Since chitosan is an important part of the cell wall of fungi, it can act as a preservative for food. Many studies have shown that chitosan does have an inhibitory effect on some microorganisms. For example, when the pork was treated with chitosan acetic acid solution and packed in vacuum, it was found that the growth of hybrid bacteria was significantly inhibited, especially the inhibition effect on Escherichia coli, staphylococcus and lactobacillus was better.
Ji Weizhi et al. used chitosan as preservation material and coated pork. The results showed that 2% chitosan solution had obvious preservation effect on pork, and the shelf life of primary freshness of pork was extended by 2 days and 6 days under the storage conditions of 20℃ and 40℃ respectively. American scholars use chitosan to make meat preservative, its dosage is 5 ‰, can prevent cooked beef in a week of refrigeration spoilage. This preservative can also be used to prevent rancidity and spoilage of fish, poultry, eggs and daily food.
Wu Biao et al. used ultraviolet radiation (uv) and coated eggs with 2% chitosan for composite treatment, and then placed them at 34±1℃ for one month. The results showed that compared with the control group (ck), the weight loss rate of eggs was reduced by 5.3%, the onset time of scattered yellow was delayed, and the scattered yellow rate was reduced by 58.3%. In addition, lysozyme activity, transparency, surface color, brightness and some other detection indexes in egg white were better than those in ck group.
Chitosan biofilm forms an extremely thin semi-permeable film on the egg surface, so it can effectively prevent the entry of contaminated bacteria on the egg surface, so as to continue egg storage and transportation, especially in high temperature weather spoilage. At the same time, it can reduce the equal evaporation of water in the egg contents and reduce the dry consumption rate of eggs. The method is simple, feasible, convenient and meets the requirements of environmental protection, so it can be used as an effective method for batch preservation of eggs, especially under high temperature conditions.
Chitosan has good film forming and biodegradability, which is very suitable for making edible packaging materials. The application of chitosan in edible packaging materials has been widely reported abroad. Voriop and Klein used chitosan to make drug capsules; Japanese scholars added chitosan into the aqueous solution of starch substances, mixed it to make a film, and treated it with alkali after the film dried to make a starch - chitosan composite film. The film is edible, oil resistant, insoluble in water, high tensile strength, can be used for packaging solid, semi-solid or liquid food; The experiment of the United States Agricultural Research Institute is successful, using chitosan and lauric acid combined to produce an edible film, the thickness is only 0.2 ~ 0.3mm, the transparency is very good, used for peeled fruit preservation, not only can achieve the purpose of preservation, but also not perceptible.
According to domestic reports, with corn starch as the base material, add chitosan, and then with a certain amount of plasticizer, thickener, preservative and other additives, through special process into composite packaging film, used for the inner packaging of preserved fruit, pastry, convenient soup and other convenient food. Its main characteristics are high tensile strength, elongation and good water resistance. The film was soaked in boiling water for 10 minutes with little change in performance.
Shinya et al. knead chitosan and resin together and extrude them to prepare food containers. At least the inner layer of the container contains chitosan, which will inhibit the growth of lactic acid bacteria and thus prolong the shelf life of food. Osamu et al. infiltrated the lactic acid solution of chitosan into the nonwoven fabric made from regenerated cellulose fibers to form the preservative material. When it contains fish, meat and other food, it can absorb exudate and prevent the growth of staphylococcus, E. coli and other microorganisms.
(Note: This is the staff's reading and learning notes for sharing and communication only. This reading note was extracted from the book "chitooligosaccharides and Human Health", editor-in-chief: Feng Yanmin, published by Jilin University Press, the second edition, November 2019, ISBN 978-7-5601-3766-7. In the later stage, we will share the oligosaccharide knowledge notes we read regularly. Please pay attention to them. If there are forwarded references, please do not use them for commercial purposes.
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