Starch

Question 1

Starch is the storage form of what simple sugar in plants?

Answer 1

glucose

Question 2

What is the general term for a complex carbohydrate made of 10 or more monomers?

Answer 2

polysaccharide

Question 3

What are the two polysaccharide molecules that make up starch?

Answer 3

amylose & amylopectin

Question 4

What is the storage form of glucose in animals and is more branched than amylopectin.

Answer 4

Glycogen

Question 5

What type of polysaccharide, made of non-glucose monomers, includes gums and pectic substances?

Answer 5

Gums and pectic substances are polymers of monosaccharides that are not glucose.

Question 6

Within a plant cell, where are starch granules made and stored?

Answer 6

leucoplasts, which are a type of plastid.

Question 7

What is the plant cell wall structure made of?

Answer 7

cellulose & hemicellulose (not just glucose monomers)

Question 8

Which component of starch is a linear chain of glucose molecules with 1,4-α linkages?

Answer 8

Amylose

Question 9

Which component of starch is a branched chain of glucose molecules with both 1,4-α and 1,6-α linkages?

Answer 9

Amylopectin

Question 10

Of common starches, which plant source has the smallest granules and which has the largest?

Answer 10

Rice has the smallest starch granules, while potato has the largest.

Question 11

What are starch granules?

Answer 11

Rings of amylopectin interspersed with amylose – both present.
(swell when heated with water)

Question 12

What is the term for the swelling of starch granules when heated in water?

Answer 12

Gelatinization
(unique to starches)

Question 13

What is starch used for in food?

Answer 13

Thickening & Gelling

Question 14

What is the first step in the process of gelatinization?

Answer 14

Heat breaks hydrogen bonds in starch granules

Question 15

During gelatinization, as water enters the starch granule (2nd step), & continues to enter, causing granule to swell (3rd step), what happens in the final step?

Answer 15

The amount of free water surrounding the granule decreases as water in granule increases

Question 16

During gelatinization, which starch molecule is primarily responsible for the swelling of the granules?

Answer 16

amylopectin

Question 17

What is the term for the formation of a gel, where a liquid is dispersed in a solid?

Answer 17

Gelation
(all liquid within solid structure)

Question 18

What happens to amylose when starch granules swell?

Answer 18

some of it leaves for water surrounding it

Question 19

During starch granule swelling, what does water form hydrogen bonds with?

Answer 19

amylose & amylopectin

Question 20

The process of gelation involves a transition from a sol to a gel upon what?

Answer 20

cooling

Question 21

What type of bonds form between amylose molecules during gelation, creating a solid matrix?

Answer 21

Stable hydrogen bonds form between amylose molecules

Question 22

Which starch molecule is primarily responsible for the process of gelation?

Answer 22

amylose
(longer chains = better for forming gel)

Question 23

What is the effect of a higher amylose content on gelation?

Answer 23

firmer gelation, as it tangles up around water & amylopectin

Question 24

What is the effect of a higher amylopectin content on gelatinization?

Answer 24

faster gelatinization and thickening as it quickly absorbs water

Question 25

Approximately what percentage of amylose is needed to form a soft gel?

Answer 25

20%

Question 26

Do all (natural) starches contain amylose or amylopectin?

Answer 26

both

Question 27

How does a larger starch granule size, like that of a potato, affect its functionality?

Answer 27

A larger granule has a better water absorbing capacity, resulting in superior thickening ability & gelatinization.

Question 28

Which category of starches, roots or cereals, tend to be better thickeners?

Answer 28

Root starches (e.g., potato, tapioca) tend to be better thickeners than cereal starches (corn, rich, wheat).

Question 29

How does a longer amylose chain length impact the final gel?

Answer 29

better for forming a gel, resulting in stronger gels.

Question 30

What does amylose chain length impact?

Answer 30

degree of gelation as mixture cools

Question 31

How do impurities like bran or protein affect the energy required for gelatinization?

Answer 31

provide stability to the granule, meaning more energy is required for gelatinization (too many impurities will interfere with gel formation)

Question 32

Where is amylose found after it leaches out of the starch granule when the mixture cools?

Answer 32

in free water outside the granule

Question 33

What happens to molecular energy as temperature decreases when the mixture cools?

Answer 33

it decreases

Question 34

What type of bond forms between amylose molecules in a lower energy state?

Answer 34

Hydrogen bonds. - Bonded amylose creates solid matrix (becomes continuous phase) - Remaining free water & swollen starch granule are dispersed phase

Question 35

Do low amylose starches form gels?

Answer 35

No

Question 36

Why does wheat flour not thicken as well as pure wheat starch?

Answer 36

Wheat flour doesn't thicken as well due to its protein content, which acts as an impurity.

Question 37

Thinking about grain/cereal, tuber/root, and waxy starch sources, what are the impurity amounts for each?

Answer 37

- grain/cereal: small amounts - tuber/root: little to none - waxy: none

Question 38

Thinking about grain/cereal, tuber/root, and waxy starch sources, what are the granule sizes for each?

Answer 38

- grain/cereal: medium, some small - tuber/root: larger - waxy: medium, some small

Question 39

Thinking about grain/cereal, tuber/root, and waxy starch sources, what is the amylose:amylopectin ratio for each?

Answer 39

- grain/cereal: relatively higher, medium chain length - tuber/root: relatively lower, long chains - waxy: bred to be 100% amylopectin

Question 40

What is the effect of adding sugar on the temperature and time required for gelatinization?

Answer 40

Adding more sugar increases the temperature and lengthens the cook time required to gelatinize.

