2024-07-25
The effects of different packaging methods on the quality of rice were studied by simulating the temperature changes during the transport of rice from northern China to Hainan Island in autumn and winter. The results showed that the quality of rice in vacuum packaging with high barrier bag was the best, and the water content, fatty acid value, mold colony number and taste score of rice were controlled in normal range by vacuum packaging with general materials and nitrogen-filled packaging. The quality of rice in ordinary plastic packaging remains poor, and the quality indicators of rice have changed greatly. The quality of rice packaged in woven bags remained the worst, and the quality indexes such as water content, fatty acid value and mold colony number of rice increased sharply. Therefore, when transporting rice from the low temperature area to the high temperature and high humidity area, it is recommended to use vacuum packaging or nitrogen-filled packaging, and avoid the use of woven bags.
Results and analysis:
Water loss or absorption of rice during storage and transportation will seriously affect the quality, safety and edible quality of rice. The water absorption of rice is higher, and microorganisms are easy to breed during rice storage, which affects the appearance quality and quality safety of rice. Rice has more water loss, rice is easy to burst, and the edible quality is reduced. The relationship between rice water content and time during the test is shown in Figure 1. As can be seen from Figure 1, the water content of rice gradually increases with the extension of transportation time. After 21 days, the rate and amount of water increase in rice were significantly higher than before, and the water increase in this period accounted for more than 73% of the total water increase in rice. In terms of different packaging methods, the moisture of class A rice increased the most, which increased by 2.7 percentage points during transportation. Followed by Class B rice, an increase of 1.6 percentage points; Category E rice increased by 1.3 percentage points, and Category C rice increased by 1.1 percentage points; The smallest was Category D rice, which increased by only 0.6 percentage points. The change of water content of rice is related to the external temperature, humidity, packaging materials and packaging methods of rice. During the test, the outside temperature of the rice changed greatly, and the surface of the rice was prone to condensation.
The relationship between rice moisture and time is different in packaging methods and packaging materials, and the ability of water molecules in the environment to penetrate into the bag through packaging materials is also different. Woven bag packaging is connected with the external environment, and has almost no barrier ability to external water molecules, so its rice absorption is the largest; Under the condition of ordinary plastic packaging, because the packaging material has a certain barrier effect on the external water, the water absorption under this condition is lower than that under the condition of woven bag; Under the condition of nitrogen-filled packaging, the nitrogen in the bag and the packaging material have a double barrier effect on the external water, which can effectively prevent the external water from spreading in the bag, so the moisture increase in the rice in the bag is low. Under vacuum storage conditions, the absorption of rice is the lowest, which may be related to the factors such as tightly packed rice in the bag, the speed of external temperature and humidity transfer between rice grains is reduced, and the surface area exposed to high-humidity environmental conditions is less than that of other methods.
It is recommended to use vacuum packaging or nitrogen-filled packaging when transporting rice from low temperature areas to high temperature and high humidity areas. If necessary, high barrier bag vacuum packaging can be used to prevent moisture absorption and mildew during storage and transportation of rice, reduce the food quality of rice, and even affect the food safety of rice.