Food preservation and fermentation Flashcards
Vacuum drying
- Foods put into a low pressure chamber
- Water evaporates more easily → ~1-3%
water
Freeze drying
- Uses sublimation
- Food frozen to ~-50 to -80°C so water
turns to ice - Placed in a vacuum to decrease pressure
and heat applied so ice→vapour
- Smoking is a process where foods are put into smokers
and exposed to burning wood in a humidity and
temperature regulated environment - Liquid smoke is also often used
- Cold smoking – dries food but does not cook it, ~__-__°C
- Hot smoking – dehydrates food and partially cooks, __-__°C
- Often used alongside salting and drying
25-35°C
74-85°C
ADDING HEAT
When food is heated to above __°C most bacteria and food spoilage organisms are killed
Can be achieved by a range of cooking methods
Temperature danger zone is between _ and __°C
Need to balance safety and sensory qualities
74°C
5 and 60°C
Pasteurisation: a food
preservation process that heats
liquids to __°C for __sec, or ___°C
for __min, or ___-___°C for -
seconds (UHT) in to kill bacteria,
yeasts, & moulds.
72°C, 15
62°C, 30
138-150°C, 2-6secs
Refrigeration:
The standards require food to be cooled from __°C to __°C in a maximum of __ hours
and from __°C to 5_°C within a further maximum period of _ hours.
60°C to 21°C
2
21°C to 5°C
4
Acid
Water activity first decreased by ______/_______
Food then submerged in vinegar - ≥ _% acetic acid
Firm vegetables and fruits are prepared, hot pickling liquid of vinegar, water, some sugar and flavours is poured over and allowed to cool.
Some foods are first ________ by simmering
salting/brining
5
softened
Fermentation
Fruits and vegetables are _____ and put in a closed container
They leach water due to _____ creating a brine – harmful microorganisms inhibited, beneficial bacteria thrive
Bacterial fermentation of sugar in the vegetables produces ____ ___ which _____ the pH
Examples include white cabbage, cucumbers and green beans
salted
osmosis
lactic acid
lowers
Alcohol
* Alcohol acts as a _______ by killing microorganisms
* Bacteria and fungi cell walls become permeable → ______ of their protein → death
* Usually involves mixing fruit, sugar and hard spirits and leaving for some time
* E.g. rumtopf
* ____ is NOT applied so alcohol remains!
preservative
denaturation
Heat
ADDING FOOD PRESERVATIVES
_________ – inhibit growth of microorganisms e.g. sulfur dioxide, nitrite, nitrate, benzoic acid, sorbic acid
__________ – reduce food oxidation e.g. vitamin C, vitamin E, vitamin A, butylated hydroxyanisole
Antimicrobial
Antioxidant
MODIFIED ATMOSPHERE PACKAGING
_____ removed and replaced with ________ _____/other gases
_________ _____: foods that have been
packaged airtight by a commercial sealing
process.
Oxygen
carbon dioxide
Hermetically sealed
The purpose of edible coatings is:
- To increase shelf life by acting as a barrier to moisture, O2,
CO2, volatile aromas & other compounds whose loss would
lead to deterioration. - To impart improved handling characteristics, such as the
ability to bend more easily without breaking. - To improve appearance through gloss & colour.
- To serve as a vehicle for added ingredients such as flavours,
antioxidants, antimicrobials, etc.
Irradiation:
a food preservation process in which foods are
treated with low doses of gamma rays, x-rays, or electrons.
Effects of irradiation on food:
renders the food less susceptible to deterioration & destroys
many of the micro-organisms
reduces spoilage
lengthens shelf life
sterilises or kills insects
can protect the public from many bacterial foodborne diseases
Define fermentation
The conversion of carbohydrates to carbon dioxide and alcohol by
yeast or bacteria
