Dados do Trabalho

Título

FROM FLOWERING TO FINAL PRODUCT: A COMPLEX STUDY OF SORGHUM GRAINS PHENOLIC PROFILE BY METABOLOMIC APPROACH

Introdução

The search for foods with biological potential for chronic diseases prevention has valued sorghum grains for human consumption. Although sorghum is a rich cereal in phenolic compounds (PC), some gaps regarding its maturation and food processing effect on its bioactive potential remain to be elucidated. This work aims to provide deep information about PC accumulation throughout sorghum grain maturation; and their changes after biological, physical and thermal processing.

Material e Métodos

Different sorghum (Sorghum bicolor L.) genotypes, varying in pericarp colors and tannin levels, were harvested at five different days after flowering (10 to 40DAF; from cellular division, grain filling, physiological maturity to mature stage; total: 10 samples). Mature grains were subjected to three different technological processes: germination (16 °C during 72 and 144 h, 60% of relative humidity; total: 9 samples), dehulling (≅15%: whole-grain, decorticated grain and bran; total: 12 samples) and cooking (1:6 sample:water ratio; 30 min; total: 24 samples). PC were sequentially extracted and analyzed by high-resolution untargeted metabolomics (UPLC-ESI-QTOF/MS).

Resultados e Discussão

Sorghum PC are synthesized during grain growth (40DAF PC content was nine-fold higher than 10DAF). In initial stages (10-17DAF), the phenolic acids class was more abundant (≅ 50%); however, at 25DAF, the flavonoids biosynthesis pathway seems to be prioritized (60%), indicating the greater action of the enzyme 4-coumarate-CoA ligase. Dimer/trimer procyanidins (8 isomers) have been tentatively identified at all sorghum stages, indicating that tannins are present even in immature grains (10DAF). For mature sorghum, chemometric analyzes were applied to highlight phenolic changes after each processing. In all cases, the most susceptible class was flavonoids. Twenty-five PC were differentially abundant after germination: 4-hydroxybelzaldehyde increased (+64% and +4-times higher) after 72h and 144h; while important sorghum PC (daidzin, caffeic acid, isoferulic acid and p-coumaric acid) decreased during germination. As expected, PC are reduced after grain decortication (-45%), and the main loss was glycosylated flavonoids and condensed tannins. Finally, cooking does not seem to impact the phenolic profile of mature sorghum grains, being only relevant in increasing their levels (+24%). Our results would contribute to stimulate sorghum human consumption and viable processing techniques options for sorghum-based foods development.

Conclusão

Our results bring new insights into sorghum PC during grain filling and processing, which can stimulate sorghum human consumption and viable options of processing techniques for sorghum-based foods development with better bioactive properties.