The High Temperature Short Time (HTST) method of pasteurization requires a temperature of :

Question

Accepted Answer

The correct option is 2:
The correct answer, $72^{\circ}C$ for 15 seconds, defines the universally accepted, standard parameters for the High-Temperature Short-Time (HTST) method of pasteurization, which is also commonly referred to as the 'flash pasteurization' method. The entire principle of HTST is to subject the milk to a high temperature for a very brief duration to achieve a minimum five-log reduction (a 99.999% kill rate) of the most heat-resistant non-spore-forming pathogen found in milk, which is *Coxiella burnetii*. This precise combination of temperature and time is the scientifically validated minimum required to ensure product safety while simultaneously minimizing heat damage to the milk's critical components. This balance is key, as it preserves more of the milk's nutritional value and its fresh, natural flavor compared to the older Low-Temperature Long-Time (LTLT) method. HTST is the industry standard for large-scale, continuous-flow milk processing globally, ensuring both food safety and economic efficiency.

The incorrect option is 1:
Option 1, $60^{\circ}C$ for 15 minutes, is incorrect because the temperature of $60^{\circ}C$ is insufficient for the High-Temperature Short-Time standard. The standard Low-Temperature Long-Time (LTLT) batch method requires a minimum temperature of $63^{\circ}C$ (or $145^{\circ}F$) to be maintained for 30 minutes. $60^{\circ}C$ would be below the thermal death point required for common milk pathogens, even if held for 15 minutes, making the milk unsafe for consumption under regulatory standards. Pasteurization must guarantee the elimination of all pathogenic organisms, especially *Coxiella burnetii*, and this combination of time and temperature fails to achieve that critical public health objective. This specific combination is therefore neither a standard HTST nor an effective LTLT process.

The incorrect option is 3:
Option 3, $72^{\circ}C$ for 04 seconds, is incorrect because, while the temperature of $72^{\circ}C$ is correct for the HTST method, the holding time of 4 seconds is too short. The minimum required holding time for standard HTST pasteurization is precisely 15 seconds to ensure the complete and verifiable destruction of all relevant pathogens. This minimum time has been established by extensive scientific and public health studies to guarantee the required reduction in microbial load. A shorter duration, such as 4 seconds, might be utilized in a process known as Higher Heat Shorter Time (HHST) or as a pre-treatment step for Ultra-High Temperature (UHT) processing, but it does not meet the legal and safety requirements necessary for standard pasteurized milk according to major food safety regulatory bodies.

The incorrect option is 4:
Option 4, $68.4^{\circ}C$ for 10 minutes, is incorrect as this specific time and temperature combination is not recognized or certified as a standard pasteurization process in the dairy industry worldwide. The thermal requirement is too low compared to the HTST standard ($72^{\circ}C$) and the duration is too short compared to the LTLT standard (30 minutes). Adopting a non-standardized process like this introduces significant public health risks because there is no scientific validation or regulatory assurance regarding the complete and effective elimination of pathogens. In the context of dairy processing, it is essential to adhere strictly to the proven parameters of either the LTLT method or the HTST method for legally and safely marketing the product as pasteurized milk.