Proteins VII Flashcards
The protein level of soy protein is typically ____%, and the lipid level is usually ____%
45%
20%
In soy protein, an increase of ___% in protein content is accompanied by a decrease of ___% in oil
1
0.5
In soy protein, oil and protein are (positively/negatively) correlated
negatively
The seed composition of soybeans is ___% protein, ___% fat, ___% carbohydrates, ___% ash
40
20
35
5
The main portion of the soybean is the _______
cotyledon
The portion of the soybean that contains mostly carbohydrates is the _____
hull
The portion of the soybean that contains the most lipids is the _____
cotyledon
The _____ and _____ portions of the soybean contain high levels of protein
cotyledon
hypocotyl
______ is equivalent to meat and eggs in terms of protein composition
Soy protein
The main content of protein in soy is found in storage sites called ________ or __________, which are subcellular structures that range in diameter from 2 to 20 um.
protein bodies
aleuronic grains
The ________ have been reported to contain approximately 10 % nitrogen, 0.8 % phosphorus, 8.5 % sugar, 7 % ash, 0.5 % RNA, 4.5 % lipids and 2 % phospholipids.
protein bodies
________ in soybeans are close to 75% proteins
Protein bodies
Apart from proteins (80%), protein bodies in soybeans contain ______________ (20%)
biologically active proteins, such as enzymes, enzyme inhibitors, and lectin
The soybean storage proteins were extracted and characterized for the first time by ______ & ______ in 1898, and they named the extracted protein ______.
Osborne
Campbell
glycinin
The simplest criterion used for the characterization of soybean proteins is their ___________.
solubility in various media
As in all legumes, the bulk of soybean proteins are _______, characterized by their solubility in _____ solutions.
globulins
salt
The solubility of soybean proteins in water is (affected/unaffected) by the pH
strongly affected
Close to 80 % of the protein in raw seeds or unheated meal can be extracted at _____ or ______ pH.
neutral
alkaline
As the (acidity/alkalinity) is increase, solubility drops rapidly and a minimum is observed at pH 4.2 to 4.6
acidity
What is the isoelectric region of soybean proteins as a whole?
4.2 to 4.6
More precise and detailed fractionation of the proteins can be carried-out by techniques such as ___________, _________, and __________
ultracentrifugation, gel filtration and electrophoresis.
It is custom to characterize soybean protein fractions by their _________
sedimentation constants
__________ made it custom to characterize the soybean protein fractions by their sedimentation constants
W. Wolff
These proteins are (homogeneous/heterogeneous) and when ultracentrifuged at pH 7.6 and 0.5 ionic strength, the fractions __S, __S, __S, and __S were given
2
7
11
15
The numerical coefficient is the characteristic sedimentation constant in water at ____oC.
20
The __S and __S fractions constitute about 70 % of the total protein in soybeans.
11S
7S
The ratio 11S/7S is a varietal characteristic and may vary from ____ to ____
0.5
3
__S fraction is composed of a-conglycinin and low molecular weight polypeptides
2
The components of __S also comprise the soybean trypsin inhibitors
2
__S is highly heterogeneous
7
The principal component of __S is B-conglycinin, a sugar containing globulin
7
__S also contains gamma-conglycinin, the enzymes (B-amylase and lipoxygenase), and hemagglutinins
7
__S is glycinin, the principal protein of soybeans with a built of 12 subunits
11
__S is a dimer of glycinin
15
_________ is the enzyme responsible for rancidity in soybean oil by oxidation of linoleic acid, the major constituent of soybean oil. Also leading to the beany smell and flavor.
Lipoxygenase
The _______ is obtained by comparing the essential amino acid composition to that of a standard reference protein
chemical score
The chemical score uses an _______ as a standard reference protein
egg
In soybean, the limiting amino acids are the ones containing ______, which are ______ and _______
sulfur
methionine
cystine
The chemical score of soybean protein is ____%
70
Soybean is exceptionally rich in _______ and can serve as a valuable supplement to cereal foods
lysine
Chemical score alone is not a satisfactory measure of protein quality since it does not account for _________ and the _____________________
protein digestibility
biological availability of the amino acids.
What are the 3 predictors that assess nutritional performance of a protein under certain experimental conditions (in rats)?
