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PLSC420 > Grain Constituents > Flashcards

Grain Constituents Flashcards

1
Q

Constituents of Grain

A

Water
Protein
Carbohydrate
Lipid
Lignin
Minerals
plus minor constituents.

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2
Q

Which crops have the highest protein %

A

Pea and Chickpea

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3
Q

Which crops have the lowest protein %

A

Corn and Rice

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4
Q

Which crops have the highest fat %?

A

canola, flax, soybean, peanut (oilseeds)

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5
Q

Which crops have the highest starch %?

A

Wheat, corn, oat, rice, barley (cereals)

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6
Q

How to measure water/moisture determination?

A
  1. dry sample in an oven (130ºC for 1 hr).
  2. measure weight loss
  3. express weight loss as % moisture.

There are other rapid methods including capacitance, near-infrared reflectance spectroscopy (NIRS).

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7
Q

What is Protein

A

polypeptides that are polymers of amino acid

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8
Q

Some essential amino acids

A

Leucine, Lysine, Methionine, Tryptophan.

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9
Q

Protein Determination

A
  1. Determine %N
  2. Multiply by conversion factor (6.25 to obtain % crude protein).

Problem: not all N is from protein, so what factor to use?

Grains and seeds contain 8-40% protein.

Kjeldhal method (flask)
Dumas Method (combustion)
NIRS

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10
Q

Amino Acid Determination

A
  1. hydrolysis of protein to constituent amino acids
  2. chromatographic separation and identification of amino acids
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11
Q

Classification of Proteins Based on Solubility (1924, Osbourne)

A

Albumins - water soluble
Globulins - salt, acid, and alkali soluble
Prolamins - alcohol soluble
Glutenlins - detergent and extreme pH soluble.

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12
Q

What are carbohydrates?

A

a substance that only contains C, H, and I.

starch, fibre, and simple sugars.

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13
Q

Starch

A

a carbohydrate polymer (polysaccharide). consists of polymers of glucose (amylose and amylopectin).

Starch granules are formed in amyoplasts. Occur in grains as layered, particulate granules.

granule size and shape and amylose/amylopectin ratio are genetically determined.

starch is important to dietary energy and its pasting and other functional properties.

grains and seeds contain 0-80% starch

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14
Q

Starch Assay

A
  1. glucose after enzymatic hydrolysis
  2. measure glucose chromotographically or chemically
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15
Q

Amylose vs Amylopectin

A

amylose - straight chain

amylopectin - branched chain

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16
Q

Fibre

A

crude, detergent, and dietary fibre.

grains and seeds contain up to 40% fibre. contain 5-25% total dietary fibre (TDF)

17
Q

2 kinds of fibre

A

Non-starch polysaccharides (NSPs)

Resistant Starch

18
Q

NSPs (Non-Starch Polysaccharides)

A

NSPs - cell wall consists of variety of carbohydrate polymers (5 and 6-carbon sugars).

Cellulose, hemicellulose, pectins, beta gluten.

Indigestible dietary component for monogastrics.

19
Q

Resistant Starch

A

non-diegestible in the small intestine of humans.

20
Q

Simple Sugars

A

glucose, fructose, sucrose, raffinose, etc.

grains and oilseeds contain 2-5% simple sugar

21
Q

Simple Sugar Assay

A

extraction with aqueous alcohol, chromatographic separation, and identification.

22
Q

Lignin

A

carbohydrate-like material associated with fibre.

Complex polymer network of simple phenolics derived from phenylalanine and tyrosine.

grains and oilseeds contain low levels of lignin.

23
Q

Lignin Assay

A
  1. soak material in 72% H2SO4 for 12 hours
  2. wash, dry, weigh residue
24
Q

Lipids

A

Neutral lipids (vegetable oils and fats)
Polar Lipids (cell membrane lipids)

consist mainly of triglycerides.

grains and seeds contain 1-50% neutral lipid and 2-3% polar lipid.

25
Q

Polar Lipids

A

Primary phospholipid.

Not extracted in the assay for crude fat.

total lipids extracted with a mixture of chloroform and methanol.

Total lipid - neutral lipid = polar lipid.

grains and seeds contain 2-3% polar lipid.

26
Q

Minerals (Ash)

A

inorganic material.

Burn away organic material (650ºC), residue is ash.

Specific minerals (Ca, Mg, Fe, etc.) may be determined by a variety of methods – atomic absorption or plasma spectroscopy, neutron bombardment.

PLSC420 (13 decks)

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