causes of quality & postharvest losses leafy...
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Postharvest HandlingLeafy Vegetables
Marita Cantwell, UC Davis
micantwell@ucdavis.edu
http://postharvest.ucdavis.edu
Causes of Quality & Postharvest LossesCauses of Quality & Postharvest Losses
Leafy VegetablesLeafy VegetablesLettucesLettucesSpinachSpinachCabbageCabbageChardChardBroccoliBroccoliCeleryCeleryHerbsHerbsEndivesEndivesAsparagusAsparagusGreen OnionsGreen Onions
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
Relative Perishability
Relative Respiration Rate
NutsNutsDatesDates
CitrusCitrusGarlicGarlicPotatoPotato
AppleAppleCarrot Carrot OnionOnion
BananaBananaTomatoTomatoPeachPeach
ArtichokeArtichokeBroccoliBroccoliStrawberryStrawberry
AsparagusAsparagusPeasPeasSweet CornSweet Corn
10 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
Storage temperature
Da
ys
(to
in
itia
te y
ell
ow
ing
)
0
5
10
15
20
25
30
35 Broccoli Shelf-life & Temperature
032
2.536
541
7.545
1050
12.5 55
1559
20°C68°F
cv. Legacy
Fresh appearance
Green florets
Tender stem
No discoloration
No breakage
No decay
No off-odors
mg
/100
g F
W
0
5
10
15
20
25
mg
/100
g F
W
0
1
2
3
4
Days
0 5 10 15 20 25
mg
/100
g F
W
05
10152025303540
Days
0 5 10 15 20 25
mg
/100
gF
W
0
5
10
15
20
25
Chlorophyll Carotenoids
Ascorbic Acid Sugars
0°C (32°F)10°C (50°F)20°C (68°F)
Limit of Salability
Broccoli Compositional Quality and Storage Temperature
Cantwell, unpublished
2
Specialty Brassicas Comparative StudyGai-lanChoi-sumBroccoli raab, rapiniBroccolini
Stem TissueFlorets
888687112176235Vitamin C, mg/100g FW
32434792100117Antioxidant activitymg Trolox/100g FW
1.11.00.52.31.41.1Ammonia, µmole/100gFW
12.014.417.43.74.55.2Total sugars, mg/gFW
10C
8d
5C
8d
Initial10C
8d
5C 8d
Initial
Component
M. Cefola, G. Hong, M. Cantwell, R. Paiva e G. Colelli. 2009
Marketable qualityMarketable qualityCompositional qualityCompositional qualityResponse to TemperatureResponse to TemperatureResponse to atmospheresResponse to atmospheres
Broccoli raab
Iceless BroccoliTemperature-yellowingMoisture loss-softening
• 0°C with very high humidity
• MA: 5-8% O2 + 7-10% CO2
Broccoli Storage Conditions
Days at 7.5°C
0 1 2 3 4
% W
eig
ht lo
ss
0
1
2
3
4
5
6
7
8
Curve 1, y = 1.55x + 0.34; R2 = 0.98Curve 2, y = 1.72x + 0.36; R2 = 0.98
Curve 1 original firmness technique
Curve 2, modified technique, mark
A. % Weight Loss
Days at 7.5°C
0 1 2 3 4 5 6 7
% F
irmn
ess
loss
0
10
20
30
40
50
60
70
80
90
100
Curve 1 original firmness technique
Curve 2, modified technique, mark
B. % Firmness Loss
ICELESS BROCCOLIMinimize delay from harvest to cooling Use plastic liners to reduce water loss Keep it cold
About 4% weight loss results in 30% decrease in firmness and this is likely the point at which a buyer would consider the head soft.
Cantwell lab, UCDavis, 2010
Leafy greengrower, SingaporeAug 2007 Leafy green
grower, SingaporeAug 2007
3
Days
0 2 4 6 8 10 12 14 16 18
Col
or s
core
, 5=
dark
gre
en, 1
=ye
llow
1
2
3
4
5
Mature Kale Leaves 20°C (68°F)15°C (59°F)10°C (50°F) 5°C (41°F)
Days
0 2 4 6 8 10 12 14 16 18
Immature Kale Leaves
LSD.05
Loss of green color by mature and immature Kale leaves stored at 4 temperatures for up to 18 days.