- Biological value (BV)
- Protein efficiency ratio (PER)
- Net protein utilization (NPU)
Attempts to develop, genetically, soybean varieties with a higher content of sulphur containing amino acids have (been/not been) successful.
not been
Soybeans, as all seeds, contain the enzyme systems necessary for ________.
germination
Technologically, the most important enzyme in soybeans is ___________, also known as ___________.
lipoxygenase
lipoxydase
________ catalyzes the oxidation of polyunsaturated fatty acids by molecular oxygen,
Lipoxygenase
__________ activity is also the reason for the occasional use of small amounts of unheated soybean flour as a bleaching (carotenoid oxidizing) agent in wheat flour.
Lipoxygenase
The enzyme ______ has served as an indicator for the adequacy of the heat treatment given to soybean meal
urease
Residual ________ activity is still sometimes used as an evidence of insufficient heat treatment.
urease
Protease inhibiting proteins are present in soybeans as ______ inhibitors
trypsin
The two types of soybean trypsin inhibitors are the _______ inhibitor (large), and the ________ inhibitor (small)
Kunitz
Bowman-Birk
It has been known for a long time that ___________ or ______________ will impair growth when fed to young rats or chicks, which is completely eliminated when the soybean is properly heated
raw soybeans
unheated soybean meal
The presence of __________ in the diet is responsible for the suppression of growth.
trypsin inhibitors
The ingestion of ______________ can result in increased pancreatic secretion and hypertrophy of the pancrease
trypsin inhibitors
Increased secretion of enzymes into the digestive tube represents an internal (gain/loss) of protein.
loss
The proteins excreted by the pancreas are particularly rich in ______ containing amino acids, the internal loss of protein could be specially important if the diet is marginal in _________/________
sulfur
methionine/cystine
True or false: trypsin inhibitors are toxic to humans.
False; there is no direct evidence, BUT it is custom to remove the trypsin inhibitors
The ______, formerly known as __________,are proteins which possess the ability to agglutinate red blood cells.
lectins
hemagglutinins
________ are widely distributed in plants and some, such as the castor bean _______, are highly toxic.
Lectins
lectin recin
The ______ found in soybeans has no observable effect and is easily inactivated by heat
lectin
Functional properties are related to the ______ structure, and the ______ and _______ structures
primary
secondary
tertiary
Soybean protein products with unique functional properties are available and constitute important tools in the formulation of the so-called _______________
fabricated foods
Soybean oil is obtained by ___________
solvent (hexane) extraction
________ used as cooking oil, but also used in the chemical industry as starting material for bio-diesel,inks,plasticizers,crayons,paints and even candles.
Soybean oil
Soy meal is obtained from grounded flakes after ________
oil extraction
_______ is used for feed (cattle, swine, poultry)
Soy meal
_______ refers to defatted soybeans where special care was taken during solvent removal to minimize denaturation of the protein
Soy flours
_______ are the starting material for protein enriched soy products
Soy flours
______ constitute 65%-85% protein content
Soy protein concentrate (SPC)
______ are usually manufactured by using alcohol to remove the soluble carbohydrates from the de-oiled soy flakes, resulting in a protein with (high/low) solubility incapable to ____ or ________
SPC
low
gel
emulsify fat
Traditional alcohol-washed _________ are used for protein fortification of foods as well as in the production of textured soy concentrates.
soy concentrates
___________ are produced using minimum heat and homogenization followed by spray drying, or by using a water-wash process at an (acid/base) pH to remove soluble _______, followed by neutralization
Functional soy concentrations
acid
sugars
_______________ hold water, emulsify fat and form a gel upon heating; they are widely used in the meat industry and are also efficient for the stabilization of high fat soups and sauces.
Functional soy concentrates
_________ contain 85% or higher of protein
Soy protein isolate (SPI)
______ are bland in flavor, light in color, and have a number of functional properties such as gelation,viscosity,emulsification,water holding capacity,and even some foaming and whipping ability.
Soy protein isolates (SPI)
What are the four cereals?
