Lecture 3: Food consumption & food chemistry Flashcards
What are phospholipids?
Contain only two fatty acids esterified to glycerol and instead of the third, a polar group containing phosphoric acid and a nitrogen group
What is the most common Emulsifier?
Phospholipids.
What are the other components of Lipids?
Sterols (cholesterol)
Tochopherols
Vitamins
pigments
What is the role of lipids in food?
5 things
- Nutrients:
- Sourse of essential fatty acids
- Add caloric density and provide satiety - Carries flavors and fat soluble vitamins
- Contribute to texture and mouthfeel
- Heat transfer medium (frying)
- Emulsifiers
What are the undesired reactions in fats?
Fats can be a source of an off-flavour when degeneration occurs (oxidation & rancidity)
What is Hydrolytic rancidity?
Free fatty acids are liberated when fat and water interact
What is a Oxidative rancidity?
A biochemical reaction between fats and oxygen in which:
- long fatty acid chains degrade
- Shorter chain fatty acid are released which are odorous.
What is added to foods to prevent oxidation?
Antioxidants such as BHT BHA Vit C Vit E
How much water is in Lettuce, Watermelon, and raw hamburger?
Lettuce: 96%
Watermelon: 93%
Raw Hamburger: 54%
What is the first major function of water in food?
Flavors, Vitamins, minerals may be dissolved in water in foods
What is the second major function of water in food?
Moisture provides lubrication for mastication and swallowing
What is the thrid major function of water in foods?
Influences texture of fruits and vegetables and tenderness of meat.
What is the fourth function of water in foods?
Facilitates heat transfer through foods during processing
What is the fifth major function of water in foods?
Supports growth of spoilage and pathogenic micros.
Is all of the water in a food available for microbes?
No, only some water is free, as water may be tied up by chemical constituents such as salt.
Why can Salted Cod be left un-refrigerate while polish sausage has to be refrigerated dispate the fact that they have the same moisture content
Salted Cod is 14% salt and thus the water is chemically tied up.
What is water activity?
Water activity is a dimensionless ratio
in food
when a(w) is close to 0 there is ____ moisture available
little
When a(w) is close to 1.0 there is _________ moisture available.
Lots
The higher the a(w) the higher the amount of _____ water to interact with microorganisms and take part in chemical deteriorative reactions
free
a(w) less than 0.6 you should see no __________&________ growth
Microbial & Bacterial
a(w) less than 0.9 you should see no ________ growth
bacterial growth
Pw is known because of the relationship between _______ & ________
Temperature and water
What is a Water Sorption isotherm?
it is used to predict reactions in foods based on a foods water activity.
True or false:
Each food has its own water sorption isotherm
True
What are the characteristic of foods with an a(w) of 0.25 or less?
Moisture content: low
Textural attributes: dry, crips
Stability levels: High
What are the characteristics of food with an a(w) of 0.50 -0.75?
Moisture content: Intermediate
Textural attributes: chewy, moist
Stability levels: intermediate stability
What are the characteristics of food with an a(w) of 0.75-1.0
Moisture content: high
Textural attributes: soft, juicy
Stability levels:
Fresh - low
processed - high stability
How do you reduce a(w) in foods?
addition of salts and sugars, as small compounds tie up moisture.
What is the secound most common way to reduce the a(w) of foods?
concentration
Evaporation
Dehydration processes
Can fresh water be removed from foods? how or how not?
Yes it can be removed rather easily
it is removed through squeezing, cutting, and pressing
Can bound water be removed from foods? how or how not?
No it cannot be remove from foods easily.
it is not free to act as a solvent for molecules, although it can be frozen at very low temperatures.
What is the application of a(w)?
Food scientists use it to predict reactions in foods based on food’s water activity.
