Modified Atmosphere Packaging of Modified Atmosphere Packaging of

freshfresh--cut fruits and vegetablescut fruits and vegetables

Luis CisnerosLuis Cisneros--ZevallosZevallos, Ph.D., Ph.D.

Department of Horticultural SciencesDepartment of Horticultural Sciences

Texas A&M UniversityTexas A&M University

MAP

• Overview MAP

• Packaging design

• Quality considerations

• Trends

Modified Atmospheres or Controlled Atmospheres

• Removal or addition of gases resulting in an atmospheric composition surrounding the commodity

that is different from that of air

• Usually involves reduction of O2 and/or elevation of

CO2

• It should be considered as a supplement to proper temperature and relative humidity management

procedures

Overview...

Examples of fresh-cut produce in MAP systems

• Spinach, trimmed, washed

• Salad mixes, mesclun, herbs, flowers

• Mushroom, sliced

• Broccoli and cauliflower florets

• Lettuce, cleaned, chopped, shredded

• Salad mixes: cabbage, carrot, broccoli

• Baby carrots, celery and carrot sticks

• Pepper, cukes, squash, jicama: sliced

and diced

• Garlic, peeled, sliced

2 - 9Strawberry slices, melon & mango cubes, citrus

segments, peach & pear wedges, grape berries

10 - 14Apple wedges, pineapple chuncks, pomegranate arils,

kiwi slices

FRUITS

4 - 9Pepper and tomato slices, cucumber slices, squash

slices, mushroom slices, jicama sticks

10 - 14Broccoli & cauliflower florets, shredded cabbage,

lettuce and broccoli, celery & carrot sticks

14 - 18Lettuce salads lettuce separated leaves, lettuce mixes,

spinach leaves, peeled potatoes

>21Baby carrots, peeled onions, peeled garlic

DaysVEGETABLES

Potential post-

cutting storage life

at 2-5C (36-41F)

Products

Storage life of fresh-cut fruits and vegetables (M. Cantwell, UC-Davis)

Effects of Modified Atmospheres or Controlled Atmospheres

• Beneficial effects• Retardation of senescence

• Reduction of fruit sensitivity to C2H4

• Alleviation of certain physiological disorders (e.g., chilling injury)

• Effects on post-harvest pathogens

• Tool for insect control

• Harmful effects• Initiation and/or aggravation

of physiological disorders

• Irregular ripening of fruits

• Development of off-flavors and off-odors

• Increased susceptibility to decay

• Stimulation of sprouting and retardation of periderm development in some root and tuber vegetables

Fruits and Vegetables tolerance to low O2

• Minimum %O2 Commodities

0.5 Tree nuts

1.0 Some cultivars of apples and pears, broccoli,

mushrooms, garlic, onion

2.0 Most cultivars of apples and pears,

kiwifruits, apricot, cherry, nectarine, peach,

plum, strawberry, papaya, pineapple, olive,

cantaloupe, sweet corn, green bean, celery,

lettuce, cabbage, cauliflower, Brussels sprouts

3.0 Avocado, persimmon, tomato, pepper,

cucumber, artichoke

5.0 Citrus fruits, green pea, asparagus, potato,

sweet potato

Fruits and Vegetables tolerance to high CO2

• Maximum %CO2 Commodities2 Apple (Golden Delicious), Asian pear,

European pear, apricot, grape, olive, tomato,

sweet pepper, lettuce, endive, Chinese

cabbage, celery, artichoke, sweet potato

5 Apple (most cultivars), peach, nectarine, plum,

orange, avocado, banana, mango, papaya,

kiwifruit, cranberry, pea, chili pepper,

eggplant, cauliflower, cabbage, Brussels

sprouts, radish, carrot

10 Grapefruit, lemon, lime, persimmon, pineapple,

cucumber, summer squash, asparagus,

broccoli, parsley

15 Strawberry, berries, fig, cantaloupe, sweet corn

Leek

Spinach

Tomato

Bell pepperLettuce

0 21105 150

21

10

5

15

O2 %

%C

O2

Asparagus

Mushroom

Strawberry

Cherry

Mango, papaya, pineapple

Grapefruit

Banana

Orange

Grape

0 21105 150

21

10

5

15

O2 %

CO

2%

How do we Design a Package?

