How Processing Affects Properties of Ingredients

Impact of Heat on Food Properties

Heat processing can change a food’s flavour, colour, and texture. For example, the Maillard reaction occurs when heat causes proteins and sugar in food to react and create new flavours while changing the food’s colour.
Heat processing helps to kill harmful bacteria in food, making it safe for consumption. This method is typically used in products such as milk (process called pasteurisation) and canned goods.
Overheating or prolonged cooking can lead to loss of nutrients in food, such as the degradation of vitamin C in vegetables.

Effects of Cold on Food Materials

Freezing food slows down the rate of bacterial growth, thereby preserving the food. However, it can alter the food’s texture as the water inside the food expands and forms ice crystals.
Cryogenic freezing is a faster, but more expensive, method of freezing which results in smaller ice crystals and thereby maintains better food texture.
Refrigeration also slows bacterial growth but doesn’t stop it completely. It’s used for short-term storage and doesn’t cause significant texture changes.

Impact of Air on Food Properties

Oxidation happens when food comes in contact with air, causing discolouration and rancidity in fats. For example, cut apples turn brown after being exposed to the air due to a reaction between enzymes in the apple and oxygen in the air.
Vacuum packing can preserve food by reducing the amount of oxygen. It can prevent both oxidation and slow bacterial growth, thus, extending food’s shelf life.

Influence of Moisture on Food Characteristics

Dehydration, which involves removing water from food, can be used to preserve food and change its texture. For example, drying fruit concentrates its flavours and provides a different, chewy texture.
Rehydrating dried foods can return some, but not all, of the food’s original texture and flavour.
Excess moisture can lead to bacterial growth, as bacteria need water to grow. Therefore, moisture control is important in food storage and preservation.

Alteration by Mechanical Processing

Mechanically processing food, for instance through chopping, grinding, or blending, changes its structure and can release flavours and aromas.
It can also affect the food’s texture and ease of digestion. For example, grinding grain into flour makes it easier to cook and digest.
Mechanical processing can sometimes lead to nutrient loss, especially if the food is rinsed after being cut or ground.