Preservation Mechanism Of Compound Biological Preservatives And The Changes In Quality Of Perch During Chilled Storage

In order to solve the problems of the spoilage of bass in the cold storage,which is becoming more and more popular,a variety of technical methods have been applied to the bass preservation.However,these preservation technologies,in different degrees,have brought about some problems,such as protein denaturation,changes in taste and chemical residues,as well as technical and costs barriers.In addition,the currently prevalent biological preservatives tend to have a narrow antibacterial spectrum especially when being used alone,which upsets us.Therefore,in order to solve shortcomings of the preservation technology for refrigerated bass as mentioned above,this experiment combines tea polyphenols?TP?essential oils,both of which are biological preservatives with excellent antioxidation and antibacterial function,to make a kind of compound preservative and study the impact of the preservatives on the bass preservation after the treatment.1.Three kinds of plant essential oils were selected which are relatively widely used,there were cinnamon essential oil,oregano essential oil and thyme essential oil.The scavenging ability of the three essential oils to DPPH radical,superoxide anion radical and hydroxyl radical,and the bacteriostatic effects of Staphylococcus aureus,Pseudomonas aeruginosa and Shiva spoilage on the dominant spoilage bacteria of perch was compared.Comprehensive evaluation of antioxidation and bacteriostatic effect of three essential oils.So that we can screen a plant essential oil for compounding.The results showed that the antioxidant and bacteriostatic effect of cinnamon essential oil was stronger.Therefore,we use of cinnamon essential oil one of the compound preservatives.2.To determine the antioxidant activity and antimicrobial effect against Staphylococcus aureus of tea polyphenols-cinnamon essential oil compound preservatives.The antioxidant capacity of compound preservatives was determined by in vitro oxidation resistance method.The bacteriostatic effect and the minimum inhibitory concentration?MIC?were determined by the size of the inhibition zone.The effect of compound preservatives on Staphylococcus aureus was evaluated comprehensively by antibacterial activity,bacterial growth curve,cell wall integrity,cell membrane permeability.Results showed that IC₅₀0 of compound preservatives scavenged DPPH radical,hydroxyl radical and superoxide anion radical were 4.02?g/mL,9.15?g/mL and 0.61 mg/mL respectively.Compound preservatives could effectively inhibit the growth of Staphylococcus aureus with the MIC of 0.5mg/mL,and could damage the cell wall and cell membrane.In summary,compound preservatives have a strong antioxidant activity,and have a very good antibacterial effect with Staphylococcus aureus.The possible mechanism of inhibition is to destroy the cell wall and affecting the permeability of the cell membrane.3.In order to study the effect of compound preservative on preservation of perch in cold storage.Fresh bass used in this experiment were randomly assigned to be used after being killed,and tea polyphenols-cinnamon essential oil formulated according to the ratio of 1:1 was formulated into three different concentrations of compound preservatives,0.1%?T1?,0.3%?T2?,0.5%?T3?,respectively.After the samples were disposed with the preservatives,the fresh-keeping effect on the bass refrigerated at the temperature of 4±1?was investigated.By measuring the value of 9 indicators of refrigerated bass,including pH,total volatile base Nitrogen?TVB-N?,thiobarbituric acid?TBA?,total colonies number?TVC?,whiteness,texture properties?hardness,elasticity?,K value,and sensory evaluation,during the shelf life,we can make a systematic evaluation on the freshness of the refrigerated bass and explore the preservation effect of the compound preservatives.The experimental results show that tea polyphenols-cinnamon essential oil compound preservatives can effectively inhibit the reproduction of spoilage microorganisms and endogenous enzyme activity,delay the degradation of a variety of nutrients,which makes it a ideal preservative.From the perspective of each index,pH value decreased at first and then started to increase,and the growth rate of experimental group was lower than that of the control group.Meanwhile,TVC,TBA value,TVB-N value,elasticity,hardness,whiteness,K value and sensory evaluation scores for the experimental group were all lower than that of the control group.In fact,we are inclined to use the compound preservative with a medium concentration?T2?,which can not only achieve the goal of preservation but also economically benefits us to some extent.