NL2032878B1

NL2032878B1 - Coolant for cold chain transportation of fruits, vegetables and fresh foods and application

Info

Publication number: NL2032878B1
Application number: NL2032878A
Authority: NL
Inventors: Chen Jing; Chu Dongliang; Tan Huiping; Wu Xiaotong; Zhao Zhangrong
Original assignee: Univ Beijing Wuzi
Priority date: 2022-08-29
Filing date: 2022-08-29
Publication date: 2024-03-12

Abstract

The present disclosure relates to a coolant for cold chain transportation of fresh fruits and vegetables. Based on the theory of physical state change of phase change materials, various aids are added to prepare the coolant which is free of adverse phenomenon, low in price and non—toxic; and the phase change temperature range of the coolant can. be controlled, to be 0—8°C. Meanwhile, the coolant provided by the present disclosure has the characteristics of uniform distribution, no phase separation phenomenon, harmlessness to the body, low price, etc. The present disclosure particularly improves the undesirable phenomenon of a sodium sulfate hydrated salt solution, and greatly improves the serious problems of supercooling and phase separation of the sodium sulfate hydrated salt solution.

Description

P1544 /NLpd

COCLANT FOR COLD CHAIN TRANSPORTATION OF FRUITS, VEGETABLES AND

FRESH FOODS AND APPLICATION

TECHNICAL FIELD

The present disclosure relates to a food transportation heat preservation and cold preservation technology, particularly to a coolant for cold chain transportation of fresh fruits and vegeta- bles and an application thereof.

BACKGROUND ART

With the rapid development of "Internet +", people's consump- tion patterns have changed from traditional physical shopping to online shopping. As a part of online shopping, the fresh food mar- ket has developed rapidly, maintaining an average growth rate of more than 80%; currently it accounts for 3.4% of the total agri- cultural products. In 2017, the transaction volume of China's fresh food online shopping market reached 153.7 billion yuan, and it is expected to reach 200 billion yuan in 2018, and there is a large space in the future; however, fresh products have a problem of a high rate of decay, with an annual loss of about 60 million tons in China, which is significantly higher than the level of de- veloped countries. The transportation preservation problem of the “last one mile” is an important part of solving this problem.

Thus, a new problem arises: how to provide a lower temperature en- vironment for fresh products, so that the fresh products are al- ways in the specified low temperature environment from the distri- bution site to the consumers, to ensure the quality and reduce the loss. Therefore, a coolant is needed as a cold source to ensure the quality of fresh products.

Fresh fruits and vegetables are perishable foods. When the storage temperature of these temperature-sensitive products is higher or lower than their optimum storage temperature, the quali- ty will be damaged, and the "broken chain” is prone to occur dur- ing the cold chain transportation process. The logistics staffs are paying more and more attention to how to keep refrigerated fresh products under a specified low temperature environment from production to transportation to consumers, to ensure product qual- ity and reduce wastage. Therefore, it is particularly important to develop a coolant that can provide a lower temperature for the surrounding environment and better preserve fresh products.

At present, there are a large number of coolant products in

China, but the phase transition temperature of most coolant prod- ucts is below zero. For perishable products such as cherries and sea cucumbers that have extremely strict temperature requirements, subzero temperatures will cause damage to their quality, and some coolants have the supercooling and phase separation phenomena.

These problems seriously affect the function and value of coolants and affect the quality of goods transported in the cold chain. Ac- cording to this situation, it is very important to develop a cool- ant that has suitable phase transition temperature and has no su- percooling and phase separation phenomenon, to realize the cold chain transportation of products above 0°C and improve the cold chain transportation.

SUMMARY

In order to overcome the above defects, the present disclo- sure provides an environment-friendly medium-temperature coolant for certain temperature-sensitive fruits and vegetables or fresh products (the optimum storage temperature is about 3-5°C).

