Study On The Antimicrobial Activity Of ε-Polylysine And Application On Livestock Products Preservation

ε-Polylysine is a natural metabolic product by microbes.It has a superordinary bacteriostatic action,that meets the demand of natural and safety.Considering the antibacterial properties and generally recognized as safe(GRAS) status ofε-Polylysine,some study ofε-Polylysine were conducted in this paper.Firstly proceeded to its antimicrobial characteristic, and on the basis of this experiment,applied it to fresh preservation of livestock products. The main results were as follows:(1) The antibacterial action ofε-Polylysine was studied by spectrophotometric method, aperture pervasion method,and dry cell weight method in this paper.The antimicrobial property included concentration,temperature,pH and matching preservative influenced toε-Polylysine by investigating.The result showed thatε-Polylysine had a notable restrainable function on six species of food common bacteria(Staphylococcus aureus,Escherichia coli,Aspergillus flavus,Bacillus subtilis,Saccharomyces cerevisiae and Lactobacillus bulgaricus).Andε-Polylysine had obvious antimicrobial actions especially to on Escherichia coli,Staphylococcus aureus and LactobacilIus buIgaricus.It is not very effective on Aspergillus flavus.The minimal inhibition concentration(MIC)was as follows: Escherichia coli,Staphylococcus aureus and Lactobacillus bulgaricus 6.25mg/L～12.5mg/L,Bacillus subtilis12.5mg/L～25 mg/L,Saccharomyces cerevisiae 400 mg/L～800mg/L,Aspergillus flavus 800 mg/L～1600mg/L.And it was proved that the more the concentration ofε-PL,the more the antimicrobialactivity it has.It was also proved thatε-PL had super stability by 100℃temperature changing and it can be effective from pH5～8. Besides,the addition of glycine or Nisin can improve antimicrobial activity.(2) Researching the application ofε-Polylysine on chilled pork preservation. Compared with Nisin which is one of natural preservative to be used widely in chilled pork preservation,ε-PL used with glycine or not in pork preservation.In this paper,the effect of preservation and quality of chilled pork was evaluated by differerent preservative solutions at 4±0.5℃during storage.All dectecing items for these samples processed covered sensory assessment,pH,H₂S test,TVB-N,TBA,protein sediment test,coliform bacteria,holding water capacity,steaming loss rate,sap run off rate,color.The results showed:ε-PL of 400mg/L showed a better preservative effect than control group(P＜0.01),ε-PL of 400mg/L had significant difference on preservative than Nisin of 200mg/L(P＜0.05),ifε-PL and Nisin were used on chilled pork preservation separately.Chilled pork by using 400mg/Lε-PL,20mg/L glycine with200mg/L Nisin or 200mg/Lε-PL,20mg/L glycine with 200mg/L Nisin could be preserved 21d in the first class of shelf life.Chilled pork by using 400mg/Lε-PL with 20mg/L glycine could be preserved 18d in the first class of shelf life.Chilled pork by using 400mg/Lε-PL could be preserved 15d in the first class of shelf life.Chilled pork by using 200mg/L Nisin could be preserved 12d,and control group(water) could only be preserved 3d in the first class of shelf life.We got a better preservative effect when matched 400mg/Lε-PL,20mg/L glycine with200mg/L Nisin,and the group didn't effect quality of chilled pork.(3)Differerent preservative solutions were added to concretionary yogurt with starter culture before yogurt fermenting.The effect of preservation of concretionary yogurt was researched at 4±0.5℃during storage.All dectecing items for these samples processed covered sensory assessment,acidity and viable count.The results showed:the main index of concretionary yogurt added different preservative solutions can not reach standard on the third day,and the time of concreting will delay than control group(water).Maybe the preservative solutions restrained lactobacillus breeding so that the main index of them can not reach standard.Therefore,the application ofε-PL on concretionary yogurt preservation was unfeasible in theory.(4) Different preservative solutions were added to stirred yogurt after yogurt stirring. The effect of preservation of stirred yogurt was researched at 4±0.5℃during storage.All dectecing items for these samples processed covered sensory assessment,acidity and viable count.The results showed:We got a better preservative effect when matchedε-PL,glycine with Nisin.Use the influential factor ofε-PL,glycine and Nisin to carry out orthogonal experiment.Through on the orthogonal design of L₉(3³ ),the best effect of acidity followed byε-PL＞glycine＞Nisin,the best effect of viable count followed by Nisin＞ε-PL＞glycine,the best effect of sensory assessment by Nisin＞ε-PL＞glycine.The results showed that the optimum formulation wasε-PL 200 mg/L,glycine 20 mg/L and Nisin 50 mg/L.