Effect Of Ozone Sterilization And Deodorization Technology On Freezing And Frozen Storage For Aquatic Products

Cold storage and freezers are important places for food storage,however,which could produce peculiar smell and breed numerous microbes when long-term storage.Therefore,the study of odorous substances and microbes in frozen or refrigerated containers has already attracted considerable attention.In this paper,the number and type of major microbes and main components of the odorous substance in the simulated cold storage(0-4℃)and simulated freezer(-20℃),which mainly store aquatic products,have been studied.In addition to this,the effect and condition of removing volatile odorous substance in cold storage and freezers by ozone and the impact of ozone on the quality of fish under low temperature storage also have been investigated.The paper aims to provide technical support for the use of ozone in sterilization and removing odorous substances of cold storage and freezers and in frozen or refrigerated fresh-water fish.The main results are as follows.1.A total of 201 volatile substances have been detected in 5 simulated cold storage(0-4℃)containing 127 substances and 5 simulated freezers(-20℃)containing 142substances.The ingredients contributing to the odorous substances of cold storage:the first major ingredients(2-ethyl-1-butanol,acetophenone,styrene,1,2-dimethylbenzene,1-pentene and methyl disulfide),the second major ingredients(methylbenzene,para-xylene and isopentyl acetate)and the third major ingredients(trichloromethane,ethylbenzene,ethyl acetate,heptanal and n-hexane).The ingredients contributing to the odorous substances of freezers:the first major ingredients(trimethylamine,ethyl mercaptan,isoamyl alcohol,styrene,para-xylene and nonanal),the second major ingredients(methyl disulfide,L(-)-camphor,butyl caproate,epoxyethane,hexyl acetate and bihexy)and the third major ingredients(n-pentane,isobutanol,n-hexane,ethyl acetate and acetic acid).2.In the cold storage,the choice of 150ppm ozone concentration of 2.5h effect of the best.For 0-4℃cold storage,the ozone concentration of 150 ppm,the role of 2.5h,all the monomer odor substances have a significant decline,Among them,small molecular odor substances such as:1-pentene,toluene,dimethyl disulfide has been completely oxidized to zero,The content of macromolecules such as 2-ethylhexanol,acetophenone,styrene,1-2-xylene and isoamyl acetate has been reduced to 3.37%;2.68%;0.79%;1.86%;4.02%;At the same time,aromatic hydrocarbons,chain hydrocarbons,aldehydes and other compounds peak area percentage has been reduced to 4.17%,2.09%,5.20%.Frozen in-20℃cold storage,Choose 200ppm ozone concentration of 4h effect of the best.when the ozone concentration of 200ppm,the role of 4h,trimethylamine,ethanethiol,isoamyl alcohol,dimethyl disulfide and other small molecules have been completely oxidized,L-camphor,nonylaldehyde and other macromolecules content of the original 2.7%and 3.6%;Aromatic hydrocarbons,chain hydrocarbons,aldehydes,alcohols and other compounds have a significant downward trend,The percentage of the peak area of these four compounds has decreased by 5.35%,2.08%,3.19%and 5.14%,respectively.3.Eight strains of bacteria were isolated from cold storage and freezers,Of which 6 cold storage,12 cold storage,8 strains of bacteria were identified as three different species:Escherichia coli;Leuconostoc citreum;Bacillus subtilis;9 fungi were isolated from cold storage and freezers,Among them,7 cold storage,2 cold storage and 9 fungi were identified as 5 different species:Penicillium citrinum;Rhodotorula mucilaginosa;Cladosporium cladosporioides;Penicilliu4;comycota.4.Ozone on the 0-4℃cold storage and-20℃freezer in the microbial has a good effect.In the 0-4℃cold storage,the choice of ozone concentration of 150ppm for 3h sterilization effect is the best,The total number of colonies of bacteria decreased from 7.3×10~3(Log cfu/m~3)to 3.1×10~2(Log cfu/m~3);The total number of yeast colonies decreased from 4.1×10~3(Log cfu/m~3)to 1.0×10~2(Log cfu/m3);Mold colony decreased from 4.4×10~3(Log cfu/m~3)to 1.5×10~2(Log cfu/m~3);For the-20℃freezer,the choice of ozone concentration of 200ppm for 4h sterilization effect is the best,The total number of bacteria colonies decreased from 3.9 x 10~3 to 2.1 x 10~2(Log cfu/m3);The total number of yeast colonies decreased from 2.1×103(Log cfu/m~3)to 0.5×10~2(Log cfu/m3);The total number of mold colonies decreased from 7.9×103(Log cfu/m~3)to 1.2×102(Log cfu/m~3).5.During the low temperature storage of grass carp,3 hours disinfection everyday by50ppm ozone could effectively inhibits the increase of the fillet pH;Ozone could inhibits the increase of TVB-N during tilapia storage so as to kill numerous bacteria and inactivate the body endogenous enzyme or reduce its activity;To a certain extent,ozone could inhibit the oxidation of fat which plays the effect of anti-corruption preservation,maintain the quality characteristics of fish,provide a better taste,improve the fish filament brightness and sensory quality and inhibit the microbial reproduction and protein decomposition of fish slowing the rate of deterioration of fish meat,so as to achieve the effect of prolonging the shelf life.