5 4 3 2 1
10°C Air 1-MCP, 10°C Air 10°C C2H4 1-MCP, 10°C C2H4
12 days; 8 ppm C2H4; 500 ppb 1-MCP
Collards
5°C Air 10°C Air 10°C C2H4
1-MCP=1-methyl-cyclopropene, SmartFresh™, AgroFresh
Broccoli ShelfBroccoli Shelf--life & Varietylife & Variety
Days 7.5°C Score 2
Cultivar Range Average % Head Rot PPPaaaccckkkmmmaaannn 111777---111999 111777...777 333333
LLLiiibbbeeerrrtttyyy 111222---111777 111555...111 000
PPPaaatttrrriiiooottt 111222---111777 111444...444 111000
GGGrrrnnn VVVaaallliiiaaannnttt 111333---111555 111444...111 000
BBBrrriiigggaaadddiiieeerrr 999---111222 111111...222 222000
MMMaaajjjeeessstttiiiccc 999---111444 111111...111 111111
AAAvvveeerrraaagggeee 111222---111555 111333...777 111111
M. Cantwell, Nov 1997
BacterialSoft rot
Napa or Chinese cabbageNapa or Chinese cabbageBlack Speck DisorderBlack Speck Disorder
Cultivar
1 2 3 4 5 6 7 8 9
Bla
ck s
pec
k in
dex
0
50
100
150
200
250
Air Ethylene
Cv #1= T-740 2= Yuki 3= Spring Flavor 4= Southern King 5= New Summer 6= Chacha 7= China Express 8= Blues 9= WR-70
Black speck development on Napa cabbage stored in air or in ethylene is the same. PAL enzyme levels similar; 1-MCP does not reduce black speck. Cultivars vary greatly in their susceptibility to black speck.
Black speck index = black speck score multiplied by %
extension.
Black Speck Disorder on Chinese CabbageBlack Speck Disorder on Chinese Cabbage
Cauliflower Qualitycolor is cream whitefreedom from mechanical injuryfreedom from decayno discoloration on cut edgesminimal number of small pieces; good integrity of cut florets good aroma and odor as fresh or microwaved foodretain high content of sugars and Vitamin C
4
Cauliflower Discoloration (in relation to storage temperature)
Marita Cantwell
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 to more 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
Tot
al a
scor
bic
acid
(m
g/1
00g
fwt.)
0
10
20
30
40 0 days7 days
LSD.05
Vitamin C (Total Ascorbic Acid)
HeartInner
Young Midsize Full sizeOuter
Romainelettuce
Res
pir
atio
n r
ate
(ml C
O2 /
kg-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
Res
pira
tion
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
-da
y)
1 2 3
4 5
Maturity Stages of Iceberg Lettuce
5
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.
Variety
1 2 3 4 5 6 7 8 9 10 11 12 13
Rus
set
Sp
ottin
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 (41°F) plus 1 week in air.
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
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
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
6
Field Pack & PalletizeField Pack & PalletizeVacuum CoolVacuum CoolNaked, Liner, Head wrappedNaked, Liner, Head wrapped
Traditional Packing of Romaine:Do not place cut lettuce on the groundWaxed cartons or cartons with liners rather than crates
Simple packaging to reduce water loss.Need to cool product before packaging (rooms or hydrocool)or 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
Naked lettuceVertical shelving
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
7
Manual harvest of bunchedSpinach; vacuum cooledNote: no longer use slickers, use aprons
http://www.ramsayhighlander.com
Mechanical harvest of young spinachfor washed and packaged product
1 2 3 4 5
110.9
121.4
123.4
126.6
129.5
Hue
0.22
0.50
0.75
1.17
1.49
Chlorophyllmg/g FW
0.10
0.16
0.18
0.26
0.29
Carotenoidsmg/g FW
5
4
3
2
1
Color score
44.659.8
31.347.6
27.545.0
21.640.7
18.139.2
ChromaL*
Color values measured in upper right hand corner of each leaf; data average 4-6 leaves per category
Yellowing Rating Scale for Spinach Marita Cantwell
9=ex
celle
nt,
1=
un
use
ab
le
1
2
3
4
5
6
7
8
9
5=g
