

[0002] Grapes are highly susceptible to dehydration, shriveling, mold, and browning after harvest. Seasonal concentrated market supply leads to significant unsold produce and losses, highlighting the urgent need for deep processing and preservation. Quick-freezing is widely used to lock in nutrients and extend shelf life, but traditional berry quick-freezing faces two major technical bottlenecks: First, slow deep freezing results in large ice crystals. Conventional cold storage (-18℃ still air) cools slowly, and grapes take a long time to reach the maximum ice crystal formation zone of -1 to -5℃. This results in large, needle-like ice crystals forming inside the cells, piercing cell membranes and walls. After thawing, juice leaks out, water loss often exceeds 15%, the pulp becomes soft and mushy, and there is significant loss of soluble solids and vitamins. Second, existing high-quality processes are costly or unsuitable. Existing technologies include vacuum freeze-drying (FD), which can maintain shape, but the equipment is expensive, the drying cycle is >20 hours, and without a free water replacement step, the grapes still shrivele, making it uneconomical. Furthermore, ordinary low-temperature frying or non-freeze-drying methods alter the original freshness of the grapes.

[0003] Therefore, there is an urgent need for a low-cost, mass-producible grape quick-freezing process that can simultaneously solve the problems of water loss, shrinkage, and browning, and thoroughly remove the skin. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a grape pulp preservation process that solves the problems of easy weight loss and low cost-effectiveness of grape pulp in the existing technology.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A grape pulp preservation process, by weight, includes the following steps:

[0007] Pre-treatment: Select plump and undamaged grape bunches, wash them with running water and disinfect them, remove the grape bunches and rinse them, then remove the grapes and collect the grapes for later use.

[0008] Peel the fruit by soaking it in a 1-3% sodium hydroxide solution for 3-7 minutes, then rinse it with clean water and separate the peel. Collect the pulp for later use.

[0009] Cold shock: Place the fruit pulp in a 0℃ ice water mixture for 25-35 minutes, then remove and set aside.

[0010] For antifreeze treatment, immerse the pulp in an antifreeze solution at room temperature for 5-10 minutes, then remove and set aside.

[0011] To protect the color, soak the pulp in a 0.5-1.0% citric acid solution for 2-3 minutes, then remove and set aside.

[0012] Pre-cooling involves air-cooling the fruit pulp from the previous step until the temperature reaches 0-4℃.

[0013] Deep freezing involves freezing the fruit pulp at -40℃ for 30-35 minutes, vacuum packaging it, and then storing it at -18℃.

[0014] Furthermore, ozone is introduced into the water for disinfection during the pretreatment process.

[0015] Furthermore, the ozone concentration is 1-3 mg / L, and the soaking time is 5-10 min.

[0016] Furthermore, the pretreatment involves rinsing with running water for 5-8 minutes.

[0017] Furthermore, the temperature of the sodium hydroxide solution during peeling is 50-70℃.

[0018] Furthermore, rinse with running water for 5-8 minutes during the peeling process.

[0019] Furthermore, the temperature of the pre-cooling intermediate air is set to 0-2℃.

[0020] Furthermore, the vacuum degree of the vacuum packaging is ≤10 Pa.

[0021] Furthermore, the antifreeze solution is a 3-7% xylitol aqueous solution.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) Through the synergistic effect of cold shock pretreatment, antifreeze impregnation and rapid deep freezing at -40℃, the moisture loss of grapes after thawing is controlled to below 2.5%, which is far lower than the water loss rate of more than 15% in traditional quick-freezing processes; effectively avoiding weight loss, and the product shape is full and not wrinkled.

[0024] 2) Rapid deep freezing forms small and uniform ice crystals, causing minimal mechanical damage to cell walls and cell membranes. After thawing, the meat remains firm and tender, overcoming the juice loss, soggy texture, and deterioration caused by traditional slow deep freezing.

[0025] 3) Due to the good cell integrity and minimal juice loss, nutrients and flavors such as soluble sugars, vitamins, and anthocyanins are well preserved; combined with color-protecting treatment (citric acid) to prevent browning, the quality is further guaranteed.

[0026] 4) Vacuum packaging isolates oxygen, and combined with -18℃ freezing, it reduces desiccation and oxidation caused by ice crystal sublimation during storage, extending shelf life and improving marketability.

