Structural changes of different starches illuminated with linearly polarised visible light

Aqueous suspensions (30% w/w) of spelt, amaranth and wheat starches were illuminated with linearly polarised visible light for 5, 15, 25 and 50 h. For native and illuminated samples, the weight-average molecular weight, the radii of gyration of the starch polysaccharide chains, and the distribution of the amylopectin structural units of the illuminated starches were determined. The susceptibility to α-amylolysis together with the iodine-binding properties and crystalline structure were studied for each of the starch samples. Illumination with linearly polarised visible light indicated changes in the crystalline structure of the polysaccharide chains and led to an increased enzymatic hydrolysis rate constant for the first stage of hydrolysis and final hydrolysis extent. Changes in the molecular structure of the starch indicate that illumination of the starches induced depolymerisation-repolymerisation reactions of starch polysaccharide chains. That rearrangements of the molecular starch structure depend on the illumination time and the botanical source of the starch.

Abiotic stress combinations improve the phenolics profiles and activities of extractable and bound antioxidants from germinated spelt (Triticum spelta L.) seeds

The aim of this study was to investigate the effects of germination of spelt seeds under different stress conditions on the antioxidant characteristics of their extractable and bound phenolics. Germination under combined stress of 25 mM NaCl and 50 mM sorbitol without subsequent mechanical stress had considerable impact on total phenolics contents and scavenging activities against different free radicals (DPPH, ABTS⁺, O₂^-, ROO). Alkaline hydrolysis of extracts from germinated seeds provided the majority of their phenolic acids, where ferulic and p-coumaric acids were the most representative. The phenolics liberated from their bound form also had greater antioxidant activities. For the extractable phenolics, p-coumaric hexoside increased the most (146%), while among the bound phenolics identified, the highest relative increase was for p-coumaric acid (171%). The germinated seeds showed no effects on intracellular oxidation in cells of the yeast Saccharomyces cerevisiae.