A gas chromatographic procedure for analysis of sterols was developed to detect possible addition of vegetable oils to milk, yoghurt and butter samples. The method involved fat extraction, saponification, hexane extraction, silylation of sterols and then analysis by gas chromatography. The sterol content of 102 samples of milk, yoghurt and butter was determined. Phytosterol content higher than 5% of total sterol was observed in four samples of milk and yoghurt. Principal component analysis showed that there was a direct relationship between the level of phytosterols and fat percentage in yoghurt samples. The described method is accurate and reliable enough to be employed regularly in food quality laboratories.

Cheese and yogurt are two kinds of nutritious dairy products that are used worldwide. The major preservatives in dairy products are sodium benzoate, potassium sorbate, and natamycin. The maximum permitted levels for these additives in cheese and yogurt are established according to Iranian national standards. In this study, we developed a method to detect these preservatives in dairy products by reversed phase chromatography with UV detection in 220 nm, simultaneously. This method was performed on C18 column with ammonium acetate buffer (pH = 5) and acetonitrile (73 : 27 v/v) as mobile phase. The method was carried out on 195 samples in 5 kinds of commercial cheeses and yogurts. The results demonstrated insufficient separation where limit of detection (LOD) and limit of quantitation (LOQ) ranged from 0.326 to 0.520 mg/kg and 0.989 to 1.575 mg/kg in benzoate and sorbate, respectively. The correlation coefficient of each calibration curve was mostly higher than 0.997. All samples contained sodium benzoate in various ranges. Natamycin and sorbate were detected in a remarkable amount of samples, while, according to Iranian national standard, only sorbate is permitted to be added in processed cheeses as a preservative. In order to control the quality of dairy products, determination of preservatives is necessary.

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Objective The use of amino acid supplements among athletes for reducing muscle injuries has become more popular. This study aims to examine the effect of branched-chain amino acids (BCAA) consumption before exhaustive exercise along with one month vitamin E supplementation on lactate dehydrogenase (LDH) and creatine kinase (CK) levels of active females. Methods In this study, 32 active female students of Razi University in Kermanshah, Iran aged 18-23 years were selected and, after obtaining the informed consent form them, were randomly divided into four groups of placebo (n=8), Vitamin E (n=8), BCAA (n=8), and Vitamin E+BCAA (n=). Vitamin E was consumed as 400 IU daily for a month and BCAA with lemon juice was consumed 2.5 hours before exercise four times with a 30-min interval. The exercise program included 30 minutes of cycling on an ergometer with 50% of the aerobic capacity, and immediately followed by cycling with 75% of the aerobic capacity until the exhaustion. Sampling was done immediately and 48 hours after the exercise, and data were analyzed using Shapiro-Wilk test, repeated measures ANOVA, Bonferroni test, and Pearson correlation test in SPSS software, version 22. Results None of the supplements had a significant effect on levels of LDH and CK immediately after the exercise (P>0.05), but 48 hours after the exercise, the mean levels of LDH and CK decreased in BCAA group (CK: 199.4±11.00, LDH: 213.2±23.44) and Vitamin E+BCAA (CK: 188.3±3.20, LDH: 208.3±40.12) compared to Vitamin E and placebo groups (P = 0.001). Their lowest levels was observed in the Vitamin E+BCAA group which was negatively correlated to plasma leucine and isoleucine levels (P = 0.001). Conclusion Although BCAA consumption alone before exhaustive exercise can reduce muscular damage indicators in active females, it seems that leucine and isoleucine along with Vitamin E supplementation is more effective in reducing muscular damage.