5. Soybeans Flashcards
what plant family are soybeans part of?
what subfamily?
family: leguminosae
subfamily: papilionoidae
what is the scientific name for soybeans?
glycine max
what components of soybeans are they mostly cultivated for?
its oil and protein
where are soybeans originated from?
eastern asia
what are factors leading to increased soybean production?
- for food and feed for humans and livestock
- as replacement for oils high in saturated fats
- feedstock (for biodiesel production as alternative fuel)
what type of genetic engineering is applied to soybeans?
GM soybeans have higher oleic and stearic acids and lower linolenic acids (to increase stability)
which FA is originally present in soybeans, which is highly susceptible to oxidation?
linolenic acid
what soils do soybeans grow well on? where do they not grow well in?
most soils, except deep sands with poor water retentions
what is optimal soil pH for soybean growth? what may be required?
6-6.5 (liming may be required)
what is liming?
treat (soil or water) with lime to reduce acidity and improve fertility or oxygen levels
what is the best growing environment for soybeans?
temperate zones
why are soybeans called “short-day plants”?
flowering occurs when the nights being to lengthen
when are soybeans planted? when are they fully mature?
planted late spring to early summer
fully mature at early mid-autumm (when leaves turn yellow and while seeds begin to lose moisture)
when are soybeans harvested?
when water content of the seed is 13%, the max safe moisture level for long range storage
what happens if moisture content is too high when soybeans are harvested?
what is moisture is too low?
too high: promotes mold growth and rancidity
too low: seeds will be very brittle. Can lead to cracking/breaking of the seeds and cause disruption of membranes to release lipases that break down
which development stage of soybeans is adequate water most important for?
pod and seed development (pod filling stage)
where does ~50% of total N of the soybean plant come from?
N-fixing capacity through symbiosis with soil bacteria
what are the 4 main components of a soybean?
- testa: seedcoat
- cotyledon: seed leaf
- plumule: shoot
- radicle: root
describe the shape of soybeans
flat disc
can be spherical or elongated
compare industrial vs elongated varieties
industrial:
- grown for oil
- spherical
- ONLY yellow
elongated:
- used as vegetables
- can be yellow, green, brown, black
- has larger seeds
how are seed sizes expressed?
as number of seeds per unit volume or weight
eg: 18-20gm/100beans
what does the cotyledones consist of?
- 2 parts: radicle and plumule
- represents 90% of seed wt
- contains almost all oil and protein in its cells
what does the moisture content of soybeans depend on?
storage conditions
what is the equation of moisture content wet basis and dry basis?
MCwb = (Wi-Wf)/Wi x 100
MCdb = (Wi-Wf)/Wf x 100
how do you convert MCdb to MCwb?
How do you convert MCwb to MCdb?
MCwb = (100xMCdb)/(100 + MCdb)
MCdb = (100xMCwb)/(100-MCwb)
what sugars are found in soybeams
- sucrose
- oligosacchraides
- pectins
- gums
- hemicellulose
- beta-glycans
what oligosaccharides are found in soybeans?
- raffinose (trisaccharide)
- stachyose (tetrasaccharide)
which sugar in soybeans is not digestible? what does this cause
oligosarrharides
causes gas prouction, bloating, abdominal discomfort
what are pectins polymers of?
anhydrogalacturonic acid
when gums are first produced, what are they? what happens with exposure to air?
viscous mucilaginous plant exudates
eventually hardens with air exposure
what are beta-glycans?
polysarracharides of monosaccharides linked together by beta-glycosidic bonds
what are types of protein in soybeans?
- reserve/storage proteins
- makes up 80% of proteins
- globular
- readily extracted in aqeous solutions at neutral to slightly alkaline pH - biologically active proteins
- makes up 20% of proteins
- eg. enzymes, lectins
how is the nutritional quality of soybeans evaluated?
by its chemical score, which compares the essential AA content of one food material to that of a reference with known high quality protein (eg. meat, egg, dairy)
what is the chemical score of soybean protein?
