Durum Wheat Bran By‐Products: Oil and Phenolic Acids to be Valorized by Industrial Symbiosis
Authors: Cardenia Vladimiro , Sgarzi Federica , Mandrioli Mara , Tribuzio Giovanni , Rodriguez‐Estrada Maria T. , Toschi Tullia Gallina 
Published: June 2018

Wheat bran represents one of the main by‐products of debranning/milling of wheat and is currently used for animal feeding. To evaluate other possibilities of by‐product valorization, the lipid matter and phenols in five different fractions of durum wheat bran by‐products obtained from debranning and milling are determined during storage. The lipid content (3.6%–6.3%) significantly changes in the different by‐products, showing an increasing content of free fatty acids (FFA) during 30‐day storage, which corresponded to a consistent decrease in triacylglycerols (TAG). The lipid matter is mainly composed of polyunsaturated fatty acids (57.20% ± 0.36%–59.43% ± 0.72% of total fatty acids), of which linoleic acid is the most representative, but it significantly decreases during storage. The detected free acidity level confirms lipase activity during storage, since the highest value (65.3%) is reached after 30‐day of storage. Total phenolic content of durum wheat bran by‐products does not significantly change during storage, nor does single phenolic acids in the soluble conjugated and insoluble bound fractions (except for caffeic acid). These results suggest that high value nutritional compounds can be extracted from durum wheat bran by‐products before being supplied for animal feeding, but as requested in food chains, the presence of contaminants should be excluded.

Practical Applications: The adoption of an industrial symbiosis approach to transfer and share resources between dissimilar industries reflects recent European strategies on decoupling economic growth from environmental impacts. These results demonstrate that durum wheat bran by‐products, instead of being addressed to animal feeding, could be also used as a source of defatted wheat bran and oil (bran and germ oil) for industrial use (pharmaceutical, cosmetic, etc.) or human consumption. The results demonstrate that it is of outmost importance to control the high free acidity, that is, the amount of FFA, of these by‐products; to overcome this problem, it is necessary to extract the oil from fresh material as soon as possible after debranning and/or milling, in order to reduce the need for strong refining conditions to lower free acidity within the legal requirements for refined oils (≤0.5%). A drastic refining process should possibly be avoided, and discouraged for environmental sustainability reasons, because it would reduce the process yield thus rendering it economically disadvantageous.

Wheat bran is one of the main by‐products of wheat milling and is widely used for animal feeding or disposed of, which produces negative environmental and economic impacts. The lipid matter and phenols in five different fractions of durum wheat bran by‐products obtained from milling and grinding are determined during storage. On the basis of these results, it is demonstrated that wheat bran by‐products can be further valorized; therefore, instead of directly addressing the final remaining product to animal feeding or inert material for building or biomass, the wheat bran could be used as a source of oil and defatted bran for raw materials and/or ingredients for industrial purposes (pharmaceutical, cosmetic, food).