• Basically by applying an interdisciplinary approach

combining concepts of Post-harvest Physiology,

Engineering and Physico-chemistry

CO2eCO2i

O2i O2e

Plastic filmArea

Volume

Permeability O2

Permeability CO2

Thickness

ProduceWeight

Oxygen uptake

CO2 production

The MAP System

Factors Affecting Establishment

of Optimal Modified Atmospheres

• Permeation: rate of gas permeation will depend on:1) nature of film (LDPE,PP, etc) PO2, PCO2

2) film thickness, L

3) film area, A

4) gradient between external & internal atmosphere (driving force)

5) Temperature , PO2, PCO2 (f; T)

• Respiration: rate of respiration depends on:

1) nature of commodity, rO2,rCO2

2) commodity weight, W

3) gas composition in package, rO2,rCO2 (f; O2i, CO2i)

4) Temperature, rO2,rCO2 (f; T)

1.2

0

0.6

0 2110

O2 %

r CO2 aerobic

anaerobic

total

Oxygen effects on respiration

LOL

0

10

20

30

40

50

60

70

0 5 10 15 20 25

% Oxygen

rCO

2 (

mL

/Kg

-h)

Respiration of fresh-cut spinach at 10C as a function of O2 level

0

20

40

60

80

rO

2(m

L/k

g h

)

0 0.05 0.1 0.15 0.2 0.25

O2 (atm)

(Leshuk and Saltveit, 1991)

(Cisneros-Zevallos et al., 1998,

unpublished)

Respiration as a function of oxygen

Carrot disks, 20C

Peeled carrots, 10C

Michaelis-Menten

respiration model

0

50

100

150C

O2

Pro

duction (

ml C

O2/k

g-h

)

0 5 10 15 20 25

Temperature (C)

Respiration rate as a function of temperature

Spinach Bossanova

Asgrow carrots

Increased respiration: Carrot slices at 10C

S lic e s

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7 8 9 10D ays

rCO

2 (m

l[C

O2]/kg

hr)

� = c o n tro l = 2 c u ts = 4 c u ts � = 8 c u ts � = 1 6 c u ts X = 3 2 c u ts

(Surjadinata and Cisneros-Zevallos, 2007)

Wounding intensity effects

on respiration

Increased respiration: Carrot sticks at 10C

S t ic k s

1 0

2 0

3 0

4 0

5 0

0 1 2 3 4 5 6 7 8 9 1 0D a y s

rCO

2 (

ml[

CO

2]/

kg

hr)

� = c o n t r o l = 2 c u t s = 4 c u t s � = 8 c u t s � = 1 6 c u t s

(Surjadinata and Cisneros-Zevallos, 2007)

Film

Gas and water vapor permeability

Diffusion

Adsorption

Desorption

gas flux

Highconcentration

Lowconcentration

CO2eCO2i

O2i O2e

Plastic filmArea

Volume

Permeability O2

Permeability CO2

Thickness

ProduceWeight

Oxygen uptake

CO2 production

The MAP System

At Steady-state conditions:

O2 uptake = O2 transfer through plastic

CO2 production = CO2 transfer through plastic

rO2W ==== (O2e

−−−− O2 i

)A PO2

L

rCO2 W ==== (CO2i −−−− CO2e)A PCO2

L

From Both equations …..

Where: rCO2 /rO2 = RQ ~1

PCO2 /PO2 = β factor

CO2i = CO2e + (RQ/ β) O2e - (RQ/ β) O2i

Strawberry

Cherry

Mango, papaya, pineapple

Grapefruit

Banana

Orange

Grape

0 21105 150

21

10

5

15

O2 %

CO

2%

LDPE β=5.0

Air β=0.8

Permeability of Films available for packaging

fresh produce

Film type Permeabilities (cc/m2/mil/day @1 atm)

CO2 O2 CO2:O2 Ratio (β factor)

Polyethylene:

(Low density) 7700 - 77000 3900 - 13000 2.0 -5.9

Polyvinyl chloride 4263 - 8138 620 - 2248 3.6 - 6.9

Polypropylene 7700 - 21000 1300 - 6400 3.3 - 5.9

Polystyrene 10000 - 26000 2600 - 7700 3.4 - 3.8

Saran 52 - 150 8 - 26 5.8 - 6.5

Polyester 180 - 390 52 - 130 3.0 - 3.5

At Steady-state conditions:

O2 uptake = O2 transfer through plastic

CO2 production = CO2 transfer through plastic

rO2W ==== (O2e

−−−− O2 i

)A PO2

L

rCO2 W ==== (CO2i −−−− CO2e)A PCO2

L

Remaining Package Design Parameters

Once a film is selected based on the β factor it is still necessary to select L, A and W:

O2i = O2e - rO2 W L /PO2 A

CO2i = CO2e + rCO2 W L /PCO2 A

As L or (W/A) increases,

O2 decreases and CO2 increases,but always along the line

Strawberry

Cherry

Mango, papaya, pineapple

Grapefruit

Banana

Orange

Grape

0 21105 150

21

10

5

15

O2 %

CO

2%

LDPE β=5.0

Air β=0.8

For different

combinations of

W L /A

Maroon carrots (effects of amount of produce)

(Cisneros-Zevallos)

