A study of the ability of bioactive extracts from brewers' spent grain to enhance the antioxidant and immunomodulatory potential of food formulations following in vitro digestion

The Effect of Upcycled Brewers’ Spent Grain on Consumer Acceptance and Predictors of Overall Liking in Muffins

The brewing industry generates large amounts of food waste including brewers’ spent grain (BSG) and leftover malted grains from beer production. BSG compositions can vary but consistently include high levels of protein and fiber. The potential nutritional and health benefits of BSG have sparked recent interest for food fortification. However, the challenges associated with BSG addition can impact food quality due to increases in fiber and protein content and reduction in starch content. Consumer testing was conducted to evaluate muffins containing varying levels of BSG (0, 20, 30% wt:wt flour) to determine the highest acceptable concentration on overall likeability, appearance, texture, moistness, sponginess, and taste attributes. Significant differences were found within appearance (F = 7.728, P = .001) and taste (F = 4.947, P = .008) ratings across all muffins. Control and 20% BSG muffins were rated significantly higher for appearance (6.74 ± 0.18; 6.64 ± 0.18) than 30% BSG muffins (6.11 ± 0.18). Muffins containing 20% BSG (7.15 ± 0.17) received significantly higher taste ratings than 30% BSG muffins (6.56 ± 0.22) and control muffins (6.49 ± 0.19). However, 30% BSG muffins maintained acceptance for all attributes showing higher allowable BSG substitutions than previously reported. Bivariate correlation analyses found that all attributes across each muffin variation were strongly, positively correlated (r > 0.6) with overall likeability excluding appearance (r = 0.359, P < 0.001) and moistness (r = .466, P < 0.001) in control muffins. Significant predictors of overall likeability were appearance (β = 0.088, P = 0.005), texture (β = 0.181, P < 0.001), sponginess (β = 0.226, P < 0.001), and taste (β = 0.494, P < 0.001). Brewers’ spent grain consumer acceptance results will guide the development of test food products for future human diet intervention compliance.

Characterisation of the in vitro bioactive properties of alkaline and enzyme extracted brewers' spent grain protein hydrolysates

Brewer's spent grain (BSG) is a co-product of the brewing industry that has been shown to contain a range of bioactive peptides encrypted within its protein sequences. Two methods were evaluated herein to generate bioactive peptides; (i) an alkaline extracted BSG protein rich fraction (BSG-PI) was hydrolysed using different combinations of proteolytic enzymes and (ii) BSG was pre-treated with carbohydrases followed by direct hydrolysis using proteolytic enzymes (BSG-DH). BSG-DH with Alcalase/Flavourzyme resulted in significantly higher (p < .05) protein yield when compared to BSG-PI (63.09 ± 0.27 and 58.90 ± 1.45%, respectively). The antioxidant activities (ORAC, FRAP and ABTS) of the BSG-PI and -DH hydrolysates differed depending on the assay and proteolytic enzyme combination preparations used for hydrolysis. Inhibition of DPP-IV by the BSG-PI hydrolysates ranged from 87.01 ± 0.15 to 89.61 ± 0.12% while inhibition by the BSG-DH hydrolysates ranged from 35.71 ± 0.72 to 85.06 ± 0.17%. A significant reduction in the release of interleukin-6 in lipopolysaccharide-stimulated RAW 264.7 cells was observed following treatment with BSG-PI hydrolysates generated with Prolyve/Protease P (58.30 ± 13.76%) and Corolase PP/Flavourzyme (48.02 ± 10.82%) when compared to untreated LPS stimulated control cells (100%). BSG-DH hydrolysates were subjected to in vitro simulated gastrointestinal digestion (SGID) which resulted in a reduction in antioxidant activity, an increase in DPP-IV inhibition and no change in the immunomodulatory activity. Ultrafiltration of selected BSG-DH hydrolysates (through 30 and 10 kDa membranes) gave some permeates with enhanced bioactivities. The results demonstrate that direct enzymatic hydrolysis of BSG is a feasible approach for the generation of bioactive peptides without the prior use of an alkali protein extraction step.

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.