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Phytosterols are among the most important plant sterol compounds. This study was conducted to identify and determine the amount of phytosterols in distributed yogurts in Tehran by gas chromatography method without derivatization. A total of 60 yogurt samples, including 20 pasteurized high -fat yogurt samples, 20 pasteurized cream yogurt samples, and 20 traditional high -fat yogurt samples, were collected randomly from dairy product supply centers in Tehran from January to March 2022. Then, the amount of cholesterol and four phytosterol compounds including brassicasterol, campesterol, stigmasterol, and beta -sitosterol in yogurt samples were determined using gas chromatography assay without derivatization. The results showed that the total sterols in high -fat, creamy, and traditional yogurt samples were 504.08±55.79, 816.21±51.87, and 332.8±41.22 mg/100mL, respectively. The highest and lowest percentage of cholesterol belongs to cream (%54.75±065) and traditional yogurt (%46.57±0.65), respectively(p<0.05). Also, the highest percentage of phytosterol belongs to traditional yogurt(%54.75±065) and there was a significant difference with other yogurts(p<0.05). The results also showed that the total phytosterols were more than the permissible limit of the national standard (3%) in all samples. According to the results, phytosterols are used in various yogurts distributed in Tehran, which is against the national standard of Iran. Therefore, periodic and regular evaluation of phytosterols in distributed yogurts should be done throughout the year by regulatory bodies and prevent the violation of consumers' rights. [ABSTRACT FROM AUTHOR]

Pomegranate is rich in polyphenols and is an excellent source of antioxidants, such as polyphenolic substance. However, the concentration of the harvest time, poor shape and inconvenient for eating have limited the sale of pomegranates. Therefore, the processing of pomegranate is beneficial to the appreciation of pomegranate resources. Yogurt a good carrier for bioactive compounds that may offer additional health benefits, is a fermented dairy product suitable for all ages, and the new type yogurts with high qualities and extra functions are more favored by consumers. In order to accelerate the development of pomegranate processing industry, enrich the variety of yogurts and improve the quality of yogurts, in this paper, 1%, 3% and 5% pomegranate juice powder (PJP) whose contents of total carbohydrate, soluble protein and total polyphenols were 0.88 g/g, less than 1.0 mg/g and 0.471 0 mg/g, respectively, was used to replace sucrose in the matrix of set yogurt and the effects of PJP replacement on the parameters in fermentation process, including pH value, titratable acidity, apparent viscosity and lactic acid bacteria vitality were analyze. The Raman spectra, textural properties, rheological properties, total phenolic content and antioxidant activity of the set yogurt with and without PJP replacement were compared. The results indicated that PJP instead of sucrose does not significantly change the pH value, titrable acidity, apparent viscosity and Raman spectrum of the yogurt matrix at the end of fermentation, but the substitution of PJP had a significant (P< 0.05) effect on lactic acid bacteria during fermentation and the properties of yogurt. The replacement of sucrose by PJP defered the solidification time of yogurt, the exponential growth time and the maximum activity time of lactic acid bacteria, but it significantly (P<0.05) increased the maximum activity of lactic acid bacteria in yogurt. It took the control, LD, MD and HD groups 300 minutes, 240 minutes, 260 minutes and 280 minutes, respectively, to reach (4.6±0.1) of pH value, suggesting PJP replacement shortened the fermentation time. The lactic acid bacteria activity of the pomegranate yogurt was 6-7 times that of the control yogurt at the completion of fermentation. What's more, the substitution of PJP could significantly improve the quality of yogurt. The firmness, consistency, cohesiveness and index of viscosity of the control were (65.6±1.9) g, (939.8±61.8) g·s, (14.5±0.8) g and (36.5±9.2) g·s, respectively; while the HD group showed 1.84, 2.26 and 1.76 times that of the control, respectively. PJP-replacement yogurt showed better texture, viscoelasticity and antioxidant activity. Compared with the control, when sucrose was completely replaced by PJP, the total polyphenol content, FRAP and DPPH clearance rate were 1.84 times, 2.26 times and 1.76 times, respectively. Sensory test results showed that PJP substitution of sucrose had a positive effect on the appearance, texture and taste of yogurt, which may be related to the phenolic substance in PJP and the casein interaction in yogurt. PJP can significantly improve the health benefits and quality of yogurt, which is expected to replace sucrose to make healthier yogurt. [ABSTRACT FROM AUTHOR]

In recent years, yogurt products are usually developed and designed by using different raw materials and food additives, less by innovations of production processes. For the development of new technology for producing yogurt, considering the technical feasibility of nanofiltration concentration's application in yogurt production process, the paper put forward an idea for developing new yogurt products by improving the workmanship. In this study, the raw milk was concentrated by nanofiltration membrane when producing yogurt with transmembrane pressure of 1.0, 1.6, 2.0, 2.4 MPa and the milk temperature of 10, 15, 55, 65°C, respectively, in order to investigate the change of milk composition during concentration and its influence on yogurt texture and rheological parameters, as while as the influence of raw milk on nanofiltration membrane performance at different temperatures and pressures. The results indicate that, under the conditions of 65°C and 2.0 MPa, the concentration was feasible and it can be applied in yogurt production when the membrane flux is 7.5 L/(m2 h) and concentration time is about 85 min. The retention rates of monovalent ions of sodium, potassium, chlorine are 40.8%, 46.5% and 17.8%, respectively, while the divalent ions of calcium and magnesium are 94.2%, 95.7%, respectively, and the other milk contents, the lactose and protein, are 92.4% and 95.7%, respectively. The non-fat dry matter increases by 1.24 times, the fat increases by 1.3 times and the milk acidity increases by 1 degree. The viscosity of yogurt producing through concentration is 27.8 Pa·s, and which of yogurt without concentration is 16 Pa·s. With the texture profile analysis (TPA) on yogurt texture, the hardness, adhesiveness, gumminess and chewiness of yogurt with concentration is 0.4605 N, -0.6492 N·s, 0.3253 N·s and 0.2987 N·s, respectively, while the indexes of yogurt without concentration is -0.1102 N, -0.4787 N·s, 0.0680 N·s and -0.0586 N·s, respectively. These texture and rheological parameters of the yogurt with concentration are all superior to those of the yogurt without concentration technology. [ABSTRACT FROM AUTHOR]