In this study, an ultraviolet LED lamp installed in the refrigerator, the air in the refrigerator compartment air circulation using sterilized, purified food storage environment. In this paper, fresh spinach and leeks were stored in a refrigerator with UV sterilization module. The chlorophyll, Vc content and soluble protein were determined to verify the preservation effect of the study on vegetables.
Experiments show that the refrigerator with UV sterilization module can reduce the chlorophyll content of spinach and amaranth, and the reduction is 10.1% and 9.4% lower than that of the sample stored in the ordinary refrigerator; it can reduce the loss of Vc in spinach and amaranth during storage. It is 1.91 times and 1.67 times more than the sample in the ordinary refrigerator; it can reduce the soluble protein content of spinach and amaranth, and the reduction is 13.2% and 17.9% lower than the sample stored in the ordinary refrigerator, which better maintains spinach and leek. The quality of the storage.
1 Introduction
With the development of the economy and the continuous improvement of people's living standards, refrigerators have entered thousands of households and become indispensable household appliances in daily life. A refrigerator is a device that artificially manufactures a low temperature environment to preserve food. Early refrigerators did not have antibacterial and bactericidal functions. They only relied on low temperatures to keep fresh food. The food in the refrigerator, especially in the refrigerator, would still spoil and deteriorate because of the bacteria in the low temperature environment. .
Fresh fruits and vegetables have high water content, rich nutrition, and easy to infect pathogenic microorganisms during the growth process. Therefore, after the harvest, the whole circulation process from the field to the consumer table often causes a large loss due to decay, aging and deterioration. In developed countries, the post-harvest loss rate of fruits and vegetables is 1.7% to 5%, while the loss rate in China is 20% to 30%.
The main way to prevent losses in the circulation of fruits and vegetables is to regulate the temperature, humidity, gas and other environmental conditions in the circulation process. At present, the use of chemical means such as chemical fungicides is also used in production to prevent the loss of decay. But fungicide residues have been found to pose a potential threat to the health of consumers, especially for children. Therefore, the research on new preservation technologies and means has received widespread attention from scientists and technicians.
Γ-ray (60Co or 137Cs) irradiation treatment has been used as a non-thermal physical sterilization technology for storage and preservation of fruits and vegetables. However, due to the high investment of γ-ray irradiation equipment, high-standard safety protection facilities are required, the operating cost is high, and the ion radiation source has certain safety hazards, which makes it greatly limited in the application of fruit and vegetable preservation. Compared with γ-rays, ultraviolet light is easy to obtain (only UV light can be used), no ion radiation source safety hazard, cheap equipment, simple operation, low operating cost, so the application of ultraviolet light in fruit and vegetable preservation has been increasingly affected in recent years. People's attention.
Ultraviolet light is a type of solar light and is a general term for radiation from 10 nm to 400 nm in the electromagnetic spectrum. According to the wavelength of ultraviolet light, ultraviolet light can be divided into long-wave ultraviolet (315~400nm, UV-A), medium-wave ultraviolet (280~315nm, UV-B), short-wave ultraviolet (200~280nm, UVC), vacuum ultraviolet ( 100~200nm). Short-wave UV is a range of sterilizable bands that kill bacteria and viruses.
Short-wave ultraviolet rays with a wavelength of 200 to 280 nm can penetrate the cell membrane of a microorganism, destroy a nucleic acid (DNA) structure, generate a pyrimidine dimer in the DNA molecule, cause a mutation, and lose the activity of the genetic material of the cell, causing the microorganism to lose reproductive ability or die. Therefore, short-wave ultraviolet rays are currently widely used in medical and health, food, water treatment and sterilization in some industrial fields.
Jiang Tianjia et al studied the effects of short-wave ultraviolet treatment on the postharvest quality of shiitake mushrooms. The results showed that after treatment with short-wave ultraviolet light, shiitake mushrooms maintained the sensory quality and nutritional value and prolonged the storage and preservation period. Lei Quwen et al studied the effect of UV treatment on the quality of fresh cut vegetables. The results show that the irradiation time is 30min, which can effectively control the growth and reproduction of microorganisms in fresh-cut kidney beans, and can effectively kill (or even completely remove) E. coli, and also have obvious inhibitory effects on fungi, lactic acid bacteria and Enterobacter; fresh cut vegetables The content of nitrate in Central Asia is the lowest, and the Vc content is best preserved compared with other treatments, and the sensory quality is good.
The traditional method of generating short-wave ultraviolet rays is to use a low-pressure mercury lamp, which is based on the principle that an electric field of a certain intensity is generated in the lamp during energization, so that the mercury vapor is ionized to generate ultraviolet rays. Due to some drawbacks, it was gradually replaced by UV led lamps . The use of ultraviolet led lamp in the refrigerator has the following advantages: 1 no heat radiation, the ultraviolet LED lamp is a cold light source relative to the ultraviolet mercury lamp, and is used in the low temperature environment of the refrigerator, does not affect the temperature; 2 environmental protection, no pollution, no heavy metal leakage , no ozone production; 3 long service life; 4 low energy consumption.
Earlier, refrigerator manufacturers introduced UV sterilization refrigerators, but more UV mercury lamps were used. Ultraviolet LED lamps are also used, but long-wave UV LED lamps are selected for cost reasons, and the sterilization effect is minimal. In this study, a short-wavelength ultraviolet LED lamp was installed in a refrigerator, and the working state of the LED lamp was controlled by a control system, and the air in the refrigerator refrigerator was sterilized by the air circulation to purify the food storage environment. In this paper, through the storage experiment of fresh spinach and leeks, the preservation effect of vegetables under the storage conditions of the research results of this project was evaluated.
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