Investigating the Effect of Ohmic Heating, Conventional Heating, and Cold Plasma on Inactivation of Raw Milk Microorganisms

As a complete food source, milk contains nutrients, minerals, and vitamins needed by the body. However, raw milk has many microorganisms that can cause a wide range of diseases for consumers, so sterilization is one of the important steps in the dairy industry that must be paid enough attention to obtain a healthy product that preserves its primary nutritional value. The current study is a review study with the aim of investigating different thermal methods such as conventional heating (CH) and ohmic heating (OH), and new non-thermal methods such as cold plasma (CP) on inactivation Raw milk microorganisms and the effectiveness rate of this methods are compared. This study includes a review of 13 experimental studies, of which 5 studies investigate the inactivation rate of OH and CH sterilization on Staphylococcus thermaphilus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium and Lactobacillus acidophilus, and 8 other experimental studies investigate the inactivation rate of CP method as a non-thermal alternative method which is less destructive to foods on Staphylococcus aureus, Enterococcus faecalis, and on microorganisms in general. According to the contents mentioned in this article, it can be concluded that OH has the ability to produce safe products by preserving nutrients, and at the same time, it does not harm the quality of the products. The amount of microbial load of milk using the OH method was much lower than the CH method, and also less time and energy is needed to reach the sterilized state of the milk, as the energy and time required by OH are 72% and 19% less than CH respectively. Also, CP affects the production of biofilm from microorganisms, especially Staphylococcus aureus and Enterococcus faecalis, and reduces the microbial load in foods through this way, and by increasing the time of CP irradiation on bacterial isolates, a significant decrease in the Bacteria growth rate is observed.