Inhibitory Effect Of Phenyllactic Acid Combined With Ultrasound On Three Common Foodborne Pathogens In Cold Fresh Chicken

In recent years,the per capita consumption of chicken has continued to increase in China,chicken has become the second largest meat consumer product after pork.Because chicken is rich in nutrients and high in moisture content,it is easily contaminated by foodborne pathogens and endangers people’s health.Staphylococcus aureus(S.aureus),Salmonella enteritidis(S.enteritidis)and Clostridium perfringens(C.perfringens)are three common food-borne pathogens in chicken.When meat products are contaminated by these pathogens,it will reduce the quality of products and cause economic losses.And when these contaminated meat products are eaten by consumers,it will also lead to food safety incidents such as food poisoning.Ultrasound(US),as an environmental friendly auxiliary sterilization method,is often used in combination with other sterilization methods to increase the sterilization effect.Phenyllactic acid(PLA)is an organic acid with broad-spectrum antibacterial activity and is widely used because of its remarkable bactericidal effect.In this study,US(270W)was combined with different concentrations of PLA(0.5%,1%)to the inhibition of three common pathogens(S.aureus,S.entritidis and C.perfringens)in cold chicken meat.The synergistic inhibition mechanism was analyzed through the observation of the change of bacterial count and bacterial status.Finally,the effectiveness of the combination treatment of US and PLA in the application of actual samples was confirmed by evaluating the bactericidal effect of combination treatment on chicken surface pathogen S.aureus,S.entritidis and C.perfringens.The research contents and results are as follows:(1)The bactericidal effects of US(270 W),PLA(0.5%,1%)and the combination of US and PLA(US+0.5% PLA,US+1% PLA)on the planktonic bacteria and biofilm of S.aureus and S.entritidis at different times(5,10,20,30 and60 min)were analyzed.The results showed that compared with the treatment of US or PLA alone,the combination treatment of US+PLA could significantly improve the bactericidal effect.The change of bacterial count under the combination treatment was significantly greater than that under the single treatment.Scanning electron microscopy revealed that US+PLA combination treatment caused obviously changes in cell morphology and even structural cleavage of the bacterial cells.Confocal laser scanning microscopy showed that US+PLA combination treatment could seriously inactivate the bacterial cells and lead to death,which resulted in the inactivation of intracellular respiratory chain dehydrogenase enzymes and the leakage of intracellular ATP.(2)The bactericidal effects of US combined with different concentrations of PLA(US+0.5% PLA,US+1% PLA)on S.aureus and S.entritidis in chicken breast meat at different treatment time(5,15 and 30 min)was first studied,and the treatment of US+0.5% PLA for 15 min was selected as the treatment condition for next storage experiment.The results showed that US+0.5% PLA combined treatment could significantly inhibit the growth of S.aureus and S.entritidis on the surface of chicken breast meat and prolong its storage period.(3)The inhibitory effect of US(270 W)combined with different concentrations of PLA(0.5%,1%)on the vegetative cells and spores of C.perfringens was studied.The results showed that US+PLA combination treatment significantly increased the bactericidal effect of C.perfringens vegetative cells by destroying the cell membrane and caused the leakage of intercellular substances.For C.perfringens spores,pretreatment with US and PLA can increase the inhibitory effect of heating treatment(US+0.5% PLA+80 ℃,US+1% PLA+80 ℃,US+0.5% PLA+90 ℃,US+1%PLA+90 ℃).The combination treatment of US+PLA+80 ℃ destroyed the integrity of spore cell membrane and increased the permeability of cell membrane,resulting in the release of intracellular pyridine dicarboxylic acid(DPA),the decrease of hydrophobicity(RHS),and the change of particle size and zeta potential.(4)According to the bactericidal effect of US combined with different concentrations of PLA(0.5%,1%)on the vegetative cells and spores of C.perfringens,US + 1% PLA treatment for 30 min was selected as the treatment condition to explore the bactericidal effect of combined treatment on the actual samples.The results showed that the counts of C.perfringens vegetative cells on the surface of chicken breast meat in the US combined with 1% PLA group was always lower than that in the control group.The storage experiment was carried out on the C.perfringens spores on the surface of chicken breast after US+1% PLA+80 ℃ combination treatment for 30 min,and the results showed that compared with the control group,the growth trend of C.perfringens spores in the combination treatment group was significantly decreased during storage,which indicated that the combination treatment could significantly inhibit the growth of C.perfringens spores,thereby prolonging the shelf life of chicken breast meat.