• Impact of pulsed electric field pre-treatment on nutritional and polyphenolic contents and bioactivities of light and dark brewer's spent grains

      Kumari, Bibha; Tiwari, Brijesh K; Walsh, Des; Griffin, Tomás; Islam, Nahidul; Lyng, James G.; Brunton, Nigel; Rai, Dilip K.; Department of Agriculture, Food and the Marine; European Union; et al. (Elsevier, 2019-04-30)
      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.
    • Ultrasound-assisted extraction of polyphenols from potato peels: profiling and kinetic modelling

      Kumari, Bibha; Tiwari, Brijesh K; Hossain, Mohammad Billal; Rai, Dilip K.; Brunton, Nigel; Department of Agriculture, Food and Marine; FIRM/11/F/050 (Wiley, 2017-02-14)
      Ultrasound‐assisted extraction (UAE) at 33 and 42 kHz has been investigated in the extraction of polyphenols from peels of two potato varieties, cream‐skinned Lady Claire (LC) and pink‐skinned Lady Rosetta (LR), commonly used in snack food production. Extraction efficacy between the UAE‐untreated (control) and the UAE‐treated extracts was assessed on the total phenolic content and antioxidant capacities (DPPH and FRAP). Application of UAE showed significantly higher recovery of phenolic compounds compared to solid–liquid extraction process alone. Lower ultrasonic frequency (33 kHz) was more effective in recovering polyphenols compared to 42 kHz ultrasonic treatment. The liquid chromatography‐tandem mass spectrometry revealed that chlorogenic acid and caffeic acid were the most prevalent phenolics in LR peels, whereas caffeic acid was dominant in LC peels. Peleg's equation showed a good correlation (R2 > 0.92) between the experimental values and the predicted values on the kinetics of UAE of phenolic compounds.