Study On Bacteriostasis Of Carboxyl Oxidized Starch And Its Application In Food Preservation

Carboxyl oxidized starch is a modified starch that converts hydroxyl groups in starch molecules into carboxyl and carbonyl groups under the action of oxidizing agent.In th is study,the antibacterial activity of Carboxyl oxidized starch(OST)was verified and its antibacterial mechanism against Staphylococcus aureus and Escherichia coli was prel iminarily.the fresh-keeping effect of OST on strawberry was studied by coating.OSTPBAT composite film with antibacterial properties was prepared by blending with Poly(butyleneadipate-co-terephthalate)(PBAT),and its application in food packaging was st udied.(1)The bacteriostatic properties of OST with oxidation degree of 13%,31% and 57%was investigated: OST-57 > OST-31 > OST-13,and has the best antibacterial effect on Staphylococcus aureus,and the Minimal inhibit concentration on Escherichia coli aureus is 5mg/m L.The antibacterial mechanism of OST-57 against Staphylococcus aureus and Escherichia coli was investigated by scanning electron microscopy,laser scanning confocal microscopy,flow cytometry and film potential detection.It was found that OST could dissipate cell film potential and destroy cell film biological function.The film formation process of OST and PBAT was preliminarily explored by blowing and hot pressing.The blown composite film still had good bacteriostatic ability,and the bacteriostatic rate of40%-OST/PBAT composite film(PBAT composite membrane with 40% OST mass fraction)could reach more than 90% within two hours of contact with bacteria.(2)The effect of OST coating on strawberry preservation within 0-8 days at 4 ℃ was evaluated by tracking the physiological and biochemical indexes such as weight loss rate,decay rate,total colony count and soluble solid content.Compared with the blank group,OST coating on strawberry can effectively reduce the growth and reproduction rate of microorganism on strawberry surface,and show significant protective ability on soluble solids and anthocyanins and other nutrients content,and can significantly prolong the freshness period of strawberry.By Inductively coupled plasma-mass spectrometry,the residual amount of heavy metals that may be brought in during the preparation of OST was measured.The residual amount of copper was 0.874 ± 0.0135 mg/kg.The residual zinc was 0.011 ± 0.0023mg/kg,far less than the limit value of relevant food safety standards.(3)Based on the good antibacterial performance of composite film,we first tested the mechanical properties of composite film and infrared spectrum characterization,and preliminarily discussed the preservation effect of OST-PBAT composite film on fresh pork and strawberry.The results show that the composite films prepared by the two methods have good mechanical properties,and OST and PBAT can achieve good composite effect through physical combination.At 4 ℃ storage environment,OST-PBAT composite film could significantly improve the changes of p H and total number of bacteria during the storage period(0-10 d)compared with the blank group,and had a better fresh-keeping effect on fresh pork.Similarly,OST-PBAT film reduced the weight loss rate and decay rate of strawberry during0-8 days of storage at 4 ℃ compared with the blank group,and showed a good inhibition on the growth of microorganisms on strawberry surface during the early storage period(0-4 d),while delaying the decline of strawberry hardness and ascorbic acid content.