Bovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with a-Lactalbumin more susceptible than b-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins.

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Objective: In this study we aimed to evaluate the effects of casein and whey protein supplementation on examination stress. We have investigated different parameters of oxidative stress and immune function.Materials and Methods: The participants were divided into three groups: control, casein and whey. Casein and whey groups were supplemented with either casein or whey protein for 15 days. Blood samples were obtained at the beginning of the study (Day 0), on the examination day (Day 16) and five days after the examination (Day 21). Antioxidant capacity, glutathione, cortisol and cytokine levels (TNF-a, IL-6, IL-12) were measured.Results: An increase in antioxidant capacity and glutathione levels of the participants using whey protein was observed. Whey protein supplementation did not affect cortisol levels, but participants taking whey protein showed an increase in serum TNF-a and IL-6 levels. Conclusion:It is suggested that the use of whey protein strengthens the response to oxidative stress by increasing antioxidant capacity and glutathione levels, while supporting the immune system via cytokine release.

ÖZETMaterials and Methods: Different preparative techniques such as thin-film hydration, reverse-phase evaporation, freezethaw and periodic sonication were used to produce liposomes. These methods were used to encapsulate different antioxidant molecules and were compared for antioxidant activity. Light microscopy, fluorescence microscopy and particle size analyzers were used in order to characterize the prepared liposomes and to analyze their particle size, distribution and shape.Results: Liposomes containing water-soluble antioxidants such as vitamin C and polyphenols and fat-soluble antioxidant vitamin E were prepared. The separation of free molecules from those that were liposomed was performed with Sephadex G-25 gel filtration chromatography. The antioxidant activity of vitamin E liposomes was highest in comparison to the others.Conclusion: Among the methods we have used for preparing liposomes sonication is the fastest and also most advantageous because organic solvents such as methanol or chloroform are not used during preparation. Both water-soluble antioxidant molecules and lipid-soluble antioxidants could be prepared with this method and preserved their activities.

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