Blueberry non-crystal cold processing preservation method

Abstract

A blueberry non-crystal cold processing preservation method, the method comprises the following steps: the blueberry is cleaned and dewaxed, and is prepared; the slightly dewaxed blueberry is placed in a microwave drying sterilization machine for drying and sterilization, and the dehydration rate is controlled at 1%-3%; the slightly dehydrated blueberry is placed in a vacuum packaging bag for vacuum sealing; the vacuum packaging bag containing the blueberry is placed in a low-temperature liquid at-30 DEG C to-35 DEG C, and is frozen for 10 min-15 min, so that the center temperature of the blueberry reaches-3.5+ / -0.5 DEG C, and then is stored at-18+ / -1 DEG C. The preservation method can store the blueberry for more than 3 months, and greatly prolongs the shelf life of the blueberry.

Description

Technical Field

[0001] This invention relates to a preservation technology, specifically to a preservation film liquid, a preservation film, a method for preparing the same, and its application in berry preservation. Background Technology

[0002] Blueberries are harvested during the hot and rainy summer months. The high humidity at harvest time leads to vigorous microbial growth and respiration. Blueberries have thin skins and are very juicy. After harvesting, their metabolism is vigorous, the flesh softens, the ripening period is short, and the quality deteriorates very easily. The main manifestations are softening, juice leakage, easy rotting, and poor taste.

[0003] Currently, blueberries are primarily preserved using physical methods such as refrigeration, modified atmosphere packaging, and plastic wrap, as well as chemical methods such as spraying and soaking with preservatives. However, while refrigeration and modified atmosphere packaging are suitable for large-scale enterprise use, they are not suitable for preserving blueberries during their supermarket sales period, and they are energy-intensive and costly. Plastic wrap has relatively poor preservation effects, and spraying and soaking with chemical preservatives can easily leave chemical residues, affecting the taste, flavor, and color of blueberries. Furthermore, the release of chemical preservatives can cause environmental pollution. Even after these treatments, blueberries still tend to soften easily, leak juice, have a high rate of spoilage, and a short shelf life.

[0004] CN116058407A discloses a method for freeze-drying blueberries, which involves dewaxing and puncturing blueberries, then freeze-drying them at -40°C or below, causing the fruit to shrink and deform by more than 95% to retain more than 90% of the anthocyanins. However, this method cannot be used for preserving fresh blueberries. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a non-crystalline cold processing method for preserving blueberries, so as to maintain the firmness of blueberries, prevent them from softening, reduce the rate of decay, and extend the shelf life of fresh blueberries.

[0006] The technical solution adopted by this invention to solve its first technical problem is a method for preserving blueberries through amorphous cold processing, which includes the following steps: (1) Mild dewaxing The blueberries are washed and dewaxed, then set aside. (2) Pre-drying, sterilization, and mild dehydration The lightly dewaxed blueberries were dried and sterilized in a microwave dryer, with the dehydration rate controlled at 1%-3%. (3) Vacuum packaging After slight dehydration, the blueberries are placed in a vacuum-sealed bag. (4) Rapid cooling and quick freezing After placing the vacuum-packed bags containing blueberries in a low-temperature liquid at -30℃ to -35℃, freeze for 10-15 minutes until the core temperature of the blueberries reaches -3.5±0.5℃, then store at -18±1℃.

[0007] Preferably, in step (1), the dewaxing specifically involves immersing blueberries in a sodium carbonate solution with a mass fraction of 6wt%-8wt% for 15-20 minutes.

[0008] Preferably, in step (2), the microwave drying and sterilizing machine is a GWM-40B tunnel microwave drying and sterilizing machine with a total microwave power of 20-40 kW and a conveyor belt speed of 4-6 m / min.

[0009] Preferably, in step (3), the thickness of the vacuum packaging bag is 8mm-12mm.

[0010] Preferably, the freezing temperature in step (4) is -33℃.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The method of this invention maintains the firmness of blueberries, prevents them from softening, reduces the rate of decay, and extends the shelf life of fresh blueberries to more than 180 days. The water loss rate after thawing is 3-5%, which has high practical application value. Attached Figure Description

[0012] Figure 1 These are before-and-after photos of blueberries after harvesting, quick-freezing, and thawing. Detailed Implementation

[0013] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0014] This embodiment of a method for preserving blueberries through amorphous cold processing includes the following steps: (1) Cleaning and mild dewaxing Remove inedible materials such as foreign objects, branches, leaves, and rotten fruit. Select 25 kg of plump blueberries of similar size as raw materials. Wash the surface of the fruit with running water to remove surface dirt, drain the water, soak the blueberries in 50 kg of 7 wt% sodium carbonate solution for 15 minutes, then gently wipe off the skin, take out the blueberries, rinse them with purified water and drain the water.

