Impact of parboiling and cultivars on the free and total amino acid composition of rice ( Oryza sativa L.)

Parboiling imparts significant changes to nutritional composition of rice. The study presents the variations in amino acid (AA) composition of rice observed during parboiling process, observed in selected Sri Lankan rice cultivars. Upon parboiling, the change in levels of free and protein bound amino acids inconsistently varied across the rice cultivars and upon the parboiling technique. In comparison to non-parboiled rice, parboiling resulted in pronounced increase in nutritional gamma amino butyric acid (GABA) levels ranging from 2 times up to 11 times rendering parboiled rice a functional food. Rice parboiled after soaking for 48 hr using steam reported the highest free AA and GABA contents, while parboiling with steeping in boiling water after 24 hr soaking accounted for higher total amino acid contents in rice. Hence, for production of parboiled rice with increased nutritive value in respect of AA levels, the significance of optimization of post-processing conditions in parboiling is highlighted. Novelty impact statement Parboiling is a post harvesting technique which improves the cooking, storage, and nutritional quality of rice. In the approach to investigate the variations in amino acid composition of rice upon parboiling, the present study discusses the significant impact caused by the cultivar and the technique being used on the amino acid composition. Hence, an insight is provided into the utilization of optimum conditions during the parboiling process to produce parboiled rice enriched with high amino acid levels including gamma amino butyric acid.