The effect of various heat treatments on the antioxidant capacity of milk before and after simulated gastrointestinal digestion

The Effects of Feeding Milled Rapeseed Seeds with Different Forage:Concentrate Ratios in Jersey Dairy Cows on Milk Production, Milk Fatty Acid Composition, and Milk Antioxidant Capacity

We aimed to evaluate the effects of milled rapeseed (MR) supplementation of low- or high-concentrate diets on milk production and composition, fatty acids (FAs) profile, and antioxidant capacity. Sixteen Jersey dairy cows were used in a 4 × 4 Latin square design, for four periods of 4 weeks, and assigned to four treatments as a 2 × 2 factorial design. Dietary treatments consisted of iso-nitrogenated total mixed rations with high (65:35; LC-low concentrate) or low (50:50; HC-high concentrate) forage:concentrate (FC) ratios, supplemented with MR to provide 30 g oil/kg dry matter (DM) (LR and HR), or without MR supplement (L and H). Increasing the proportion of concentrates led to an increase in DM intake (DMI), net energy (NE_L) intake, and milk production, but milk fat and protein content decreased. Supplementing diets with MR led to an increase in NE_L intake and milk production, but did not affect DMI and milk composition. Diets supplemented with MR caused a decrease in the concentration of FAs with atherogenic effect and the increase in the level of FAs beneficial for human health (C18:1 cis-9, C18:1 trans-11, and C18:3 n-3), while the decrease in the FC ratio had a negative effect on omega-3 FAs. An improvement in the antioxidant capacity of milk was observed with diets with the high FC ratio but also by supplementing the feed with MR. These results could contribute to the development of effective strategies to improve the nutritional quality of milk without affecting the productive performance of cows.

Food Protein-Derived Antioxidant Peptides: Molecular Mechanism, Stability and Bioavailability

The antioxidant activity of protein-derived peptides was one of the first to be revealed among the more than 50 known peptide bioactivities to date. The exploitation value associated with food-derived antioxidant peptides is mainly attributed to their natural properties and effectiveness as food preservatives and in disease prevention, management, and treatment. An increasing number of antioxidant active peptides have been identified from a variety of renewable sources, including terrestrial and aquatic organisms and their processing by-products. This has important implications for alleviating population pressure, avoiding environmental problems, and promoting a sustainable shift in consumption. To identify such opportunities, we conducted a systematic literature review of recent research advances in food-derived antioxidant peptides, with particular reference to their biological effects, mechanisms, digestive stability, and bioaccessibility. In this review, 515 potentially relevant papers were identified from a preliminary search of the academic databases PubMed, Google Scholar, and Scopus. After removing non-thematic articles, articles without full text, and other quality-related factors, 52 review articles and 122 full research papers remained for analysis and reference. The findings highlighted chemical and biological evidence for a wide range of edible species as a source of precursor proteins for antioxidant-active peptides. Food-derived antioxidant peptides reduce the production of reactive oxygen species, besides activating endogenous antioxidant defense systems in cellular and animal models. The intestinal absorption and metabolism of such peptides were elucidated by using cellular models. Protein hydrolysates (peptides) are promising ingredients with enhanced nutritional, functional, and organoleptic properties of foods, not only as a natural alternative to synthetic antioxidants.

Protective effects of whey protein hydrolysate on Bifidobacterium animalis ssp. lactis Probio-M8 during freeze-drying and storage

We evaluated the potential of whey protein hydrolysate as a lyoprotectant for maintaining the cell viability of Bifidobacterium animalis ssp. lactis Probio-M8 during freeze-drying and subsequent storage. The moisture content and water activity of the lyophilized samples treated by different concentrations of whey protein hydrolysate were ≤5.23 ± 0.33 g/100 g and ≤0.102 ± 0.003, respectively. During storage at 25°C and 30°C, whey protein hydrolysate had a stronger protective effect on B. lactis Probio-M8 than the same concentration of whey protein. Using the Excel tool GinaFit, we estimated the microbial inactivation kinetics during storage. Whey protein hydrolysate reduced cell damage caused by an increase in temperature. Whey protein hydrolysate could protect cells by increasing the osmotic pressure as a compatible solute. Whey protein hydrolysate improved cell membrane integrity and reduced the amounts of reactive oxygen species and malondialdehyde produced. The findings indicated that whey protein hydrolysate was a novel antioxidant lyoprotectant that could protect probiotics during freeze-drying and storage.

