The aim of the work was to evaluate the influence of prebiotic additives on gluten-free breads, and to assess the effectiveness of gluten-free bread supplementation with the selected prebiotics: inulin, oligosaccharide syrup and bitter-free chicory flour. The breads with the 3, 5 or 8% additions of the mentioned prebiotics were baked and stored for 48h. During this period the following analyses were performed: a texture profile, the content of mono-and oligosaccharides, and of inulin. The best effects on sensory features of gluten-free bread were observed when applied medium doses of prebiotics, being a 5% inulin supplemented bread the highest sensory scored. The addition of 5 and 8% of inulin, FOS syrup and chicory flour at all applied doses reduced the crumb hardening rate during the 3 days storage period. Content of fructooligosaccharides with DP 3–5 in standard bread was 0.1%, and in the supplemented breads did not exceed 0.3%. Addition of Frutafit preparation and bitter-free chicory flour enriched bread with inulin up to 1–3.5g/100g, the highest preservation level was observed in the case of chicory flour addition.

Ellagitannins are known to possess many beneficial and health-promoting properties, including antioxidant and antimicrobial effects, arising from the activity of both native compounds and the products of their degradation or metabolism. The wide range of beneficial properties is attributable to the great structural variety of these compounds, even though all of them belong to the same polyphenolic group, namely hydrolyzable tannins. Therefore, the potential of individual ellagitannins must be studied separately with the view to their application, as natural substances, in medicine or the food industry. The objective of the present work was to elucidate the effects of temperature and medium pH on the stability of the two main raspberry ellagitannins, i.e., lambertianin C and sanguiin H-6, in aqueous solutions. Experiments were conducted within the temperature range of 20–80 °C and pH 2–8 over 0–24 h of incubation. The content of the studied ellagitannins and the products of their decomposition was investigated using HPLC-DAD and LC–MS, respectively, with an Orbitrap detector. It has been found that the studied ellagitannins are stable in acidic conditions, but are rapidly degraded in neutral and mildly basic media at elevated temperature (60–80 °C). In mildly acidic conditions (pH 6) ellagitannins hydrolyze to intermediate products, that is, sanguiin H-10 isomers, sanguiin H-2, and galloyl-HHDP-glucose isomers, with the main end products being ellagic and gallic acids. In addition to hydrolysis, ellagitannins may also undergo oxidation to compounds containing a dehydrohexahydroxydiphenoyl (DHHDP) group, also accompanied by the presence of brevifolin carboxylic acid, a product of DHHDP hydrolysis.

Purpose We investigated the effects of dietary supplementation with strawberry extracts rich in ETs and fructo-oligosaccharides (FOS) on the intestinal microbiota and the formation of bacterial metabolites in the distal intestine, as well as the absorption of ET metabolites and antioxidant status in rats. Methods Rats were allocated into six groups of eight animals each and fed for 4 weeks with a control diet (group C), a control diet supplemented with FOS (group C + FOS) or modifications of these diets, in which a monomeric or dimeric ET-rich extract was added (groups ME and ME + FOS or DE and DE + FOS, respectively). Results The extract addition, the FOS addition and their interaction significantly affected the total and selected bacterial counts in the caecal digesta (all P < 0.005). The total bacterial count was the highest in group C + FOS, lower in group DE and the lowest in group ME + FOS (10.6, 10.3 and 8.52 log cells/g, respectively; P ≤ 0.05). The total caecal content of ET metabolites was higher in the ME and ME + FOS group than in the DE and DE + FOS group, respectively (67.8 and 89.5 vs. 13.0 and 18.0 µg/g, respectively; P < 0.001). The total plasma concentration of ET metabolites was higher in the ME + FOS and DE + FOS group than in the ME group (248 and 281 vs. 8.13 ng/mL, respectively; P < 0.001). Conclusions ETs of the monomeric ET-rich extract are more prone to intestinal breakdown than those of the dimeric ET-rich extract, and absorption of their metabolites can be increased by dietary FOS; however, together, they evoke strong antibacterial activity.