70%
which AA is soybean protein especially rich in? what is this especially valuable in?
lysine
valuable supplement to cereal foods where lysine is a limiting factor
how are soy proteins characterized?
based on solubility in various media
describe the solubility of soy proteins
soluble in salt solution
what is the solubility of soy proteins in water strongly affected by?
pH
describe how the solubility of soybeans is affected by pH at:
A) neutral or alkaline pH (above isoelectric region)
B) acidic pH
A) around 80% of proteins in raw seeds of unheated meal can be extracted
B) solubility drops
what is the isoelectric region of soybeans?
pH 4.2-4.6
how is the pH dependence of solubility of soybeans used for manufacturing?
at neutral or slightly alkaline pH, defatted and unheated meal is extracted with water
this allows proteins to be precipitated from the filtered extract by acidification to the isoelectric point
what can the different sizes and characteristics of soybean proteins be separated based on?
what techniques can be used?
based on centrifugation
techniques: ultracentrifugation, gel filtration, electrophoresis
what are protein sedimentation fractions denoted by?
sedimentation constants (Svedber units, “S”)
when soy proteins are centrifuged, what fractions are produced?
2S
7S
11S
15S
which soy bean fractions constitute most of the total protein in soybeans?
11S and 7S
which soy protein fractions depend on the variety of soybean? how can they vary?
11S to 7S
can vary from 0.5 to 3
describe the 2S soy protein
- alpha conglycinin
- low molecular wt polypeptide
- includes soybean z-trypsin inhbitors (zkunite and bowman-birk inhibitors)
describe the 7S soy protein
- large molecular wt heterogenous protein mix
- Main component is beta-conglycinin (sugar containing globulin)
- also contains gamma-conglycinin, enzymes (eg. beta-amylase, urease and lipoxygenase) and lectins (eg. hemagglutinins)
which soy protein is the principle and most abundant soybean protein?
describe its characteristics
glycinin (11S)
large molecular wt and mostly reserve proteins
which soy protein is a dimer of glycinin?
15S
what are two main soy protein enzymes
lipoxygenase (LOX)
urease
which is the most important enzyme in soybeans?
what is its main function?
what are other functions?
lipoxygenase (LOX)
main function:
- responsible for oxidative rancidity in soybean oil
- It oxidizes linoleic acid of soybean oil into breakdown products, which leads to the “Beany” smell and flavor of soybean
other functions
- bleaching agent for flours
what is the function of urease?
what is the result of this function?
to break down urea to form uric acid
this can cause adverse flavour effects
what is used as an index of adequacy of the heat treatment given to soybean meal?
the inactivation of urease, since it is heat stabile
what are protease inhibiting proteins?
some proteins (eg trypsin inhibitors and lectins) that exert physiological effects and inhibit other serine proteases (eg. chymotrypson and elastin)
if these digestive materials are inhibited, we would expect the organ producing the enzymes (pancreas) to work overtime to produce more of the enzymes to enable their carrying out of normal digestive function in the intestine
what does SBTI stand for?
soybean trypsin inhibitors
is SBTI ingestion harmful to humans?
no evidence to prove it
what are the 2 types of SBTIs?
- kunitz inhibitor
2. bowman-birk inhibitor
how do raw soybeans affect rats or chickens?
how is this eliminated?
can impair their growth
can eliminate this by properly heating soybeans
describe the heat stability of SBTIs
they are heat labile
what happens when SBTIs are ingested?
- inhibits proteases (eg. trypsin and chymotrypsiin) in the GIT of the animal, to impair protein digestibility and utilization
- increases pancreatic secretion and hypertrophy of the pancreas
- increases secretion of enzymes into GIT and represents and internal loss of protein
when can the ingestion of SBTIs cause a crucial loss of protein?
- since ingestion of SBTIs would cause increased secretion of enzymes into GIT and represent an internal loss of protein
- if the diet is marginal in methionine and cystein, the internal loss of sulphur containing AAs would not be good
describe the toxicity of SBTIs
- no direct evidence to physiological effect of SBTIs on humans
- however, you should take precaution of removing or inactivating trypsin inhibitors from soybean products intended for human consumption
what is the function of lectins?
causes agglutination of RBCs (due to high net negative charge)
what are characteristics of lectins?
