The consumption of polyphenols in green tea has been associated with beneficial health effects. Although polyphenols are unstable in the intestinal environment, they may be protected by interactions with dairy proteins during digestion. The objectives of this study were to evaluate the effect of a green tea extract on the digestibility of different dairy matrices and to monitor the antioxidant activity of these matrices with or without the green tea extract during digestion in a simulated gastrointestinal environment. Milk, yogurt and cheese with similar fat-to-protein ratios were subjected to simulated digestion. Matrix degradation, protein and fat hydrolysis, polyphenol concentration and radical scavenging activity were analyzed during gastric and intestinal digestion phases. Cheese was the matrix most resistant to protein and fat digestion. The addition of the green tea extract significantly decreased proteolysis in the gastric phase but had no effect in the intestinal phase. The kinetics of fatty acid release was reduced by the presence of the green tea extract. Transition from the gastric phase to the intestinal phase induced a 50% decrease in the antioxidant activity of the control (tea extract dispersed in water) due to the degradation of polyphenols. The presence of dairy matrices significantly improved polyphenol stability in the intestinal phase and increased the antioxidant activity by 29% (cheese) to 42% (milk) compared to the control. These results suggest that simultaneous consumption of green tea and dairy products helps to maintain the integrity and antioxidant activity of polyphenols during digestion.

A simple approach is proposed to recover native protein and phospholipid fractions from butter-making process using equipments available in dairy-processing plant. A washing treatment was used to remove protein from the cream and increase the phospholipids purity in buttermilk. Cream from a first separation was diluted with milk ultrafitration permeate and separated a second time. A 10X dilution factor reduced protein concentration in the cream from 1.6 ± 0.2 to 0.52 ± 0.03%. As a result, the phospholipids to protein ratio in buttermilk increased from 53 ± 10 to 172 ± 7 mg g )1 . In butter-making process, an important portion of total phospholipids (26%) is retained in butter. Butter serum made from washed cream could then be used to produce phospholipid concentrates with phospholipids to protein ratio of 473 ± 3 mg g )1 . Interestingly, the extracts from butter serum are characterised by a higher proportion of sphingomyelin compared with those from buttermilk.

Foods are complex nutrient assemblies which are subjected to various industrial processes that can influence their nutritional value. The food matrix acts as a nutrient-release regulator, and further understanding of its behavior during digestion is essential. The objective of this study was to compare the kinetics of matrix degradation and fatty acids release for different cheeses in a gastro-intestinal environment. The relationship between the physical characteristics of the cheeses (rheological properties, microstructure) and their digestion pattern was also studied. Rheological measurements, compositional and microstructure analyses were performed on mild Cheddar, aged Cheddar, light Cheddar and Mozzarella cheeses. Cheese samples were subjected to simulated digestion. Matrix degradation index, free oil, free fatty acids and fat droplet distribution were analyzed after 5, 30, 60, 120, 150, 180 and 240 min of digestion. Mozzarella cheese showed the highest rate of matrix degradation, free oil and fatty acids release. Aged Cheddar cheese showed rapid degradation during the gastric phase, but was more resistant to the duodenal environment. Light Cheddar showed the opposite behavior, being highly resistant to the gastric environment; however, it underwent extensive degradation at the end of the duodenal phase. The extent of matrix degradation for mild Cheddar was similar to that of Mozzarella in the gastric phase but was much lower than that of other cheeses in the duodenal phase. The cheeses under study exhibited very different digestion patterns, and these differences are discussed in relation to cheese matrix composition, microstructure and rheological properties. Results suggest that cheese degradation and kinetics of fatty acids release are mainly driven by cheese physical characteristics.

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A washing treatment was applied to caprine cream before churning in order to improve phospholipids and MFGM protein purification from buttermilk and butter serum. Cream obtained from a first separation was diluted with water and separated a second time using pilot plant equipment. Regular and washed creams were churned to produce buttermilk and butter, from which butter serum was extracted. The washing treatment allowed a significant decrease of the casein content. As a result, the phospholipids-to-protein ratios in washed buttermilk and butter serum were markedly increased by 2.1 and 1.7-folds respectively, which represents an advantage for the production of phospholipids concentrates. However, when compared with bovine cream, lower phospholipids-to-protein ratios were observed when the washing treatment was applied to caprine cream. A higher concentration of MFGM protein and a lower retention of phospholipids during washing treatment are responsible for the lower phospholipids-to-protein ratios in buttermilk and butter serum obtained from caprine cream. The phospholipids distribution in the butter making process was similar to the one obtained from bovine regular and washed cream. Phospholipids were preferentially concentrated in the butter serum rather than the buttermilk fraction. This simple approach permitted the production of caprine and bovine butter sera extracts containing up to 180 and 240 g phospholipids/kg sera, respectively, on a dry basis.