Research On Preservation Technology Of Reed Shoots Of Triarrhena Lutarioriparia L Liu

The reed shoots are the young stems of the plant Triarrhena lutarioriparia L Liu.Reeds are widely distributed in China's lakes and wetlands,and the annual growth ofTriarrhena lutarioriparia L Liu is huge.After the paper-making from reed became a history,the processing of the reed shoots has became a new way for the reed industry.The preservation and processing of the reed shoots not only guarantees the annual supply,but also greatly increases the added value.However,there are few studies on the preservation and processing of reed shoots.In this study,reed shoots from the South Dongting Lake was used as raw materials to determine the nutrient composition and safety index,to study the pretreatment process of quick-freezing of reed shoots,and to investigate its techniques of drying and preservation,pickling and preservation as well as safety,in order to find out the key technology for the preservation of reed shoots and provide a basis for the development and utilization of the resources of reed shoots.1.Research on quick-freezing pretreatment(blanching)process of reed shootsTaking the color of fresh reed shoots as the evaluation index,the blanching temperature,time and the concentration of color-keeping agent as the treatment factors,the Box-Behnken test design was used to optimize the blanching process with response surface methodology.The optimum blanching conditions of reed shoots were as follows:the blanching temperature was 92?;the blanching time was 3 min;and the concentration of color-keeping agent was 0.3%.Under this condition,the color difference between the blanched and the fresh reed shoots was the smallest(p<0.05).2.Analysis of nutrient compositions and safety index of reed shootsIn fresh reed shoots,the moisture content was 92.5%,the protein was 3.29%,the total sugar was 3.97%,the vitamin C was 7.67 mg/100g,and the total dietary fiber(dry basis)content was up to 39.64%,of which soluble fiber(dry basis)was 5.21%,and the insoluble fiber(dry basis)was 34.12%.The mineral element content was as follows:sodium 29.2 mg/Kg,potassium 4.69×103 mg/Kg,selenium 0.0592 mg/Kg,copper 1.85 mg/Kg,zinc 10.0 mg/Kg,calcium 336 mg/Kg,magnesium 229 mg/Kg.The content of rutin in fresh reed shoots was 9.974 mg/g(dry basis).In fresh reed shoots,the contents of cadmium,chromium,lead,arsenic and mercury were all lower than the limits of national standard.3.Study on the effect of different dry storage techniques on the quality of reed shootsThe reed shoots were treated with vacuum freeze drying,hot air drying and vacuum drying respectively.The rehydration rate and speed of reed shoots after vacuum freeze-drying were the highest,reaching 10.05 g/g after 30 min,while hot-air drying and vacuum drying were 5.23 g/g and 3.93 g/g after 50 min respectively;except for L value of reed shoots after vacuum freeze-drying,other chromaticity values changed significantly(p<0.05),and the order of total chromaticity difference from small to large was vacuum freeze drying,vacuum drying,and hot air drying;the hardness,resilience,elasticity and chewiness of reed shoots treated with three drying techniques all increased.Compared with fresh reed shoots,the hardness,elasticity and chewiness of freeze-dried reed shoots did not change significantly(p>0.05),while hot air drying and vacuum drying had significant effects on the texture characteristics of reed shoots(p<0.05).The content of vitamin C of reed shoots treated with three methods had significant difference(p<0.05).Vacuum freeze-drying and vacuum drying had no significant effect on the content of rutin(p>0.05).The contents of rutin and vitamin C were arranged from large to small as follows:vacuum freeze-drying,vacuum drying,and hot air drying.Compared with the three drying technologies,vacuum freeze-drying could be used as an ideal drying method for the preservation of reed shoots,but the cost of this method was the highest.4.Study on the effect of pickling preservation on the quality and safety of reed shootsFresh reed shoots were dry-pickled at 10%,11%,12%,13%,14%,and 15%salt addition respectively for 8 months.With the prolongation of pickled time,the content of protein and vitamin C in all concentration groups gradually decreased.With the increase of salt concentration,the protein content decreased,and the rule of vitamin C was the opposite.The changes of acidity and coliform flora number in all concentration groups showed a trend of increasing firstly and then decreasing,and a trend of the higher the salt concentration,the lower the acidity and the number of coliform flora,which indicated the correlation between the two.At the end of the pickled period,the number of coliform flora in the 12%and 15%concentration groups was less and the safety was relatively higher.The nitrite content of each concentration group decreased with the prolongation of pickled time,and increased firstly and then decreased with the increase of salt concentration.All detected nitrite contents were lower than the national standard limit,which could ensure the food safety of pickled reed shoots.The 16s rRNA sequencing results of the pickled final reed shoots showed that the 12%and 15%concentration groups promoted the growth and reproduction of Acdiobacteria and inhibited the proliferation of Phylum Firmicutes and Actinobacteria.After comprehensive consideration,adding 12%salt dry pickled to reed shoots,could not only ensure its safety,but also maximized the growth of acid bacteria in the pickled system,therefore,such concentration was the optimum one for dry pickled reed shoots.