L1 Water Acids and pH
The definition of Water Activity
What is the relative humidity of the atmosphere of the food
This process describes enzymatic browning
Reaction between oxygen and phenolic compounds in plant tissue. Catalyzed by polyphenol oxidase (PPO)
This is the difference between Amylose and Amylopectin, the two polymers of glucose found in starch granules
Amylose: Linear chain of glucose(~2000 units)
Amylopectin: Branched chain of glucose (10x-20x)
Gliadin is to ___ as Glutenin is to ___
Gliadin (globular protein, provides viscosity) and Glutenin (fibrous protein, provides elasticity)
An Enzyme is a ___
An enzyme is a protein which
accelerates the rate of a reaction, and which is
selective for only a few chemicals as reactants
or substrates
– Decrease activation energy of a reaction
– Not consumed in reactions (catalyst)
– Specificity to substrates
These are the 2 of the 3 direct methods of lowering water activity
___+____+____
2 Monosaccharides are connected by this in a disaccharride
Glycosidic Bond (Covalent)
This is the difference between Suspensions, Colloidal Dispersions, and, Solutions
Solutions: homogeneous mixtures of a solute
dissolved in a solvent
• Suspensions: unstable, heterogeneous
mixtures of two or more substances
• Colloidal dispersions: stable, heterogeneous
mixtures of two or more substances
– Consists of a dispersed phase (the isolated particles) and a continuous phase (the dispersing medium)
Aspartame is this
Sugar substitute 200x sweeter than sucrose
Corn Syrup is made by ?
treating starch with amylase ((a cuts randomly) (b cuts off maltose) .
HFCS is made with glucoamylase (Cuts off glucose), then glucose isomerase (Glucose > Glucose+Fructose)
Most foods are in the pH range of ___ (Hint: the lower number is the maximum pH for shelf stable foods)
What is 4.6-7
This is the difference between the two types of Non-Enzymatic Browning.
Caramelization is the thermal decomposition/dehydration of carbohydrates.Occurs when sugars are heated to a very high temperature (above their melting point)
Maillard: Reaction occurs between free amino groups
and reducing sugars
Glycogen is to ___ as Cellulose is to ___
Energy Storage(animals+fungi) (Branched more than amylopectin)
Cell Structure (Plants) (Linear)
Bonds in a proteins primary structure refer to these bonds while bonds in the 2nd/tertiary structure refer to these bonds.
Peptide (Covalent), Hydrogen
Name 3 ways enzymes are controlled in foods
Compartmentalization
• Temperature
• pH (Change the charge of an active site residue)
• Water Activity (optimal Aw > 0.9)
• Cofactors or inhibitors
Water is a ___ for small molecules
What is a solvent
These can be 2 undesirable effects of maillard browning
Color - changes in color during
storage
• Flavor - changes during processing
and storage
• Nutritional loss - essential amino
acids, vitamin C degradation
• Toxicity/mutagenicity
Starch Retrogradation is caused by this
When chains of (mostly) amylose re-associate and re-order into crystalline aggregates
Results in Starch gels undergoing shrinkage and
syneresis (separation of liquid from solid)
(Stale Bread)
MSG is derived from this
The sodium salt of glutamic acid first isolated from seaweed
Name 2 inhibitors of enzymes
sulfites and trypsin inhibitors
These are 3 of the 6 organic acids and the foods they are commonly found in
Malic --> Apples
Tartaric --> Grapes
Citric --> Citrus Fruit
Fumaric --> Mushrooms
Lactic --> Fermented Dairy Products
Acetic --> Vinegar
This is the process that creates invert sugar
Sucrose is hydrolyzed into a mixture of glucose
and fructose by an enzyme, invertase
: (Less likely to crystallize than sucrose
– Absorbs small amounts of water)
2 properties of Stabilizers (>Hydrocolloids>Gums)
Control water (Hydrophilic)
• Form gels (Interact with itself)
• Control viscosity (Open structure)
• Prevent separation
Locust bean gum prevents whey-off in dairy products
This is the difference between protein denaturation and protein coagulation
Denaturation: Any modification in the secondary, tertiary or
quaternary structure of the protein not
accompanied by breaking peptide bonds
– Generally, irreversible
– Proteins become less soluble
and more viscous
Can occur during food processing
– High temperatures (thermal)
– Pumping, mixing, filling (mechanical)
– Many foods are acidic (fermented foods)
Results in more linear structure
Coagulation:
Clumping of denatured proteins which results
in thickening or hardening (Heat,acid, enzymes,salt)
Pectinase is used in juice manufacture in these 2 ways
During the extraction process to increase yield
To the juice extract to clarify the juice