Study On The Processing Conditions And Storage Properties Of Roast Shrimp

In this paper,Penaeus vannamei was used as materials to process into high moisture roast shrimp based on the hurdle technology.This paper mainly discusses the effect of sterilization conditions,the moisture content and the influence of Nisin on the shelf life of roast shrimp.First,different sterilization conditions were set up,and the best sterilization conditions were determined by measuring the color,texture,commercial sterility and sensory quality.Secondly,controlling the drying time to get roast shrimp with different water content,then using the optimum sterilization parameters to protect them from bacteria.Therefore,we can study the influence of different water content on the roast shrimp.However,the process conditions of roast shrimp were mildly that leads to the dominant spoilage bacteria of roast shrimp at the end of shelf life is Bacillus cereus.Nisin can restrain the growth of spoilage bacteria,hence we added different contents of Nisin to inhibit the growth of Bacillus cereus.Thus,we explored the influence of Nisin on the quality and shelf life of high water roast shrimp.The results are as follows:1.Effect of secondary sterilization on quality changes of roast shrimp(Penaeus vannamei)Effect of secondary sterilization on quality changes of roast shrimp(Penaeus vannamei)with high contents according to hurdle technology were investigated.The experiment was conduct with series treatments.We set up several different sterilization temperatures and sterilization time,and then determined the color,textural properties,sensory quality,pH and commercial sterility of roast shrimp under different sterilization conditions.The results were shown followed with that,with the increasing of sterilization temperatures,all the values of L*,a* and b* decreased.When sterilization time increased,L* slightly decreased.However,a* and b* increased slightly.On the other hands,when sterilization temperatures raised,the hardness,gumminess,chewiness and springiness increased at first but decreased afterwards,while the adhesiveness had an increasing tendency,and the shear force and cohesiveness presented a decreasing tendency.The hardness,adhesiveness and chewiness were declined,while,the adhesiveness and shear force were on the contrary when sterilization time increased.In addition,the gumminess of roast shrimp reached the lowest point but the springiness obtained the peak when sterilization time prolonged.The pH changed dramatically when sterilization temperatures increased,and it raised after the prolongation of sterilization time.The roast shrimp can reach commercial sterility under the best conditions of 90℃ for 30 min.2.Effect of water content on the quality change of roast shrimpThe analysis methods,such as water activity(aw),color,texture profile analysis(TPA),sensory evaluation and commercial sterilization measurement,were used to study the effect of different water content(wc)on the quality of roast shrimp.The results showed that the wc of roast shrimp was better linear with aw.With the increasing of wc,the value of aw,L* and springiness increased,while the value of a*,b*,hardness,gumminess,chewiness,the maximum shear force and adhesiveness decreased,but its cohesiveness was little effect.Besides this,the wc of samples has the significant influence on its chewiness,gumminess,the maximum shear force,hardness and adhesiveness(P<0.05).When wc≤45%,roast shrimp can reach the periods of commercial sterilization,but wc≥45%,roast shrimp was in good quality for sensory evaluation.Therefore,the wc of roast shrimp should be controlled at 45%.3.Effect of Nisin on the quality of roast shrimp with high water content when store at 25℃Nisin is used as a food-safe antimicrobial agent and has been widely studied to daily food products to prevent bacterial growth.Different levels of Nisin(0,20 mg/kg,60 mg/kg and 100 mg/kg)were added into high water content roast shrimp(48%,51%,53%)to avoid the growth of spoilage organisms,especially Bacillus cereus when store at 25℃.We use the total number of colonies,the total number of B.cereus,TVB-N and pH as indicators,combined with sensory evaluation,then study the effect of Nisin on the quality of high watet content roast shrimp.As the extension of storage time,the total number of colonies,the total number of B.cereus,TVB-N and pH increased,while the sensory score decreased gradually.With the total number of colonies as the key factor to judge the end of shelf life,it is concluded that the shortest shelf life is 4 days,the longest is 14 days,and the addition of Nisin can extend the shelf life for 2~8 days.The more Nisin added the slower rising of total number of colonies,total number of Bacillus cereus and TVB-N.Nisin can inhibit the growth of Bacillus cereus which was the dominant spoilage bacteria.At the meantime,it can improve the shelf life at least 2 days of high water content roast shrimp.