U9 Flashcards
true or false: egg white is high in carb and lipid content
false! 1%
main 4 protein constituents in albumin
- ovalbumin
- ovotransferrin
- ovomucoid
lysozyme
what kind of protein is ovalbumin
phosphoglycoprotein
what is special about ovalbumin that the other egg white proteins dont have
free sulfhydryl group
how stable is ovalbumin
not very stable - easily coagulated in heat and easily denatures when exposed to new surfaces
what are 2 important functions of ovalbumin
stabilizes foam
gelling agent
what kind of gel does ovalbumin create (in heat)
transparent, turbid gel
what process is used to purify ovalbumin
- half-saturate with ammonium sulfate
- filter
- sulfuric acid lowers the pH to pL 4.6-4.8
- recrystallizations
what kind of protein is ovotransferrin
iron-binding transferrin
what kind of prosthetic group does ovotransferrin have
carbohydrate
what allows ovotransferrin to have bacteriostatic and bactericidal avticities
iron-sequestering properties
how to purify ovotransferrin
- half-saturate with ammonium sulfate
- precipitate with more ammonium sulfate or alcohol fractionation
or ion exchange chromotography
what is the most easily heat-denatured egg protein
ovotransferrin
wht kind of protein is ovomucoid
glycoprotein
what is the quaternary structure of ovomucoid like
3 homogenous domains crosslinked
where are the polysacchridees of the ovomucoid
attached to Asp
how are ocomucoids purified
complete saturation with ammonium sulfate or adding excess alcohol
what kind of protein is lysozyme
bacteriolytic enzyme
what is the function of lysozme
Catalyzes hydrolysis of glycosidic links between NAM and NAG in bacterial cell walls
optimal ph activity for lysozyme
5.3-6.4
what funcitonal characterisitc is special about lysozyme
heat stable and stable during drying
what is avidin
basic protein
what is ovoglobulin
foaming protein
what is ovoinhibitor
inhibits trypsin, chymotrypsin, elastase
what is flavoprotein
binds riboflavin
what does yolk act like in food and why
lipid - it has high proportions of phosphoplipids and lipoproteins
what function does yolk have
emulsifier
4 classes of yolk proteins
Lipoproteins - LDL and HDL
lipid-free globular proteins
phosphoproteins
minor proteins
what is heat coagulation
thermal denaturation and aggregation of proteins in albumen and yolk
what is denaturation
breaking of h-bonds, uncoiling of peptide chains, exposure of reactive groups
what do proteins form when denatured and with what bonds
aggregate to form a 3D gel network via h-binds, electrostatic links, disulfide links
what effect does heating albumin have
increased viscosity and opacity
what effect does heating have on yolk
viscosity increases (65C) and solidifies (70C)
how does increasing temperature and heating time affect gel
strengthens it
what does the oH of the gel depend on
net charge of the protein
describe the gel at its isoelectric point
protein aggregates into a curd, forming an opaque gel
describe the gel at basic pH
protein denatures, forming a translucent, rubbery gel
describe the gel at acidic pH
poor winding capacity, forming a coarse, open gel structure
describe the gel at pH 9
lots of crosslinking, forming a firm gel with high WBC
how does dry heating affect the egg protein’s propertie
improves foaming, gelling, and emulsifying properties
how is dry heating performed
storing the dried egg white at 80C with controlled humidity for 7-10 days, forming a partially denatured structure
how does conjugating a protein with a polysaccharide effect the proteins properties
favors protein-protein interactions, so it protects the protein from thermal denaturaion and increases amphiphilic properties
how do enzymes work
they bind with high specificity and lower the activation, speeding up chemical reactions
what are oxidoreductases
catalyze oxidations or reductions of substrates
what does lipoxygenase do
lipid oxidation - adding O to a fatty acid
what does polyphenol oxidase do
enzymatic browning - oxidizes phenols in food
what do hydrolases do
catalyzes hydrolysis of substrates using water
what do proteases do
cleave the peptide bonds in proteins, affecting texture and protein modification
what do amylases do
cleave glycosidic bonds in carbohydrates, affecting texture and carbohydrate modification
wht do lipases do
cleave ester bonds, affecting hydrolytic rancidity and fat crystallization modification
what do isomerases do
catalyze intramolecular rearrangements
what does glucose isomerase do
convert aldose to ketose (glucose to fructose)
what do glycoside hydrolases do
hydrolyze glycosidic bonds in stach
a-amylase
hydrolyze alpha 1-4 link within starch. Releasing dextrins, maltose, and maltotriose
b-amylase
hydrolyze beta 1-4 links from the non-reducing end of starch. Releasing maltose
glucoamylase
hydrolyzes alpha 1-4 and alpha 1-6 links in starch. Can go all the way to glucose
pullulunase
hydrolyzes alpha 1-6
where are glycoside hydrolases supplied from
microbes or food systems
what 3 processes are glycosde hydrolysases used in
production of corn syrup, baking, and brewing
what occurs in corn syrup production
- a-amylase breaks down amylose into amylopectin
- glycoamylase breaks it down into glucose OR b-amylase / pullulanase break down into maltose - depending on what is desired
what occurs in baking
- a-amylases dextrinize dirsupted starch granules
- b-amylase hydrolyze dextrins into maltose
- the fermentable sugar maltose is used by yeast amd causes produciton of CO2
- the bread rises
what occurs in brewing
amylases in barley malt hydrolyze starch to form maltose during mashing which is then used by yeast o produce CO2 and ethanol
what kind of enzyme is invertase
glycoside hydrolase
what does invertase do
hydrolyzes glycosidic bond in sucrose, resulting in an invert sugar - fructose and glucse
what kind of enzyme is lactase
glycoside hydrolase
what does lactase do
hydrolyzes glycosidic bond in lactose
what effect does lactase have on products
less crystallization , sweeter, and lactose-free
what kind of enzyme are pectinases
hydrolase
what do pectinases do
hydrolyze the methyl ester link in pectin
what effect do pectinases have on products
less cloudy juices
what kind of enzyme are proteases
hydrolases
what do proteases do
hydrolye peptide bonds in proteins
what is papain
protease found in papaya used as a meat tenderizer to break down collagen
what are papains used in
meat tenderizers, make beer more clear (proteins aggregate to make it cloudy)
what are examples of digestive proteases
trypsin, chymotrrypsin, pepsin, chymosin, microbial proteases,
what kind of enzyme are lipases
hydrolases
what do lipases do
hydrolyze ester bond between FA and glycerol
1,3-lipases v 2-lipases
1,3: cleaves sn1 and sn2 ester
2: cleaves sn2 ester
