Final answer:
Fruit curds are typically incubated at 37°C (98.6°F) with Lactobacillus cecai for 6-8 hours to promote curdling and prevent rapid bacterial growth that can occur between 4°C and 60°C (40°F and 140°F). Excessive temperatures well above 100°C are used for killing certain bacteria like C. botulinum, but not for curd making.
Step-by-step explanation:
Fruit curds should be cooked to a specific temperature to ensure that the microorganisms within them, such as Lactobacillus cecai, can effectively ferment the sugars into lactic acid, promoting proper curdling. For preformed curd, which contains this microbe, the recommended incubation is at 37°C (98.6°F) for 6-8 hours. This temperature range is crucial for the transformation of lactose into glucose and galactose, and subsequently into lactic acid, which lowers the pH of the milk and results in casein precipitation to form fine micelles, thereby thickening the milk into curd.
It's important to maintain temperature control because bacteria multiply most rapidly between 4 and 60 degrees C (40 and 140 degrees F), and foods left in this range for extended periods may become unsafe to eat. Excessive temperatures, such as those required to kill C. botulinum endospores (116°C or 240°F) are not applicable here and require specialized equipment like pressure canners.