1

Causes of Quality & Postharvest LossesCauses of Quality & Postharvest Losses

Leafy VegetablesLeafy VegetablesLettucesLettuces

SpinachSpinach

CabbageCabbage

ChardChard

BroccoliBroccoli

CeleryCelery

HerbsHerbs

EndivesEndives

AsparagusAsparagus

Water lossWater loss

Mechanical damageMechanical damage

Loss of chlorophyll and Loss of chlorophyll and other nutrientsother nutrients

Respiration ratesRespiration rates

Microbial growthMicrobial growth

Sensitivity to ethyleneSensitivity to ethylene

Marita Cantwellmicantwell@ucdavis.edu;

Effect of Temperature on Deterioration

25422.51.540104

14715.02.03086

8137.52.52068

3333.03.01050

11001.0--032

Daily Loss (%)

Relative Shelf-life

Relative Velocity of Deterioration Q10

Temp. °C

Temp. °F

Q10 = rate of deterioration at T+10°rate of deterioration at T

2

0.220.44Phenolics (A320)

7.523.9Vitamin C (mg/100 g)

20.020.4Sugar (mg/g)

1.65.9Carotenoids (mg/100 g)

5.121.5Chlorophyll (mg/100 g)

IcebergRomaineConstituent (fresh wt. basis)

Opportunities related tomore nutritious lettuces

Cantwell and Ermen 2006

Tot

al s

uga

rs (

mg/

g fw

t.)

0

5

10

15

0 days7 days

HeartInner

Young Midsize Full sizeOuter

Leaf Position

Total sugars

LSD.05

Leaf Position

To

tal a

sco

rbic

aci

d (

mg

/10

0g

fwt.)

0

10

20

30

40 0 days7 days

LSD.05

Vitamin C (Total Ascorbic Acid)

HeartInner

Young Midsize Full sizeOuter

Romainelettuce

3

Res

pir

atio

n r

ate

(ml C

O2/k

g-h

)

0

5

10

15

20

25

30 Lettuces, EndivesSpinach, ChardsArugula , Brassicas

0°C (32°F) 10°C (50°F)

Immature Leaves

Iceberg LettuceRomaine LettuceLooseleaf Lettuces

Mature Heads

0°C (32°F) 10°C (50°F)

Respiration rates of specialty salad greens and full size lettucRespiration rates of specialty salad greens and full size lettuces.es.

From M. Cantwell, UC Davis 1998

Temperature

0 5 10 15 20

Resp

iration

rate (mg

CO

2 /kg-h

r)

0

15

30

45

60

75

90

Iceberg (air)Romaine (air)Looseleaf (air)Iceberg (2% O2)

32 41 50 59 68°F°C

3300

6600

9900

13200

16500

19800

Vit

al H

eat

(BT

U/t

on

-day

)

4

Lettuce Lettuce MaturityMaturity

Head firmnessSize, number of leaves

Russet SpottingRusset SpottingEthyleneEthylene--induced Disorder on Lettucesinduced Disorder on Lettuces

Large differencesLarge differencesamong varietiesamong varietiesin susceptibilityin susceptibility

Russet spot scores ~ 1 (none), 3, 6 and 9, respectively.

5

Variety

1 2 3 4 5 6 7 8 9 10 11 12 13

Rus

set

Spo

ttin

g S

core

1=n

one,

9=

seve

re

1

2

3

4

5

6

7

8

1=Sonoma 2=Spreckles 3=Salinas 521 4=Raider 5=Salinas 517 6=Buena Vista 7=Stinger 8=Van Sal 210 9=Salinas10=Ace11=Champ12=Salinas 8813=Ridgemark

A. Iceberg Lettuces

Variety

1 2 3 4 5 6 7

B. Romaine Lettuces

1=Paris Island Cos2=Romo3=Red Eye Cos4=Gx8005=Corazon6=Red Hot Cos7=Nero

Development of Russet Spot Disorder on Iceberg and Romaine Lettuces.Intact heads were stored in 5ppm ethylene at 5°C (1°F) plus 1 week in air.

Russet spotting was evaluated on a scale of 1 to 9, where 1=none, 3=slight, 5=moderate, 7=moderately severe and 9=severe.

