UTILIZATION OF HIGH ACID MILK

Abstract

Mozzarella cheese is a good source of nutrients namely protein, fat, minerals and vitamins. Investigation was carried out to develop an appropriate technique to utilize high acid cow milk (HAM) for preparation mozzarella cheese. Mozzarella cheese was made using cow's milk. Resulted Mozzarella cheeses were made using different rennet and starter culture combination. Therefore, this investigation was carried out in three parts. Part I: Physicochemical and bacteriological qualities of high acid milk were evaluated in order to determine changes occur in milk. Samples have been left each at room temperature for 24 hours. The total bacterial count, coliform count and psychrotrophic bacteria of fresh milk were lower than that of high acid milk. Lactose content and pH value were higher in fresh milk than in high acid milk, but the titratable acidity had a tendency to increase by the time. Part II: Utilization of high acid milk in manufacture of Mozzarella cheese: The milk was divided into three parts A, B and C by the manufacturing procedures. First part (A): four types of Mozzarella cheese were manufactured, using only rennet. Second part (B): five types of Mozzarella cheeses were manufactured, using a starter culture and rennet. Third part (C): one type of Mozzarella cheese was manufactured, without using a starter culture or rennet. These parts were divided according to the age of the milk at setting (0, 4, 6,12and 24h). The resultant cheese was analyzed for chemical, physical, rheological and microbiological properties. Color analyses revealed that: Cheese samples prepared using rennet showed higher L-values than those prepared by use of starter culture and rennet. The yield value for Mozzarella cheese remarkably decreased by the increase age of the milk (pH decreasing), The yield of cheese samples B (0,4and 6h) was higher than A. All tested cheese samples showed recoverable elasticity and did not reached the fracture state at the end of the deformation test. Part III: Physiochemical and rheological properties of Mozzarella cheese utilizing high acid milk: In this part, six types of Mozzarella cheese were selected (6,12 and 24h). First part (A): three types of Mozzarella cheese were manufactured, using only rennet. Second part (B): three types of Mozzarella cheeses were manufactured, using a starter culture and rennet, as in conventional manufacture of the control cheese. The data indicated that the highest ratio of TS, fat and protein lost in the whey resulted during manufacture of B24 treatment. Cheese A12 had remarkably the highest level of protein and TS, (30.93 and 53.31, respectively ).The fat content of the B12, A24 cheeses was remarkably higher than that of the B6, B24, A6 and A12 cheeses, which had a similar fat content. Non remarkable difference was found in ash and salt content of all cheeses samples. The results revealed that a gradual increase was observed in acidity value during storage of all treatments. The data indicated that A6 treatment had the highest meltability, oil separation and free oil values, while B24 possessed the lowest value. As the time period of storage increased, these values in all the cheeses increased remarkably but the trend of increase remained same. The stretch length of the tested cheese samples ranged between 58.2 to 280 mm. The highest value was in A12, followed by A6 and B12(280.8,271.2 and 114 respectively ). The lowest hardness, cohesiveness, springiness values and consequently the chewiness value (mouth work energy) were recorded for the cheese values prepared from milk with start pH of 4.6 . There is a relationship between gumminess and chewiness values. The higher the chewiness values, the higher are also the gumminess values of the tested cheese samples. The hardness values obtained by 60% compression were at least double those obtained for 25% compression. On other side, the cohesiveness and springiness values were drastically decreased by 60% compression compared with those obtained by 25% compression. No remarkable differences have been observed in chewiness and gumminess values between samples compressed by 60% and those compressed by 25%.

It could be generally concluded from the obtained results that there were a remarkable difference between mozzarella cheese manufacturing with different rennet and starter culture combined. Deliver the pH of the thrombus limit to 5.1 during the industry can get acceptable mozzarella cheese, depending on the acidity degree of milk. Naturalization acidity of milk leads to increase the fat lost during the manufacturing. Manufacturing at 6 hours of raw milk storage without adding starter culture gave the cheese very good rheological properties.

Key words: Mozzarella, stretchability , TPA, pH, .high acid milk.