Cereal milling by-products as sources of nutrients and antioxidant phenolic compounds

CereaIs are staple food crops and major sources of nutrition wor1dwide, but their processing generates a large amount of by-products. In addition to environmental and economic aspects, cereal milling by-products represent a significant loss of natural resources and nutrients when discarded as useless waste [1,2]. Thus, in order to promote the upcyc1ing of these by-products as valuable raw materiaIs, this study was carried out to provide a compositional and bioactive characterisation of wheat, maise and rye by-products current1y produced in large quantities by the cereal grain milling industry. The cereal by-products were studied for their proximate composition folIowing official methods of food analysis, and organic acids, soluble sugars, fatty acids and tocopherols were analysed by different chromatographie techniques [3]. After preparation of hydroethanolic extracts, the detected phenolic compounds were characterised by HPLC-DAD-ESIIMSnand the antioxidant activity was evaluated through in vitro assays for the ability to inhibit lipid peroxidation by monitoring the formation of thiobarbituric acid reactive substances (TBARS), and to inhibit oxidative hemolysis caused by free radicals generated in the in vitro system [3]. Regarding the compositional results, expressed in dry weight (dw), carbohydrates (56.35-78.12 g/100 g) were the major proximate constituents of the studied cereal by-products, folIowed by proteins (11.2-30.0 g/100 g). The higher energy value (432.3 kcal/l00 g) was presented by wheat germ, which also presented the highest citric acid content (0.86 g/100 g). Sucrose was the most abundant soluble sugar in alI cereal by-products, reaching 10.4 g/100 g in wheat germ, 3.84 g/100 g in maise bran-germ mixture, and approximately 2.9 g/100 g in wheat and rye bran samples. Unsaturated fatty acids predominated in alI samples, given the high contents of linoleic (53.9- 57.1 %) and oleie (13.4-29.0%) acids. Wheat germ had the highest leveis of tocopherols (22.8 mg/l00 g) and phenolic compounds (5.7 mg/g extract, with a high content of apigenin-C-pentoside-C-hexoside). In turn, while the wheat bran extract was particularly etIective in inhibiting the formation of TBARS, the rye bran extract was the on1y one capable of protecting sheep erythrocytes from oxidative haemolysis. OveralI, these results are valid arguments to support the use of cereal by-products as underexploited alternative sources of nutrients and bioactive phenolic compounds with potential health benefits for consumers.To the Foundation for Science and Technology (FCT, Portugal) for financiaI support by national funds FCTIMCTES to CIMO (UIDB/00690/2020), R.V.C. Cardoso's PhD grant (SFRH/BD/137436/2018) and national funding by FCT, P.L, through the institutional scientific employment program-contract for L. Barros, A. Fernandes, M.L Dias, and C. Pereira and the individual scientific employment prograrn-contract for J. Pine1a (CEECIND/01011/2018) and M. Carocho (CEECIND/00831/2018). To FEDER-Interreg Espaiía-Portugal prograrn for fmaneial support through the project TRANSCoLAB 0612_ TRANS CO LAB 2].