[0027] 5) Compared with the expensive vacuum freeze drying, this process has lower equipment and operating costs and higher efficiency, solving the problem that the existing two technologies cannot balance quality and economy. Detailed Implementation

[0028] The present invention will be further described in detail below through specific embodiments:

[0029] This solution provides a grape pulp preservation process, which, by weight, includes the following steps:

[0030] After harvesting, pre-treatment is carried out. Plump, undamaged grape bunches are selected, washed with running water, and then disinfected in an ozone solution with an ozone concentration of 1-3 mg / L for 5-10 minutes. The bunches are then rinsed with running water for 5-8 minutes, followed by threshing. The grapes are collected and soaked in a 1-3% sodium hydroxide solution at 50-70℃ for 3-7 minutes. They are then rinsed with running water for 5-8 minutes, separating the skin during rinsing (the skin is lighter and will be carried away by the water). The pulp is collected and chilled in an ice-water mixture at 0℃ for 25-35 minutes. After draining, it is immersed in a 3-7% xylitol solution at room temperature for 5-10 minutes. After draining, it is soaked in a 0.5-1.0% citric acid solution for 2-3 minutes. After draining, the material is air-cooled at 0-2℃ until the temperature reaches 0-4℃ (measured value of the material's center temperature). Then, it is deep-frozen at -40℃ for 30-35 minutes. Finally, it is vacuum-packed and stored at -18℃. The vacuum degree of the vacuum packaging is ≤10 Pa.

[0031] Please refer to the table below for specific parameters to conduct the experiment and statistically analyze the results:

[0032]

[0033] Note: Water loss after thawing refers to the water loss rate of the pulp collected after separating the peel compared to the pulp obtained after thawing.

[0034] The products obtained in Examples 1-3 all had low moisture loss rates after thawing, below 2.5%, while the products in Examples 4-7 had moisture loss rates exceeding 2.5% to varying degrees. This indicates that the process provided by the present invention can effectively control the moisture loss rate after thawing. Specifically, by rapidly lowering the core temperature of the material to near 0°C through cold shock, the time spent passing through the maximum ice crystal zone during subsequent quick-freezing is shortened, facilitating the formation of fine ice crystals. Furthermore, the peeling step uses scalding with sodium hydroxide at 50-70°C (sodium hydroxide soaking treatment, which also assists in simultaneous scalding, softening the alkali under heat to facilitate subsequent rinsing with water). Cold shock immediately terminates the heat treatment, preventing overcooking and softening, and... The shrinkage and firming of the peel and pulp lays the foundation for maintaining cell integrity during subsequent antifreeze impregnation and deep freezing. The antifreeze used is a xylitol aqueous solution, which has the characteristics of low sweetness, non-crystallization, and the ability to reduce water activity and freezing point. During the impregnation process, it can replace some free water, lower the freezing point, and reduce large ice crystals. Deep freezing allows the core temperature of the material to quickly cross the maximum ice crystal zone, and ice crystals are simultaneously and finely precipitated inside and outside the cells, causing minimal damage to the cell walls. Furthermore, the pre-cooling of the pulp to near freezing point by the pre-cold shock, the replacement of some free water by xylitol impregnation and the lowering of the freezing point, and the rapid deep freezing at this time prevent the recrystallization of ice crystals, ultimately controlling the moisture loss after thawing to below 2.5% and minimizing weight loss.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A grape pulp preservation process, characterized by, by weight, Includes the following steps: Pre-treatment: Select plump and undamaged grape bunches, wash them with running water and disinfect them, remove the grape bunches and rinse them, then remove the grapes and collect the grapes for later use. Peel the fruit by soaking it in a 1-3% sodium hydroxide solution for 3-7 minutes, then rinse it with clean water and separate the peel. Collect the pulp for later use. Cold shock: Place the fruit pulp in a 0℃ ice water mixture for 25-35 minutes, then remove and set aside. For antifreeze treatment, immerse the pulp in an antifreeze solution at room temperature for 5-10 minutes, then remove and set aside. To protect the color, soak the pulp in a 0.5-1.0% citric acid solution for 2-3 minutes, then remove and set aside. Pre-cooling involves air-cooling the fruit pulp from the previous step until the temperature reaches 0-4℃. Deep freezing involves freezing the fruit pulp at -40℃ for 30-35 minutes, vacuum packaging it, and then storing it at -18℃.

2. The grape pulp preservation process as described in claim 1, characterized in that, Ozone is introduced into the water for disinfection during the pretreatment process.

3. The grape pulp preservation process as described in claim 2, characterized in that, Ozone concentration 1-3 mg / L, soaking time 5-10 min.

4. The grape pulp preservation process as described in claim 3, characterized in that, Rinse with running water for 5-8 minutes during pretreatment.

5. The grape pulp preservation process as described in claim 1, characterized in that, The temperature of the sodium hydroxide solution during peeling is 50-70℃.

6. The grape pulp preservation process as described in claim 5, characterized in that, Rinse with running water for 5-8 minutes after peeling.

7. The grape pulp preservation process as described in claim 1, characterized in that, The temperature of the pre-cooling air is set to 0-2℃.

8. The grape pulp preservation process as described in claim 1, characterized in that, The vacuum level of vacuum packaging is ≤10 Pa.

9. The grape pulp preservation process as described in claim 1, characterized in that, The antifreeze solution is a 3-7% xylitol aqueous solution.

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