Cantwell, UC Davis, unpublished

Days at 5°C0 2 4 6 8 10 12

Rus

set

spot

sco

re,

1=no

ne,

9=se

vere

0

1

2

3

4

5

6

7

LSD.05

Air

5 ppm Ethylene

1-MCP, Air1-MCP, 5 ppm Ethylene

1-MCP Prevents Russet Spot Disorder on Iceberg Lettuce

Test#2, midribs; 1000 ppb 1-MCP; Tarraza and Cantwell, Nov 2002

Control + Ethylene

1-MCP + Ethylene

6

Brown StainBrown StainCO2 >3%CO2 >3%

Lettuce disordersLettuce disorders•• Brown stainBrown stain——CO2CO2•• Pink rib Pink rib ––overmatureovermature headsheads•• Heart leaf injuryHeart leaf injury–– O2/CO2O2/CO2

Pink ribHeart Discoloration

Symptoms of Freezing in Lettuce

Normal Frozen

Romaine

Freeze Injury

7

Sclerotinia in iceberg lettuce

If the lettuce head is of marketable quality, no reductionIn shelf-life occurs if the roots are infected

Lettuce Storage ConditionsLettuce Storage Conditions

•• 00°°C (32C (32°°F) but freezing point is F) but freezing point is --0.20.2°°C (31.5C (31.5°°F)F)

•• ShelfShelf--life:life:–– 00°°C (32C (32°°F): >4 weeksF): >4 weeks

–– 55°°F (41F (41°°F): ~3 weeksF): ~3 weeks

•• High relative humidity, avoid free moistureHigh relative humidity, avoid free moisture

•• Controlled atmospheresControlled atmospheres–– Low O2 beneficial, CO2 >3% damagingLow O2 beneficial, CO2 >3% damaging

•• Ethylene sensitiveEthylene sensitive

8

Lettuce mobile packing units

Broccoli mobile packing unitPhotos from http://www.ramsayhighlander.com

Field Pack & PalletizeField Pack & PalletizeVacuum CoolVacuum Cool

9

Traditional Packing of Romaine:• Do not place cut lettuce on the ground• Waxed cartons rather than crates

10

Simple packaging to reduce water loss.Need to cool product (usually hydrocooling) before packagingor used vented packaging and vacuum cool (romaine lettuces)

Open

Bag

8 days

0.5°C (33°F) 5°C (41°F) 10°C (50°F)

5.2% 10.3% 13.9% weight loss

0.4% 0.5% 0.7% weight loss

11

Lettuces and other leafy greens in supermarket displays

Belgian Endive

12

Spinach Quality ParametersSpinach Quality Parameters

•• Green and uniform colorGreen and uniform color

•• Minimum breakageMinimum breakage

•• No dirt ; Clean and disinfectedNo dirt ; Clean and disinfected

•• No decayNo decay

•• CompositionComposition–– nitrates, oxalatesnitrates, oxalates

•• ShelfShelf--lifelife

Manual harvest of bunchedSpinach; vacuum cooledNote: no longer use slickers, use aprons

Ocean Mist, Salinas, 2006

13

http://www.ramsayhighlander.com

Mechanical harvest of young spinachfor washed and packaged product

Spinach varieties differ in rate of chlorophyll loss during storage

Low temperature is veryeffective in reducing chlorophyll loss of spinach

14

Quality categories (leaf damage)

for commercial packaged spinach

Leaf pieces comprised of <25% of leaf areaLeaf Pieces5

4

3

2

1

Category number and name

Partial leaves and partial leaves with numerous damaged areas

Severe damage

Intact or near intact* leaves with several damaged areas Moderate damage

Intact or near intact* leaves with 1 notable damaged area (tear, fracture)

