MS-IMAGING: IN SITU INVESTIGATION OF SECONDARY METABOLITES OF ORYZA SATIVA L. VARIETIES BEFORE AND AFTER COOKING

Rice (Oryza sativa L.) is an important cereal in human nutrition due to its richness in vitamins, minerals, and bioactive compounds. The processing steps to which paddy rice is subjected after harvesting, while on the one hand making it edible improving its sensory quality and cooking, on the other hand, from a nutritional point of view could result in the depletion of many micronutrients and phytonutrients that are concentrated in the germ and bran. An effective processing technique to reduce cooking time of rice is parboiling, a hydro-thermal treatment that allows the water-soluble components of the germ and outer parts to diffuse within the caryopsis. The aim of the work to define the best procedure for the application of MALDI-MSI to investigate the localization and migration of two different classes of rice micro-components after industrial processing and domestic cooking: steryl ferulates and anthocyanins, which are known to provide positive physiological effects on human health. Spectra acquisitions with IMS were conducted on a MALDI-LTQ-Orbitrap XL and the ionic intensity of the signal associated with the different distribution of the analyte in the tissue was evaluated. The Oryza sativa L. varieties studied were 'Carnaroli' (white rice), 'Oro' (white parboiled rice), 'Nerone', (black pigmented rice), and 'Venere', (black pigmented parboiled rice). About domestic cooking methods, all rice varieties were analyzed raw, after boiling in water and after steaming. The sample preparation steps were optimized to obtain reproducible results by MSI. As regards steryl ferulates, the study allowed to verify their localization in the different rises, highlighting a negligible migration of these compounds towards the endosperm in the parboiled rice. Regarding anthocyanins, it was found that steaming or boiling the pigmented rice provides a consistent migration of these compounds in the endosperm. The obtained results provide a solid basis for the definition of future experimental designs for the study of rice secondary metabolites in raw and cooked rice and for monitoring the effects of parboiling.