[0015] (2) Pre-drying and moderate dehydration The lightly dewaxed blueberries were placed in a GWM-40B tunnel microwave drying and sterilizing machine, with the total microwave power set to 30kW, the conveyor belt speed to 5.0 m / min, and the dehydration rate controlled at 1.5%.

[0016] (3) Vacuum packaging and rapid cooling Place moderately dehydrated blueberries into a 10mm thick vacuum-sealed bag; (4) Packaging and rapid cooling After vacuum packaging, the blueberries were placed in a -33°C cryogenic liquid and frozen for 12 minutes. The core temperature of the blueberries was monitored to be -3.5°C. After freezing, they were stored at around -18°C for 3 months. The water loss rate after thawing was 3.69%.

[0017] Photos of blueberries after harvest, after vacuum packaging, and after thawing three months later. Figure 1 As shown. Example 2

[0018] This embodiment of a method for preserving blueberries through amorphous cold processing includes the following steps: (1) Cleaning and mild dewaxing Remove inedible materials such as foreign objects, branches, leaves, and rotten fruit. Select 50 kg of plump blueberries of similar size as raw materials. Wash the surface of the fruit with running water to remove surface dirt, drain the water, soak the blueberries in 150 kg of 6 wt% sodium carbonate solution for 20 minutes, then gently wipe off the skin, take out the blueberries, rinse them with purified water and drain the water.

[0019] (2) Pre-drying and moderate dehydration The lightly dewaxed blueberries were placed in a GWM-40B tunnel microwave drying and sterilizing machine, with the total microwave power set to 35kW, the conveyor belt speed set to 4.0 m / min, and the dehydration rate controlled at 3%.

[0020] (3) Vacuum packaging and rapid cooling Place moderately dehydrated blueberries in an 8mm thick vacuum-sealed bag; (4) Packaging and rapid cooling After vacuum packaging, the blueberries were placed in a -30°C cryogenic liquid and frozen for 15 minutes. The core temperature of the blueberries was monitored and then stored at around -18°C for 2 months. The water loss rate after thawing was 4.82%. Example 3

[0021] This embodiment of a method for preserving blueberries through amorphous cold processing includes the following steps: (1) Cleaning and mild dewaxing Remove inedible materials such as foreign objects, branches, leaves, and rotten fruit. Select 100kg of plump blueberries of similar size as raw materials. Wash the surface of the fruit with running water to remove surface dirt, drain the water, soak the blueberries in 200kg of 8wt% sodium carbonate solution for 18 minutes, then gently wipe off the skin, take out the blueberries, rinse them with purified water and drain the water.

[0022] (2) Pre-drying and moderate dehydration The lightly dewaxed blueberries were placed in a GWM-40B tunnel microwave drying and sterilizing machine, with the total microwave power set to 30kW, the conveyor belt speed to 5.0 m / min, and the dehydration rate controlled at 1.5%.

[0023] (3) Vacuum packaging and rapid cooling Place moderately dehydrated blueberries into a 10mm thick vacuum-sealed bag; (4) Packaging and rapid cooling After vacuum packaging, the blueberries were placed in a -35°C cryogenic liquid and frozen for 15 minutes. The core temperature of the blueberries was monitored and then stored at around -18°C for 4 months. The water loss rate after thawing was 4.78%. Example 4

[0024] This embodiment of a method for preserving blueberries through amorphous cold processing includes the following steps: (1) Cleaning and mild dewaxing Remove inedible materials such as foreign objects, branches, leaves, and rotten fruit. Select 75kg of plump blueberries of similar size as raw materials. Wash the surface of the fruit with running water to remove surface dirt, drain the water, soak the blueberries in 150kg of 7% sodium carbonate solution for 20 minutes, then gently wipe off the skin, take out the blueberries, rinse them with purified water and drain the water.

[0025] (2) Pre-drying and moderate dehydration The lightly dewaxed blueberries were placed in a GWM-40B tunnel microwave drying and sterilizing machine, with the total microwave power set to 25kW, the conveyor belt speed set to 4.0 m / min, and the dehydration rate controlled at 1%.

[0026] (3) Vacuum packaging and rapid cooling Place moderately dehydrated blueberries into a 10mm thick vacuum-sealed bag; (4) Packaging and rapid cooling After vacuum packaging, the blueberries were placed in a -30°C cryogenic liquid and frozen for 12 minutes. The core temperature of the blueberries was monitored to be -3.5°C. After freezing, they were stored at around -18°C for 4 months. The water loss rate after thawing was 4.23%.

