Time-temperature relationships for IQF shrimp with liquid nitrogen and itsquality assessment

Experiments were conducted to study the time temperature relationship durin g freezing of individual raw shrimp by dipping in Liquid Nitrogen. Four set s of experiments were conducted. The first set involved the assessment of t he temperature profile of the gaseous nitrogen environment in a thermocole container with varying quantity of liquid nitrogen. The next two sets of ex periments involved direct dipping of the raw shrimp in a liquid nitrogen ba th in a thermocole container using perforated stainless steel tray suspende d by means of a wire loop, one in a single tier and the other in a double t ier. The fourth set was conducted in a laboratory model tunnel provided wit h immersion freezing facility. In each case, the dipping time was progressi vely increased from 5 s to 30 s at 5 s increments. The time-temperature rel ationships 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 co mmercial limit.