The present disclosure provides a coolant for cold chain transportation of fresh foods, fruits and vegetables. A phase change energy storage technology is used as a theoretical basis, namely a phase change material absorbs or releases a large amount of heat in the physical state change process so as to achieve the aims of regulating and controlling the environment temperature and utilizing energy. The adopted phase change material in the present disclosure is a sodium sulfate aqueous solution (the mixing ratio of anhydrous sodium sulfate to water is 71: 90); various aids are added into the sodium sulfate aqueous solution to prepare the coolant which is free of adverse phenomenon, low in price and non- toxic; and the phase change temperature range of the hydrous salt coolant can be controlled to be 0-8°C. Meanwhile, the coolant pro-

vided by the present disclosure has the characteristics of uniform distribution, no phase separation phenomenon, harmlessness to the body, low price, etc.

According to the most preferable embodiment of the present disclosure, the present disclosure particularly provides a coolant with a phase change temperature of 3.5°C, a supercooling degree of 0.6°C, and a phase change duration of about 60 min. The coolant can be particularly applied to fresh foods which are easy to rot and cannot be stored at a low temperature, such as oysters, sea cucum- bers and cherries.

The coolant disclosed by the present disclosure comprises the following components in parts by weight: 7,000-9,000 parts of a sodium sulfate aqueous solution; 300-400 parts of fumed silica; 30-40 parts of agar; 250-350 parts of borax; 250-350 parts of boric acid; 700-900 parts of potassium chloride; 1,100-1,300 parts of ammonium chloride.

Most preferably, the coolant comprises the following compo- nents in parts by weight: 8,000 parts of a sodium sulfate aqueous solution; 350 parts of fumed silica; 35 parts of agar; 300 parts of borax; 300 parts of boric acid; 800 parts of potassium chloride; 1,200 parts of ammonium chloride.

The present disclosure particularly improves the undesirable phenomenon of a sodium sulfate hydrated salt solution, and borax is adopted as an anti-supercooling agent to eliminate the super- cooling phenomenon of a mixed system; boric acid is added to neu- tralize the pH value in the system so as to obtain a neutral solu- tion system; agar and fumed silica are added as phase separation preventing agents to solve the phase separation phenomenon togeth- er; and cooling agents KCl and NH;Cl in different proportions are added to reduce the phase change temperature of the mixed system,

and finally the coolant with the phase change temperature of about 0-8°C is prepared, and thus the adverse phenomenon of the sodium sulfate hydrated salt solution is greatly improved. The technical effects of uniform distribution, no phase separation phenomenon, no harm to bodies, lower price and the like are achieved. Mean- while, the coolant with the phase change temperature of 3°C, 3.5°C, 4°C, 4.5°C or 5°C and the like can be obtained by properly adjusting the use amount of the components, the coolant can be selected and adjusted for use according to the types of fruits and vegetables and the types of fresh foods, fruits and vegetables, and the cool- ant is more suitable for cold chain transportation of foods such as fresh foods, fruits and vegetables.

The present disclosure has a special effect that the phase separation phenomenon is solved by adopting fumed silica and agar together. As the market price of the fumed silica is high, the agar is adopted as a thickening agent, and the use amount of the fumed silica is reduced, so that the purpose of reducing the cost is achieved. However, as the sodium sulfate hydrated salt solution contains a large number of ions, the ions possibly influence the texture property of the agar, and therefore, the influence of fac- tors such as the pH value, sodium ions and potassium ions on the agar is fully considered. According to the present disclosure, bo- ric acid is added to neutralize the pH value of the solution sys- tem and maintain the pH value at 7, thus the gel wrapping property of the agar is not influenced; meanwhile, the molar ratio of the sodium ions to the potassium ions in the mixed system is con- trolled, and the maximum elasticity of agar gel is ensured. Final- ly, the phase separation phenomenon of the coolant is perfectly solved by accurately controlling the use amount of each component.