Wheat, corn, barley, rice
Cereals all contain ______ as their major component along with 6-20% _______
starch
protein
Wheat proteins are often isolated as a byproduct of ______ manufacture
starch
The protein fraction of starch is termed _____
gluten
______ is used to produce protein hydrolysates and is used as an additive to strengthen soft wheats
Gluten
________ is the ground _______ of the wheat kernel made up of _____ granules held within a ____ matrix
Wheat flour
endosperm
starch
protein
_______ are unique in being capable of providing loaf volume
Wheat proteins
The two main protein groups that are responsible for providing loaf volume are ______ and ______
glutenin
gliadin
______ and ______ contain sulphur in the form of cysteine and cystine
Glutenin
gliadin
_______ are wheat proteins that are soluble in dilute alkali or acid
Glutenin
______ are wheat proteins that consist of a heterogeneous group of proteins, which are crosslinked by (intra/inter)molecular disulfide bonds
Glutenins
inter
If ______ proteins are hydrated, it forms a very tough elastic mass (like chewing gum)
Glutenin
________ is a hydrophobic prolamine
Gliadin
______ is a wheat protein that requires alcohol for solubilization
Gliadin
_______ consists of heterogeneous group of proteins which (are/are not) crosslinked, and contain extensive (intra/inter)molecular disulfide bonds and free SH groups
Gliadin
are not
intramolecular
If isolated and hydrated, _____ will form a very viscous solution
gliadin
When _____ and ______ are mixed together, a ________ mass (dough) is formed
glutenin
gliadin
viscoelastic
The unique viscoelasticity of dough is due to the interaction of glutenin and gliadin, via the reaction of their sulfur ____ and ____ groups
S-S
S-H
In dough, ____________takes place via the reaction of free SH groups with S-S groups to polymerize the proteins
sulfhydryl interchange
During kneading the ____________ reaction takes place and bonds are broken and reformed to produce a cohesive _____ mass
sulfhydryl interchange
viscoelastic
Wheat dough uses _____ to produce ______, which allows the dough to rise
yeast
CO2
__________ is capable of trapping CO2, expanding and providing increased loaf volume
Viscoelastic mass
When the heat loaf volume expands, _____ gelatinizes, proteins _____ and products set, resulting in a desirable expanded, light product
starch
denature
Can corn bread attain the desirable texture of wheat-based products?
Corn bread
Single cell protein, including _____, ______, and ______
bacteria
yeasts
molds
What is the major problem with all microbial sources as a source of protein?
Their high nucleic acid content, which cannot be handled by our livers in excessive amounts if consumed on a substantive scale (liver damage, gout)
Most unconventional proteins have poor _______ properties
functional
What is the problem with bacteria as a source of protein?
The toxicological aspects due to pathogenicity
Ingestion of more than 100 grams per day of ______ leads to nausea, vomiting, and abdominal pains
algae
____ and _____ proteins need some functional or cost edge to compete with soy proteins
Pea
bean
________ can be produced by pin milling beans, followed by air classification to separate the heavier starch from the lighter protein fraction
Bean protein
________ are used in hamburgers, bread and sausage formulations, and in high-protein extruded snacks
Pea proteins
There is substantial protein present in _______ of most plants, a good portion of which is a harvest waste product
leaves (leaf protein)
The main problems of _____ protein are stability, yield, and palatability
leaf
The reason enzymes are able to speed up chemical reactions is because they are able to lower the _______ energy of the reaction
activation energy
_______ catalyze oxidations or reductions of substrates
Oxidoreductases
Lipoxygenase and polyphenol oxidase, which is responsible for ______, are _______ enzymes
browning
oxidoreductase
_________ catalyze a shift of a chemical group from a donor to acceptor substrate
Transferases
______, ______ and _______ enzymes are not so important in foods
Transferases
lyases
ligases
_________ catalyze the hydrolysis (along with water) of substrates
Hydrolases
_______ are the most important enzymes with respect to food quality and used in food processing
Hydrolyases
Proteases, amylases, and lipases are ________ enzymes
hydrolase
_______ catalyze the removal or addition of chemical groups to substrates
Lyases
________ catalyze intramolecular rearrangeements
Isomerases
Glucose isomerase, which converts ____ to ____, is an _______ enzyme
glucose
fructose
isomerase
________ catalyze combinations of substrates
Ligases
What are the three types of glycoside hydrolases?
