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    Processing of yogurt-based products with pulsed electric fields: Microbial, sensory and physical evaluations
    (Wiley, 2004) Yeom, HW; Evrendilek, GA; Jin, ZT; Zhang, QH
    Yogurt-based products similar to a dairy pudding dessert were formulated and processed by mild heat and pulsed electric fields (PEF) to investigate the effects of combined mild heat and PEF treatment on the microbial stability and quality of high viscosity foods. Commercial plain low fat yogurt was mixed with fruit jelly and corn syrup and processed by mild heat treatment at 60C for 30 s and 30 kV/cm electric field strength for 32 mus total treatment time using OSU-2C pilot plant scale PEF system. Control and processed products were aseptically packaged and stored at 4 and 22C. Mild heat combined with PEF treatment significantly decreased the total viable aerobic bacteria and total mold and yeast of yogurt-based products during storage at both 4 and 22C (P less than or equal to 0.05). Mild heat treatment alone without any PEF treatment did not prevent the growth of microorganisms in yogurt-based products. Sensory evaluation indicated that there was no significant difference between the control and processed products (P :5 0.05). Color, pH and degreesBrix were not significantly affected by mild heat and PEF processing conditions.
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    Safety and quality evaluation of a yogurt-based drink processed by a pilot plant pef system
    (Wiley, 2004) Evrendilek, GA; Yeom, HW; Jin, ZT; Zhang, QH
    Yogurt-based drink samples were prepared by mixing plain yogurt, water, sugar, and strawberry flavored fruit syrup. The samples were treated by both the mild heat (60C for 30 s) combined with a pilot plant pulsed electric field (PEF) system and the mild heat only in order to determine changes in the product safety and quality. Changes in the product safety were measured as microbial count, and changes in the product quality as L, a, b, degreesBrix and pH values. The treated and control samples were stored at 4 and 22C for microbial, physical and sensory evaluations. Since the 60C-treated samples exploded after 14-day storage, the safety and quality evaluations for 91 days were performed for the 60C+PEF and control samples, only. Microbial count of the 60C+PEF samples was significantly lower than that of the control samples at the two temperatures for the 91-day storage (P < 0.05). There was no significant difference in the L, a, b values, degreesBrix and pH between the control and 60C+PEF samples (P < 0.05). The control and 60C+PEF samples revealed no significant difference in the selected sensory attributes (P < 0.05).