Question 41

How does the addition of sugar affect the strength of a starch gel?

Answer 41

The addition of sugar decreases gel strength, making it more tender.

Question 42

What process occurs when acid and heat are combined with starch, breaking down amylose chains?

Answer 42

Acid combined with heat causes hydrolysis of amylose chains, which means less thickening & more tender gel

Question 43

What are ways to prevent acid from excessively weakening a starch gel?

Answer 43

- Add the acid AFTER gelatinization has already occurred. - Rapid heating = less time for hydrolysis

Question 44

What starch-digesting enzyme is found in egg yolks?

Answer 44

α-amylase.

Question 45

Why must egg yolks be heated sufficiently when used in a starch-thickened product?

Answer 45

Egg yolks must be heated sufficiently to denature the α-amylase enzyme, which would otherwise prevent gelation.

Question 46

What happens to starch granules if heated for too long during **gelatinization**, and what is the effect on viscosity?

Answer 46

The granules can implode into small fragments, which decreases viscosity.

Question 47

The lecture warns against over-agitating or stirring a starch mixture during the cooling (gelation) phase. Why is this detrimental?

Answer 47

Agitation interferes with the formation of the amylose matrix, weakening the final gel strength (disrupts formation of hydrogen bonds needed for gelation).

Question 48

What is **Syneresis** (a potential issue for gelation)?

Answer 48

The process where amylose molecules in a gel draw closer together over time, causing free water to seep out.

Question 49

What happens to starch granules if heated for too long during **gelation**?

Answer 49

extended heating can break amylose starch chains into small fragments resulting in pasty texture (lumpy gravy) and weak gel.

Question 50

What is **Retrogradation** (a potential issue for gelation)?

Answer 50

The rearrangement of amylose molecules into a more crystalline structure, resulting in a grittier texture & decreases quality.

Question 51

How can the effects of retrogradation in products like old puddings or gravies be undone?

Answer 51

Retrogradation can be undone with gentle heating, which breaks the amylose hydrogen bonds & allows gelling process to happen again.

Question 52

What is **Dextrinization** (a potential issue for gelation)?

Answer 52

the splitting of amylose and amylopectin into shorter molecules when starch is heated without water (example: flour on breaded meat, toasting flour in a dry pan before making a gravy)

Question 53

What are **Native** **starches**?

Answer 53

Starches available from a plant source in their unmodified state (cereal, root, tuber, tree)

Question 54

What type of genetically engineered starches are composed of nearly 100% amylopectin?

Answer 54

Waxy starches are genetically engineered to be nearly 100% amylopectin (thickening without gelling)

Question 55

What are undesirable characteristics of Native Starches?

Answer 55

1. Stringiness, Cloudiness 2. Overly viscous textures 3. Gelling when not desired 4. Swollen, broken granules leads to loss of viscosity, gummy texture 5. Retrogradation and syneresis

Question 56

What type of genetically engineered starches are composed of up to 75% amylose?

Answer 56

High-amylose starches

Question 57

What are modified starches?

Answer 57

Starches modified from their native state by chemical or physical means

Question 58

What is a pre-gelatinized starch?

Answer 58

It is a modified starch that has been gelatinized and then dehydrated, often used in 'instant' products.

Question 59

Which type of modified starch is treated to minimize retrogradation and act as an effective thickener?

Answer 59

Crosslinked starches are modified to minimize retrogradation by substituting -OH groups (Starch phosphates – replace with phosphates)

Question 60

What type of modified starch requires no heating?

Answer 60

Cold-water swelling (pre-gelatinized)

Question 61

What type of modified starch results in thin sol & strong gel?

Answer 61

Thin-boiling starches due to debranched amylopectin

Question 62

What type of modified starch results in a soft gel?

Answer 62

Oxidized starches due to debranched amylopectin + alkaline

Question 63

Which starch has a higher percentage of amylose: wheat or corn?

Answer 63

Corn starch has a higher percentage of amylose (28%) than wheat starch (26%).

Question 64

Based on their amylose content, which starch would be an appropriate substitute for corn starch (28% amylose) in a lemon meringue pie filling that needs to gel?

Answer 64

Wheat (26% amylose) or Arrowroot (21% amylose) would be appropriate substitutes as they have a similar high amylose content needed for gelling.

Question 65

In a tapioca pudding, what is the likely cause of a weakened gel if you taste it with a spoon and then use the same spoon to stir the mixture?

Answer 65

Saliva from the spoon introduced amylase, a starch-digesting enzyme, into the pudding, which broke down the starch and prevented proper gelation.

Question 66

A student notices that their refrigerated, starch-thickened gravy has become gritty and is weeping water. Which process is responsible for this change in texture?

Answer 66

Retrodegradation. It involves the realignment of amylose molecules into a more crystalline structure during cooling or storage, which forces water out and creates a gritty texture

Question 67

When making a lemon pie filling, a recipe instructs to add the lemon juice (an acid) after the cornstarch mixture has already thickened. What is the primary reason for this specific instruction?

Answer 67

To avoid hydrolysis of starch chains during heating. Adding acid, along with heat, breaks down amylose chains (hydrolysis), which weakens the starch's ability to thicken & form a strong gel.

Question 68

A food scientist is developing a product that requires rapid thickening when heated but should not form a firm gel upon cooling. Which starch would be the most suitable choice?

Answer 68

Waxy Maize Starch. Composed of 100% Amylopectin, this starch excels at gelatinization (thickening) but lacks the amylose needed for gelation (forming a firm gel)