[0027] Table 1 shows a comparison of the quality parameters of blueberries after cold processing and storage for three months in Example 1 with the quality parameters at harvest.

[0028] Detection method: (1) Horizontal and vertical diameters Measure the lateral dimension (width): Gently clamp the widest part of the fruit with the outer jaws (larger jaws) of the vernier caliper.

[0029] To measure the longitudinal dimension (length): Rotate the fruit 90° and gently clamp the longest two ends of the fruit using the same method. Ensure that the measuring claws are parallel to the length direction to avoid overestimating the result due to oblique measurement.

[0030] Reading method: For the main scale, read the whole millimeter value to the left of the "0" mark on the vernier scale. For the vernier scale, find the mark on the vernier scale that is most aligned with the main scale and read the value. Final result: Main scale reading + Vernier reading. Repeat the measurement 3 times and take the average to reduce error.

[0031] (2) Hardness Three fruits were randomly selected from each group. A GY-2 pointer-type fruit firmness tester was used. After removing 3×3 mm of the skin at the equator, the firmness was measured. Results were expressed in kg·cm². -2 express.

[0032] (3) Total sugar Samples were tested using a total sugar content assay kit (BC2715, Beijing Solarbio Science & Technology Co., Ltd.), and results are expressed in mg / g and mg / mL.

[0033] (4) Vitamin C The samples were tested using a vitamin C (Vc) content detection kit (A009-1-1), and the results were expressed in mg / 100g.

[0034] (5) Determination of soluble solids and titratable acids For the determination of soluble solids, three fruits were selected for each group. The juice was squeezed out by wrapping the fruits in gauze, and the juice was dropped onto a handheld refractometer. The soluble solids content was measured and recorded. The experiment was repeated three times, and the results were expressed as a percentage (%). The titratable acid content was determined using the sodium hydroxide titration method.

[0035] (6) Anthocyanins The method was slightly modified from that of Fan Cunfei et al. 1 g of pericarp and pulp tissue were weighed from each group of samples, added to 10 mL of pre-cooled 1% hydrochloric acid-methanol solution, and thoroughly ground in an ice bath. Extraction was then carried out at 4℃ in the dark for 20 min. After filtration, the supernatant was collected, and the absorbance was measured at wavelengths of 600 nm and 530 nm, respectively. The result was expressed as Δ(OD530 - OD600). -1 ) / g represents.

[0036] (7) Thawing water loss rate Sample pretreatment: Select blueberries of uniform size and ripeness, removing any damaged fruit. Weigh and record the initial weight W0 (accurate to 0.01 g). Thawing after quick-freezing: Thaw in a constant temperature water bath (e.g., 20℃); Draining and weighing: Place the thawed blueberries on a strainer or gauze to drain for 2 minutes (simulating actual processing conditions) to remove surface moisture. Quickly weigh and record W1.

[0037] Calculate the water loss rate: Substitute into formula (1) to calculate. Repeat each experiment ≥ 3 times and take the average value.

[0038] (1) Table 1. Quality of fresh blueberries after three months of storage

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preserving blueberries through amorphous cold processing, characterized in that, Includes the following steps: (1) Mild dewaxing The blueberries are washed and dewaxed, then set aside. (2) Pre-drying, sterilization, and mild dehydration The lightly dewaxed blueberries were dried and sterilized in a microwave dryer, with the dehydration rate controlled at 1%-3%. (3) Vacuum packaging After slight dehydration, the blueberries are placed in a vacuum-sealed bag. (4) Rapid cooling and quick freezing After placing the vacuum-packed bags containing blueberries in a low-temperature liquid at -30℃ to -35℃, freeze for 10-15 minutes until the core temperature of the blueberries reaches -3.5±0.5℃, then store at -18±1℃.

2. The blueberry amorphous cold processing preservation method according to claim 1, characterized in that, In step (1), the dewaxing process specifically involves immersing blueberries in a sodium carbonate solution with a mass fraction of 6wt%-8wt% for 15-20 minutes.

3. The blueberry amorphous cold processing preservation method according to claim 1, characterized in that, In step (2), the microwave drying and sterilizing machine is a GWM-40B tunnel microwave drying and sterilizing machine with a total microwave power of 20-40 kW and a conveyor belt speed of 4-6 m / min.

4. The blueberry amorphous cold processing preservation method according to claim 1, characterized in that, In step (3), the thickness of the vacuum packaging bag is 8mm-12mm.

5. The blueberry amorphous cold processing preservation method according to claim 1, characterized in that, In step (4), the freezing temperature is -33℃.

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