Lecture 11: Natural polymers

Question 1

what are examples of natural polymers?

Answer 1

cellulose
lignin
starch
chitin
chitosan
protein

Question 2

describe the structure of cellulose

Answer 2

repeating beta 1,4 glucan unit

Question 3

cellulose is difficult to process in what?

Answer 3

solution or as a melt

Question 4

what are solvents used with cellulose?

Answer 4

NMMO
DMAc
ionic liquid
NaOH/urea

Question 5

describe the structure of natural polymers

Answer 5

repeating alpha-1,4-glucan and alpha-1,6-glucan units

Question 6

amylose is ____ and amylopectin is ____

a) linear
b) amylopectin

Answer 6

amylose is linear

amylopectin is branched

Question 7

what are some characteristics of natural polymers?

Answer 7

gelatinization

poor wet mechanical properties

Question 8

describe the structure of chitin

Answer 8

N-acetylglucosamine units connected by beta-1,4-linkages

Question 9

what is the main component of exoskeletons of arthropods?

Answer 9

chitin

Question 10

how is chitosan formed?

Answer 10

deacetylation of chitin using sodiun hydroxide

Question 11

what are some properties of chitin?

Answer 11

antibacterial

anti-inflammatory

Question 12

how is protein formed as a natural polymer?

Answer 12

condensation polymerization of AAs

Question 13

what is a bioplastic?

Answer 13

biopolymer that can be shaped or molded via plastication or crosslinking

Question 14

what is a problem for synthetic plastics?

Answer 14

disposal problems

• limited recycling option
• limited landfill space
• incineration may release toxins
• higher dependence on fossil fuels

Question 15

what is PLA? what is it from?

Answer 15

polylactic acid

type of bioplastic

derived from corn

Question 16

what is PHA? what is it from?

Answer 16

polyhydroxyalkanoates

type of bioplastic

harvested from bacteria

Question 17

what is cereplast?

Answer 17

starch based bioplastic

Question 18

what are proteins used for protein based bioplastics?

Answer 18

soy
casein
corn zein

Question 19

what is soyOyl?

Answer 19

veg oil based bioplastic

Question 20

what are advantages of biopolymers?

Answer 20

• renewable feedstock
• domestically grown
• CO2 neutral
• compostable
• biocompatible /bioabsorbable
• energy saving w/ lower processing temp

Question 21

what are disadvantages of biopolymers?

Answer 21

• more expensive
• low end mechanical properties
• low service temp
• not as durable in harsh environments

Question 22

what kind of proteins are used for protein bioplastics?

Answer 22

vegetal (corn zein, wheat gluten, soy, sunflower)

or animal (Caseins, whey, gelatin, myofibrillar)

Question 23

in protein bioplastics, what happens to the proteins during processing?

what are they formed into?

Answer 23

proteins go into solvent or thermoplastic process\

formed into coatings, films, molded materials

Question 24

describe wheat gluten

Answer 24

co-product of starch industry

Question 25

what are advantages of what gluten based materials?

Answer 25

• good film forming properties
• high availability at low price
• biodegradability and non-ecotoxicity
• unique functional properties (adhesive, high gas barrier/perm-selectivity)

Question 26

what are unique functional properties of gluten-based materials

Answer 26

adhesive
high gas barrier
high gas perm-selectivity

Question 27

what are drawbacks of wheat gluten based materials?

Answer 27

poor water resistance

poor mechanical properties

Question 28

describe the tensile strength and strain of

a) wheat gluten based materials
b) biodegradable polyesters
c) conventional polymers

Answer 28

wheat gluten materials has lowest tensile strength and breaks at lower strain

biodegradable materials break at higher strains

conventional polymers have intermediate tensile strength and resistance to strain

Question 29

how are barley protein films made?

Answer 29

barley protein is the byproduct of starch or beta-glucan processing

barley protein + glycerol undergoes hot pressing to produce films

Question 30

in protein based bioplastics, what are properties that can be modulated?

Answer 30

1. crosslinking
2. lamination
3. composites

Question 31

what is the equation for gas selectivity?

Answer 31

s = P (co2) / P(o2)

Question 32

how are SPI/cellulose nanocrystal composites produced?

Answer 32

1. cotton linter pulp + sulfuric acid
2. cellulose nanocrystals + SPI + glycerol
3. hot pressing

Question 33

describe the crystallinity of natural polymers

Answer 33

natural polymers have:

1. crystalline regions
2. amorphous regions
3. void regions
4. interfibrillar tie molecules between microfibrils to form a fiber

Question 34

what properties do natural polymer nanocrystals have?

Answer 34

• reinforcing mechanical properties
• improving barrier properties
• stabilizing food emulsions
• swelling properties
• thermal stability

Question 35

how does oat protein gel in a cold gelation process?

Answer 35

1. oat protein + OPI solution at pH8
2. add GDL (glucono-delta-lactone)
3. cool

Question 36

what are functions of oat protein gelation?

Answer 36

protects enzymes and probiotics in harsh stomach conditions

controls release of bioactive compounds

Question 37

what are surface multilayer structures of electrospun micro/nano fibers?

Answer 37

• branched
• porous
• necklace-like
• non-cylinder

Question 38

what are inner multilevel structures of electrospun fibers?

Answer 38

• peapod
• wire in tube
• multiwalled
• multichannel

Question 39

what are uses of electrospun fibers?

Answer 39

• gas sensors for food safety

- smart food preservation