Changes in protein nutritional quality in fresh and recombined ultra high temperature treated milk during storage.

The objective of this study was to determine the changes in nutritional quality of protein in stored UHT milk. Commercial fresh and recombined ultra high temperature (FUHT and RUHT respectively) treated milk samples were used. Pasteurized milk (P-milk) samples were used for comparison. Milk samples were freeze-dried for the use in diet formulation. Pasteurized milk samples were freeze-dried within 24 h of production. FUHT and RUHT milk samples were freeze-dried after production (zero time), 3 and 6 months of storage at 37 degrees C. Three nitrogen balance experiments were done at zero time, after 3 and 6 months of storage. The diet used in all experiments were similar in composition except for protein source. In each experiment egg white (low protein), casein (control), P-milk, and either 0, 3 or 6 months old FUHT and RUHT milk samples were used as the source of protein in the diets. In each experiment 30 (six for each diet) male Sprague-Dawley rats were used. Apparent digestibility (AD), true digestibility (TD), biological value (BV), and net protein utilization (NPU) were calculated for protein in casein and all milk samples. The nutritional quality of protein in FUHT milk before storage was similar to that of protein in pasteurized milk, but it decreased during storage for 3 months and then remained at the same quality up to 6 months of storage. BV and NPU of protein in FUHT milk after storage for 3 and 6 months were lower than that of protein in pasteurized milk by 4% (not significant) and 5% respectively. On the other hand, the nutritional quality of protein in RUHT milk before storage was lower than that of protein in pasteurized milk and remained at the same level after storage for 3 months: however, it decreased significantly after storage for 6 months. AD and TD of protein in RUHT milk stored for 6 months were lower than that of protein in pasteurized milk by 5% and BV and NPU were lower than that of protein in pasteurized milk by 9 and 12% respectively. The above reduction in nutritional quality of protein in UHT milk may be of significant value in feeding young children who might be dependent on this type of milk in their diet.

Comparative Study on the Deterioration of Oils by Microwave and Conventional Heating.

Refined cottonseed oil and hydrogenated palm oil were heated by two methods, conventionally by gas-cooker (deep fat frying) and by microwave energy. Quality assurance methods such as refractive index, color, diene content, acid value, peroxide value, thiobarbituric acid value, iodine value, petroleum ether insoluble oxidized fatty acid content, and degree of polymerization were determined. Exposing the oil samples to various heating times and microwave oven power levels caused some hydrolysis to free fatty acids and accelerated the formation of hydroperoxides and secondary oxidation products. The value from each test increased with both the power settings of the microwave oven and the time of heating. In general, the development of rancidity for refined cottonseed oil heated by microwaves was twice as fast as that produced by conventional heating. Also, the chemical values indicating deterioration for refined cottonseed oil were much higher for refined cottonseed oil than for hydrogenated palm oil in all cases. Gas-liquid chromatographic analysis of fatty acids obtained from the heated oils indicates the occurrence of oxidative degradation and production of short-chain acids.

The influence of dietary folate supplementation on the incidence of teratogenesis in zinc-deficient rats.

Two studies were conducted to investigate the possibility that pteroylmonoglutamic acid supplementation would alleviate teratogenesis in zinc-deficient rats. Pregnant rats of the Wistar strain were fed on Zn-deficient (less than 0.5 mg Zn/kg) or Zn-supplemented (75 or 95 mg Zn/kg) diets from mating until day 18.5 of gestation. The basal level of pteroylmonoglutamic acid added to all diets (0.56 mg/kg) was supplemented with 30-200 mg/kg in selected diets. Dietary Zn deprivation resulted in fetal resorption, fetal growth retardation and reduced concentrations of Zn in fetuses and maternal plasma and tibia. Low maternal body-weight at conception emerged as an important determinant of risk of resorption in Zn-deficient rats. Dietary Zn deficiency resulted in reduced maternal plasma folate concentrations and these values were inversely correlated with litter size or weight in Zn-deficient rats. Pteroylmonoglutamic acid supplementation increased maternal plasma folate concentrations, but did not reduce the high incidence of teratogenesis which occurred in Zn-deficient rats. Supplementation of Zn-deficient rats with pteroylmonoglutamic acid significantly increased the incidence of clubbed foot and tended to increase the incidence of brain or meningeal abnormalities, or both, and cleft palate, but did not reduce maternal or fetal Zn status. Pteroylmonoglutamic acid supplementation also increased the weights of Zn-supplemented control fetuses.

Antimicrobial Activity of Some Egyptian Spice Essential Oils.

Six spice essential oils (sage, rosemary, caraway, cumin, clove, and thyme) and their basic ingredients were tested for their inhibitory effect against 3 strains of Gram-negative bacteria, 4 strains of Gram-positive bacteria, one acid fast bacterium, and one yeast. Preliminary screening of antimicrobial activity of the essential oils was done using the filter paper disc agar diffusion method. The minimum inhibitory concentration for each essential oil against various micro-organisms was also measured. Very low concentrations (0.25 - 12 mg/ml) of the various essential oils were sufficient to prevent microbial growth. The data show that Gram-positive bacteria were more sensitive to the antimicrobial compounds in spices than Gram-negative. The inhibition zones of different microbial growth produced by various essential oils were similar to those produced by their basic compounds. Thyme and cumin oils possessed very strong antimicrobial activity compared with the other essential oils. There was a relationship between the chemical structures of the most abundant compounds in the essential oils under investigation and the antimicrobial activity.