Slight damage

Intact leaves with no or only minor damageNo damage

Category Description

*Near intact refers to leaves cut at the base with mechanical harvester

DEFECTS ON FIELD-GROWN PACKAGED LEAFY GREENSDAMAGE FOLLOWED BY DECAY, MOSTLY BACTERIALAugust 2008

Stored 7d 5C

White chardGreen romaine

Red romaine

Red chard

Tango

15

9=

exc

elle

nt,

1=

un

use

able

1

2

3

4

5

6

7

8

9

5=

gre

en, 1

=ye

llo

w

1

2

3

4

5

Days

0 3 6 9 12 15 18

1=

no

ne

, 5=

sev

ere

1

2

3

4

5

Days

0 3 6 9 12 15 18

1=

no

ne

, 5=

sev

ere

1

2

3

4

5

Visual Quality Color

Decay Off-odors

2.5°C 36°F5°C 41°F

7.5°C 45°F10°C 50°F

Spinach: Spinach: washed and baggedwashed and baggedproduct stored at 4 product stored at 4 temperaturestemperatures

Cantwell, UC Davis

BUT….Target Temp.0ºC (32ºF)

Impact of Temperature on Quality Changes

g/g

fre

sh w

eigh

t

0.0

0.5

1.0

1.5

2.0LSD.05 = 0.32A. Ammonium

mg

/g fr

esh

we

ight

0.0

0.2

0.4

0.6

0.8

1.0

Days at 5°C (41°F)

mg

/g fr

esh

we

ight

0.00

0.05

0.10

0.15

0.20

0.25

0 21

B. Chlorophyll

C. Carotenoids LSD.05 = 0.027

LSD.05 = 0.092

g/g

fre

sh w

eigh

t

0.0

0.5

1.0

1.5

2.0LSD.05 = 0.32A. Ammonium

mg

/g fr

esh

we

ight

0.0

0.2

0.4

0.6

0.8

1.0

Days at 5°C (41°F)

mg

/g fr

esh

we

ight

0.00

0.05

0.10

0.15

0.20

0.25

0 21

B. Chlorophyll

C. Carotenoids LSD.05 = 0.027

LSD.05 = 0.092

Changes in ammonium, chlorophyll Changes in ammonium, chlorophyll and and carotenoidcarotenoid concentrations concentrations in spinach after 0 and 21 days in airin spinach after 0 and 21 days in airat 5C (41F). Data averaged from at 5C (41F). Data averaged from 11spinach cultivars.11spinach cultivars.

Days

0 2 4 6 8 10 12 14 16 18

mg

/g fr

esh

we

ight

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

2.5°C 36°F 5°C 41°F 7.5°C 45°F 10°C 50°F

Ammonium concentration

Days

0 2 4 6 8 10 12 14 16 18

mg

/g fr

esh

we

ight

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

2.5°C 36°F 5°C 41°F 7.5°C 45°F 10°C 50°F

Ammonium concentration

16

mg/

g F

W

0.0

0.5

1.0

1.5

2.0

A. Ammonia 10°C (50°F) 9 days

Untreated+ MCP

mg

/g F

W

0.00

0.05

0.10

0.15

0.20

0.25

B. Ammonia 5°C (41°F) 18 days

Untreated+ MCP

Initial Air 1 ppm 10 ppm

LSD.05

LSD.05

Ethylene exposure Ethylene exposure increases deterioration in increases deterioration in leafy vegetables. leafy vegetables.

A new technology, 1A new technology, 1--MCP MCP ((SmartFreshSmartFresh™™, , AgroFreshAgroFresh) ) blocks ethylene effects. blocks ethylene effects.

11--MCP treatment maintained MCP treatment maintained low levels of ammonia in low levels of ammonia in spinach, even when stored spinach, even when stored at 10at 10°°C.C.

100µm

50ppm N (80% nitrate-20%ammonia) 200ppm N (80% nitrate-20%ammonia)

OlderLeaf 8

(only part of leaf)

Palisadecells

Spongy mesophyll

High N results in more fragile leaves; associated with more breakage during harvest, washing, packaging---increased decay and reduced shelf-life

SPINACHGREENHOUSEGROWN

Gutierrez and Cantwell 2007

17

Figure1 Texture profile of smooth spinach leaves

00.20.40.60.8

11.21.41.61.8

2

0 0.5 1 1.5 2 2.5 3 3.5 4

Distance (mm)

Fo

rce

(N

)

Smooth-No-Vein1

Wrinkled-No-Vein1

---- Young and/or thinner less fragile

---- Older and/or thicker more fragile

Texture Profile of Spinach Leaves

Young less fragile: less ‘crisp’, more force & work to breakThicker more fragile: ‘crisper’, less force & work to break

