Week7-Course2 Flashcards
What is the formula to calculate the water activity or available water?
ππ€ = π(π)/π0(π)
- P = partial vapour pressure of water over a sample of food
- P0 = partial vapour pressure of pure water
- T = temperature
Higher is the aw (water activity) _____ is the perishability
Higher
Aw is on a scale of 0 to ___, ___ representing pure water
1
T or F : canned fruit is less perishable than dried fruit
false, because there is more free water in canned fruit
Name three preservation technique you can do to reduce the free water content
- Drying
- Concentration
- Freezing
The fungi are the most resistant kind of microorganisms and they canβt be active at a free water content of ___-
0.8
The product that will have lower water activity is the product in which the water will be ____
bounded
What is a contaminant or polluant in the case of water
anything that makes the water impure or unsafe
What are the three classes of common polluant
- biological
- physical
- chemical
What is the reason why potable water from municipality is not used in food processing
all the variability needs to be controlled when making food and mineral present in municipal water may interact with food constituants
Can you explain the B.O.D ?
Biological oxygen demand : Amount of oxygen that aerobic microorganisms in a body of water require to break down all the
organic matter present. It is an indicator of the organic contamination of water.
How is the BOD measured?
milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 Β°C
Higher the BOD ___ is the contamination
higher
T or F : high BOD leaves insufficient oxygen for fish
True because more oxygen is used by the microorganisms for the breakdown of organic matter
T or F : removal of water is one of the most common and effective food preservation technique
T