Antioxidant Activity of Milk and Dairy Products

The aim of the study was to present a review of literature data on the antioxidant potential of raw milk and dairy products (milk, fermented products, and cheese) and the possibility to modify its level at the milk production and processing stage. Based on the available reports, it can be concluded that the consumption of products that are a rich source of bioactive components improves the antioxidant status of the organism and reduces the risk of development of many civilization diseases. Milk and dairy products are undoubtedly rich sources of antioxidant compounds. Various methods, in particular, ABTS, FRAP, and DPPH assays, are used for the measurement of the overall antioxidant activity of milk and dairy products. Research indicates differences in the total antioxidant capacity of milk between animal species, which result from the differences in the chemical compositions of their milk. The content of antioxidant components in milk and the antioxidant potential can be modified through animal nutrition (e.g., supplementation of animal diets with various natural additives (herbal mixtures, waste from fruit and vegetable processing)). The antioxidant potential of dairy products is associated with the quality of the raw material as well as the bacterial cultures and natural plant additives used. Antioxidant peptides released during milk fermentation increase the antioxidant capacity of dairy products, and the use of probiotic strains contributes its enhancement. Investigations have shown that the antioxidant activity of dairy products can be enhanced by the addition of plant raw materials or their extracts in the production process. Natural plant additives should therefore be widely used in animal nutrition or as functional additives to dairy products.

How processing may affect milk protein digestion and overall physiological outcomes: A systematic review

Dairy is one of the main sources for high quality protein in the human diet. Processing may, however, cause denaturation, aggregation, and chemical modifications of its amino acids, which may impact protein quality. This systematic review covers the effect of milk protein modifications as a result of heating, on protein digestion and its physiological impact. A total of 5363 records were retrieved through the Scopus database of which a total of 102 were included. Although the degree of modification highly depends on the exact processing conditions, heating of milk proteins can modify several amino acids. In vitro and animal studies demonstrate that glycation decreases protein digestibility, and hinders amino acid availability, especially for lysine. Other chemical modifications, including oxidation, racemization, dephosphorylation and cross-linking, are less well studied, but may also impact protein digestion, which may result in decreased amino acid bioavailability and functionality. On the other hand, protein denaturation does not affect overall digestibility, but can facilitate gastric hydrolysis, especially of β-lactoglobulin. Protein denaturation can also alter gastric emptying of the protein, consequently affecting digestive kinetics that can eventually result in different post-prandial plasma amino acid appearance. Apart from processing, the kinetics of protein digestion depend on the matrix in which the protein is heated. Altogether, protein modifications may be considered indicative for processing severity. Controlling dairy processing conditions can thus be a powerful way to preserve protein quality or to steer gastrointestinal digestion kinetics and subsequent release of amino acids. Related physiological consequences mainly point towards amino acid bioavailability and immunological consequences.

In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence

The antioxidant potential (AP) is an important nutritional property of foods, as increased oxidative stress is involved in most diet-related chronic diseases. In dairy products, the protein fraction contains antioxidant activity, especially casein. Other antioxidants include: antioxidant enzymes; lactoferrin; conjugated linoleic acid; coenzyme Q10; vitamins C, E, A and D3; equol; uric acid; carotenoids; and mineral activators of antioxidant enzymes. The AP of dairy products has been extensively studied in vitro, with few studies in animals and human subjects. Available in vivo studies greatly differ in their design and objectives. Overall, on a 100 g fresh weight-basis, AP of dairy products is close to that of grain-based foods and vegetable or fruit juices. Among dairy products, cheeses present the highest AP due to their higher protein content. AP of milk increases during digestion by up to 2·5 times because of released antioxidant peptides. AP of casein is linked to specific amino acids, whereas β-lactoglobulin thiol groups play a major role in the AP of whey. Thermal treatments such as ultra-high temperature processing have no clear effect on the AP of milk. Raw fat-rich milks have higher AP than less fat-rich milk, because of lipophilic antioxidants. Probiotic yoghurts and fermented milks have higher AP than conventional yoghurt and milk because proteolysis by probiotics releases antioxidant peptides. Among the probiotics, Lactobacillus casei/acidophilus leads to the highest AP. The data are insufficient for cheese, but fermentation-based changes appear to make a positive impact on AP. In conclusion, AP might participate in the reported dairy product-protective effects against some chronic diseases.