טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLiezerson Shirly
SubjectEffects of Ohmic Heating on the Quality of Orange Juice
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Dr. Eyal Shimoni


Abstract

Preservation techniques in the food industry ensure product safety and shelf life stability. Heat is the most common way to inactivate microorganisms and enzymes, but may result in the manufacture of low quality product. Moreover, consumers demand higher quality food products, which eventually lead to utilizing alternative preservation processes. Ohmic heating of food products provides rapid and uniform heating, resulting in less thermal damage to the product. The objective of this research was to examine the effects of ohmic heating on the quality and shelf life stability of orange juice with comparison to conventional pasteurization. Freshly squeezed orange juice was ohmically heated at various conditions, or by applying conventional pasteurization. For each treatment, we investigated the effects of ohmic heating on several quality factors. During ohmic heating, effective inactivation of both microorganisms and pectin esterase (PE) was achieved with similar effects as in conventional pasteurization, while maintaining ascorbic acid concentration, flavor components and sensory attributes. Shelf life experiment was conducted on ohmic heated and pasteurized orange juice stored at 4oC. The sensory shelf life was determined based on the Weibull-Hazard method. For the purpose of comparison, the juices were processed at equivalent F-values in both techniques. The shelf life of ohmic treated orange juice was two times longer than conventionally pasteurized juice. Therefore, the potential use of electrical heating as an alternative preservation technology was demonstrated on orange juice. Additional work should be done to investigate the effects of ohmic heating on other highly heat sensitive components.