Tomczyńska-Mleko M., Kamysz E., Sikorska E., Puchalski C., Mleko S., Ozimek L., Kowaluk G., Gustaw W., Wesołowska-Trojanowska M. (2014): Changes of secondary structure and surface tension of whey protein isolate dispersions upon pH and temperature. Czech J. Food Sci., 32: 82-89.The secondary structure of proteins in unheated and heated whey protein isolate dispersions and the surface tension of the solutions were investigated at different pH. Heating protein solutions at 80°C results in an increase of unordered structure. Nevertheless, the difference between the contents of unordered structure in the unheated and heated samples increases with increasing pH of the solution. At low protein concentrations the surface tension decreased with increasing protein concentration to about 5 mg/ml. For the heated solution, a similar trend was observed in the decrease in the surface tension with increasing concentrations of protein. In both cases, the curves depicting the surface tension as a function of protein concentration could be fitted to the exponential function with a negative exponent, but with the heated solutions lower values of surface tension were observed. Studies on the surface tension of whey protein isolate solutions prove that the unfolding of whey proteins, revealed by changes in the secondary structure, causes a decrease in the surface tension.

The aim of the paper was to investigate the effects of the addition of whey protein isolate (WPI) and whey protein concentrate (WPC80) on physicochemical properties of high‐protein yoghurts. Changes in storage, loss moduli, phase angle values, flow behaviour and textural parameters were determined. Surface properties (roughness, contact angles) were also estimated. The properties of yoghurts depended on the preparation type and their concentration. The application of WPI resulted in accelerated gel formation in comparison with the yoghurts produced with WPC80. This technology is addressed to particular consumers who search for new foods to meet their daily protein requirements.

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A new synthesis method of benzimidazoles, dihydroquinazolines, and other related compounds containing a 2,4‐dihydroxyphenyl moiety was elaborated. Their structures were identified from elemental, infrared, 1H NMR, 13C NMR, and mass spectra analyses. The minimal inhibitory concentration values of the compounds toward eight reference bacterial strains were determined by the two‐fold serial microdilution broth method. The compounds exhibited substantial inhibitory effects against the Gram‐positive strains tested contrary to Gram‐negative ones. The compounds of imidazopyridine, N‐methylbenzimidazole, and dihydroquinazoline structures exhibited the largest activity. The magnification of covering a two‐nitrogen atom heterocyclic ring fused to a benzene one decreases the biological effect. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:265–275, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21012

The aim of this study was to obtain whey protein concentrate-WPC/montmorillonite-MON biopolymers. Mixed whey protein/montmorillonite biopolymers were formed as heat-induced gels and hardened by water evaporation. Increase in protein concentration caused an increase in storage and loss moduli of the gels. Adding 5 % of MON to whey protein gel matrix caused an increase in the moduli value. Obtained biopolymers behaved as weak physical gels as loss tangent was in a range 0.25-0.45. Increase in protein concentration and addition of MON caused increase in viscosity of the biopolymers measured by dissipation of ultrasound vibrations. Addition of MON generally caused reinforcement of the structure of the mixed gels and the material was more resistant to puncture. Addition of MON caused changes in the microstructure of whey protein gel, which became more fine-stranded. It was probably caused by adsorption of the ions by MON. Drying of WPC/MON gels caused formation of very hard biopolymer, which can be applied as natural biodegradable material.