In addition to nearly 100,000 rice processing units in rural townships and simple rice mills in rural areas, China currently has more than 7,000 large- and medium-sized rice processing plants with a relatively high technological level, and its annual production and processing capacity is over 40 million tons. The main producer of urban commodity rice [5]. Due to the limitation of storage conditions, the vast majority of high-quality rice and poor quality rice are mixed, affecting the finishing of rice. Due to the backwardness of storage facilities and technology, a large number of food pests occur each year, and they have to be fumigated with chemical agents to contaminate the food. After processing, the quality of food is reduced. Finished grain storage is a weak link in China's grain system [6]. This is because the currently widely used "three low" (low oxygen, low temperature, low concentration phosphine) storage method is suitable for large grain storage, but it has certain limitations for the finished grain in the transportation and sales links. In China, the time from the processing of rice to the hands of the residents is usually 3 to 6 months. The time spent on rice in the field is longer. Among them, there are no effective guarantee measures for the quality preservation of rice at various points in transit points, transportation, food stores, and households. China's peasant households account for 80% of the total grain storage, and the national warehousing capacity only accounts for about 20% of the total market demand. The effect of grain preservation is relatively low. The main storage methods are: sacks, woven bags, storage, storage, storage, storage, cement storage, cylinders, storage, rack storage. The annual national food loss rate is about 15%, about 6 million tons. ?
2.2 Status of rice packaging In the early 1990s, rice packaging in China was mainly sacks, plastic woven bags, and cloth bags. Each bag contained 15kg, 25kg, 50kg, etc. The bagging and cracking were serious and the loss was high. It was obviously not satisfied. Quality rice packaging requirements. But at the time, it only paid attention to the loss in quantity, and the quality loss has not been given due attention by people. In view of the current status of rice packaging, the grain packaging industry has proposed the guidelines for “large and small, heavy-duty†and development of small packages. In recent years, sales and packaging of rice has developed rapidly. In 1990, the penetration rate of 2.5kg high-quality rice packaging in Guangzhou reached 20%. In 1991, Shanghai supplied 2 to 2.5kg of rice in the first half of the year without washing rice. At present, in China's cities where small rice packaging has emerged, the rice varieties on the market include fragrant rice, soft rice, and non-scouring rice. However, it is not universal, but it is packaged well in individual cities. In most areas, the technology and level of rice sales and packaging are not high.
3 Rice Storage Techniques Food grain grows with the storage time, and its quality gradually declines as it ages. The speed of aging depends on different storage methods. The main storage forms of rice are stored at room temperature, low-temperature storage, anoxic (natural anoxic, filled with CO2, filled N2, vacuum) storage, chemical storage, mechanical refrigeration storage, plastic film sealed storage (rice heap), coating film preservation technology Storage etc.
3.1 Room temperature storage Room temperature storage is now the most widely used and is the most common rice storage in China. After the farmers harvest rice, they are sun dried to a sufficient level (below the safe moisture level), then milled into rice for normal temperature storage, cylinders, barrels, and woven bags. The main reason is to use low moisture content of rice to delay the deterioration of rice quality. As long as the storage method controls the moisture content of rice, the operation is relatively simple, but the amount and quality of rice are relatively serious.
The moisture content and temperature of rice are significantly positively correlated with the decline of rice storage quality. Water content and temperature are high, making it more susceptible to deterioration and microbial growth. The relative safe moisture of different temperature rice is shown in Table 1.
Table 1 Relatively safe rice moisture content at different temperatures Temperature (°C) 0 5 to 10 20 25 30 35 40
Relatively safe moisture (%) 16 to 18 ≤ 16 ≤ 14 13 to 13.5 <13 <12 <11
3.2 Low-temperature storage Low-temperature storage is a better method currently [7]. There are two ways to achieve low temperatures: First, the use of mechanical ventilation to the natural winter and spring temperatures into the grain piles, so that the temperature of the rice in the warehouse to a low temperature, and the use of food thermal resistance, small thermal conductivity characteristics, so that food is longer The time is kept low; the second is to use window-type air conditioners to supplement the cold source in the summer and autumn hot seasons to keep the grain temperature at a quasi-low temperature, but due to its high cost, it is still difficult to promote in large quantities at present and in the future.
2.2 Status of rice packaging In the early 1990s, rice packaging in China was mainly sacks, plastic woven bags, and cloth bags. Each bag contained 15kg, 25kg, 50kg, etc. The bagging and cracking were serious and the loss was high. It was obviously not satisfied. Quality rice packaging requirements. But at the time, it only paid attention to the loss in quantity, and the quality loss has not been given due attention by people. In view of the current status of rice packaging, the grain packaging industry has proposed the guidelines for “large and small, heavy-duty†and development of small packages. In recent years, sales and packaging of rice has developed rapidly. In 1990, the penetration rate of 2.5kg high-quality rice packaging in Guangzhou reached 20%. In 1991, Shanghai supplied 2 to 2.5kg of rice in the first half of the year without washing rice. At present, in China's cities where small rice packaging has emerged, the rice varieties on the market include fragrant rice, soft rice, and non-scouring rice. However, it is not universal, but it is packaged well in individual cities. In most areas, the technology and level of rice sales and packaging are not high.
3 Rice Storage Techniques Food grain grows with the storage time, and its quality gradually declines as it ages. The speed of aging depends on different storage methods. The main storage forms of rice are stored at room temperature, low-temperature storage, anoxic (natural anoxic, filled with CO2, filled N2, vacuum) storage, chemical storage, mechanical refrigeration storage, plastic film sealed storage (rice heap), coating film preservation technology Storage etc.
3.1 Room temperature storage Room temperature storage is now the most widely used and is the most common rice storage in China. After the farmers harvest rice, they are sun dried to a sufficient level (below the safe moisture level), then milled into rice for normal temperature storage, cylinders, barrels, and woven bags. The main reason is to use low moisture content of rice to delay the deterioration of rice quality. As long as the storage method controls the moisture content of rice, the operation is relatively simple, but the amount and quality of rice are relatively serious.
The moisture content and temperature of rice are significantly positively correlated with the decline of rice storage quality. Water content and temperature are high, making it more susceptible to deterioration and microbial growth. The relative safe moisture of different temperature rice is shown in Table 1.
Table 1 Relatively safe rice moisture content at different temperatures Temperature (°C) 0 5 to 10 20 25 30 35 40
Relatively safe moisture (%) 16 to 18 ≤ 16 ≤ 14 13 to 13.5 <13 <12 <11
3.2 Low-temperature storage Low-temperature storage is a better method currently [7]. There are two ways to achieve low temperatures: First, the use of mechanical ventilation to the natural winter and spring temperatures into the grain piles, so that the temperature of the rice in the warehouse to a low temperature, and the use of food thermal resistance, small thermal conductivity characteristics, so that food is longer The time is kept low; the second is to use window-type air conditioners to supplement the cold source in the summer and autumn hot seasons to keep the grain temperature at a quasi-low temperature, but due to its high cost, it is still difficult to promote in large quantities at present and in the future.
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