Development of Functional
Cellulose Nanofiber Coating for
Preserving Pre- and Post-harvest
Fruit Quality and Thermally
Processed Fruits
A multidisciplinary team effort among Food
Science and Wood Science at OSU
- Jooyeoun Jung, Yanyun Zhao, John Simonsen
Edible Coating Technology
Edible coating
•
•
•
•
Bioactive compounds
Water-resistant
Controlled hydrophilicity
Low (but controllable) permeability
Homogenous
• Stable
• Physical interaction with matrix
• Chemical interaction with
matrix
• Different releasing rate
required depending on
applications and fruit type
The problem and our solution
Conventional coatings
CNF-based
Highly water-soluble
Less water soluble
Difficult to control the
release of bioactive
compounds due to
chemical interactions
Easier control the release
due to nanoporous
structure of composite
with physical interactions
High permeability
Low permeability
More complicated due to
the mixture of various
substances
Simplified by using
nanocelluose-based
composite
Cellulose Nanofiber vs.
Nanocrystal
Cellulose nanofiber (CNF)
Cellulose nanocrystals (CNC)
Materials
No charge
Negatively charged
Long flexible fiber network
Needle-like crystal
Amorphous and crystalline
Highly crystalline
Films
Superior mechanical properties and water resistant
Flexible
Rigid
Translucent
Transparent
Cellulose Nanofiber (CNF)
[CNFfilm]
• Flexible water-resistant film
• Hydrophilic carrier for antimicrobial
or antioxidant agents
• Easy incorporation of functional
substances and/or polysaccharides
• Optimize formulation to minimize the
impact of plasticizer and/or
surfactant on water-resistance of film
PtSB = potassium sorbate
[CNFfilmwithPtSB]
Barrier Properties
• CNF is a good barrier
Liquid
O2
CNF film
Outside
Inside
CO2
O2/CO2 ratio often controls ripening rate
Aulin etal.,Cellulose,2010
Controlled Release System
• CNF low porosity prolongs the release of active
compounds
• Active substance release can be simply controlled by
using different types and concentrations of plasticizer or
surfactant
[0.20%surfactant]
voids
[0.05%surfactant]
CNF‐basedcoatings
Active
compounds
Crosslinking
agent
Liquid
O2
CO2
Surfactant
Hydrophobic
agent
Optimization required for each
food product and application:
pre-, post-harvest
UV-light
Development of Antimicrobial CNF
Coatings for Preserving Pre- and
Post-harvest Fruits
Targeted Applications

Pre-harvest application targets
• Cherry cracking
• Wine grape molds
• Sunburn of apples or pears

Post-harvest application targets
• Shelf-life extension of fresh produce
Different Criteria for
Pre- and Post-harvest Fruits
Pre-harvest
(grape & cherry)
Post-harvest
(apple, mango,
banana & orange)
Anti-microbial
function
Higher
Med
Releasing rate of
antimicrobials
Faster
Slower
Water-resistance
Higher
Lower
Hydrophobicity
Higher
Higher
Flexibility
Higher
Lower
Fruit firmness
Higher
Higher
Pre-harvest Targeted Functional Properties
• ⬇Contact angle
• ⬆Wettability

⬆Elongation (%)

⬆Flexibility (balloon test)