Leaves between plates; punctured with rounded cylindrical probe, 0.95 mm2

•• Young and mature spinach leaves respond Young and mature spinach leaves respond similarly to storage conditionssimilarly to storage conditions

•• Young leaves have less physical damageYoung leaves have less physical damage•• Excessive N fertilization results in weaker leavesExcessive N fertilization results in weaker leaves•• Low temperatures are essential for adequate Low temperatures are essential for adequate

shelfshelf--lifelife–– 00°°C (32C (32°°F): 3 weeksF): 3 weeks–– 55°°C (41C (41°°F): 2 weeksF): 2 weeks

•• Modified atmospheres, keep CO2 at 5% or lessModified atmospheres, keep CO2 at 5% or less•• High COHigh CO22 atmospheres stressful to spinachatmospheres stressful to spinach

Spinach StorageSpinach Storage

18

Storage Conditions for Fresh HerbsStorage Conditions for Fresh Herbs

•• 00°°C (32C (32°°F) but freezing point is F) but freezing point is --0.20.2°°C (31.5C (31.5°°F)F)–– ShelfShelf--life at 0life at 0°°C (32C (32°°F): 3F): 3--4 weeks4 weeks–– ShelfShelf--life at 5life at 5°°C (41C (41°°F): 2F): 2--3 weeks 3 weeks -- ShelfShelf--life based on aroma quality: 1life based on aroma quality: 1--2 week2 week-- Exception: chilling sensitive basil Exception: chilling sensitive basil 12.512.5°°C (55C (55°°F) bestF) best

•• High relative humidity, protective packaging, but avoid High relative humidity, protective packaging, but avoid free moisture condensationfree moisture condensation

•• Modified atmospheres can be beneficialModified atmospheres can be beneficial

•• Ethylene sensitiveEthylene sensitive

Vis

ual Q

ualit

y

1

2

3

4

5

6

7

8

9

Aro

ma

1

2

3

4

5

% D

ecay

0

1

2

3

4

5

Col

or S

core

1

2

3

4

5

0° 5° 10° 15°C 0° 5° 10° 15°C

C D

A B

Storage temperature Storage temperature

O2=12-17%CO2=3-5%

Commercially washed & packagedcilantro8 days

Visual Quality

Green color

% Decay

Aroma

19

Color Score 5 4 3 2 1

L* 49.5 52.4 62.2 68.1 71.7

Chroma 23.9 28.2 41.5 44.4 46.2

Hue 125.5 125.1 118.3 111.1 108.1

Chlorophyll* 1.77 1.61 0.85 0.60 0.40

Carotenoids* 0.28 0.25 0.17 0.12 0.06

CILANTRO AND ITALIAN PARSLEY LEAVES

Color scores, color values and pigment concentrations

5

4

3

2

1

*mg/g FW

5

4

3

2

1

Color Score 5 4 3 2 1

L* 42.4 55.3 62.5 64.0 65.5

Chroma 15.9 30.9 35.9 42.7 43.2

Hue 133.4 120.7 117.7 116.8 109.9

Chlorophyll* 1.79 1.20 0.68 0.49 0.25

Carotenoids* 0.22 0.19 0.15 0.14 0.13

Detrimental ethylene effectsDetrimental ethylene effectsYellowingYellowingEpinastyEpinastyAbscission Abscission

20

BasilHighly susceptible to water lossVery chilling sensitive

Situation:Excellent quality cropHarvesting late in dayHigh temperatures, ~30°CLow RH, ~50%; Little protection from ambientLong delays to packinghouse

What can be done to improve this handling???

Greenhouse Fresh Herb ProductionColombia, Sept 2007Export to Canada

21

Days

1 2 3 4 5 6 7 8 9

C

hil

lin

g S

co

re0=

no

inju

ry; 8

=se

vere

0

1

2

3

4

5

6

7

8 0°C (32°F)

2.5°C (36°F) 5°C (41°F)

7.5°C (45°F)

10°C (50°F)

Basil loses moisture very rapidly

Basil is very chilling sensitive

Basil stored 2 days in plastic bags

0°C 5°C 10°C32°F 41°F 50°F

July 31, 2006