The correct answer is 63°C. Low-temperature long-time pasteurization is referred to as heating of milk to 63°C for 30 minutes in a double jacket vat. Heating and cooling are done by spraying or circulating hot water /stream of chilled water between the inner and outer jacket of the vessel. The milk is kept gently agitated mechanically to ensure uniform heating/cooling. This process is known as Low-temperature long-time pasteurization. This method is suitable for small quantities ranging from 200-1000 liter requiring a low initial cost of equipment.