⬆Antimicrobial effect

⬆Releasing rate

⬆Surface morphology (SEM)
Optimization
of coating
formulations
for preharvest
fruits in the
field
Illustration of coating flexibility by monitoring change of
water level in U-shape glass tube connecting to balloon
(A)
(B)
0.4-0.9 mm
Reference
mark
• Increase of water level indicates the pressure from dried coating materials
• (A) is standard coating with plasticizer
• (B) is 0.5% potassium sorbate/0.5% CNF coating aqueous solution with
0.1% wetting agent (1 Tween 80:1 Span 80) without plasticizer
Two hour water soak at ambient conditions
Different levels of
factors
Potassium (K)
content (%)*
Physicochemical
properties
Mechanical
properties before
pH
Conc.
of
glycerol
(%)
Conc. of
wetting
agent
pH1
Gly1
W1
10.48a
0.14a
66.24a
283.88ab
2.38a
5.8ab
pH2
Gly1
W1
10.05a
0.65b
64.79a
428.38a
4.01a
7.36a
pH1
Gly2
W2
14.69b
0.05a
65.88a
147.97b
5.27ab
3.68ab
pH2
Gly2
W2
9.64a
0.13a
61.71a
229.64b
9.19b
3.43b
Water
Water
Tensile Elongation
Before
After
solubility absorption strength at break
soaking soaking
(%)
(%)
ability (%) (MPa)
* Measured by Energy dispersive x-ray analysis (EDXA)
Pre-harvest Study
30%
Decay ratio (%)
25%
Week 1
Week 2
20%
15%
10%
5%
0%
0.1% wetting
agent
0.05% wetting 0.05% wetting
agent
agent and 0.1%
sorbitol
Commercial
product
Control
Cherry Cracking Lab Test
The number of cracked cherries after 8 h soaking in distilled water
Treatments
Cracked cherries / Total number
Cracking ratio (%)
Control
12/19
63.16
Formula A
2/15
13.33
Formula B
0/15
0.00
Formula C
0/15
0.00
Formula D
0/15
0.00
Formual E
0/15
0.00
Formula F
0/19
0.00
Formula G
0/19
0.00
Before coating
After coating
After soaking
November 2014 Field Trial in Chile
First spray at straw stage of cherries
Several formulations show promise
Preservation of Post-harvest Fruits
Targeted Properties:
different formulations for different fruits
Apple or mango
Orange
Strawberry
Water-solubility
Med
Med
Med
Antimicrobial
effect
Low
Med
High
Releasing rate
Slow
Med
Fast
Permeability
Low
Med
High
(tolerant up to 0.5% O2)
(tolerant up to 5% O2)
(tolerant up to 15% CO2)
Elongation at
break
Low
Low
Low
Contact angle
High
High
High
Kader et al., Critical Review in Food Science and Nutrition, 1989
Functional Substances
•
Polysaccharide (MC, CMC, or Chitosan) with CNF:
• Nanocellulose surface modification via polysaccharide adsorption (bilayer attachment)
• Adsorbed amount is affected by backbone and charge
• Heterogeneous
• Expected outcome: modification of permeation and surface
characteristics
Polysaccharides
CNF is matrix
•
Polysaccharide (MC, CMC, or Chitosan) with CNC:
• CNC fills porous matrix of polysaccharide
• Backbone and charge affect film matrix.
• Expected outcome: modification of permeation and hydrophobicity
CNC is filler
Functional Substances
• Fatty acids (stearic acid, oleic acid, and avocado oil):
• Nanocellulose surface modification via fatty acid
crystallization
• Heterogeneous
• Expected outcome: alteration of permeation,
hydrophobicity, and surface characteristics of CNF film
Fatty acid
Surfactant
Functional Substances
• Antimicrobial agent (methyl paraben or
chitosan nanoparticle):
• Antimicrobial nanoparticles interact with
CNF nanopores
• Antimicrobial particles alter surface
characteristics of films
• Expected outcome: slow release rate of
antimicrobial compounds during storage
Antimicrobial
crystals on the
surface of CNF
films
Antimicrobial
nanoparticles
Nanoporous
structure of
nanocelluose
After 2 hour
soak in water
Post‐harvestStudy
Coatedpears
10days
25days
Non‐coatedpears
Post‐harvestStudy
Coatedpears
Non-coated
40
Coated
35
1
30
0.8
Firmness (N)
Retained chlorophyll (%)
1.2
Non‐coatedpears
0.6
0.4
25
20
15
10
0.2
5
0
0
Day 7 Day 9 Day 11 Day 14 Day 16 Day 18 Day 21
Ambient storage (days)
Day 16
Day 21
Ambient storage (days)
Post‐harvestStudy
0day
1day
2day
3day
5day
7day
10day
Non‐
coated
Commercial
Semper
freshTM
Inno‐
freshTM
Extendingboth“green‐life”and“yellow‐
life”withlessabrasion
Post‐harvestStudy
120
Extensionof“greenlife”in
coatedbanana
Non-coated
Semperfresh
Retained chlorophyll (%)
100
Innofresh
80
b
60
b
b
40
a
b
b
ab
a
20
a
b
a
0
0
1
2
Ambient storage (days)
3
5
ab
Post‐harvestStudy
Non‐coatedmango
Coatedmango
Weight loss (%)
10
8
8 days
11 days
14 day
6
4
2
0
Mango_control
Mango_coated
Fruits_treatment
Preservation of Anthocyanin
Pigments in Thermally Processed
Blueberries through Metalpolysaccharide-complexation and
Layer-by-layer Cellulose Nanofiber
Coating
Anthocyanin
R, R’ = OH or OCH3
http://www.intechopen.com/books/food-industry/differentiated-foods-for-consumers-with-new-demands
Anthocyanins
http://preventdisease.com/news/12/090612_Higher-Anthocyanin-Intake-Found-inFruits-and-Veggies-Improves-Cardiovascular-Health.shtml
http://www.intechopen.com/source/html/44143/media/i
mage2.jpeg
Preservation Mechanism – step 1
- Anthocyanin Complexation
•
Metal complexation: Fixation occurs, but is unstable in
aqueous solution
•
Use of surfactant (Tween 80): Enhance interactions of
metals to anthocyanin by helping transport from the
outer to the inner surface through the cuticle of fruit
Oxygen
C-3-G
C-3-G
D-3-G
P-3-G
P-3-G
D-3-G
P-3-G
D-3-G
P-3-G
C-3-G
D-3-G C-3-G
P-3-G
Light
Metal ions and
Tween 80
Temperature
C-3-G
Fe3+
Fe3+C-3-G3+
D-3-G
Fe
Fe3+
P-3-G
Fe3+P-3-G
D-3-G
P-3-G
Fe3+
D-3-G
Fe3+P-3-G Fe3+
Fe3+
D-3-G
D-3-G
Fe3+
3+
Fe P-3-G
Preservation Mechanism – step 2
Layer-by-layer Coating Technology

