In vitro digestion and colonic fermentation of phenolic compounds and their bioaccessibility from raw and roasted nut kernels.

Roasting and digestion affect nut kernel phenolic compounds' bioaccessibility and bioactivity. In this study, three types of raw and commercially roasted nut kernels (almonds, cashews, and walnuts) were treated by in vitro digestion and colonic fermentation. The objective was to analyze the effect of roasting on their phenolic content, associated antioxidant potential, bioaccessibility, and short chain fatty acid (SCFA) synthesis altering. Among these, raw and roasted walnuts performed best, with significantly higher total phenolic content (TPC), total flavonoid content (TFC), free radical scavenging (2,2'-diphenyl-1-picrylhydrazyl (DPPH) assay) values, and ferric reducing antioxidant power (FRAP) values after completing gastrointestinal digestion. With the exception of cashews, roasting had no significant effect on antioxidant capacity during digestion from oral to small intestinal phase. Almonds showed the highest DPPH values after 16-hour colonic fermentation, reaching above 7.60 mg TE per g. Roasting had a positive effect on the free radical savagery capacity of walnuts within 16-24 hours of fecal fermentation. Significant differences were found in the bioaccessibility of individual compounds in raw and roasted nuts. As for almond and walnut, roasting increases the release and breakdown of phenolic compounds during colonic fermentation and have a positive impact on the bioaccessibility of specific phenolic compounds. The colonic bioaccessibility of most phenolic compounds was the highest. Due to heat polysaccharide breakdown, the total SCFAs produced were limited up to 0.03 mM. Raw almonds produced the most SCFAs at 16-hour fermentation and illustrated more benefits to gut health.

Biological properties of almond proteins produced by aqueous and enzyme-assisted aqueous extraction processes from almond cake.

The almond cake is a protein-rich residue generated by the mechanical expression of the almond oil. The effects of the aqueous (AEP) and enzyme-assisted aqueous extraction processes (EAEP) on the biological properties of the almond cake protein were evaluated. Total phenolic content (TPC), antioxidant capacity, inhibitory effects against crucial enzymes related to metabolic syndrome, antimicrobial potential, and in vitro protein digestibility profile were assessed. EAEP provided the best results for antioxidant capacity by both ORAC (397.2 µmol TE per g) and ABTS (650.5 µmol TE per g) methods and also showed a high (~ 98%) potential for α-glucosidase inhibition. The AEP resulted in protein extracts with the highest lipase inhibition (~ 70%) in a dose-dependent way. Enzymatic kinetic analyses revealed that EAEP generated uncompetitive inhibitors against α-glucosidase, while EAEP, AEP, and HEX-AEP (used as control) generated the same kind of inhibitors against lipase. No protein extract was effective against any of the bacteria strains tested at antimicrobial assays. An in silico theoretical hydrolysis of amandin subunits corroborated with the results found for antioxidant capacity, enzyme inhibitory experiments, and antimicrobial activity. Digestibility results indicated that the digestive proteases used were efficient in hydrolyzing almond proteins, regardless of the extraction applied and that HEX-AEP presented the highest digestibility (85%). In summary, EAEP and AEP skim proteins have the potential to be used as a nutraceutical ingredient. The biological properties observed in these extracts could help mitigate the development of metabolic syndrome where EAEP and AEP skim proteins could be potentially used as a prophylactic therapy for diabetes and obesity, respectively.