Topic 3B Flashcards
what are the roles of PRO in food?
water binding gel formation thickening emulsion foam formation Maillard rxn
what elements do PROs contain?
C H O N S
how many AAs are there?
20
how many AAs are essential?
9
how many AA are conditionally essential?
1
how do AAs differ from among each other?
side chain
What is unique about a PRO?
AA sequence
the balance of AAs in a PRO determines what about its quality?
biological value
nutritional quality
what does it mean when a PRO has a high biological value?
complete PRO contain adequate amounts of essential AAs
complete PRO
contains all essential AAs
what foods contain PROs of high biological value?
animal products (ex: milk, eggs, cheese, meat & poultry)
how does a vegan lifestyle acquire a complete PRO source?
combination of diff plant PROs
primary structure
series of AAs
what determine the primary structure of a PRO?
genetics
secondary structure
side chains of AA interact with one another in the PRO molecule
tertiary structure
alpha helices & beta sheets interact with one another
what structure creates the 3D shape of the PRO?
tertiary
quaternary structure
multimeric PROs
what type of envr will cause denaturation of a PRO?
acidic
PRO shape can be:
globular
fibrous
buffering
resist change in pH
amphoteric
same molecule can take & donate protons in nature
PROs are more soluble at what pH? & why?
PROs are more soluble at alkaline pH b/c there are more net OH- ions & thus more interactions with water (H-bonds) remain dissolved in water
what groups on the PROs accept & donate H+?
amine = accept
carboxyl = donate H+
what is an ex of PRO buffering in humans?
blood carrying various substances altering the pH which could be harmful
the blood buffers the pH
denaturation
interactions b/w side chains have changed thus, causing the PRO to acquire a new shape
what structures are disrupted during the denaturation of a PRO?
tertiary & quaternary
what causes denaturation?
change in the envr –> acids, alkalis, alcohol, heat, heavy metals (ex: Hg), UV radiation
how does denaturation affect the solubility of PROs?
reduces, form aggregations
when is denaturation desirable? & how is this accomplished?
digestion & by gastric acid containing HCl, causes the side chains to open up & enables enzymes to break them down
when is denaturation undesirable?
transport of harmful materials in the blood
foaming & how does this happen?
PROs form films around air bubbles
films have repulsive interactions & don’t let the air bubble coalesce stabilizing the foams
PRO films are line with what kind of charge in foaming?
negative
gelation
PROs can form a gel matrix balancing PRO-PRO interactions & PRO-solvent (water) interactions
water holding capacity
the amount of water it can bind to without the water leaking away from it
what factors affect the water holding capacity of a PRO?
pH
salt
temp
when does a PRO have the least water holding capacity?
isoelectric pH
PRO is compact & not interacting with PRO molecules (insoluble)
isoelectric pH
pH where the PRO has a net charge of 0
what causes the increase in WHC?
addition of salt
& increase in temp up to a certain point in gel-forming PROs
how does an isoelectric pH affect a PRO’s solubility?
insoluble
how does a pH above the isoelectric pH affect a PRO’s charge? how does this affect solubility?
net negative charge
increases
how does a pH below the isoelectric pH affect a PRO’s charge? & how does this affect solubility?
net positive charge
increases
emulsification
ability to keep oil & water mixed
what type of PROs are good emulsifiers?
PROs with both hydrophobic & hydrophilic properties
what is the pH of milk PRO?
6.6
what are the PROs included in milk PRO?
casein alpha, beta & kappa
kappa
keeps alpha & beta-casein from precipitating
what causes alpha & beta to precipitate?
pH change causing casein to become non-functional
what are the whey PROs in milk?
Lactoalbumin, Lactoglobulin, lactoferrin, lysozyme, lactoperoxidase
what are 2 high PRO products made from milk?
whey PRO isolate
whey PRO concentrate
whey concentrate has more ____ than whey isolate
impurities
what causes whey PROs to denature?
heat ONLY
what are the 2 major parts of an egg?
egg white
egg yolk
older the egg is, the ____ the egg white
thinner
what decreases an eggs foaming capacity?
age
what part of the egg is nutritious?
yolk
how is the quality of eggs determined?
candling
haugh unit
candling
a light enables seeing in the egg where they look for cracks & air cell size
haugh unit
higher the unit better the quality egg
test buoyancy –> older the egg is, the larger its air cell & the more buoyant the egg
what is the major PRO of the egg called? & what characteristic does it have?
ovalbumin
high foaming capacity
what PROs are found in egg yolk?
