Chap 1:Corn structure and chemical composition

Question 1

synonyms of corn grain

Answer 1

kernel, caryopsis

Question 2

4 parts of corn kernel

Answer 2

pericarp, endosperm, germ, tip cap

Question 3

where are protein soluble in water

Answer 3

in corn germ

Question 4

what can we see by breaking the tip cap

Answer 4

the hilar layer (where water comes so the more of humidity)

Question 5

corn kernel representation by prof

Answer 5

• plastic bag=pericarp
• bubbles=starch particles which are either round and soft or hard and polygonal
• glue=protein matrix
• sponge=oil germs

Question 6

structure of corn kernel (6 parts)

Answer 6

• dead cell walls
• cross cells (water circulation with hollow fiber)
• tube cells (water circulation)
• seed coat (semi-permeable)
• aleurone layer
• starch granules

Question 7

What contain aleurone layer?

Answer 7

Oil bodies and protein bodies

Question 8

what does germ contain?

Answer 8

oil (81-85% of the corn oil)

Question 9

what is btw germ and endosperm(2)?

Answer 9

cementing layer and epithelium

Question 10

what does contain endosperm (2)?

Answer 10

starch granules

• translucent hard and polygonal one -> tightly packed and held together by protein matrix (zein)
• opaque, soft, spherical one covered with protein matrix

Question 11

how is measured true density?

Answer 11

by endosperm hardness

Question 12

what is the chemical structure of starch?

Answer 12

polymer of six-C sugar D-glucose

Question 13

Are starch soluble in water

Answer 13

not under 110°C for 5 min with enzyme bcse of shape

Question 14

what are the two polymers in starch?

Answer 14

• amylose (linked by alpha 1-4)-helical chain

- amylopectin (alpha 1-6) structured in A(liaison), B, C (trunc) chain

Question 15

4 types of proteins in starch and properties

Answer 15

• albumins (active protein) soluble in water
• globulins (active protein) soluble in dilute salt solution
• glutelins (storage protein) soluble in dilute acide-base
• prolamins (storage protein)=zein, soluble in 70% alcohol

Question 16

how do we estimate protein content of cereal grains?

Answer 16

N2 content * 6.25

Question 17

which kind of protein does endosperm mainly has

Answer 17

storage protein (prolamins, glutelins)

Question 18

Why wet milling produce more oil in germ?

Answer 18

Because proteins go out of the germ when the corn is put in water, so the oil concentration can increase

Question 19

where are fibers?

Answer 19

Pericarp (cellulose which is crystalline and insoluble)

Question 20

Compo of corn kernel

Answer 20

• 10% proteins
• 10% fibers
• 72% starch
• 4% fat
• 4% others (ash, sugar, other)