Development of shelf-stable, ready-to-eat (RTE) shrimps (Litopenaeus vannamei) using water activity lowering agent by response surface methodology

Three water-activity-lowering agents (composite phosphate, sorbitol and glycerol) were used to develop a kind of shelf-stable, ready-to-eat (RTE) shrimp. Formula of water-activity- lowering agents was optimized by response surface methodology (RSM) using a central composite design. Model equation was proposed with regard to the contents of composite phosphate (X1), sorbitol (X2) and glycerol (X3) : \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ Y = {1}.000{4} - 0.{5851}{{\text{X}}_1} - 0.0{322}{{\text{X}}_2} - 0.0{243}{{\text{X}}_3} + 0.0{167}{{\text{X}}_1}{{\text{X}}_2} + 0.0{156 }{{\text{X}}_1}{{\text{X}}_3} + {1}.0000 \times {1}{0^{ - {3}}}{{\text{X}}_2}{{\text{X}}_3} + {1}.0{\text{844X}}_1^2 + {3}.{35}00 \times {1}{0^{ - {3}}}{\text{X}}_2^2 + {2}.{6}000 \times {1}{0^{ - {3}}}{\text{X}}_3^2 $$\end{document}. The model with a very low probability value (P < 0.0003) was highly significant and the value of lack-of-fit was 0.4028, indicating that the model could predict water activity of shrimps using different agents. Composite phosphate of 0.22%, sorbitol of 3.12% and glycerol of 2.51% were found to be the optimal condition to obtain the lowest water activity of 0.884. Compared to the control shrimps, RTE shrimps treated with water-activity-lowering agents had a longer shelflife and higher sensorial acceptability. During storage at temperature of 35 °C, the quality of RTE shrimps in term of appearance, flavor and texture was found to be superior to the untreated ones. Texture profile, TBARS value, contents of astaxanthin and free amino acid of treated samples were found to be decreased slower from origin value compared to that of untreated samples. These RTE shrimps were biologically safe and sensorially acceptable after 30 days of storage at temperature of 35 °C. Briefly, the application of water-activity-lowering agents extent the shelflife of RTE shrimps obviously and would be beneficial for the exploitation of white shrimp.