Food Chemistry
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What is water activity
Aw is the water activity is a term that relates to the ability of a microbe to grow in a particular environment
Moisture sorption isotherm
Moisture sorption isotherm is used to determine relationship between water content & water activity
Water-holding capacity
Water-holding capacity (WHC) results from the physical entrapment of water within a food matrix that restrict flow but no other physical properties of water
How are carbohydrates bonded
Glycosylic bonds
Retrogradation
Retrogradation is the crystallization of starch molecules such that they begin to separate from other molecules present in the product
How are digestible and non-digestible carbohydrates differentiated
Recognition
Is glucose an aldehyde or ketone
aldehyde
What are reducing sugars
Carbohydrates that are aldehydes are reducing sugars and can react with amino group of protein / amino acids i.e. Maillard reaction
Why are carbohydrates soluble
Prescence of oh group
What is tollens reagent used for
to identify reducing sugars/ aldehydes
What are lipids
Soluble in organic solvents but not water
3 main groups of lipids
triglycerides, sterols, phospholipids
Triglycerides
3 fatty acids side chain
Phospholipids
1 polar head with 2 fatty acid chains
Sterols
ring structure but does not contain fatty acids
What are Saturated fatty acids
They contain no c-c double bonds
What can lipids act as
antioxidants & pro-vitamins
What are trans fatty acids at room temperature
Solid
Saturated fatty acids are _ are room temperature
solid
Lipid hydrolysis
Lipid hydrolysis involves separation of a fatty acid from the glycerol backbone or phospholipid I produces a free fatty acid & glycerol If the free fatty acid is short-chained, it will be volatile and contribute to the odor of the food (Hydrolytic rancidity)
Lipid oxidation
Lipid oxidation is a reaction of lipids with oxygen that proceeds through a free radical mechanism Free radical consist of carbon atom with an extra electron resulting from removal of hydrogen atom allowing oxygen to attach to the free electron resulting in lipid hydroperoxide It can generate volatile compounds that have an off-flavor Saturated fatty acids are unable to undergo lipid peroxidation due to lack of double bonds and they tend to be more stable
What do antioxidants do
Antioxidants inhibit or retard oxidation through one or more mechanisms
Why does trans fatty acids have better van der Waals interactions
Saturated fatty acids tend to have stronger van der Waals interactions with other saturated fatty acids because they can stack together and form a repeating structure, very similar to a crystalline structure
Why dies cis fatty acids have weaker van der waals interactions
Cis double bonds form a kink in fatty acids which interfere with stacking & interactions causing weaker Van Der Walls interactions causing it to be liquid at room temperature