No description available.

No description available.

No description available.

Milk coagulation consists of four overlapping phases: enzymic hydrolysis, micelle aggregation, gelation and syneresis. The objectives of this study were to determine the effects of added CaCl2 on milk coagulation and the relationship between enzymic hydrolysis and micelle aggregation with substrate at different concentrations. Addition of CaCl2 to milk is widely practiced in industry and in laboratories. This changes calcium concentration, pH and ionic strength. It is impossible to separate these three variables and investigate each one independently. Addition of low levels of CaCl2 shortens coagulation time and increases curd firming rate. Low levels of CaCl2 also accelerate the enzymic hydrolysis process. Calcium ions increase hydrolysis rate, but this effect is much smaller than that of lowered pH. Increase of ionic strength due to addition of CaCl2 has an adverse effect on enzymic hydrolysis. This dominates at high CaCl2 concentration, and the overall coagulation process slows down. Adding CaCl2 also promotes micelle aggregation. However, aggregation is retarded by high levels of added CaCl2. Results of this study show that about 90% of the κ-casein is hydrolyzed for diluted milk (1/3) to coagulate. Samples at normal concentration (12 g NDM/100 ml solution) require only 60% conversion of κ-casein to para-κ-casein. Addition of CaCl2 significantly decreases this percentage. This suggests a different aggregation and gelation process in samples containing added CaCl2 When pepstatin A is used to stop enzymic hydrolysis at different times, different degrees of κ-casein conversion are obtained. Micelles aggregate even at very low percentages of hydrolysis. Previous reports have stated that a micelle cannot participate in aggregation until almost all of its κ-caseins have been hydrolyzed.

Current vitamin D intakes in Canada are inadequate. The extension of vitamin D fortification to additional foods may be an effective and appropriate strategy for increasing vitamin D intakes in the general population. Cheese is potentially an ideal candidate for vitamin D fortification. We introduce the potential use of casein proteins as a vehicle for vitamin D3 fortification in industrially made cheeses where we found that over 90% of vitamin D3 added to milk was retained in both Cheddar and Mozzarella cheeses. Use of casein proteins for vitamin D3 fortification did not fully prevent vitamin D3 loss into whey. However the loss was minimized to approximately 8%. We then show that vitamin D3 is bioavailable from fortified Mozzarella cheese baked with pizza suggesting that the high temperature baking process does not significantly breakdown vitamin D3. Our findings could have important implications in increasing fortified food options for Canadians.

Current vitamin D intakes in Canada are inadequate. The extension of vitamin D fortification to additional foods may be an effective and appropriate strategy for increasing vitamin D intakes in the general population. Cheese is potentially an ideal candidate for vitamin D fortification. We introduce the potential use of casein proteins as a vehicle for vitamin D3 fortification in industrially made cheeses where we found that over 90% of vitamin D3 added to milk was retained in both Cheddar and Mozzarella cheeses. Use of casein proteins for vitamin D3 fortification did not fully prevent vitamin D3 loss into whey. However the loss was minimized to approximately 8%. We then show that vitamin D3 is bioavailable from fortified Mozzarella cheese baked with pizza suggesting that the high temperature baking process does not significantly breakdown vitamin D3. Our findings could have important implications in increasing fortified food options for Canadians.

No description available.

It is now generally accepted that casein is a heterogeneous material. Due to the development of more effective fractionation methods, the heterogeneity of casein is now known to be even more complicated than was indicated a few years ago. [...]

Selenium, an essential trace mineral that becomes anticarcinogenic at supranutritional levels, is readily incorporated into milk proteins when cows are fed high levels of selenium. The objective of this study was to investigate the effects of selenized milk protein on human mammary tumor progression. Four isonitrogenous diets with Se levels of 0.16, 0.51, 0.85 and 1.15 ppm were formulated by mixing low- and high-selenium milk protein isolates with a rodent premix. MCF-7 human breast cancer cells were inoculated into the mammary fat pad of female BALB/c nude mice implanted with slow-release 17 β-estradiol pellets. Mice with palpable tumors were randomly assigned to one of four diets for 10 weeks. Increasing Se intake reduced final tumor volume and the number of tumors > 500 mm3 in volume. There was a two-fold higher proportion of apoptotic cells in tumors exposed to the highest Se level. / Financial support was provided by Dairy Farmers of Ontario, Alltech Canada, Inc., and NSERC Canada.

The Mac-T cell system was used to investigate the role of the prolactin (PRL) receptor in cell proliferation and the regulation of milk protein synthesis. This study was designed to investigate whether overexpressing the PRLR in the Mac-T cell line resulted in a change in its growth rate and an enhancement of its ability to produce milk proteins. To accomplish these goals, Mac-T cells were stably transfected with the rabbit prolactin receptor gene. Fifteen clones and a pool of transfectants were obtained. Of these, one clone and the pool were positive for the PRL receptor expression. The clone (S15) and pool (SP) cells were sorted into high (H), medium (M), and low (L) expressors, of the PRLR. The high expressors were used for all subsequent experiments. The presence of high levels of the PRLR on the surface of S15 and SP cells was further confirmed by receptor binding assay and Western Blot. Following the establishment of these cell lines, the cells were used to investigate the effect of increased levels of PRLR on cell proliferation and milk protein synthesis. / It was found that the growth rate of parental cells was depressed in the presence of 5 mug/ml of PRL. In contrast, the growth rate of the transfectants was enhanced by the addition of 5 mug/ml PRL to the culture medium. In addition, both "SP" and "S15" cells produced higher levels of STAT5 upon long-term (48 h) PRL stimulation. No effect on the synthesis of alpha S1- and beta-caseins was noted. It is likely that no differences in protein synthesis were observed because the cells have lost the ability to differentiate, even when cultured on collagen gels in the presence of lactogenic hormones.