Combination of transglutaminase and sourdough on gluten-free flours to improve dough structure.

The aim of this work was to evaluate the effects of microbial transglutaminase (mTG) and sourdough on gluten-free (GF) flours. Besides deamidation and incorporation of amines, mTG catalyses protein cross-links, modifying dough structure. Sourdough from lactic acid bacteria (LAB) and yeast modifies dough protein composition, determining proteolysis, which induce the formation of aroma precursor metabolites. The chemical-physical interactions of volatile molecules with various constituents of the matrix affect the retention of aroma compounds. Here, the effect on volatile molecule profiles and on protein networks formation after mTG treatment in sourdoughs obtained with four GF flours belonging to cereals, pseudo-cereals and legumes (rice, corn, amaranth and lentil) was investigated. Sourdough was prepared with a two-step fermentation using Lactobacillus sanfrancisciensis (LSCE1) and Candida milleri (PFL44), then mTG was added after 21 h of fermentation at increasing levels. The results showed that mTG had the capacity to modify GF flour proteins and improve protein networks formation, involving mainly the prolamin protein fraction. This is particularly relevant for the production of GF backed goods generally lacking of technological, structural and sensorial features compared with products obtained with wheat flour sourdough fermentation. Interestingly, mTG treatment of sourdough affected also the volatile composition and indeed possibly the final organoleptic properties of the products.

Exploitation of starch industry liquid by-product to produce bioactive peptides from rice hydrolyzed proteins.

Small peptides show higher antioxidant capacity than native proteins and may be absorbed in the intestine without further digestion. In our study, a protein by-product from rice starch industry was hydrolyzed with commercial proteolytic enzymes (Alcalase, Neutrase, Flavourzyme) and microbial whole cells of Bacillus spp. and the released peptides were tested for antioxidant activity. Among enzymes, Alcalase was the most performing, while microbial proteolytic activity was less efficient. Conversely, the antioxidant activity was higher in the samples obtained by microbial hydrolysis and particularly with Bacillus pumilus AG1. The sequences of low molecular weight antioxidant peptides were determined and analyzed for aminoacidic composition. The results obtained so far suggest that the hydrolytic treatment of this industrial by-product, with selected enzymes and microbial systems, can allow its exploitation for the production of functional additives and supplements rich in antioxidant peptides, to be used in new food formulas for human consumption.

Role of cereal type and processing in whole grain in vivo protection from oxidative stress.

The reduced risk of chronic diseases related to whole grain consumption is in part attributed to their high antioxidant content. Many studies have been performed on the in vitro antioxidant capacity of cereals, but in vivo studies are necessary. We have evaluated and compared the effect of whole grain durum wheat bread and whole grain Kamut khorasan bread on the oxidative status in rats. Two different bread-making processes were used for whole grain Kamut khorasan, sourdough and baker's yeast. After 7 weeks on the experimental diets rats were divided into two subgroups, one receiving an oxidative stress by doxorubicin injection. Our results evidenced both wheat durum and Kamut khorasan as good sources of antioxidants, and a lower oxidative state in rats fed the cereal-based diets. Furthermore, Kamut khorasan bread fed animals had a better response to stress than wheat durum fed, especially when a sourdough bread was supplied. Although further studies are needed, data herein reported suggest whole grains, particularly whole ancient grains, as a safe and convenient way of increasing antioxidant protection.