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Impact of pulsed electric field pre-treatment on nutritional and polyphenolic contents and bioactivities of light and dark brewer's spent grains
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2019-04-30
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Kumari, B., Tiwari, B., Walsh, D., Griffin, T., Islam, N., Lyng, J., Brunton, N. and Rai, D. Impact of pulsed electric field pre-treatment on nutritional and polyphenolic contents and bioactivities of light and dark brewer's spent grains. Innovative Food Science & Emerging Technologies, 2019, 54, 200-210. doi: https://doi.org/10.1016/j.ifset.2019.04.012
Abstract
Pulsed electric field (PEF) pre-treatment, at 2.8 kV/cm with 3000 pulses of 20 μs pulse-width, was applied on brewer's spent grains (BSG) followed by aqueous extraction at 55 °C, 220 rpm for 16 h. PEF pre-treatment showed significantly increased yields (p < 0.05) of carbohydrate, protein, starch and reducing sugar in extracts from dark BSG compared to untreated samples. Light BSG extracts had significantly higher (p < 0.05) levels of free d-glucose and total free amino acids (18.5–33.3 and 21–25 mg/g dry weight extract (Dwe)), compared to dark extracts (5 and 1.2 mg/g Dwe respectively). Dark BSG extracts showed significantly higher (p < 0.05) total phenolics (3.97–4.88 mg GAE/g Dwe) compared to light BSG extracts (0.83–1.40 mg GAE/g Dwe). Furthermore, PEF treated light BSG showed higher antimicrobial activity with minimum inhibition concentration (MIC) of 50 and 25 mg/mL against Salmonella typhimurium and Listeria monocytogenes, respectively compared to the untreated extracts (>50 mg/mL) with lowest MIC value of 1.56 mg/mL against Staphylococcus aureus. All the BSG extracts induced the release of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and chemokines (IL-8, MCP-1 and MIP-1α) confirming immunomodulatory activity.