Natural Polymers

Question 1

Common natural polymers: (6)

Answer 1

cellulose, lignin, starch, chitin/chitosan, protein

Question 2

Other less common natural polymers: (4)

Answer 2

alginic acid
hyaluronic acid
xanthum gum
curdlan

Question 3

What does the traditonal viscose processing method of cellulose involve?

Answer 3

dissolve pulp with NaOH + CS2 -> used to spin fibre

Question 4

major problem with procesesing cellulose:

Answer 4

difficult to process in solution or as a melt

Question 5

cellulose is made of repeating ______ units

Answer 5

B 1,4 glucan

Question 6

What are some new cellulose solvents? (4)

Answer 6

NMMO
DMAc
Ionic liquid
NaOH/urea aqueous solvent

Question 7

Starch is made of what monomers?

Answer 7

a 1,4 glucan (and a-1,6 glucan)

Question 8

the 2 forms of starch:

Answer 8

amylose (linear)

amylopectin (branched)

Question 9

characteristics of starch: (2)

Answer 9

gelatinization

poor wet mechanical property

Question 10

chitin is made of what units?

Answer 10

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

Question 11

Good source of natural chitin:

Answer 11

arthropod exoskeletons

Question 12

How is chitin converted to chitosan?

Answer 12

deacetylation (>55%) using NaOH

Question 13

Good properties of chitin & chitosan:

Answer 13

antibacterial, antiinflammatory

Question 14

How are amino acids polymerized into proteins?

Answer 14

condensation reactions -> form peptide bond

Question 15

the general structure of an amino acid:

Answer 15

amino end, carboxyl end
R group (variable)

Question 16

What is a bioplastic?

Answer 16

biopolymer that can be shaped/molded via plastication or crosslinking

Question 17

problems with conventional plastics (synthetic) that bioplastics aim to address: (4)

Answer 17

limited recycling
limited landfill space
toxins from incineration
fossil fuel consumption

Question 18

some bioplastic examples (and their sources)

Answer 18

PLA (Polylactic acid) from corn
PHA from bacteria
soy/casein/corn protein
Cereplast - starch based
SoyOyl - veg oil based

Question 19

How can bioplastics be combined with conventional plastics?

Answer 19

composite materials

Question 20

Are all bioplastics biodegradeable?

Answer 20

No:

soy oil plastics, soy protein-formaldehyde, casein-formaldehyde are NOT biodegradeable

Question 21

What is a material that is biodegradeable but not renewable?

Answer 21

PCL (polycaprolactone)

and other biodegradeable synthetics

Question 22

biopolymers that are both renewable + biodegradeable:

Answer 22

PGA
PLA
soy protein plastics
starch based plastics
PHA

Question 23

advatnages of biopolymers: (6)

Answer 23

renewable feedstock (raw materials)
domestically grown
CO2 neutral
biodegradeable
biocompatible
energy-saving (lower process temp)

Question 24

disadvantages of biopolymers: (4)

Answer 24

more $$$
low mechanical properties
lower functional temperatures
less durable in harsh environments

Question 25

proteins are usually ____polymers

Answer 25

hetero

Question 26

T/F: starch based polymers are more diverse than protein based

Answer 26

false: proteins have very large variety of polymer network structures -> large spectrum of chem functionalities

Question 27

Common plant proteins (4) common animal proteins (4)

Answer 27

corn zein wheat gluten soy protein sunflower proteins caseins whey gelatin/collagen myofibrillar

Question 28

Wheat gluten is majorly sourced from where?

Answer 28

starch industry (co-product)

Question 29

advantages of gluten based materials:

Answer 29

``` good film formation high availability + low $ biodegradable/nontoxic adhesive properties high gas barrier + perm selectivity ```

Question 30

How does energy usage and CO2 emissions for wheat gluten compare to LDPE?

Answer 30

over 5x less!

Question 31

What happens to the barrier properties of wheat gluten if Aw is increased?

Answer 31

increases by thousands of times! | very poor barrier at high moisture

Question 32

Increasing Aw will (increase/decrease) the gas permeation selectivity of wheat gluten

Answer 32

increase | better selectivity at high moisture

Question 33

downside of wheat gluten materials (2)

Answer 33

poor water resistance | poor mechanical properties

Question 34

Where is barley protein obtained from

Answer 34

byproduct of starch or beta glucan processing

Question 35

How is barley protein made into a film?

Answer 35

barley protein + glycerol hot pressing (>100C, 20MPa, 10 min) forms barley protein film

Question 36

How can properties of protein bioplastics be modulated? (3)

Answer 36

crosslinking lamination composites (mix with other materials)

Question 37

What is a common crosslinking agent for protein bioplastics? What does it achieve, and what is a concern?

Answer 37

formaldehyde improve mechanical and barrier properties concern: toxicity

Question 38

How is lamination used to enhance protein bioplastics?

Answer 38

apply onto another material (paper) as coating agent; paper acts as support coating will provide functionality: give MAP/selectivity properties to paper, or controlled release of antimicrobial compounds, etc

Question 39

What are some natural antimicrobial compounds that could be emitted by protein bioplastics?

Answer 39

``` carvacrol menthol cinnamaldehyde AITC Eugenol ```

Question 40

How is SPI/cellulose nanocrystal composite made?

Answer 40

cotton pulp -> sulfuric acid -> cellulose nanocrystals combine with SPI (soy protein isolate) + glycerol hot pressing cellulose/soy composite material

Question 41

the molecular structure of natural polymers:

Answer 41

fibre (made of microfibrils connected by interfibrillar tie molecules) made of crystalline regions + amorphous regions

Question 42

What are natural polymer nanocrystals used for? (4)

Answer 42

reinforces mechanical properties improves barrier properties stabilizes food emulsions swelling properties

Question 43

polyurethane can be reinforced with _____ nanocrystals

Answer 43

starch (or starch + cellulose)

Question 44

____ nanocrystals are used as a Pickering emulsion stabilizer

Answer 44

cellulose

Question 45

biopolymer microspheres can be used as a:

Answer 45

edible delivery vehicle

Question 46

What can be used to make edible delivery vehicle?

Answer 46

barley protein alginate-whey oat protein gels

Question 47

Why are edible delivery vehicles useful? (2)

Answer 47

protect enzymes/probiotics/vitamins from harsh stomach condition or controlled release of some active substances

Question 48

How are micro/nanofibres produced?

Answer 48

electrospinning | polymer solution ejected through syringe/spinneret connected to high voltage - draws out long thin threads

Question 49

Uses for electrospun micro/nanofibres: (2)

Answer 49

gas sensors for food safety | 'smart' food preservation (atmosphere, pH, light, temp)