Physical quality changes of precooked Chinese shrimp Fenneropenaeus chinensis and correlation to water distribution and mobility by low-field NMR during frozen storage

Abstract

The relationship of physical quality to low-field nuclear magnetic resonance transverse relaxation (NMR) T2 data in precooked Chinese shrimp Fenneropenaeus chinensis at −18 °C were investigated. The hardness, gumminess, and chewiness increased with the increasing time, while springiness, cohesiveness, and resilience decreased. the hardness, Gumminess, and Chewiness in the frozen shrimps were strongly correlated with all of NMR T2 data, moisture content, and water holding capacity (WHC) except for T22*. L* and b* value reduced with the storage time increasing and were furthermore correlated to the T2 data, moisture content and WHC (p < .01 or p < .05) except for T22*, the appearance quality of precooked shrimps could be evaluated by L* and b* value changes during frozen storage. Low-field NMR results showed that the entrapped or immobilized water changed to tightly bound water during the frozen storage. Practical applications Chinese shrimp Fenneropenaeus chinensis is an important marine-cultured shrimp species in China, which was susceptible to melanosis and perishable during postmortern storage, precooked and forzen storage was often used to extend the shelf-life of the shrimps, but water holding capacity and physical quality indicators (i.e., texture and color) was changed during long time frozen storage. In this study, the majority of changes of textural and color were strongly corrected with low-field NMR T2 data, indicating that low-field NMR relaxometry was an effective technique for predicting the reduction of these physical quality indicators.