Antioxidant properties of whey protein hydrolysates as measured by three methods

Four microbial proteases (Alcalase, Flavourzyme, Neutrase and Protamex) were used for the preparation of whey protein hydrolysates. The aim of this research was to find out whether these hydrolysates can be used as a source of whey derived antioxidants. Hydrolyzed samples, including their unhydrolyzed protein solutions were tested by the ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) decolorization assay, by the total radical-trapping potential method and by the assay of liposomes peroxidation (fluorescence photometry). Antioxidant properties were enhanced by hydrolysis in most of cases. Alcalase hydrolysates were found as the most effective antioxidants as determined by ABTS assay (~50% of antioxidant activity at 0.1 mg ml⁻¹ of hydrolysate in reaction) and fluorescence photometry. Liposomes were oxidized ~50% less (1.1 μM of α-tocopherol equivalent) with Alcalase hydrolysates additive (at 5.85 mg ml⁻¹ of hydrolysate in reaction). Hydrolysates did not inhibit the oxidation of liposomes at concentrations below 1.0 mg ml⁻¹ in reaction. On the contrary, results of total trapping potential method did not agree with findings observed in other tests. In this assay, Neutrase hydrolysates showed the best antioxidant properties. Pro-oxidant properties were observed in solutions containing (prior to the enzyme Protamex addition only) intact whey protein as determined by the measurement of the liposome peroxidation. The ABTS assay was optimized for the evaluation of the antioxidant activity in whey protein hydrolysates. The reaction time should be prolonged to avoid underestimation of the antioxidant activity.     

Contribution to the investigation of microsegregation processes in 13% Cr 4% Ni steel during long-term annealing at 400°C

The present paper deals with the study of the development of microsegregation processes in the 13% Cr 4% Ni martensiteaustenite stainless steel during long-term annealing. The long-term annealing of 13% Cr 4% Ni steel at 400°C is accompanied by the decrease in notch impact toughness values, which is associated with an increasing tendency to the occurrence of the brittle failures. The conditions for the transition from the transcrystalline brittle failure to the intercrystalline brittle failure depend on the initial heat treatment affecting the achieved microstructure of investigated steel. The higher frequency occurrence of intercrystalline failure on the fracture surfaces of notch impact toughness specimens is accompanied by an enrichment of the prior austenite grain boundaries by phosphorus and nitrogen. At the same time the enrichment of intercrystalline fracture surfaces by nickel, or chromium was also observed. The application of an additional intercritical annealing after quenching accelerates the formation of intercrystalline failure towards shorter times during the isothermal annealing at 400°C.     

Early stage of diamond growth at low temperature

We investigate the first stages of nanocrystalline diamond (NCD) thin film growth at low substrate temperature. NCD films were grown on silicon substrates by microwave plasma enhanced chemical vapor deposition (CVD) for 0–300 min at a temperature of 410 °C. Si substrates were ultrasonically seeded in suspension of detonation nanocrystalline diamond powder. The seeding density approached values up to 1 ⁎ 10¹² cm^− 2, which allows growth of ultra-thin fully closed layers. Stagnation of the AFM roughness indicates that the low temperature NCD growth is a) delayed due to the surface contamination of the used nanodiamond powder and b) possibly dominated by the growth in the lateral direction. XPS measurements showed that the measured surface exhibits changes from a multi-phase composite (seeding layer) to single-phase one (NCD layer).