Can irrigation conditions influence characteristics and cooking behaviour of rice?

Purpose: Rice (Oryza sativa L.) is adapted to grow both in submerged and aerobic soils. The different irrigation conditions, however, may influence rice composition and its cooking quality. This work aims at investigating the effect of different water managements on rice milling yield, biometric characteristics, nitrogen and amylose content, pasting properties and cooking behavior. The effectiveness of Near Infrared (NIR) to provide comprehensive information of the effects of water management on the quality traits of rice was evaluated. Approach and methods used: In the two consecutive harvesting years (2011 and 2012), four rice varieties (Baldo, Gladio, Loto and Selenio) were grown in three agricultural systems, characterized by a progressively more intense use of water: dry seeding and delayed flooding; dry seeding and rotational irrigation; water seeded and continuous flooding. NIR spectral data were collected in reflectance mode using a FT-NIR spectrometer. The spectral data were correlated with biometric, chemical and rheological parameters by Principal Component Analysis (PCA) and PLS regression algorithm. Key results: Considering the overall dataset, it was not possible to highlight a univocal influence of the water-soil regime on grain properties, since the quality characteristics seem to be mainly related to the rice variety (in particular to its amylose content) and harvesting year. In fact, the PCA analysis performed, taking into consideration the quality traits of all samples, evidenced a lower influence of the three water management systems in comparison with the variability due to the genotype and the harvesting year. The Principal Component Analysis of NIR spectra was effective in discriminating both harvesting year (PC1+PC2; total explained variance of 84%) and rice variety (PC1+PC3; total explained variance of 77%). Moreover, good correlations were found through PLS algorithm for nitrogen content (R2= 0.98), viscoamylographic breakdown (R2= 0.93) and optimal cooking time (R2= 0.89). Synthesis and Applications: The irrigation conditions seem to play a minor role on quality characteristics of rice than cultivar and harvesting year. The NIR spectroscopy has proven to be a reliable and sensitive technique, suitable to quickly evaluate not only chemical indices but also cooking attributes.