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This research aimed to develop a reliable, easy-to-perform and cheap method for measuring protein oxidation in complex samples such as aquaculture feed within various protein sources. For that purpose modified 2,4-dinitrophenylhydrazine (DNPH)-based method for quantification of protein carbonyls was employed whilst the modification of the method consisted of using different solutions for the extraction (distilled water and different concentrations of KCl and NaCl solutions), time of protein extraction (after homogenization and over the night) and concentration of trichloroacetic acid (10 and 25% TCA) for protein precipitation. Extraction during the night, higher TCA concentration and the use of 0.5 M KCl extraction solution resulted in the highest protein amount measured by the Lowry method and 280 nm protein estimation. On the other hand, the lowest protein yield was obtained by using distilled water for the extraction. Furthermore, the lowest amount of protein carbonyls was in the case when extraction was performed with distilled water (DW), while the highest content of protein carbonyls was reached with 0.15 M KCl and 0.5 M KCl extraction solutions. It was observed that the amount of proteinbound carbonyls compounds was increasing during storage under accelerated conditions and, in comparison to the original method, the modified method for measuring protein oxidation resulted in a higher amount of carbonyls during all points of storage.

Kombucha beverage is a fermented product obtained by kombucha culture fermentation of, usually, black or green tea. Besides black and green tea, kombucha also ferments water extracts of medicinal herbs. The obtained products possess antioxidant activity. The aim of this paper was to establish the antioxidant potential of kombucha beverages with black tea, green tea, and medicinal herbs after pepsin and pancreatin in vitro digestion. The radical scavenging ability of DPPH and hydroxyl radical, as well as reducing power of kombucha products was determined. At the end of the digestion process, the highest antioxidant potential towards hydroxyl radical showed only kombucha beverages with peppermint and stinging nettle extract. Results for reducing power and antioxidant capacity to scavenging DPPH radical showed a decrease in values after the digestion process.

In this study some functional properties and the in vitro digestibility of protein isolates from plum oil cakes, obtained by supercritical fluid extraction and cold pressing, as a control, were described and compared. Amygdalin contents in the protein isolates were at amounts considerably lower than regulatory. Solubility profiles of both protein isolates were typical for this type of plant proteins. Proteins showed good digestibility, which was assessed by gastrointestinal proteases (pepsin and pancreatin). SDS-PAGE analysis was used for characterisation of protein digests which showed that the protein isolates were completely digested. In vitro antioxidant capacity by three complementary methods and enzyme inhibitory effects towards Angiotensin-I Converting Enzyme (ACE) related to the onset of hypertension were determined. All obtained protein hydrolysates acted as DPPH and ABTS scavengers, as reducing agents and also as ACE enzyme inhibitor. Hence, the protein isolates obtained from plum kernel cake showed to be a potential source of natural products for food applications, with good digestibility and beneficial bioactive properties.

The objective of this study was to evaluate the potential of pumpkin oil cake protein isolate in production of millet bread. For that purpose, breads were created by substitution of millet flour with proteins at 5, 10 and 15% level. Dough rheological properties and both physical and sensory characteristics of obtained bread were determined. The increase in pumpkin oilseed cake protein (POCP) concentration influenced increase in dough viscosity, as determined using farinograph and fundamental rheological measurements. This is additionally confirmed by lower elasticity of supplemented breads as determined by texture analysis and sensory panel. Substitution of millet flour with POCP at all tested levels did not exhibit any influence on bread specific volume. However, 24 h after baking, breads supplemented with higher amount of POCP showed less pronounced hardening of the crumb, indicating that these proteins might retard starch retrogradation. The supplementation of millet bread with POCP had several beneficial effects on the sensory quality of bread, such as loss of bitter taste and aftertaste originating from millet flour. Additionally, bread granularity decreased and bread dissolving speed in mouth increased along with the increase in POCP concentration.

The wheat flour represents a complex system whose quality is influenced by several factors such as genotype, growing conditions and the complex interaction of genetic and environmental factors. In recent years, wheat quality fluctuation has become a major issue for millers and bakers. Requirements of bakery industry for providing wheat flour of uniform quality impose the need for further investigation in direction of monitoring/improving wheat flour quality. Therefore, the objective of the present study was to evaluate wheat varieties, grown in different locations, by breadmaking potential and proteolytic activity in dependence of climate conditions. Wheat flour of four wheat varieties (Pobeda, Zvezdana, Gordana and Apache), from seven locations in Serbia characterized by different climatic conditions in two production years, were used in this study. The analyses included a determination of proteolytic activity and the rheological properties of dough. Rheological properties of wheat flour dough were determined by Gluten index and Brabender equipment (Farinograph, Extensograph and Amylograph). The studies ended with a trial baking and estimation of textural properties of obtained bread. Large variability for all attributes evaluated was observed, with wider ranges in quality parameters across varieties than among growing locations. Wheat flour samples from 2012 production year were characterized by inferior quality parameters. Proteolytic activity and bread specific volume values for 2012 production year were significantly lower compared to 2011. These results indicate that level of proteolytic activity was under optimum for obtaining bread with higher specific volume.