Thermophysical Properties of Brackish Water Shrimp (Litopenaeus vannamei) for Process Design and Optimization

Abstract

The proximate compositions, moisture (74.2%), protein (28.07%), ash (2.62%), lipid (3.39%), and carbohydrate (4.39%) of brackish water shrimp (Litopenaeus vannamei) were determined. The density, specific heat, thermal conductivity, thermal diffusivity, and latent heat obtained as functions of the proximate composition of the shrimp and found to be 1110 kg/m3, 394 kJ/kgK, 0.5113 W/mK, 1.1773 × 10−6 m2/s, and 256.39 kJ/kg, respectively. The thermophysical values obtained were correlated with the proximate composition value. Correlation analysis reveals that specific heat (0.83), thermal conductivity (perpendicular model) (0.99), and latent heat (0.12) have positive correlation with protein content of shrimp. On the contrary, thermal diffusivity (−0.92) and thermal conductivity (parallel model) (−0.99) have negative correlation with protein content of shrimp. Further, latent heat of shrimp has a weak positive correlation (0.12) with protein content of shrimp and strong positive correlation with carbohydrate (0.82), fat (0.94), and water (1.0). Thermal conductivity (perpendicular model) has weak positive correlation with fat (0.18) and water (0.19), and has strong positive correlation with protein (0.99) and ash (0.81). Shrimp density has strong correlation with protein (0.98) followed by ash (0.86). Heat may be transferred better across the fibers of the shrimp than along the fiber. Context: Shrimp is one of the most valuable sources of high-grade protein among the seafood category. Shrimp has healthy fat a unique source of essential nutrients, including long-chain omega-3 fatty acids, iodine, vitamin D, and calcium. The global shrimp production has increased at a compound annual growth rate (CAGR) of 3.2% during the period 2011 to 2017. High market demand and consumer preference for shrimp food are attributed due to the attractive and sleek appearance, substantial flesh, ease of preparation for processing (mainly due to absence of scales), etc. With the potential and promise of further increases in production, it is essential to provide a firm base for development of technologies suitable for the value-added products from shrimp to further enhance its market expansion. Understanding on thermal properties of foods plays an important role in the design and prediction of heat transfer operations during the handling, processing, canning, storing, and distribution of foods. In addition, they are fundamentally important in mathematical modeling studies for the design and optimization of food-processing operation involving heat and mass transfer. Aims: The aim of the present study is to determine some thermophysical properties of shrimp as a function of its proximate composition to provide data for the development of appropriate equipment and processing technology for brackish water shrimp (L. vannamei). Settings and design: Proximate composition of the brackish water shrimp (L. vannamei) was measured. Prediction equations were developed to predict the thermophysical properties of shrimp. Correlation matrix was prepared to understand the dependence of proximate composition and thermophysical properties of shrimp. Materials and methods: Shrimp (L. vannamei) were obtained from an aquaculture farm in Nagapattinam. Shrimp were handled in accordance with the Codex General Principles of Food Hygiene (CAC/RCP 1-1969) and Code of Practice for Fish and Fishery Products (CAC/RCP 52-2003). The Kjeldahl method was performed according to method 981.10 of the AOAC International. Total lipids in tissue sample were extracted and analyzed by the method. Water content was determined by oven drying at 105°C, and ashing by incineration in a muffle furnace at 525°C. Carbohydrate content was determined by difference method as given in the following equation: % Carbohydrate = 100–% (Crude protein + Total fat + Ash) × 100. Comprehensive models were used predict volume and thermal properties. Statistical analysis used: Correlation matrix of proximate composition and the thermophysical properties of shrimp were prepared to understand the dependence of thermophysical properties with the proximate composition of shrimp. Results: The predicted values of the thermophysical properties of farmed shrimp were in accordance with the already published values. The density of the shrimp is slightly higher side when compared with water alone, indicating the influence of proximate composition. Correlation matrix thus prepared, better explains dependence of thermophysical properties (specific heat, thermal conductivity, thermal diffusivity, latent heat, and density) with the proximate compositions (moisture, protein, ash, lipid, and carbohydrate) of brackish water shrimp (L. vannamei).Shrimp is “nature’s superfood,” an important source of proteins and healthy fat, and a unique source of essential nutrients, including long-chain omega-3 fatty acids, iodine, vitamin D, and calcium. The knowledge of its engineering properties is essential to its processing and preservation to increase its value as food. The thermophysical data obtained in this study could be used as input in heat transfer calculations and to establish critical control points during the drying, freezing, and thermal processing of shrimp meat.