The correct option is (c) 1 and 3 only.
Explanation
Food preservation techniques utilize temperature control to manage microbial activity. High temperatures are generally used to destroy microorganisms, while low temperatures are employed to inhibit their metabolic activities and growth rates.
Statement 1 is Correct:
Boiling is a common method of food preservation that involves heating liquid to a high temperature. This high heat effectively kills many vegetative microorganisms, including bacteria and fungi, by denaturing their proteins and enzymes.
Statement 2 is Incorrect:
Low temperatures, such as those maintained in a refrigerator (typically between 0°C and 5°C), do not accelerate microbial growth. Instead, they inhibit the growth of microbes. The metabolic reactions of microorganisms are slowed down significantly at low temperatures, preventing the food from spoiling quickly.
Statement 3 is Correct:
Pasteurization is a process designed to ensure food safety and extend shelf life. It involves heating a food product (commonly milk) to a specific temperature (e.g., about 70°C for 15 to 30 seconds) to kill harmful bacteria, followed by sudden chilling and storage. This thermal shock helps in eliminating pathogens while preserving the quality of the food.
Key Takeaway:
Heat (boiling, pasteurization) is used to kill microorganisms, whereas cold (refrigeration) is used to inhibit or slow down their growth. Pasteurization specifically utilizes a cycle of heating followed by rapid cooling.