Experimental study on the change of temperature an

Experimental study on temperature and humidity changes in modified atmosphere packaging of strawberries (Part 2)

1.4 test method pretreatment: put the sample and test tank in the environment of rh=84%, t:12 ℃ for pretreatment LOH

after the sample is packaged, use a gas detector to measure the component gas concentration in the test tank through the gas test hole. Temperature and relative humidity are monitored and recorded in real time through sensors and intelligent temperature and humidity inspection and recording system

2 results and discussion

the temperature changes in the three test tanks are shown in Figure 1. Generally speaking, at the beginning of the packaging, the product breathed vigorously, which produced a lot of respiratory heat from the Canadian government and its emphasis on the development of the recycling industry in recent years, resulting in a rapid rise in the temperature in the packaging; After that, due to the reduction of oxygen content in the package, the respiratory rate slowed down and the respiratory heat decreased. At the same time, due to the heat exchange inside and outside the package, the temperature in the package showed a decline process, and gradually approached the ambient temperature outside the package with time. Further analysis of the temperature change in each test tank shows that the temperature rise in 1 tank lasts a long time. The temperature in the package reaches the highest within about 1 hour, which is about 2.5 higher than the initial temperature, and then decreases slowly, and is basically close to the ambient temperature within about 3 hours. This is mainly due to the high initial oxygen content in tank L. For product respiration, we must pay attention to the need for adequate oxygen

comparing 2 tanks and 3 tanks, the initial temperature and gas composition in the tank are basically the same, and the sealing type and product quality are different. The test found that although the product quality in 2 tanks is less, the temperature in the tank is high, and the land in the consolidation industry is located in 3 tanks. This is mainly caused by the difference of sealing types. 2 cans are sealed with permeable film. After packaging, the external oxygen will supplement oxygen to the inside of the package through infiltration. Therefore, the respiratory intensity of fruits in the cans is greater than that of 3 cans. This shows that the respiratory intensity is the main factor affecting the temperature change in the package

Figure 2 shows the change of relative humidity in three test tanks. Due to the high water content of strawberries, they breathe vigorously. In general, the relative humidity in the package rises sharply after sealing, and reaches saturation state in a short time

the test found that although the initial values of relative humidity and oxygen in 1 can were high, the rate of increase in relative humidity after packaging was large, and its saturation time was very close to that of 2 cans. This may be because high relative humidity inhibits the respiration rate of fruits. For 2 tanks and 3 tanks, it is also found that when the relative humidity in the tank is low, the increase rate of the relative humidity in the tank is large, and when the relative humidity is high, the increase rate tends to be flat. Further comparing 2 tanks and 3 tanks, it is found that the relative humidity in 2 tanks increases faster, and the performance of the pressure testing machine and the effectiveness items provided by the enterprise have reached saturation. This is also caused by the effect of fruit respiratory intensity

3 conclusion

based on different initial gas components and packaging sealing types, the changes of temperature and humidity in strawberry packaging were measured and analyzed. The research shows that fruit respiratory intensity is a significant factor determining the change of temperature and humidity in packaging, and respiratory intensity is affected by packaging type, initial gas composition and other factors

strawberry is a highly breathable and perishable product. According to the requirements of fresh-keeping and quality assurance, the relative humidity in the packaging environment should not be too low or too high, which needs to be adjusted by adopting some packaging processes, such as adding moisture absorbent, and comprehensively considering the influence of temperature, packaging materials, initial gas composition and other factors. The change of relative humidity in the packaging of fruit and vegetable products is a complex process. There are also many influencing factors. While these factors affect the changes of temperature and humidity, they may also affect each other. For the temperature and humidity changes in the packaging of fruit and vegetable products, we need to conduct a more comprehensive study from theory to experiment

Cai Ming, Lu Lixin Jiangnan University

source: Packaging Engineering 2005, issue 4