NMR water transverse relaxation time approach to understand storage stability of fresh-cut 'Rocha' pear

Fresh-cut fruit is an important segment in fruit market due to the increasing demand for healthy/ convenient foods. However, processing promotes a decrease in fruits stability with faster physiological and microbiological deteriorations. Food stability is strongly attributed to its molecular dynamics and "water availability". Understanding changes in water location/mobility is of utmost importance, since water dynamics profoundly influences physic-chemical and microbiological quality of foods. Nuclear magnetic resonance spectroscopy (NMR) is a methodology used to study the food constituents' molecular dynamics. The aim of this study is to use NMR to evaluate changes in water mobility that occurred in fresh-cut pear tissues during storage, by measuring the transverse relaxation time (T-2) parameter. Results showed the existence of three water classes in the cells after processing, with T-2 values of 10 ms, 187 ms and 3s for cellular wall, cytoplasm and vacuole, respectively. Also, the obtained results demonstrated that T-2 was affected by processing and storage. Moreover, a relationship between T-2, microstructure and the quality parameters was established. T-2, maximum value increased with pear hardness as well as water activity. On the contrary, a decrease in total colour difference (TCD) was found with T-2. Results demonstrate the usefulness of the application of NMR relaxometry in food studies. (C) 2016 Elsevier Ltd. All rights reserved.