Lecture 7 - Processed Food and Food Processing
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What is food processing?
Any deliberate change in a food that occurs before it is available for consumers to eat. Foods can be minimally processed or ultra-processed.
What are the different types of food processing techniques?
Physical Processing: Freezing/Drying/Concentration Chemical Processing: Addition of preservatives (E.g. SO2 and benzoic acid) Heat Processing: UHT/Pasteurisation/Sterilisation
What is the primary reason for food processing?
To reduce or eliminate harmful microbes from growing in our foods so as to extend its shelf life and to make it safer for consumption
What are some other reasons for food processing?
Improve the taste Make it easier for storage and transportation Improve/Preserve the food’s nutritional content
What are the positive effects of food processing?
Less perishable More convenient More shelf-stable Lower in price Safer Enhance sensory experience Maintain nutritional quality
What are the negative effects of food processing?
Chemical processing involves the addition of preservatives (which may be toxic if added in excess - amount higher than the what is legally permitted) Risk of contamination Induce potential microbial environment May result in some loss of nutritional quality
What are some examples of Heat Processing? Pros and Cons?
Blanching/Pasteurization/Sterilisation +ve: Kill microbes -ve: Destruction of nutrients (especially water soluble vitamins like vitamin C, B6 and B12) health benefit enzymes may be denatured (but may still be nutritional if the amino acid residue is not completely destroyed by the heat)
What are the conditions for Low Temp Long Time Pasteurisation?
63 - 65 degrees for 30 mins Minimal change in colour, flavour and texture but more destruction to nutrients and quality
What are the conditions for High Temp Short Time Pasteurisation?
72 to 74 degrees for 15 - 30 seconds Less destructive to nutrients and quality but gives a cooked flavour
What are the conditions for Sterilization?
121 degrees for 15 min Kills all microbes and increase shelf life (no refrigeration required) Greater changes in colour, flavour and texture
What are some of the pros and cons of freezing?
Allows to stop the growth of bacteria, yeasts, and moulds and to kill parasites Allows preservation of taste, texture, and nutritional value in foods better than any other method May not be effective against microbes that thrive at low temperatures (psychrophiles)
What is the minimum temperature required for bacteria growth?
-5 degrees
What are the pros of drying
Remove water from foods -> remove water content and water activity (improve safety and extend shelf life)
What is the food processing method that encourages the growth of microbes? / What is the food processing method that does not prioritise the removal of microbes?
Fermentation It encourages the growth of beneficial microbe to compete with spoilage and pathogenic microbes. microbes are able to form natural chemical preservatives formaldehyde, lactic acid and ethanol
What is cold sterilisation also known as?
Irradiation (exposing foods to ionising radiation)
What are some food processing methods that reduces the water activity of foods?
Freezing, Drying, Concentration, Dehydration and Crystallization
What are the pros and cons of curing?
Decrease the amount of water that is available to microbes (reduce water activity) overconsumption of nitrates and nitrites may lead to an increased risk of colorectal cancer
What are the pros and cons of high pressure processing?
Kills microbes and does not result in the destruction of nutrients and quality Expensive
What are the consequences of food processing?
Shelf Life Nutrition Quality Safety Packaging considerations
What is the relationship between the shelf life and the extent of destruction of microbes?
The greater the extent of destruction of microbes, the longer the shelf life