RESUMO
Numerous reactive oxygen species (ROS) entities exist, and hydrogen peroxide (H2O2) is very key among them as it is well known to possess a stable but poor reactivity capable of generating free radicals. Considered among reactive atoms, molecules, and compounds with electron-rich sites, free radicals emerging from metabolic reactions during cellular respirations can induce oxidative stress and cause cellular structure damage, resulting in diverse life-threatening diseases when produced in excess. Therefore, an antioxidant is needed to curb the overproduction of free radicals especially in biological systems (in vivo and in vitro). Despite the inherent properties limiting its bioactivities, polysaccharides from natural sources increasingly gain research attention given their position as a functional ingredient. Improving the functionality and bioactivity of polysaccharides have been established through degradation of their molecular integrity. In this critical synopsis; we articulate the effects of H2O2 on the degradation of polysaccharides from natural sources. Specifically, the synopsis focused on free radical formation/production, polysaccharide degradation processes with H2O2, the effects of polysaccharide degradation on the structural characteristics; physicochemical properties; and bioactivities; in addition to the antioxidant capability. The degradation mechanisms involving polysaccharide's antioxidative property; with some examples and their respective sources are briefly summarised.
RESUMO
The continued increase in Nigeria's rice production makes product diversification very fitting, even to underutilized indigenous/local varieties. Further, rice converted to malt can bring about useful products like syrup with enhanced characteristics. In this context, a comparative study involving some functional properties of syrup from malted and unmalted rice of different varieties was carried out. Syrup from either filtered or centrifuged starch hydrolysates of enzyme hydrolyzed rice (malted/unmalted) flours gave rise to filtered unmalted (FUHR), filtered malted (FMHR), centrifuged unmalted (CUHR), and centrifuged malted hydrolyzed rice (CMHR) groups. From these, functional properties, that is, pH, total soluble proteins (TSP), total dissolved solids (TDS), total solids (TS), dextrose equivalent (DE), titratable acidity (TA), apparent brix (°B), specific gravity (SG), syrup yield (SY), and some minerals [calcium (Ca), iron (Fe), magnesium (Mg), and zinc (Zn)] were determined. Results showed syrup from malted with significantly higher (P < 0.05) SY, Brix, pH, SG, TS, TDS, and TSP, but significantly lower (P < 0.05) TA, DE, and mineral contents (Ca, Zn, Fe, and Mg) over the unmalted group. Some significant interactions (P < 0.05) were found, between rice variety, treatment and separation method (TS, TDS, DE, Brix, SY, and Ca), rice variety and treatment (TSP, Zn, Mg, and Fe), as well as rice variety and separation method (TSP, pH). In addition, some positive and negative significant (P < 0.05) correlations between the studied functional properties were found. Overall, malting and processing methods can influence the functional properties of rice syrup-an acceptable specialty ingredient for brewing/beverage production. PRACTICAL APPLICATION: Through the application of exogenous enzymes, rice syrup has been successfully produced from locally bred/improved rice varieties commercially available in Nigeria. By comparing some functional properties of syrup from malted and/or unmalted rice, the current research provides useful evidence that locally available rice varieties are potential candidates for product diversification to the food/brewing, pharmaceuticals, and other industries, not only in Nigeria but also in the West Africa subregion.
