Class 2: Food Preservation Flashcards
How much food is wasted every year around the globe? How much of it is from human consumption?
1.3 billion of tones
1/3
Food lost and wasteages amounts to which squandering of resources? name 4
water
land
energy
labour and capital
How much food lost and waste is lost to spoilage?
25%
What is food spoilage?
• Decomposition, loss of nutritive value
Who consumes the spoiled food?
rodents, flies, microorganisms…
food spoilage vs food contamination
FS: Obvious & detectable
– Due to decreased quality (appearance, taste, texture,
odour)
FC: not obvious and dangerous for health
What food is most likely to spoil?
high pro +/or water
Name 3 types of changes that lead to food spoilage and give examples
• Biological – Yeasts, bacteria, molds • Chemical – Enzymes (naturally present) - non enzymatic • Physical – Water loss, separation
Changes that lead to food spoilage=> Biological=>Yeast=> 1. what is it 2. function 3. utility
– Fungus (plant that lacks chlorophyll)
– Ferments sugars (CHO = CO2 and alcohol)
– Used for producing food products e.g. bread and alcohol
Changes that lead to food spoilage=>
Biological=>Bacteria and Mold
1. what do they produce
2. mold vs bacteria appearance and function
– Bacteria and molds can produce toxins – Molds are visible; bacteria are not
– Bacteria can ferment sugars
How to destroy/inhibit yeast and bacteria and mold
boiling, refrigeration, drying, curing (high sugar/ salt)
Changes that lead to food spoilage=>
Chemical=> enzymes=>
1. how are they categorized
2. mode of action
– Categorized by • Substrate • Mode of action – Protease (proteolytic enzyme): proteinsàAA – Lipase: TGàFA + glycerol – Carbohydrase: CHOàglucose – Others (e.g. polyphenol oxidase (PPO))
Changes that lead to food spoilage=>
Chemical=> non enzymatic=>
1. what is it
2. mode of action
– 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
Changes that lead to food spoilage=>
Physical=>
2 types
+ consequences
• Evaporation / dehydration
• Separation: – drip loss
– emulsion breakdown – syneresis (gel
consequence: damage/mechanical bruising, tearing of tissues
6 Methods of food preservation
Methods of food preservation
• Hightemperaturetodestroymicroorganisms& enzymes
• Lowtemperaturetocontrolgrowthofmicroorganisms
• Removal/tyingupofmoisturetocontrolmicrobial
growth
• Additionofchemicalpreservativestoinhibit
microbial growth
• Keepingoutmicroorganisms
• Ionizingradiationstodestroymicroorganisms& control enzyme activity
Methods of food preservation: curing
- What?
- With what?
- For what?
- Preservation with use of salt & drying
- Sugar, spices, nitrates may be added
- Meat/fish may also be smoked (for added flavour and preservation)
Methods of food preservation: pickling
- What?
- With what?
- Preservation by acidification (addition of acid/vinegar OR fermentation)
- Spices/herbs may be added for flavour
Methods of food preservation: drying
- What?
- Example
- conventional uses (4) ?
1. • Removes water in food • Inhibits growth of microorganisms 2. E.g. sun-drying or commercial drying of Pandanus, seaweed, fish 3. • Conventional (uses heat) – Drying room, tunnel drying, spray drying, drum drying • Vacuum (uses low pressure) • Osmotic (uses strong syrup) • Freeze-drying (ice crystals vaporize)
Methods of food preservation: drying
- What?
- Function
- A thin layer of edible material (CHO, PRO or FAT) used on fruits, vegetables, cheese, nuts, dried fruit, processed meats…
- • Increases shelf life
– Barrier to moisture, O2, CO2, volatile aromas
• Improves handling – Less breaking/damage
• Improves appearance – By increasing gloss, color
• Vehicle for added ingredients – Flavours, antioxidants, antimicrobials
Methods of food preservation: drying
- for what?
- process
- two methods
1.
Fruits, vegetables & meats
2.
process:
a) Food packed into sterilized containers & sealed
b) Containers “canned”/heated to destroy microorganisms & enzymes
– Extended boiling/ heating to temperatures much higher than regular boiling point
3. 2 methods: 1. Boiling water process - good for low pH items 2. Pressure canning - for higher pH items - boiling at higher temps under pressure - to destroy Clostridium botulinum
Canning – high acid foods
- for what
- process
1.
For fruits & tomatoes (pH 4.5 or below)
2.
• Safely canned in a boiling water bath
• Heat resistance of microbes is decreased by the acidic pH ∴ can be destroyed in reasonable processing times
• Surviving organisms will not grow in acidic environments
Canning – low acid foods
- for what
- process
1.
For vegetables, meat, fish, poultry & milk (pH above 4.6)
2.
• Requires relatively high processing T° to destroy all spore-forming organisms, particularly C. Botulinum
• Requires a pressure canner where T° > usual boiling point of water can be achieved
3 types of heat preservation methods
- Boiling:
• simplest method; 10 minutes - Pasteurization:
• Liquids are heated to a certain T for a certain period of time
• Eg 71°C (160°F) à 15 sec OR 138oC (280oF) à 2 sec
• Kills bacteria, yeasts, molds - Ohmic heating:
• Electrical current passed through food, generating heat that destroys microorganisms
• Liquid eggs, fruit juices
2 types of cold preservation methods, just name them
Refrigeration
Freezing