Furthermore, the coolant of the present disclosure can be prepared into capsules, and polypropylene (PP) is preferably se- lected as a raw material of a capsule shell, thus the coolant product is packaged, the specific surface area of the coolant is increased, the contact surface between the coolant of unit mass and the surrounding environment is increased, and as a result, the refrigeration effect of the coolant is improved; and the coolant prepared in the capsules can meet the requirements of commodities with different shapes.

BRIEF DESCRIPTION OF THE DRAWINGS

5 FIG. 1 is a cooling curve of the coolant of Example 3;

FIG. 2 is a temperature rise curve of the coolant of Example 3 at a constant temperature of 25°C;

FIG. 3 is a schematic diagram showing an application of a coolant capsule of Example 4.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to further illustrate the present disclosure, spe- cific description is given in conjunction with the following exam- ples.

Example 1

This example provided a coolant with a phase transition tem- perature of about 0°C, which comprised the following components in parts by weight: 9,000 parts of a sodium sulfate aqueous solution; 300 parts of fumed silica; 40 parts of agar; 250 parts of borax; 250 parts of boric acid; 900 parts of potassium chloride; 1,300 parts of ammonium chloride;

The above components were stirred uniformly in a water bath at a temperature of 40°C.

Example 2

This example provided a coolant with a phase transition tem- perature of about 8°C, which comprised the following components in parts by weight: 7,000 parts of a sodium sulfate aqueous solution; 400 parts of fumed silica; 30 parts of agar; 350 parts of borax; 350 parts of boric acid; 700 parts of potassium chloride;

1,100 parts of ammonium chloride;

Example 3

This example provided a coolant with a phase transition tem- perature of about 3.5°C, which comprised the following components in parts by weight: 8,000 parts of a sodium sulfate aqueous solution; 350 parts of fumed silica; 35 parts of agar; 300 parts of borax; 350 parts of boric acid; 800 parts of potassium chloride; 1,200 parts of ammonium chloride;

Experiment Example 1

According to the component ratio of the Example 3, 40 g of a sodium sulfate aqueous solution, 1.75 g of fumed silica, 0.175 g of agar, 1.5 g of borax, 1.5 g of boric acid, 4 g of potassium chloride and 6 g of ammonium chloride were added into a beaker, stirred uniformly in a water bath kettle at a temperature of 40°C and allowed to stand for 30 min, wherein phase separation was not found; samples were distributed uniformly; no granular object was found; the temperature was measured once every 30 s in a constant- temperature environment of -4°C by an electronic thermometer; and a cooling curve was drawn as shown in FIG. 1.

The phase change temperature of the finally prepared coolant was 3.5°C, the degree of supercooling could reach 0.6°C, and the phase change duration could be maintained for 60 min.

Experiment Example 2

The experiment was used for verifying the cooling effect of the coolant in the Example 3 directly applied to cold chain trans- portation. 500 g of a coolant was prepared based on the component ratio in the Example 3, the coolant was contained in a sealing bag and sealed through a heat sealing machine, the sealing bag was placed in a low-temperature environment of -15°C in advance to be frozen for 10 h till the coolant was completely solidified, and the seal- ing bag was taken out and placed in a constant-temperature envi- ronment of 0°C together with a foam box and fruits to be precooled for 5 h.

The foam box and fresh oysters were placed in a constant- temperature box together to be precooled for 5 h, then the sealed coolant was placed on the upper layer and the lower layer of the foam box, an electronic thermometer probe was placed in the center of the foam box, a heat preservation box was taken out after com- plete sealing, and placed in the constant-temperature environment of 25°C, the temperature was recorded once every 1 min, a tempera- ture curve was drawn as shown in the FIG. 2, and the refrigeration duration was analyzed.

Conclusion: the prepared coolant had a certain refrigeration effect; as shown in the temperature curve, the temperature in the foam box slowly and stably rose, and the temperature rose by 1- 1.3°C per hour on average; based on the temperature data measured by the probe that the temperature in the box could be kept for 398 min from 0°C to 10°C; and the coolant had a certain refrigeration effect, and the quality of commodities could be guaranteed within a certain period of time.