1) Enzymes that hydrolyze glycosidic bonds
2) Invertases
3) Lactases
_______ hydrolyses a-1-4 glycosidic bonds within starch
a-amylase
Hydrolysis by ________ results in dextrins, maltose, and maltotriose
a-amylase
________ hydrolyses a-1-4 glycosidic bonds from the non-reducing end of starch
B-amylase
Hydrolysis by ________ results in maltose
B-amylase
________ hydrolyses a-1-4 and a-1-6 glycosidic bonds in starch
Glucoamylase
______ can hydrolyze all the way to glucose
Glucoamylase
__________ hydrolyses a-1-6 glycosidic bonds in starch
Pullulunase
Glycosidic hydrolases are important for ___________ production, _______, and ________
corn syrup
baking
brewing
A cocktail of enzymes starch can be converted to glucose syrup, which is a ______ sugar
dextrose
Corn syrup production starts with _________ to break _____ and ___________ to smaller units
a-amylase
amylose
amylopectin
Following a-amylase, corn syrup production uses _______ to break down _______
glucoamylase
glucose
If maltose is desired in corn syrup production, __________ and __________ enzymes are used
B-amylase
pullulanase
___________ are important to “dextrinize” the disrupted starch granules in baking
a-amylases
The dextrins produced by a-amylases in baked are hydrolyzed to maltose by ________, which gives fermentable _____ for yeast to produce _______
B-amylase
sugar
CO2
________ enzymes play an important role on the final texture and quality of bread, and are added to minimize staling
Amylases
High levels of _______ in barley malt
amylases
During mashing in the brewing process, ______ hydrolyze starch to give ______ for yeast and produce CO2 and _______
amylases
maltose
ethanol
________ is an enzyme that hydrolyzes the glycosidic bond between glucose and fructose in sucrose
Invertase
Invertase results in an ______ sugar
invert
________ are sweeter than sucrose, and has a (higher/lower) tendency to crystallize
Invert sugars
lower
_________ is an enzyme that hydrolyzes the glycosidic bond between galactose and glucose in lactose
Lactase
_______ enzymes are used in the dairy industry to minimize crystallization in ice cream
Lactase
_________ occur widely in fruits and vegetables and are responsible for the degradation of pectic substances
Pectinases
________ hydrolyze the methyl ester linkages of pectin
Pectin methyl esterase
__________ causes loss of cloud in citrus juice
Pectin methyl esterase
________ converts colloidal pectin to non-colloidal pectin
Pectin methyl esterase
_______ is added when clarity is desired (ex: apple juice)
Pectin methyl esterase
________ are enzymes that hydrolyze peptide bonds in protein
Proteases
________ enzymes are found in papaya
Papain
______ enzymes have a broad pH (3-11) and temperature stability, and thus are very popular for a variety of food applications
Papain
_______ is used as a ________ on inferior meat cuts
Papain
meat tenderizer
_______ makes its way into the muscle and hydrolyzes connective tissue proteins and soften muscle
Papain
You have to use low amounts of ______ to prevent liquefaction of muscle
papain
If you mix raw papaya into Jello, it (will/will not) form a gel
will not
Apart from papain, other popular tenderizing enzymes are _____ (from figs), ______ (from pineapple) and microbial proteases
ficin
bromelain
_______ can be used to clear turbidity (chill haze) in beer
Papain
When bottled or canned beer is kept below 10oC, a ____ can form because of interactions between _________ and _________ in beer
haze
proteins
tannins
The haze formed below 10oC in beer can be prevented by ______, in which a ______ is added during (pre/post)-fermentation maturation to hydrolyze proteins to prevent large aggregates to form on cooling
chill-proofing
protease
post
_____ and ______ are digestive proteases that are found in animal pancreas
Trypsin and chymotrypsin
_______ and ________ can cause quality problems in muscle foods if contamination from intestines occurs, which results in ______ of the meat
Trypsin
chymotrypsin
over-softening
______ and _______ are often used to make protein hydrolysates for the food, beverage, and the pharmaceutical industry
Trypsin
chymotrypsin
________ and ________ are most active at pH 7-9
Trypsin
chymotrypsin
_______ has a very acidic activity optima (pH 1.8), which somewhat limits its use
Pepsin
