Study On The Synthesis, Characterization And Application Of Modified ε-polylysine

The use ofε-polylysine（ε-PL）as a natural food preservative has been increasing,because it is water soluble,wide antimicrobial and heat stability.The practical problem when applyingε-PL in processed foods is thatε-PL tends to interact with proteins and acidic polysaccharides,leading to the possible loss of antimicrobial activity.Moreover,ε-PL has poor emulsifying properties.The usage ofε-PL has been restricted mostly to starch-based foods.Therefore we begin to hydrophobically modifiedε-PL for expand the range of its applications,provide the basis for its application in food,health care products and drugs.（1）Hydrophobically modifiedε-PL withα-TOS.The effect of the reaction time,temperature,substrate quality ratio and catalyst amount on synthesis process of modifiedε-PL were studied.The optimum parameters were obtained as below:reaction at 45°C for 18h,reaction substrate quality ratio 10:6 and reaction catalyst amount 3mL.The yield was 97.45%.Structure of modifiedε-PL was characterized through ¹H NMR,FT-IR,differential thermal scanning,laser particle size analyzer and surface tension.The emulsification of modifiedε-PL was obviously enhanced,the emulsion particle size was reduced from 1340 nm to 55 nm.（2）The antimicrobial activity of different degree of substitution（DS）modifiedε-PL were evaluated by comparing the minimum inhibitory concentrations withε-PL.These experiments allowed us to identify that different DS modifiedε-PL retain the antimicrobial activity.Acute toxicity-LD₅₀ of modifiedε-PL to kun-ming mice,adult zebrafish and embryos were determined.The maximum tolerance dose for kun-ming mice of modifiedε-PL was 28.6 g/kg,which confimed the high safety of modifiedε-PL.Modifiedε-PL had no toxic effect to adult zebrafish,zebrafish embryos survival,zebrafish embryos hatching and zebrafish embryos heart rate,at the same time modifiedε-PL promoted the growth and development of zebrafish embryos,the body length of zebrafish embryos became longer.（3）Results of orthogonal test design of lingzhi spore oil microcapsules showed that the optimum conditions using modifiedε-PL and acacia senegal as wall material were:the quality ratio between modifiedε-PL and acacia senegal was 1:6,solid concent was15%,the quality ratio of core and wall materials was 4:1,and the resulting encapsulation efficiency and encapsulation efficiency were 94.56%,96.88%and POV was 73.25（meq/Kg）.（4）The effect of modifiedε-PL on keeping fresh of chilled pork stored at 4°C was investigated with respect to the pattern of change in the aerobic plate count（APC）,pH value,total volatile basic nitrogen（TVB-N）,2-thiobarbituric acid reactive substances（TBARS）,and sensory quality.Chilled pork without treated could srore 2-3 d,chilled pork was treated withε-PL could srore 8 d,chilled pork was treated with modifiedε-PL could srore 12 d,modifiedε-PL inhibited remarkably the decline in sensory quality,the growth of bacteria,the increase of pH and the accumulation of TVB-N.On the12th day,the APC,pH value,TVB-N value with modifiedε-PL were 5.79 log CFU/g,6.57,18.13mg/100 g,the indexes were in accordance with the standard of chilled pork.