Abstract
Using of traditional milk pasteurization methods caused fouling by heat, particularly rapid pasteurization by ohmic heating at 220 volts resulted protein denaturation, when milk holding of 15 seconds under ohmic heating at 72°C. So to control these properties a Non-thermal treatment by different electrical fields at 20, 27.5, 55 V/cm (80, 110, 220V, AC) and quickly milk pass between poles in a long narrow tube during less than 0.8 seconds. The study focused on applying different electrical fields in milk pasteurization as a non thermal treatment and calculates the electrical conductivity, viscosity of milk, final output milk temperature, holding time, productivity at 55 V/cm, performance coefficient, pH, acidity, chemical composition, microbiological characteristics and storage periods for the pasteurized milk. The obtained results indicated that the final output milk temperature was reached 40°C and electrical conductivity was increased and viscosity was decreased with increasing temperature and productivity and performance coefficient were 1140 L/h, 99.8 respectively. More over pasteurized milk chemical composition and its pH were not influenced in electrical field. Resulting of bacteria elimination and alkaline phosphatase was inhibited by the electrical field as well. The results showed that the electrical field is better than other electrical fields (20, 27.5 V/cm).
Highlights
Manufacture of virtually all milk and dairy products involves heat treatment, which is mainly aimed to kill microorganisms and inactivation of enzymes or to achieving some other, mainly chemical changes
Electrical conductivity is the measurement of a substance transmits electric charge, expressed in Siemens per meter, which is a ratio of the substance density to electric field strength and is affected by the chemical composition of a substance [28]
Results showed that the electrical conductivity was increased with increasing milk temperature for all electrical fields (55, 27.5 and 20 V/cm) respectively
Summary
Manufacture of virtually all milk and dairy products involves heat treatment, which is mainly aimed to kill microorganisms and inactivation of enzymes or to achieving some other, mainly chemical changes. This depends on the intensity of the treatment, i.e., the combination of temperature and duration of heating. Pasteurization is a mild process, designed to inactivate the major pathogenic and spoilage bacteria found in raw milk. It should produce minimal chemical, physical and organoleptic changes in the product [2]. Virgiliu [7] stated that the methods of pasteurization are used may be slow pasteurization or low pasteurization at the temperature of 62-65°C for 30 minutes, respective 20 minutes, where as midst pasteurization or shorten pasteurization is performed at the temperature of 72-78°C for 15 seconds, known as, High Temperature Short Time pasteurization (HTST) is performed between 85-90°C, for a few seconds, followed by sudden cooling at 10°C
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