Reduced water absorption of CNF film

Enhanced mechanical properties

Improved water-resistance

Adhesion to fruit surface
CNF + MC/ Chitosan + CaCl2
Preservation Mechanism – step 2
Layer-by-layer Coating Technology
CNF-based
coating
•
•
CNF+MC or Chitosan+CaCl2
Hydrophobic coating
Sodium alginate bath
Formation of
versatile layerby-layer
coating system
Calcium chloride bath
• Insoluble calcium alginate layer
• Good adhesion
Preservation Mechanism – step 3
Packing Solution

•
•
pH is adjusted to ~4.0 by using
1% formic acid to stabilize
calcium alginate beads
Sugar (~15%) to equilibrate inside and outside
of blueberries
Prepared sample is thermally treated at 93 °C
for 7-8 min
Coating removal being investigated
Thermally Processed Fruits
after 2 days
Non-coated
No
pretreatment
Better than FeCl3
treated
FeCl3
pretreatment
FeCl3/CMC
pretreatment
CNF/CaCl2
coated
CNF/CaCl2/MC
coated
Commercially Processed
Blueberry Cans
Prepared blueberries filled into cans with syrup
(~30° - 34° Brix corn syrup), and then sealed
↓
Thermally processed at ~91 °C for 5 min
Non-coated
Complexation and coated
Coated only
SEM Analysis
CNF
CNF/CaCl2 after soaking in
sodium alginate
Second layer coating with
sodium alginate treatment
CNF+CaCl2 layer
CNF/CaCl2
CNF/CaCl2/MC
CNF/CaCl2/MC after soaking in
sodium alginate
Second layer coating with
sodium alginate treatment
CNF+CaCl2+MC layer
Summary
Functional cellulose nanofiber coating
technology has been successfully utilized for
preserving quality and extending shelf life of
pre- and post-harvest fruits and thermally
processed fruits by incorporating various
functional substances
Surface characteristics and/or nanoporous
structure of CNF films can be improved
through incorporating different functional
substances
Acknowledgements

Co-Inventors
◦
◦
◦
◦
◦
Yanyun Zhao
John Simonsen
Jooyeoun Jung
George Cavender
Les Fuchigami

Funding
◦ OSU Venture Development
Fund (VDF)
◦ Oregon Nanoscience and
Microtechnologies Institute
(ONAMI)