Yogurt base was prepared from reconstituted skim milk powder (SMP) with 2.5% protein and fortified with additional 1% protein (wt/wt) from 4 different milk protein sources: SMP, milk protein isolate (MPI), micellar casein (MC), and sodium caseinate (NaCN). Heat-treated yogurt mixes were fermented at 40 degrees C with a commercial yogurt culture until pH 4.6. During fermentation pH was monitored, and storage modulus (G') and loss tangent (LT) were measured using dynamic oscillatory rheology. Yield stress (sigma(yield)) and permeability of gels were analyzed at pH 4.6. Addition of NaCN significantly reduced buffering capacity of yogurt mix by apparently solubilizing part of the indigenous colloidal calcium phosphate (CCP) in reconstituted SMP. Use of different types of milk protein did not affect pH development except for MC, which had the slowest fermentation due to its very high buffering. NaCN-fortified yogurt had the highest G' and sigma(yield) values at pH 4.6, as well as maximum LT values. Partial removal of CCP by NaCN before fermentation may have increased rearrangements in yogurt gel. Soluble casein molecules in NaCN-fortified milks may have helped to increase G' and LT values of yogurt gels by increasing the number of cross-links between strands. Use of MC increased the CCP content but resulted in low G' and sigma(yield) at pH 4.6, high LT and high permeability. The G' value at pH 4.6 of yogurts increased in the order: SMP = MC < MPI < NaCN. Type of milk protein used to standardize the protein content had a significant impact on physical properties of yogurt. Practical Application: In yogurt processing, it is common to add additional milk solids to improve viscosity and textural attributes. There are many different types of milk protein powders that could potentially be used for fortification purposes. This study suggests that the type of milk protein used for fortification impacts yogurt properties and sodium caseinate gave the best textural results.
Micronutrients, such as beta-carotene and vitamins A and E, are potential chemopreventive agents; however, their concentrations in human target tissues are largely unknown. Because these micronutrients may exert their action at the site of target tissues, the tissue concentrations of the micronutrients need to be determined. In this cross-sectional study, we have measured the concentrations of seven carotenoids, two retinoids, and two tocopherols in paired plasma, buccal mucosal cells (BMC), and skin samples from 96 healthy subjects (ages 26-82 yrs). The plasma-tissue, as well as the diet-plasma and diet-tissue relationships of the micronutrients, and the impact of various potential confounders on the micronutrient concentrations were evaluated. The micronutrient concentrations of plasma and BMC used in the evaluation were the average of three measurements over a one-month period. Our data indicated that 1) the correlations between the plasma and BMC (Spearman r = 0.40-0.91, p < 0.05) and the plasma and skin (r = 0.24-0.75, p < 0.05) concentrations of most micronutrients were significant in all subjects, suggesting that the status of these micronutrients in the BMC and skin may be estimated from their plasma concentrations; 2) the correlations between the diet and plasma/tissue concentrations of the micronutrients were generally not as strong as the plasma-tissue relationships; the diet-plasma and diet-tissue relationships of the carotenoids were particularly poor in the smokers; 3) the plasma and tissue concentrations of most micronutrients were lower in smokers than in nonsmokers and higher in vitamin supplement users than in nonsupplement users; the differences remained significant after adjustment for age, gender, and diet intake estimates; 4) among the seven carotenoids examined, lycopene was unique, because its concentration was not lower in smokers or higher in supplement users but was inversely associated with age.
With increasing solar ultraviolet (UV)-B radiation reaching the Earth's surface and the incidence of skin cancer rising steadily, there is an ever-increasing need to determine agents that modulate photocarcinogenesis and to understand the mechanisms underlying this modulation. Our laboratory has demonstrated that topical application of the dl-alpha-tocopherol form of vitamin E to mice prevents skin cancer and the immunosuppression induced by UVB irradiation. However, dl-alpha-tocopherol has limited stability at room temperature. The current study was designed to ask whether the thermostable esters of vitamin E, alpha-tocopheryl acetate, or alpha-tocopheryl succinate prevent skin cancer and immunosuppression induced in mice by UV radiation. In the alpha-tocopheryl acetate study, skin cancers developed in 70% of UVB-irradiated control mice and in 90%, 73%, and 90% of mice receiving topical applications of 12.5, 25, and 50 mg of dl-alpha-tocopheryl acetate, respectively. In the alpha-tocopheryl succinate study, skin cancer developed in 59.3% of control UVB-irradiated mice and in 82%, 100%, and 81.5% of mice treated with 2.5, 12.5, and 25 mg d-alpha-tocopheryl succinate, respectively. Thus neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented photocarcinogenesis. At 12.5 and 25 mg/treatment, alpha-tocopheryl acetate and alpha-tocopheryl succinate, respectively, enhanced photocarcinogenesis (p = 0.0114 and 0.0262, respectively, log rank test). On the basis of high-performance liquid chromatography analysis at 16-17 weeks after the first vitamin E treatment, the esterified forms of vitamin E applied epicutaneously accumulated in the skin, but the levels of free alpha-tocopherol remained low. Neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented the induction by UV radiation of immunosusceptibility to implanted syngeneic antigenic UV-induced tumor cells. Thus alpha-tocopheryl acetate or alpha-tocopheryl succinate not only failed to prevent photocarcinogenesis, but may have enhanced to process. Considering that alpha-tocopherol esters are included in many skin lotions, cosmetics, and sunscreens, further studies are needed to determine the conditions under which topical alpha-tocopheryl acetate and alpha-tocopheryl succinate enhance photocarcinogenesis.
Although distal lesions can predict the risk of advanced proximal polyps, a substantial portion of Chinese with advanced proximal polyps is not associated with any distal sentinel lesions. These data have implications for screening policy of colon cancers in Taiwanese Chinese.
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