TIME-TEMPERATURE RELATIONSHIPS FOR IQF SHRIMP WITH LIQUID NITROGEN AND ITS QUALITY ASSESSMENT

Experiments were conducted to study the time temperature relationship during freezing of individual raw shrimp by dipping in Liquid Nitrogen. Four sets of experiments were conducted. The first set involved the assessment of the temperature profile of the gaseous nitrogen environment in a thermocole container with varying quantity of liquid nitrogen. The next two sets of experiments involved direct dipping of the raw shrimp in a liquid nitrogen bath in a thermocole container using perforated stainless steel tray suspended by means of a wire loop, one in a single tier and the other in a double tier. The fourth set was conducted in a laboratory model tunnel provided with immersion freezing facility. In each case, the dipping time was progressively increased from 5 s to 30 s at 5 s increments. The time‐temperature relationships obtained were compared with those from available literature and were found to exhibit similar trend. The quality of the frozen shrimp was also studied in terms of pH, TVB, TMA and Indole content. It was observed that dipping shrimp in liquid nitrogen for the specified period retained the quality well within the acceptable commercial limit.