Characterizing physicochemical, nutritional and quality attributes of wholegrain Oryza sativa L. subjected to high intensity ultrasound-stimulated pre-germination

When ultrasonic stimulation is applied to plant seeds it may promote the development of new adaptive characteristics during germination, thus providing an alternative to regulate nutritional and physicochemical attributes of germinated seeds. However, there is rather limited information concerning high-intensity ultrasound (HIU) effects on the germination process of crop seeds as foodstuff. This investigation aimed at examining the effects of a novel processing pattern, which coupled HIU stimulation (28 kHz, 17.83 W cm(-2)) to a pre-germination stage, on the physicochemical, nutritional and quality changes of wholegrain brown rice (WBR; Oryza sativa L.). Results suggested that HIU stimulation significantly accelerated the germination progress of WBR and a 5-min duration obtained the highest germination rates within 5-30 min of exposure durations examined. During pre-germination, the HIU-pretreated grains showed a more obvious decrease in starch contents and increase in reducing sugar than the untreated samples. Stimulative effects of HIU treatments on starch decomposition were further confirmed by scanning electron microscope, simultaneously indicating an HIU-induced reduction in starch granule size. HIU treatment prior to germination led to the accumulation of gamma-aminobutyric acid, antioxidants and proline. In addition, nutritional index of free amino acids as well as the in vitro bioaccessibility of calcium and iron were also improved greatly. These results consistently demonstrated that HIU stimulation of WBR prior to soaking could be used as a potential strategy to further amplify nutritional characteristics derived from pre-germination process.