Study On Fresh-keeping Technology And Quality Control Of Edible Coating Fresh Shrimp

The paper mostly studied the effect of edible coating on shrimp and confirms appropriate films.The primary coatings were chitosan and sodium alginate applling shrimp preservation. Mostly study included following five aspects:(1) The researches about chitosan liquor property:the effects of different temperature, concentration and the value of pH on viscosity of lims and characteristic of gelatin had been studied.The result of the experiment showed that:the viscosity increase with the increase of film concentration and decrease with the increase of temperature.As the increase of the value of PH, the viscosity increase at first and decrease later.The chitosan gelling is feebleness and its intensity can be improved by augmenting chitosan concentration or adding additive.(2) Mensuration of chitosan film capability:the effects of different factor on mechanical capability of chitosan film had been studied by using the L₉(3⁴) orthogonal experimental design. Their mechanical and barrier properties were studied.The result of analysis of variance showed that:concentration of chitosan(P＜0.1) had evidently influence on tensile strength,but temperature(P＞0.1 ) and pH(P＞0.1 ) affected indistinctively.The result showed that:The influential order was concentration,temperature,pH.The best scheme was A₃B₂C₂.Film formed with 2%concentration of chitosan and drying temperature at 60℃has best mechanical capability. The tensile strength was 42.73MPa.The tensile strength of the blended films decreased with the addition of polyols and fatty acids,whereas the percent elongation was increased in polyol blend films except stearic acid.Polyol blend films showed increase in the water vapor and gas permeability;however stearic acid blend film showed decrease.(3) Study on the gelling properties of sodium alginate:The L₉(3⁴) orthogonal experimental design was used to study the effects of different factors on gelling properties.The result of analysis of variance showed that:the concentration of sodium alginate(P＜0.025)and calcium chloride(P＜0.1) had evidently influence on gel hardness,but temperature(P＞0.1) affected indistinctively.The concentration of sodium alginate(P＜0.01) had evidently influence on gel springiness,but the concentration of calcium chloride(P＞0.1) and temperature(P＞0.1) affected indistinctively.Three factors(P＜0.05) had evidently influence on gel water-holding capacity. The result showed that:The influential order was the concentration of sodium alginate,the concentration of calcium chloride,temperature.The character of sodium alginate was best with 3%sodium alginate and 5%calcium chloride gelling in 60℃.The gel hardness was 787g.The gel springiness and water-holding capacity were 1.72mm and 46.40%.(4) The application study of edible coatings on shrimp:Effects of different concentration chitosan,additive and sodium alginate on shrimp preservation by coating were studied.The result of experiment indicated that shrimps coated could maintain better characterisitics than those uncoated.The best concentration of chitosan was 1.5%.The effect of the chitosan with additive was better than other groups.The effect of Nisin and BHT was best.Thawing waste,cooking loss,dehydration date and the change of texture were regularly measured after being stored a period of time.The effect on the quality of edible coating shrimp stored different condition was studied.The result of analysis of variance showed that the different disposal(P＜0.05) had evidently diversity.Edible coating can evidently decrease thawing waste,cooking loss and dehydration date,also can keep better hardness and springiness The effect of preservation of coating by chitosan is better than that of coating by sodium alginate.We researched the effects on shrimp preservation by coating from aspects of Sodium dodecyl sulfate-polyacrylamide gelation electrophoresis(SDS-PAGE) and protein gel characteristic.SDS-PAGE analysis showed that straps of small molecular weight on map of uncoated group was more than coated group.Gel texture and water-holding capacity had difference between different disposals.Edible coating can keep better hardness,springiness, gumminess and water-holding capacity.(5) Application of HACCP system in preservation of shrimp by coating with chitosan was studied.