| Abstrakt: |
Background: Milk is a complex physiological and biological liquid that contains water, protein, lactose, fat, vitamins, and minerals. Milk proteins (lactoferrin and lactoperoxidase) are known to have antimicrobial and immunomodulatory effects. More than half of the world's population consumes buffalo milk and milk products. Due to its unique properties, buffalo milk is highly regarded in developing countries and has been cultured in Iran for a long time. The main proteins of milk are casein and whey. Casein exists in the form of micelles, and 80% of milk proteins include alpha S1 casein, alpha S2 casein, beta casein, and kappa casein. Whey proteins comprise about 20% of milk proteins, which have four main components, including betalactoglobulin, alphalactalbumin, bovine serum albumin, and immunoglobulin. Lactoferrin, peptone protease, calmodulin, prolactin, and folate-binding proteins are also found in milk and are considered accessory proteins. Milk proteins have positive effects on different structures of the body, such as the immune, nervous, digestive, and cardiovascular systems. In addition, milk proteins are considered to contain a wide variety of biologically active peptides with superior nutritional and immunological activities. Therefore, obtaining complete information about the physicochemical properties of milk from different species and its nutritional value seems essential for liquid milk technology. Milk proteins have been analyzed continuously, and the information about this very important and complex system has been increasingly rising in recent years, mainly due to technological advances. In addition, the scope of research work on the analysis of proteins in milk has increased significantly due to the increased knowledge of bioactive proteins in milk. The present study aimed to measure the total protein values of cow and buffalo milk samples in the climatic conditions of Khuzestan province. The electrophoretic pattern of buffalo milk proteins was also compared with cow milk. Methods: Milk samples were collected from 30 apparently healthy cows and 30 buffaloes from the surrounding villages of Shushtar City and cattle farms of Masjid Suleiman City. Raw milk proteins were then evaluated by the Kjeldahl method. To measure milk proteins, milk was first digested with the addition of sulfuric acid with gentle heat. Complete digestion continued until the milk became colorless. After cooling, distillation was done by adding boric acid and methyl red, and the contents were titrated with 0.1 normal tetrazole sulfuric acid. The first color change marked the end of the titration, followed by calculating the protein content. After separating milk serum, the milk protein content in these two types of animals was compared with the sodium dodecyl sulfate (SDS) plate method. In this technique, milk protein molecules are linearized using SDS, and their movement is based on weight, that is, the larger the protein, the shorter the traveled distance. The relationship between the distance traveled by proteins and the logarithm of their molecular weight was investigated and milk proteins were identified in the samples. T-test statistical analysis was used to compare the average total protein in cows and buffaloes at a 95% confidence level as the statistical significance (p < 0.05). Results: In sodium dodecyl sulfate plates, standard samples were able to create 14, 18, 22, and 70 kD bands for alpha-lactalbumin, beta-lactoglobulin, casein, and albumin proteins according to the protein marker. The average protein contents of buffalo and cow milk samples were equal to 4.71±1.79 and 3.91±1.19 mg/liter, respectively, meaning that the total protein content in buffalo milk is significantly higher than that of the cow (p < 0.05). In addition, cow's milk contained lower levels of beta-lactoglobulin and casein than buffalo's milk while the amount of alpha-lactalbumin in cow's milk was higher than in buffalo's milk. The bands obtained from the electrophoresis of casein and alpha-lactalbumin on the gel showed genetic diversity among the subunits of casein and alpha-lactalbumin in cow and buffalo milk samples. Conclusion: In the comparison of the protein profile in animal milk, various reports show that protein profiles of milk are different in animal species. So far, the protein profile of buffalo milk has not been compared in the literature, which was investigated in this study. In general, the present study shows that cow and buffalo milk are different in terms of the protein profile due to the higher total protein content, especially the casein and beta-lactoglobulin levels in buffalo's milk than in cow's milk. It seems that the nutritional value of buffalo milk is higher than cow milk. [ABSTRACT FROM AUTHOR] |
