Abstract
In line with the need to better utilize agricultural resources, and valorize underutilized fractions, we have developed protocols to increase the use of wheat bran, to improve utilization of this resource to additional products. Here, we report sequential processing for extraction of starch, lipids, and proteins from wheat brans with two different particle sizes leaving a rest-material enriched in dietary fiber. Mild water-based extraction of starch resulted in maximum 81.7 ± 0.67% yield. Supercritical fluid extraction of lipids by CO2 resulted in 55.2 ± 2.4% yield. This was lower than the corresponding yield using Soxhlet extraction, which was used as a reference method, but allowed a continued extraction sequence without denaturation of the proteins remaining in the raw-material. Alkaline extraction of non-degraded proteins resulted in a yield corresponding to one third of the total protein in the material, which was improved to reach 62 ± 8% by a combination of wheat bran enzymes activation followed by Osborne fractionation. The remaining proteins were extracted in degraded form, resulting in maximum 91.6 ± 1.6% yield of the total proteins content. The remaining material in both fine and coarse bran had a fiber content that on average corresponded to 73 ± 3%. The current work allows separation of several compounds, which is enabling valorization of the bran raw-material into several products.
Highlights
Wheat bran is a by-product from the milling process in the production of refined grains and has an estimated annual production of ∼100–150 million tons/year world-wide (Hell et al, 2014)
Extraction of starch from wheat bran using water as solvent was evaluated at two different temperatures and times (30◦C for 30 min and 55◦C for 4 h)
The protein extraction yield from fine bran was higher than that from coarse bran at the corresponding pH and time. These results showed the effect of particle size, where the smaller size with higher surface to volume ratio seemed beneficial
Summary
Wheat bran is a by-product from the milling process in the production of refined grains and has an estimated annual production of ∼100–150 million tons/year world-wide (Hell et al, 2014). Bran makes up the outer layer of wheat grains and consists of the tissues termed aleurone, hyaline, testa, and pericarp (Prinsen et al, 2014). The main components of wheat bran tissues include starch (15–25%) and non-starch polysaccharides including dietary fibers (50–60% of which 52–70% is arabinoxylan, 20–24% is cellulose and ∼6% is ß-glucan), lignin (6–12%), proteins (10–25%), lipids (2–4%), and minerals (3–8%) (Apprich et al, 2014; Hell et al, 2014). The outer bran layer, the pericarp, is composed of mainly insoluble dietary fibers and lignin.
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