_______ is used in cheese making, chill-proofing and also in making protein hydrolysates, which are used for animal and fertilizer purposes
Pepsin
________ is essential for the manufacture of good quality cheeses
Chymosin (rennin)
_______ is found in the fourth stomach of a suckling calf’s
Chymosin (rennin)
It is very expensive and “inhumane” to process _______ so it has been engineered into a bacteria that mass produces it
chymosin
_____ has a very specific activity and hydrolyzes only one bond in __-casein
Chymosin
K
______ breaks up the casein complex and it aggregates to form a clot, the first step in cheese production
Chymosin
__________ have almost equal ability to form cheese clots like chymosin
Fungal proteases
A _____ cocktail from ____________ is used to partially break down glutens to reduce mixing time and making them more extensible
protease
Aspergillus oryzae
__________ are added to help with flavor and texture development and speeding up fermentation in fermented dairy products
Microbial proteases
__________ are also used to tenderize meat
Fungal proteases
__________ are used in combination with papain in beer chill-proofing
Bacterial proteases
_________ are enzymes that all hydrolyze ester bonds between fatty acids and a glycerol molecule
Lipases
Lipases work at the _________ interface
water-oil
_________ preferentially hydrolyze ester bonds at sn1 and sn3
1-3-lipases
_______ preferentially hydrolyze ester bonds at sn2
2-lipases
_______ have a dramatic impact on the quality of food products
Lipases
______ lead to hydrolytic rancidity
Lipases
Lipases are (good/bad) when free fatty acids are released in muscle foods and react with proteins to denature them and ________, which happens on ___________
bad
gives them a tough texture
freezing muscle
Lipases are (good/bad) when they are not inactivated in milk since they release short-chain FA that are very volatile
bad
can oxidize
Lipases are (good/bad) when used in fermented products
good
Lipases are (good/bad) in ripening of cheeses and dry-sausages
good
Lipases are (good/bad) when short-chain fatty acids are released from milk fat
good
_________ are used to modify lipid crystal structure to give different textures and melting points
Enzymes
______ produce mono- and diglycerides for use as emulsifiers
Enzymes
The enzyme is located in the ______ droplet of a water-in-oil emulsion and acts on the ____ surrounding of the water droplet
droplet
oil
_______ catalyze the (intra/inter)molecular arrangement within a molecule
Isomerases
intramolecular
__________ is the most important enzyme for the food industry, and catalyzes isomeric rearrangement of glucose to fructose
Glucose isomerase
Glucose isomerase converts an _______ to a __________
aldose
ketose
________ gives a sweeter product than corn syrup, which is called _________
Glucose isomerase
high fructose corn syrup
High-fructose corn syrup is made from corn syrup, which is made by _______ digestion of starch
amylase
________ enzymes are immobilized in large columns where the reaction takes place, which allows them to be reused
Glucose isomerase
________ are found in a wide variety of plants (legumes) and have also been identified in animal tissue (fish)
Lipoxygenase
_________ are specific for the oxidation of fatty acids that have a cis,cis-penta-1,4-diene unit so there can be three naturally occurring fatty acids that can be substrates:
_________ (2 double bonds), _________ (3 double bonds), and __________ (4 double bonds)
Lipoxygenase
Linoleic acid
Linolenic acid
Arachidonic acid
Lipoxygenase is (desirable/undesirable) in their role in bleaching of wheat and soybean flours
desirable
_______ contributes to the formation of S-S bonds in gluten in dough, without having to add chemical oxidizers
Lipoxygenase
Lipoxygenase can lead to the bleaching of chlorophylls and carotenes, which is (desirable/undesirable)
undesirable
Lipid oxidation can be delayed by using _______
antioxidants
__________ is found in plants (fruits and vegetables), animals, insects and microbes
Polyphenol oxidase (PPO)
________ catalyzes the oxidation of phenolic compounds (mono and/or diphenols) in the presence of _____ to give ______, which polymerize into ______ pigments (desirable or undesirable)
Polyphenol oxidase (PPO)
O2
quinones
melanin
PPO oxidase can be inhibited by:
- Removing ___
- pH < ___
O2
4.5
______ can be inhibited by vitamin C, bi-sulfites, and EDTA
Polyphenol oxidase
