Arnold’s Food ChemistryLesson 5: Food

Preserving/Processing Methods

Food Preservation• Food preservation is the process of treating and

handling food in such a way as to stop or greatly slow down spoilage to prevent foodborne illness and extend its shelf-life. (Detailed description)– Basically idea is to slow down activity of disease-causing

bacteria as well as to kill the bacteria altogether

• Food processing methods that are used to preserve foods include: – Refrigeration and freezing

– Canning

– Irradiation

– Dehydration

– Freeze-drying

– Pickling

– Pasteurizing

– Fermentation

Food Preservation (cont.)• How it works…• All of the food preservation processes work by

slowing down the activity and growth of disease causing bacteria, or by killing the bacteria all together. They also slow down or stop the action of enzymes which can degrade the quality of the food. – Temperature

–Water Activity

– pH

Food Preservation (cont.)

• All food contain bacteria unless it is sterile*. – i.e., bacteria naturally living in milk will spoil the

milk if left outside; however, by putting the milk in the fridge, you slow down the bacteria (not kill)

• In some cases, a preservation could possibly destroy enzymes naturally found in a food that cause it to spoil quickly.– To review, an enzyme is a special protein that acts

as a catalyst for a chemical reaction, and enzymes are fairly fragile.

– By increasing the temp. of food to 66 degrees C, enzymes are destroyed

Common Methods

• Drying• Smoking• Freezing• Vacuum packs• Salting• Sugaring• Pickling

Drying

• Most ancient method used by humans

• Reduces the water content in the product and lack of water delays the bacterial growth very much

• Drying is the most common technique to preserve or process cereal grains (i.e., wheat, maize, oats, rice, barley, grams and rye)

Smoking• Many foods such as meat, fish and

others are processed and preserved by this method.

• Very simple as the combination of smoke to preserved food without actually cooking it and the aroma of hydro-carbons generated from the smoke processes the food and makes it even tastier to eat.

Freezing

• Conducted in big cold storages which can stockpile huge amount of food stuffs which can be used in national emergencies.

• A wide range of products can be frozen to preserve and process.

Vacuum Packs

• Food is packed in airtight bags and bottles in a vacuum area.

• Used in processing food as the air-tight environment doesn’t provide oxygen needed by germs, especially bacteria, to survive.– This then, prevents food from getting

rotted

Salting

• Meat is the best example of the food processed by salting as nitrates are used very frequently to treat meat.

• Used in food processing as it sucks out the moisture from the food.– Done through the process of osmosis

Sugaring

• Fruits are cooked with sugar until they are crystallized and then it is stored dry.

• This method is very frequent where it comes to preserve fruits.

Pickling

• Food is cooked in chemicals and materials which destroy microorganisms.

• Very commonly seen in vegetables such as cabbage and peppers.