Corn Flashcards
Corn Latin name
Zea mays L.
Native to
Mexico / Central America
domesticated by indigenous peoples in southern Mexico 10,000 years ago
annual production
1148 million tonnes in 2019.
30% in USA, 23% in China.
Corn is a minor crop in Canada (13 million tonnes). Canada imports significant quantities of corn.
Primary global uses
primarily as human food in Central and South America, India, and Africa.
Primarily a feed grain in Europe.
Uses in USA
40% fuel alcohol and distillery
35% feed
10% exports
10% edible products
Corn Kernel
Naked Caryopsis
Very Large Kernel (10x wheat)
Very large embryo (germ).
Corn Bran
makes up 6% of kernel (compared to 15% in wheat)
Coloured corn variants
coloured variants have pigmented aleurone and pericarp. yellow corn has carotene in the starchy endosperm.
Corn constituents
Bran - 15%
Starchy Endosperm - 82%
Embryo - 12% (contains 35% of the seed oil)
Corn protein and oil
9-10% protein
6% high linoleic acid oil
Storage protein in corn
Prolamin (Zein)
deficient in lysine, threonine, tryptophan.
Corn Market Class depends on what?
Market Classes are based primarily on starchy endosperm structure/composition. It is based on the proportion and location of soft and hard endosperm. Also distinguishable based on colour.
Therefore, corn market class is based on the basis of colour, and starch type.
Market Classes
Dent (waxy, high amylose, flour, & sweet corn).
Flint (popcorn).
Soft Endosperm
Opaque and floury.
Called Starchy Endosperm
Usually in the middle of kernel.
Hard Endosperm
Transluscent and rough.
Called Horny Endosperm.
Usually on the periphery of kernel.
Dent Corn
contains a hard endosperm on two sides of the kernel with a central core of soft endosperm in the middle of the hard endosperm.
variants of dent corn are waxy corn, high amylose corn, flour corn, and sweet corn.
waxy corn
a variant of dent corn.
Starch is almost exclusively amylopectin
high amylose corn
a variant of dent corn.
50-70% amylose in starch (Amylomaize starch)
flour corn
a variant of dent corn.
All soft endosperm, no hard endosperm.
sweet corn
a variant of dent corn.
An immature kernel with tender bran, sugary endosperm and sweet flavour.
Good for eating.
Flint Corn
Has a hard endosperm that completely encases soft endosperm (hard endosperm goes all the way around compared to dent corn which only has it on two sides).
popcorn
a variant of flint corn.
has a thick, hard, bran.
What ways can corn be processed?
- Can be be ground into whole grain corn meal for feed, fuel alcohol, or food.
- Can be dry milled to separate anatomical constituents.
- Can be wet milled to separate the chemical constituents where starch is the major product.
Objective of Corn Dry Milling
separates the bran, germ, and starchy endosperm from one another. Maximize the yield of grits and meal while minimizing flour yield.
Maximize recovery (purity) of germ. Minimize contamination of grits and meal with the germ or germ oil.
Corn Dry Milling Steps
- Cleaning removes foreign material.
- Conditioning - tempers to 20% moisture to soften the starchy endosperm and loosen bran and germ.
- Degermination - a cone mill (Beall degerminator) tears open kernels, peels away bran and germ.
- Screening separates coarse bran from germ and flaking grits from finer material
- Roller Milling of coarse grits from screening and separates into grits, meal, flour, bran, and germ using finely corrugated sizing rolls (similar to break roll milling of wheat).
- Dry milled products to a safe storage moisture
How is corn bran utilized
feed, food
How is corn germ utilized
oil and corn meal
How is corn grits, meal, and flour used
alcohol, corn flakes, cereal, snacks, porridge (grits, polenta), corn bread, muffins, tortillas, chapatis, brewing adjunct, adhesives.
Corn meal
Corn meal is simply ground up corn kernels with no parts removed. It is gritty and coarse and not ground finely.
Corn flour
Yellow powder made from finely ground corn with no parts removed. It is ground very finely. Differs from cornmeal by texture only.
Corn starch
the central starchy, soft endosperm of the corn kernel, all other parts removed.
Corn grits
ground corn with the bran and germ removed, but all of the endosperm, both horny and soft, remain.
Polenta
made with flint corn which contains more horny endosperm and is coarsely ground.
Wet Milling of Corn Objectives
The objective of wet milling is to separate the corn kernels into their chemical constituents – starch, protein, fibre, germ, and solubles.
Wet Milling Steps
- Cleaning removes foreign material.
- Steeping in water to 45-50% moisture for 2 days. some SO2 is added to inhibit microbial growth and reduce disulphide bonds. the pH declines as lactic acid is produced during fermentation.
- Degermination (coarse milling) uses a stud, pin, or plate mill to shred kernels. The germ is released intact and recovered by flotation or hydrocyclone.
- Milling (fine milling) de-germed material to a fine slurry. Releases fibre (bran and cell wall), starch, and solubles (protein)
- Screening separates fibre (overs) from the starch and solubles (unders)
- Centrifugation/Hydrocyconing – unders are separated into starch and solubles. starch is purified by washing, and drying. Protein and other solubles are blended with fibre and steep water, and dried, which results in corn gluten meal.
Corn gluten meal
a byproduct of corn wet milling made up of the main proteins of the endosperm.
Corn oil
derived when the bran is initially crushed. the germ is separated during the third step, determination.
What is leftover byproduct steep water utilized for?
fermentation media and feed (corn gluten meal)
what is fibre (bran) utilized for
feed (corn gluten meal)
what is corn protein utilized for
feed (corn gluten meal)
what is corn germ utilized for
corn oil, and corn meal
what is corn starch utilized for
sweeteners, food starch (corn starch), adhesives, binders, paper, alcohol.
Masa (Nixtamal)
a corn dough that comes from nixtamalized corn to make corn tortillas, tamales, taco shells, chips, and other sheet extruded dough products.
Nixtamalization
corn is soaked and cooked in an alkaline solution, usually limewater, washed, and hulled
Nixtamalization steps
- corn is heated in water with 1% Ca(OH)2 to alkalize the water.
- temperature is brought to 82C for an hour.
- mixture cooled overnight. corn is scoured to remove bran and washed to remove Ca(OH2) and then ground to coarse texture.
Why is the Calcium Hydroxide added during nixtamalization?
the Ca(OH)2 provides flavour, loosens bran, and alters protein and starch functionality. it also releases any bound niacin.
