## 2 Thermal Methods  
Thermal methods used in the dairy industry are divided into conventional and unconventional methods. Table 1 presents conventional thermal methods applied in the dairy industry. Among the conventional thermal processing methods, pasteurization and sterilization are frequently used to control _L. monocytogenes_ in food products [13,29]. Pasteurization, performed at temperatures between 60 and 80 \({}^{\circ}\)C, destroys microorganisms and inactivates enzymes, while sterilization, at temperatures above 100 \({}^{\circ}\)C, destroys bacterial spores. The D value measures the time required to eliminate 90% of microorganisms, and a higher D value indicates increased thermal resistance. For example, in milk, the D value of _L. monocytogenes_ varies between 1683.7 s at 52.2 \({}^{\circ}\)C and 0.7 s at 74.4 \({}^{\circ}\)C [22]. Post-packaging pasteurization is gaining popularity to reduce the risk of contamination after processing. This involves heating already packaged foods with steam or hot water, but not all foods withstand high temperatures without losing their sensorial qualities. Among the unconventional technologies, microwaves, radio frequencies (RF), ohmic heating, and direct steam injection have been introduced to maintain the sensory and nutritional characteristics of food products. Microwaves and radio frequencies use non-ionizing radiation from the electromagnetic spectrum, between 30 and 300 MHz for RF and 300 MHz and 300 GHz for microwave. These technologies use uniform, volumetric, and non-contact heating of food products, which is effective against microorganisms [30]. Studies have shown that microwaves at 915 MHz can destroy _L. monocytogenes_ and other bacteria while maintaining product quality by denaturing cell proteins and disrupting the bacterial membrane [31]. Also, [PERSON] et al. (2005) [32] evaluated the effectiveness of RF for inactivating _L. monocytogenes_ in milk, obtaining a reduction of up to 5 log at 1200 W, 65 \({}^{\circ}\)C, and 55.5 s. \begin{table}
\begin{tabular}{l l c c} \hline \hline
**Method** & **Description** & **Product** & **Reference** \\ \hline \multirow{4}{*}{Thermalization} & Preheating procedure in which milk is heated at low temperatures for a brief time & milk & [33] \\  & prior to further processing: 57–68 \({}^{\circ}\)C /10-20 s & & [34] \\ \cline{2-3}  & Heat treatment of milk at 57–68 \({}^{\circ}\)C /15 s & cheese & [34] \\ \cline{2-3}  & Heat treatment of sheep milk at 62 \({}^{\circ}\)C /20 s or 68 \({}^{\circ}\)C/20 s & cheese & [34] \\ \hline \multirow{4}{*}{Pasteurization} & Pasteurization LTLT (low temperature, long time)—the process of heating & & \\  & every particle of milk to at least 63 \({}^{\circ}\)C/30 min. & & \\  & Pasteurization HST (high temperature, short time)—the process of heating & & \\  & every particle of milk to at least 72 \({}^{\circ}\)C/15 s & & \\  & Vacuum pasteurization—90.5-96.1 \({}^{\circ}\)C under & & \\  & vacuum pressure & & \\  & 62.8 \({}^{\circ}\)C/30 min. or 71.7 \({}^{\circ}\)C/15 s & & \\ \cline{2-3}  & 65.6 \({}^{\circ}\)C/30 min. or 74.4 \({}^{\circ}\)C/15 s & & \\ \cline{2-3}  & 68.3 \({}^{\circ}\)C/30 min. or 79.4 \({}^{\circ}\)C/25 s & ice cream mix & [38] \\ \cline{2-3}  & Milk before fermentation: 90-95 \({}^{\circ}\)C/ 5-10 min. & & \\  & Milk before fermentation: 85-95 \({}^{\circ}\)C/15 min. & & \\ \hline \hline \multicolumn{3}{l}{Heat treatment of milk at 63 \({}^{\circ}\)C / 30 min.} & soft cheese & [36] \\ \cline{2-3}  & Heat treatment of milk at 72 \({}^{\circ}\)C, no hold & semi-hard cheese & [36] \\ \cline{2-3}  & Heat treatment of milk at 64–68 \({}^{\circ}\)C/10 s & hard cheese & [36] \\ \cline{2-3}  & Heat treatment of cream at 65 \({}^{\circ}\)C /10 min. & butter & [36] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Conventional thermal methods applied in the dairy industry. Ohmic heating, or Joule heating, treats foods by passing an electric current through them.