Pasting properties and retrogradation behaviour of different rice varieties

During gelatinization, starch granules undergo an irreversible swelling; on cooling, the starch paste increases in crystallinity and firmness. The objective of this study was to analyze the pasting properties and the retrogradation behaviour of six traditional and five aromatic Italian rice varieties. The pasted gels, after cooling, were evaluated by dynamic rheological measurements for up to7 days of storage at 4°C. The samples were also analyzed by FT-NIR spectrometer, equipped with an integration sphere. The pasting properties and the short term retrogradation behaviour of white rice flours strongly depended on the rice varieties and especially on their amylose content; on the other hand, similar pasting patterns were observed for the different samples of brown rice flour. The NIR data showed that the ageing time had a greater influence on the spectra of the white varieties. Gel spectra of brown rice, on the contrary, did not show any evident dependence on the storage time. The spectra of white rice were correlated with the rheological parameters.