Example 4

This example provided a cold-preserving product for cold chain transportation of fresh foods, fruits and vegetables, and the coolants in the Examples 1 to 3 were respectively added into capsule shells and then sealed by glass cement. Because the cool- ant capsules were small in shape and could perfectly wrap commodi- ties in various shapes, so the refrigeration effect was better.

Polypropylene (PP) was the most preferable raw material of the coolant capsule shell and was composed of the elements C, H and O, which couldn’t not cause harm to the environment no matter the coolant capsule shell was recycled, incinerated or buried; the polypropylene (PP) had excellent plasticity; because the Vicat softening temperature of the polypropylene (PP) was 150°C, the pol-

ypropylene (PP) was high in crystallinity, good in surface rigidi- ty, mechanical property and chemical stability, resistant to tem- perature and impact and not hydrolyzed. Therefore, the PP did not have the problems of environmental stress cracking and hydrolysis, and the application and large-scale production of the coolant cap- sule were feasible. Meanwhile, compared with an ice bag, the cool- ant capsule per unit mass had larger surface area and was better in refrigeration effect theoretically. The prepared sodium sulfate hydrous salt coolant was placed in the coolant capsule and used for absorbing heat of the surrounding space, the heat conduction coefficient of the polypropylene (PP) was an important factor in the heat conduction process, the substance with high heat conduc- tion coefficient had good heat conduction performance, and the heat conduction coefficient of the polypropylene (PP) was 0.21- 0.26 W/mK and was higher than that of PVC, PE, polystyrene and other materials, so that PP was the optimal material for the cap- sule shell.

The structure of the finally prepared coolant capsule in the example was shown in the FIG. 3 (cold chain transportation for oyster). Because the coolant capsule was small in shape and could perfectly wrap commodities in various shapes, the refrigeration effect was better.

The foregoing examples merely describe the preferred embodi- ments of the present disclosure, and do not constitute restriction on the scope of the present disclosure. Technicians of ordinary skill in the art can make various modifications and improvements to the technical solutions of the present disclosure without de- parting from the design spirit of the present disclosure, and these modifications and improvements shall fall within the scope of protection defined by the appended claims of the present dis- closure.

Claims

CONCLUSIONS

1. Refrigerant for the transport of fresh fruit and vegetables in the cold chain, where the phase change temperature of the refrigerant is 0 to 8 °C.

A coolant according to claim 1, wherein the phase change temperature of the coolant is 3.5°C.

Coolant according to claim 2, wherein the degree of subcooling of the coolant is 0.6 °C and the phase transition duration is 60 minutes.

Use of the coolant according to any one of claims 1 to 3 in cold chain transport.

Use according to claim 4, wherein capsules are made from the coolant and used in cold chain transport.

Coolant according to claim 1, comprising the following components in parts by weight:

7,000 to 9,000 parts of an aqueous sodium sulfate solution; 300 to 400 parts fumed silica; 30 to 40 parts agar; 250 to 350 parts borax; 250 to 350 parts boric acid; 700 to 900 parts potassium chloride; 1100 to 1300 parts ammonium chloride.

Coolant according to claim 2, comprising the following components in parts by weight:

8,000 parts of an aqueous sodium sulfate solution; 350 parts fumed silica; parts agar; 300 parts borax;

300 parts boric acid; 800 parts potassium chloride; 1200 parts ammonium chloride.

A method for preparing the coolant according to claim 6 or 7, wherein the components are stirred uniformly in a water bath at 40°C.

Cold preserving product for cold chain transport of fresh fruit and vegetables, wherein the coolant according to any one of claims 1 to 3 or any of claims 6 to 7 is made into a coolant capsule by loading it into a capsule shell.

Cold preservation product according to claim 9, wherein the raw material of the capsule shell is polypropylene.