Food commodities: properties and nutritive value: Practice Questions

According to recommended personal food hygiene practices, what is the minimum duration recommended for washing hands thoroughly with soap and running water before handling food?

In food preservation, applying heat through pasteurisation is primarily intended to achieve which of the following?

Ultra-High Temperature (UHT) processing of milk involves heating milk to very high temperatures (e.g., 135-150°C for a few seconds) to achieve commercial sterility. This method is an example of a more intense form of which general heat application preservation technique?

Which moist heat cooking method involves gently heating food in a liquid, such as water, stock, or milk, that is maintained at a temperature just below boiling point (approximately \(85^{\circ}\mathrm{C}\) to \(93^{\circ}\mathrm{C}\)), often used for delicate items like fish or eggs?

In the production of a stable emulsion like mayonnaise using advanced preparation equipment (e.g., a blender), what component found in egg yolk acts as the primary emulsifying agent to stabilise the mixture of oil and water?

Which primary type of heat transfer is responsible for cooking food placed inside a convection oven?

Explain the functional property of protein denaturation and coagulation that occurs when making a simple custard, and why heat is required for this process.

Analyse the scientific principles behind both sous-vide cooking and pressure cooking, specifically comparing their heat transfer mechanisms and their respective effects on the retention of heat-sensitive nutrients in vegetables and the tenderisation of tough cuts of meat. Based on this analysis, recommend which method would be more advantageous for a home cook aiming to maximise both nutritional value and tenderness, providing a concise justification.

Heat transfer is essential in the cooking process. The three main types of heat transfer in cooking are conduction, convection, and radiation.

Briefly describe how convection transfers heat to food during cooking, providing one common example of a cooking method that relies primarily on this mechanism.

Classify the following two cooking methods as either a moist method or a dry method, and explain the key difference between these two categories in terms of the medium used for heat transfer:

Food preservation techniques are crucial for maintaining food safety, nutritive value, and extending shelf life. Two common methods involving temperature control are chilling and freezing.

Compare chilling (storage typically \(0^{\circ}\mathrm{C}\) to \(5^{\circ}\mathrm{C}\)) and freezing (storage below \(-18^{\circ}\mathrm{C}\)) in terms of their respective effects on microbial activity and enzymatic activity.

Explain the scientific principle behind how freezing preserves food, focusing on the changes in water activity that occur during the process.

Besides temperature control, the addition of certain chemicals is a common preservation method. Give one example of a chemical additive (e.g., high concentration of sugar, salt, or an acid) used in food preservation and briefly state its primary mechanism of action against spoilage microorganisms.