- widely distributed in plants. Some are highly toxic (Eg. castor bean lectin ricin)
- can bind to surfaces in the distal part of the SI to damage SI villi and disrupt SI metabolism
- readily inactivated by heat
what are examples of isoflavones?
genistein
daidzein
glycitein
what are isoflavones?
- naturally occuring polyphenols
what are functions of isoflavones
- many isoflavones act as phytoestrogens in mammals (harmful property)
- Some isoflavones have antioxidant and anticancer abilities
what are two methods of modification of anti-nutritional factors?
- heat processing: roasting or heating to inactive trypsin inhibitors and lectins
- high pressure processing: pressure above 500MPa can inactivate several enzymes or denature proteins. Ca also alter molecular structure of antigens
what are 5 main utilizations of soybeans?
- oil
- whole bean
- flour
- soy protein concentrate (SPC)
- milk
what are food and non-food uses of soybean oil?
food use: cooking oil
non-food uses: starting material for bio-diesel, inks, plasticizers, crayons, paints and candles
what are the steps of soybean oil production?
- pre-treatment: cleaning or flaking
- oil extraction: by solvent extraction with hexane
- purification: filtration, degumming, alkali refining, bleaching, deodorization
- further processing: wintering, partial or full hydrogenation
in the production of soybean oil, describe the two methods of pre-treatment
A) cleaning
- sieving with screen to remove particles
- drying (reduce moisture content to 10-12%)
- magnetic separation to remove pieces of metal
B) flaking
- heating to 75C
- slicing into flakes to increase SA
- heating to coagulate soy proteins to increase yielf
describe the FA composition of soybean oil
60% PUFAs
25% MUFAs
16% satFAs
what is the major PUFAs, MUFAs and satFAs in soybean oil?
PUFAs: linoleic and alpha-linolenic acid
MUFAs: oleic acid
satFA: palmitic acid and stearic acid
how are whole roasted soybeans and their flour used?
as ingredients in confectionary products and snacks
how are immature whole green soybeans used?
for consumption as a vegetable
what are mature dry soybeans not used for?
not used as a cooked veg
how is soybean flour produced?
what special care is taken during this production?
from solvent removal or defatted soybeans
special care is taken to minimize denaturation of protein
what is soybean flour produced from?
powdered roasted soybeans
what is soybean four used for?
to add texture and flavor to products
what are the 2 types of soybean flour?
- natural/full fat soy flour (FFSF). Also called grits
2. defatted soy flour
what is the principle use of FFSF (full fat soy flour)?
in the bakery
what two types of flour does FFSF use? what is each type used for?
- enzyme active: prepared without heat treatment and used mostly in bakery products, mainly for its LOX activity. Used for white bread and rolls
- o enzyme inactive: prepared with heat treatment. Used in the heavier types of cake batters, ie sponge cakes and pound cakes
compare FFSF and defatted soy flour
full fat soy flour: contains all natural oils foundi n the soybeans
defatted soy flour: has oils removed during processing
describe the production process of defatted soy flour
- solvent extraction
- solvent removal (flash de-solventization)
- steam heating
- drying and milling
what are common uses of defatted soy flour?
protein supplement in bread, tortillas, pasta, cereal products
what is SPC?
soy protein concentration
how is SPC produced? what characteristics does SPC have?
production: uses alcohol to remove soluble CHO from defatted soyflakes
results in a protein with low solubility and good H2O holding capacity, but incapable to form gels or emulsifying fat
what are the uses of SPC?
- bakery products
- meat products
- stabilized dispersions in milk-like beverages
- stimulated dairy products in bakery products
describe the steps of the production process of SPC from DFSF
- heat denaturation/water extraction process
- acid wash process
- aqueous alcohol wash process
- drying and milling
what can soy milk be made from?
whole soybeans of full fat soy flour
describe the production steps of soymilk
- dry beans are rehydrated by soaking in water (minimum 3 hours)
- beans are wet milled with water (10w/v) to form a slurry
- the resulting slurry is heated close to boiling point for 15-20min (this step improves nutritional value by heat inactivating soybean trypsin inhibitor, improve flavor and sterilize the product)
- the boiled slurry is cooled and filtered to remove insoluble residue (soy pulp fiber or okara)