0

2

4

6

8

10

%C

O2

0 5 10 15 20

%O2

115g

93.7g75g56.2g

37.5g18.7g

LOL

CO2 Vs O2 plots for fresh-cut spinach Ark-310 stored in LDPE bags at 15 C (1250cm2)

(Cisneros-Zevallos)

0

5

10

15

20

%C

O2i

0 5 10 15 20

%O2i

0

5

10

15

20

0 5 10 15 20

10 C

2.5 C

% C

O2i

CO2 Vs O2 plotsfor peeled carrots stored in LDPE bags

(Cisneros-Zevallos et al., 1998unpublished)

LOL

Quality considerations

Spinach…..quality studies

• Overall visual quality

9=excellent, 7=good, 5=fair, 3=poor, 1=extremely poor

• Phytochemical determination

Vitamin C

Chlorophyll

Carotenoids

Phenolics

0

20

40

60

80

100

0 2 4 6 8 10

Time (days)

Rela

tive Q

ua

lity

Ch

an

ges

(%)

Vit C

Chlorophyll

Phenolics

Carotenoids

OVQ

Quality changes through time (21%O2 at 10C)

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25

% Oxygen

Qu

ali

ty r

ate

ch

an

ges (

%/d

ay)

Vit C

Chlorophyl

Phenolics

Carotenoids

OVQ

Rates of quality change

Oxygen concentration effects(14 days storage)

1

3

5

7

9

Overa

ll V

isua

l Q

ualit

y

0 5 10 15 20

%O2

15 C

10 C Excellent

Good

Fair

Poor

Extremely poor

80

90

100

110

120

130

Hu

e a

ng

le

0 5 10 15 20

%O2

15 C10 C

0

5

10

15

20

25

Chro

ma

0 5 10 15 20

%O2

10 C

15 C

Oxygen concentration effects….(14 days storage)

Slide 1

Abraded

Cut with a

sharp knifeheat

water

CO2

O2

cell wallsepidermis

White blush effect

RH effects on quality appearance of fresh-cut carrots

Low RH

Hygroscopic coatings retain surface moisture at high RH

Control

CaCl2 2% x 1 min

Peeled carrots stored 1 month in LDPE bags

(Cisneros-Zevallos, Saltveit & Krochta)

(Cisneros-Zevallos & Krochta, 2002)

O2e

CO2e

Oxygen and carbon dioxide transfer from a fruit

O2c

O2i

CO2i

RH will affect gas transfer through coating systems

0

5

10

15

20

25

30

% C

O2

0 5 10 15 20 25

92%

82.5%

75%

64%

54%

control

Internal CO2 vs O2 of WPI-Coated Fuji Apples

Stored at Different RHs for 2d at 20°°°°C

(Cisneros-Zevallos & Krochta, 2003) LOL

8 days 12 days5 days2 days

Control

WPI coating(0% glycerol)

WPI coating

(15% glycerol)

WPI coating

(40% glycerol)

Banana fruit coated with different formulations of WPI-glycerol

and stored at 20°C. RH will affect coating formulation performance

( L. Cisneros-Zevallos)

Additional Methods to Alter Modified

Atmospheres and Extend Shelf Life

1. O2 absorbents or “scrubbers” (“Ageless” iron powder in a sachet takes up O2 to form iron oxide).

2. CO2 absorbents (“Fresh Lock” calcium hydroxide reacts with CO2 to form calcium carbonate).

3. Preservative films. Packaging films may be

impregnated with various antimicrobial agents:

a. Fungicides e.g. Imazalil for Citrus fruit

b. Sorbate

c. Hydrogen peroxide

d. Ozone

e. Antibiotic e.g. Pimaricin

f. Ethanol

4. Ethylene absorbents e.g. potassium permanganate imbedded in silica gel, the silica absorbs the ethylene and the permanganateoxidizes it to acetate and ethanol.

5. Humectants to control relative humidity. Salts such as NaCl and CaCl2 have been used to reduce % RH in commercial products e.g. Dow’s Summerfield Tomato Pack.

6. Waxes and edible films may also be used to establish modified atmospheres:

a. Casein + ascorbic acid - prevent browning of

sliced apples.

b. Sucrose polyester- “Semperfresh” has been

tested on bananas, apples, and pears.

c. Methocel + fatty acid

d. Cellulose casing for baby carrots.

Desirable Characteristics of MAP Filmsfor Fresh Produce

1. Required permeabilities for the different gases

2. Good transparency and gloss

3. Light weight

4. High tear strength

5. Low temperature heat stability

6. Nontoxic

7. Nonreactant with produce

8. Ease of handling

9. Ease of printing for labeling purposes

10. Environmentally friendly - great marketing tool

Trends for MAP systems

• Microwaveable tray packs

• Veggie Mixes

• Fruit Mixes

• Time-temperature indicators

• Mathematical models for selection of

packaging films

• Smart films

Questions?