Studies On The Application Of Epsilon-polylysine Hydrochloride In Instant Wet Noodle And Its Synergetic Ways

Instant wet noodle is a new kind of convenient nutritious food which is easily to be putrefied for its high water content.Adding food preservatives can prolong its shelf life.The ?-polylysine(?-PL)and its derivatives,as biological preservatives,have been applied to food industry in Japan,South Korea,US and China for its good properities in water-solubility,therm-stability,safety,wide spectrum of activity and the wide pH range,etc.The ?-PL and its derivatives combined with anions in protein and polysaccharide which lead to compromise its antibacterial activity.Therefore we also studied the methods to increase the ?-PL antimicrobial activity way.We isolated and purified three kinds of spoilage microorganisms in instant wet noodle.Identification results showed that three strains were Bacillus licheniformis,Rasamsonia argillacea and Rasamsonia brevistipitata.We found that B.Licheniformis was sensitive to pH,R.argillacea and R.brevistipitata were sensitive to temperature,while R.argillacea and R.brevistipitata survived after the treatment about 80?,30 min and B.licheniformis about 95?,30 min.We studied the antibacterial activity of ?-polylysine hydrochloride(?-PL·HCl),nisin,natamycin,sodium dehydroacetate and calcium propionate on instant wet noodle.The minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)value proved that:?-PL·HCl had a good antibacterial activity to all;nisin had a good antibacterial activity to B.licheniformis;natamycin had a good antibacterial activity to R.argillacea and R.brevistipitata;the antibacterial activity of sodium dehydroacetate and calcium propionate were inferior.Hence we chose ?-PL·HCl,nisin and natamycin as preservatives to study the complex synergistic effect on instant wet noodle.The cooperativity researches showed that:?-PL·HCl and nisin played a cooperative effect on B.licheniformis;?-PL·HCl and natamycin also had a cooperative effect on R.argillacea and R.brevistipitata.Response surface analysis showed:the mixture of ?-PL·HCl,nisin and natamycin at the ratio of 103.18,41.57 and 6.36,respectively,were able to minimize the number of microorganisms,which be the best preservation on instant wet noodle.In the case of the optimal ratio and cost,we studied about the addition impact on the sensory quality and shelf life of the instant wet noodle.The optimal dosage of the compound preservatives was determined 260 mg/Kg.The results showed that,the higher concentration of synergist SA,the higher antibacterial activity of ?-PL·HCl on Escherichia coli,Pseudomonas aeruginosa and B.Licheniformis.Considering of prices and other factors,we determined the ICC4 as the best ratio of ?-PL·HCl and SA.The MIC of ICC4 on Candida,R.brevistipitata,Aspergillus niger were 30,40 and 30 mg/Kg,respectively.Compared to the MIC of?-PL·HCl(80,220,80 mg/Kg,respectively),the results indicated that SA enhances the antibacterial activity of ?-PL·HCl.The effects of temperature,pH and time on the antibacterial activity of ICC4 were studied.The results showed that the antibacterial activity of?-PL·HCl decreased with the temperature and pH increased,but there was no significant decline in antibacterial activity of ?-PL·HCl,indicating that ICC4 has a strong thermal stability and wide pH range.The results also showed that the antibacterial activity of ICC4 has no significant change in 30 days in 0.05 confidence interval,which indicate that there was a good stability of antibacterial activity.