HDL
LDL
what are the functional characteristics of an egg?
emulsification
foaming
coagulation
emulsification in eggs & when is this used?
lipoproteins & phospholipids present in the egg yolk help to keep fat dispersed in water
mayonnaise
foaming in eggs
PROs in the egg white have a high capacity to form strong PRO films that surrounds air bubbles to produce stable foams
coagulation in eggs
egg white PROs can set & form a gel during heating
denature easily at high temps
red meat eaten in Canada mainly comes from:
cattle
pigs
chicken
animal flesh consists of:
muscle tissue or fibres
connective tissue
fatty (adipose) tissue
muscle cells are comprised of:
water
PROs
minerals
Vitamins (especially B12)
myoglobin
fat
connective tissue PROs:
collagen
elastin
collagen & what does it form? & what effect does it have when cooked?
major PRO in the connective tissue in & around the muscle fibres & tendons is mostly collagen
forms a gel
becomes soft & soluble when cooked
collagen solubility
water soluble
elastin & what effect does it have when cooked?
the ligaments which join 2 bones together are mostly made up of elastin (present in tendons & ligaments)
remains tough even when cooked
(yellow colour)
muscle fibers are composed of what PROs:
actin & myosin
muscle fiber length varies due to:
Length of fibres varies
Depending on location of muscles in body
Some muscles will be used more than others (ex: legs vs. ribs on cows)
Type of animal
Ex: fish have smaller muscle fibers
Age of animal (more collagen will be deposited)
fine muscle fibres & what happens when cooked?
tend to come from the muscles of young animals or in older animals from the muscles which do the least work
contain little collagen & are tender even when cooking
thick muscle fibres & how does it need to be cooked?
tend to be from older animals & also muscles which do the most ‘work’ (ex: neck & skin)
Meat is tougher & needs long, slow cooking with moisture to make it tender (ex: casserole)
what are 2 methods of lowering the pH of meat? & why do you want to do this?
make the meat more tender
add acid = increase water holding capacity (marinate)
mechanical pounding, break down starch –> tenderization
visible fat
found in meat underneath the skin, cover fat (subcutaneous fat) & b/w the muscles (intermuscular fat)
seen with the eyes
creamy white colour
invisible fat
small amount of fat is found in connective tissue surrounding the bundles of muscle fibres
not obvious to the eye
removal of what type of fat affects the tenderness of meat? & what is the result?
invisible fat
causes it to be dry
what causes the colour of meat?
myoglobin & hemoglobin (varries with the types of muscle)
colour diffs in meat are due to:
mainly the metabolism of the species & function of the muscle
(also age & exercise)
darker meat comes from what kind of muslces?
muscles that have been used a lot more & are older
oxymyoglobin
myoglobin bound with oxygen
metmyoglobin
oxymyoglobin oxidized
how does oxidation affect the colour of meat?
darker = more oxidized
why are nitrides (antioxidants) added to meat?
prevent browning & growth of microbes
why is salt added to meat?
prevents growth of microbes & increases water holding capacity
what are the principle PROs in wheat?
gliadin & glutelin
gluten
complex formed form gliands & glutelins following hydration (water) & mixing of wheat flour
gliadin + glutelin = gluten
why are water & mixing important in the formation of gluten?.
triggers the formation of disulfide bonds b/w glutelin
mixing increases the rate of disulfide bond formation
hydrated gluten provides what type of structure? & what characteristics does it provide to the wheat flour?
3-D viscoelastic network
valued dough & bread making characteristics
what does gluten prevent from escaping?
CO2
gliadin ___b/w ___ molecules
floats
glutelin
what property does gliadin provide?
viscosity
what property does glutelin provide?
elastic property
pulse & oilseed storage PROs contain very little of what PROS & what is their main PROs?
gliadin & glutelin
majority of PROs are albumin & globulins
single celled PROS come from:
yeasts, bacteria & fungi
mycoPRO
PRO from a fungus
consumption from F. venenatum has been approved
mycoPRO supplies:
50% PRO
13% lipids
25% fibre
(no cholesterol)
what is the trade name of myco PRO?
Quorn
food use of mycoPROs:
Muscle fiber replacer in the manufacture of simulated meats like vegetarian burgers
Fat replacer
Cereal replacer in the manufacture of breakfast cereals
