Food Preservation

Step 1: Understand enzyme inhibition in food. This involves treating food to slow down or stop the activity of enzymes that cause spoilage (e.g., browning, texture loss, off-flavor development).
Step 2: Analyze the given techniques.

A. Heat: Applying heat (e.g., blanching, pasteurization) denatures enzymes, irreversibly destroying their structure and function. This is a very common method.
B. Sugar: High concentrations of sugar lower the water activity of the food. This reduces molecular mobility and can inhibit enzyme function, but it's primarily a method for controlling microbial growth.
C. Variation of pH: Most enzymes have an optimal pH range. Making the food more acidic (e.g., by adding lemon juice or vinegar) or alkaline can drastically reduce enzyme activity. This is a common method.
D. Sulphur dioxide: Sulfites (like sulphur dioxide) are powerful chemical inhibitors, particularly effective against the polyphenol oxidase enzyme that causes enzymatic browning in fruits and vegetables. \end{itemize} All four methods are used in food preservation. However, Heat (A), pH variation (C), and chemical inhibitors like Sulphur dioxide (D) are considered primary and direct methods of controlling enzyme activity. Sugar (B) is also effective but its primary role is often seen as water activity control. Given the options, the combination of A, C, and D represents the most direct and widely used techniques specifically for enzyme inhibition.