Investigating the Physicochemical Properties of Healthy Yogurt Containing Bitter Gourd Powder

 Yogurt is one of the most widely consumed fermented milk products, which, like any other dairy products, is prone to spoilage and poor quality. On the other hand consumers have become more cautious about their diet and health. Their is an increasing demand for food products with higher nutritional values and health benefits. The continuous improvement of the production process and the quality of yogurt is at the heart of manufacturers’ concerns. Also, finding a safe, cheap and affordable solution that, in addition to controlling blood sugar and preventing the complications of diabetes, relieves the pain of diabetic patients; has always been of interest to researchers. The medicinal plant Bitter gourd (Momordica charantia L.) from the cucurbitaceae family is used in traditional medicine to control blood sugar. Carla fruit is a rich source of phytochemical compounds such as proteins, steroids, alkaloids, mineral compounds, lipids, triterpenoids and polyphenols. Functional yogurt is one of the dairy products that can contain bioactive compounds in order to increase its acceptability and improve its nutritional and medicinal properties. Therefore, this study was carried out with the aim of producing colored yogurt containing Carla fruit powder in order to increase the variety of appearance, marketability of the product and improve the nutritional characteristics of yogurt with emphasis on the consumption of novel product.

 In this study, the effects of adding Carla powder to yogurt were investigated with the aim of producing a beneficial food for diabetics. Carla fruit was collected from the medicinal plants collection of the Agriculture Institute, Research Institute of Zabol, Zabol, Iran. Then it was washed with water and cut into thin layers. These parts were completely dried in an electric oven at 40 ºC for 48 hours and pulverized with an electric mill. Carla fruit powder was added to the samples in four levels of 0 (control), 0.2, 0.4 and 0.6%. Physicochemical properties of samples such as pH, acidity, viscosity (using Brookfield spindle viscometer) and water holding capacity were measured. Total phenol content was measured by Folin Ciocalteu reagent method. Antioxidant properties were investigated by scavenging rate of DPPH free radicals. The results were analyzed by SPSS version 21 statistical software at the probability level of 5% (P˂ 0.05). Duncan's multiple range test was performed to determine the statistically significant difference between the means.

 The results of this study showed that the highest pH (4.17) was detected in the control and the addition of Carla fruit powder led to a decrease in pH. Storage time also lower the pH in yogurt samples. The highest acidity (1.3%) was measured in the treatment containing 0.6% Carla fruit powder and the lowest (0.59%) was in the control. It means that adding Carla powder to yogurt leads to an increase in acidity. The highest amount of phenolic compounds (475.63 μg equivalent of gallic acid/ml yogurt), was calculated in a sample containing 0.6% of Carla fruit powder. However, extended storage time, decreases the amount of phenolic compounds. By increasing the percentage of Carla fruit powder in yogurt samples, the amount of antioxidant activity increased. So that the highest antioxidant activity (93%) was related to the treatment containing 0.6% Carla powder on the 28th day of the storage. In the present study, the highest percentage of water holding capacity (84%) was observed in samples containing 0.6% Carla powder. The lowest water holding capacity (57.61%) was measured in the control sample at the first day of storage.

 According to the results of this study, adding Carla powder to yogurt at the level of 0.6%, in addition to maintaining appearance properties, can increase its physicochemical properties and produce a novel food. In general, Carla powder can play a significant role in improving the textural properties of yogurt, and by increasing the viscosity and the water holding capacity, can reduce the negative effects of the storage period.