Lecture 2-Food preservation
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How much food is lost to spoilage?
25%
What’s a big proportion of the food that is lost to spoilage?
Fruits and veggies
__% of landfill in US = food
20% of landfill in US = food
What speeds up decomposition?
Heat, light and oxygen speed up decomposition
What is lost due to decomposition?
Nutritive value is lost
Does food have to be contaminated to be spoiled?
No
What is obvious and detectable- decomposition or contamination or both?
Decomposition is both obvious and detectable. Contamination isn’t
Why is decomposition obvious and detectable?
Due to decreased quality- appearance, taste, texture, odour
Which qualities does the most perishable foods have?
High pro or/and water
What are the 3 types of changes that lead to food spoilage?
• Biological • Chemical • Physical
What are the biological changes in food due to yeast. Uses, actions
– Fungus (plant that lacks chlorophyll) – Ferments sugars (CHO = CO2 and alcohol) – Used for producing food products e.g. bread and alcohol
Give examples of biological changes in food
Yeasts, bacteria, molds
Give examples of chemical changes in food
Enzymes (naturally present)
Give examples of physical changes in food
Water loss (evaporation/dehydration), separation. damage/mechanical bruisign, tearing of tissues
What are the biological changes in food due to bacteria and molds Difference between 2, actions
– Bacteria and molds can produce toxins – Molds are visible; bacteria are not – Bacteria can ferment sugars
How to destroy/inhibit factors behind biological changes in food
Boiling, refrigeration, drying, curing (high sugar/salt)
How are enzymes categorsied?
Based on substrate and mode of action
What are the 4 modes of actions of enzymes
– Protease (proteolytic enzyme): proteins-> AA – Lipase: TG-> FA + glycerol – Carbohydrase: CHO -> glucose – Others (e.g. polyphenol oxidase (PPO))
Talk about proteases in fish
Proteases in fish start working straight away Fish is more susceptible to spoilage
How can you slow down the action of proteases?
Cooler temperatures can do that
Downside of dry milk?
Lactose in dry milk can react with proteins and create new compounds Bioavailability of protein in milk is also decreased
What can oxidation of fat lead to?
Can lead to off odors and flavors- rancid flavor
What are the non-enzymatic chemical changes in food
– Oxidation of fat – Maillard reaction: • May occur with long storage of non-fat dry milk (lactose + pro = nonenzymatic browning) • BV of protein may decr: AA involved in reactions not readily released during digestion
What are the types of separation that cause physical damage?
– drip loss E.g. liquid from frozen meat- less moist product – emulsion breakdown – syneresis (gel)