Food packaging and preservation technology

[China Packaging Network News] In recent years, food safety issues have closely influenced the general public's sensitive nerves. Recently, Hainan Food and Drug Administration's sampling results showed that four batches of aquatic products failed. As a result, it has been found that the safety of aquatic products has long existed. Consumers have occasionally caused damage to the body through the consumption of spoiled fish. After the death of fish, various enzymatic reactions, redox reactions and microbial reactions occur in the body. Under the joint action of these chemical reactions, the loss of fresh fish meat is caused. As the world’s largest fishery country, China’s aquatic products account for 1/3 of the world’s total aquatic product output. The huge production capacity makes the demand for preservation of aquatic products increasingly urgent.

In this article, the author uses fresh fish packaging as an example to test the effect of different fish packaging on the preservation of fresh fish, analyze the factors affecting the preservation of fish packaging, and provide useful reference for the development of seafood preservation packaging technology.

Fish packaging preservation effect test

The author used eight different fresh-keeping technologies and packaging techniques to combine the fresh-keeping packaging, packaging the octopus, and storing the packed octopus in a refrigerated environment at a temperature of 4°C for a long period of time, at 4 days and 8 days, respectively. , 12 days, 16 days, and 20 days for sensory scores. The score is based on the sensory requirements of GB/T 18108-2008 "Fresh Saltwater Fish", 8 to 10 is divided into grades, 6 to 8 is graded 2, and 6 is not fresh. The score results are shown in Table 1.

Table 1 Sensory Evaluation of Different Preservation Formats of Hairtails

From Table 1, it can be seen that the different combinations of packaging technology and preservation technology have a very different effect on the preservation of fish meat. Comparing samples #1, #2, and #3, samples #1 to #4 showed a state of partial scale detachment, poor elasticity, and slight odor, and they were completely fresh and corrupted on the 8th day. In contrast, 2# And the 3# samples did not show corruption until the 20th and 16th days. It can be seen that the vacuum packaging and modified atmosphere packaging is twice as long as air packaging. The 4# and 5# samples are based on the air package form of sample #1, and the chemical preservation technology for soaking the fish meat with a potassium sorbate solution with a concentration of 2.5% and the chitosan film with a mass fraction of 1.0% are respectively added. The effect of preservation is very obvious, and the point of complete corruption is delayed until the 16th day. It can be seen that when the packaging technology and the preservation technology are combined, the preservation effect is significantly enhanced.

The 3#, 6#, 7#, and 8# samples all use modified atmosphere packaging. In contrast, No. 3 samples with no additional application of fresh-keeping technology have the shortest decay time of 16 days, followed by No. 6 and No. 8 samples. It was 20 days, while the 7# sample was stored for only 20 days and showed no staleness and no spoilage occurred. Because the same preservation technology was used for the 6#, 7#, and 8# samples, it can be seen that the difference in preservation effect mainly comes from the packaging technology.

Analysis of Factors Affecting Preservation Effect of Fish Packaging

Fish fresh-keeping packaging is mainly based on the two forms of modified atmosphere packaging and vacuum packaging. The characteristics of packaging materials and the differences in the molding process will affect the preservation effect.

1. Factors affecting the fresh-keeping effect of modified atmosphere packaging of fish

(1) Influence of CO2 content

For fresh fish, the role of CO2 in modified atmosphere packaging is to inhibit microbial growth. Studies have shown that increasing the content of CO2 can strengthen the ability to inhibit the growth of microorganisms, and as the content of CO2 continues to increase, the inhibitory effect will gradually increase, thereby enhancing the fresh-keeping effect of modified atmosphere packaging. This is also why the 7# sample has a longer shelf life than the 6# sample. However, when the CO2 content reaches more than 50%, its antibacterial enhancement effect is no longer significant.

So, how to scientifically determine the CO2 content of fish modified atmosphere packaging? The author believes that the content of CO2 should be determined based on the initial microbial species and quantity of fish. If the original microorganism of the contents is dominated by anaerobic bacteria or facultative anaerobic bacteria, excessive CO2 content will promote its growth and reproduction. This explains, to a certain degree, the reason why the 8# sample modified atmosphere packaging in Table 1 has a high CO2 content, but the preservation effect is less than that of the 7# sample.

(2) The effect of changes in gas atmosphere in modified atmosphere packaging on the preservation effect

After determining the appropriate gas composition and content ratio, the change of gas atmosphere during the storage and sale of fishmeal atmosphere-modified packaging is also one of the main factors affecting the fresh-keeping effect of modified atmosphere packaging. In order to further verify the gas changes in modified atmosphere packaging, I took 9 samples of KPET/PE modified atmosphere (60%CO2+10%O2+30%N2) of the tapering fish, and used HGA-02 headspace gas at regular intervals. The analyzer tests the O2 content in 3 modified atmosphere packages and averages them. The test results showed that the initial O2 content was 10.02%, after 2 days it was 10.07%, after 4 days it was 11.39%, and after 6 days it was 12.87%. It can be seen that the atmosphere inside the modified atmosphere package is constantly changing. This is because there is a concentration difference between the “low O2 high CO2” atmosphere in the modified atmosphere packaging and the “high O2 and low CO2” atmosphere in the packaging atmosphere. The O2 and CO2 molecules inside and outside the packaging penetrate and diffuse with each other through the packaging materials, along with storage. With the increase of time, the O2 content in the packaging gradually increased, and the CO2 content gradually decreased, eventually reaching the equilibrium of the gas concentration inside and outside the packaging. This change is conducive to the growth and reproduction of microorganisms in the packaging and accelerates corruption.