reen
, 1=
yell
ow
1
2
3
4
5
Days
0 3 6 9 12 15 18
1=n
on
e, 5
=se
vere
1
2
3
4
5
Days
0 3 6 9 12 15 18
1=n
on
e, 5
=se
vere
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: CommericalCommericalwashed 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
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
8
g/g
fre
sh w
eig
ht
0 .0
0.5
1.0
1.5
2.0LSD .05 = 0.32A. Am monium
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 LS D.05 = 0.027
LS D.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 (Cantwell, 2001)11spinach cultivars (Cantwell, 2001)
0
200
400
600
800
1000
1200
1400
1600
0°C 5°C 10°C
AMMONIA
INCR
EASE
%
25
27
29
31
33
35
37
39
TOTA
L GS
ACT
IVIT
Y
AMMONIA INCREASE GS TOT
6 days, Catalano and Cantwell, 2007
Ammonia increases in spinachIn response to temperature andStressful atmospheres
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 with larger cells; can be more breakage during harvest and handling, resulting in increased decay and reduced shelf-life
Greenhouse spinach, Gutierrez and Cantwell 2007
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
Texture Profile of Spinach Leaves---- less fragile
---- more fragile
•• 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
2-3°C (34-36°F) best temperature; Asparagus is slightly chill sensitiveCA with high CO2 is beneficial
Asparagus
AsparagusAsparagus
M. Cantwell, UC Davis
TTIIPP Cell DivisionCell Enlargement
Sugars LOWProtein & Acidity HIGHSlight Lignification
MIDDLE Cell ElongationHydration
Total Solids 8-14%% Water High
BASE Cell WallThickening
Sugars HIGHProtein & Acidity LOWMaximum Lignification
Asparagus packinghouse in Peruhttp://www.freshplaza.com/fotoarchief/apr11.htm
9
Asparagus storage conditions• 2.5°C (slightly chilling sensitive
• High humidity
• 1-2 weeks; 3 weeks MA
• Modified atmospheres
– O2 5-10%
– CO2 7-10%
Days storage
0 3 6 9 12 15 18 21 24 27 30 33 36
Qu
alit
y sc
ore
1
2
3
4
5
6
7
8
9
Asparagus: Deterioration and Temperature
Excellent
Good
Fair
Poor2.5°C15°C 10°C 5°C
Tip decay (bacterial)
Frozen and then thawed
mg
/10
0g
fre
sh w
eig
ht
5
6
7
8
9
10
11
12
mg
/10
0g
fre
sh w
eig
ht
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Days 2.5°C (36°F)
0 7 14 21
mg
/g f
resh
we
igh
t
6
8
10
12
14
Days 2.5°C (36°F)
0 7 14 21
µg
/g f
resh
we
igh
t
20
40
60
80
100
120
E. Chlorophyll F. Carotenoids
G. Sugars H. Ammonia
UC115
UC157
UC115UC115 compared to UC157. UC157. Asparagus stored at 2.5°C (36°F) up to 21 days.
Data averaged over 2 Tests & 2 Fields, 2004
UC157 UC115
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
9=ex
celle
nt,
1=
unus
able
1
2
3
4
5
6
7
8
9A. Visual Quality CILANTRO
1=
gre
en, 5
=ye
llow
1
2
3
4
Days
0 2 4 6 8 10 12 14
1=
non
e,
5=se
vere
1
2
3
4
0°C 32°F5°C 41°F10°C 50°F15°C 59°F
0°C 32°F5°C 41°F10°C 50°F15°C 59°F
B. Color
C. Decay
LSD.05
1
2 4
3 5
0.060.120.170.250.28Carotenoidsmg/g FW
0.400.600.851.611.77Chlorophyll mg/g FW
108.1111.1118.3125.1125.5Hue
46.244.441.528.223.9Chroma
71.768.162.252.449.5L*
54321
Paulenas and Cantwell, 2008
Detrimental ethylene effectsDetrimental ethylene effectsYellowingYellowingEpinastyEpinastyAbscission Abscission
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???
10
Days
1 2 3 4 5 6 7 8 9
C
hill
ing
Sco
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
Chilling injuryScore 3
Basil stored 2 days in plastic bags
0°C 5°C 10°C32°F 41°F 50°F
July 31, 2006
Shiso, a basil relative, is alsochilling sensitive
Exposed
Covered
0°C 10°C 20°C 30°C
32°F 50°F 68°F 86°C
2 days
Vapor pressure deficit, mm Hg
0 2 4 6 8 10 12 14 16
Wei
ght
loss
, %
pe
r da
y
0
3
6
9
12
15
18
21
24
Strawberry y = 0.506x + 0.35 R2 = 0.91
Broccoli y = 1.01x + 0.34 R2 = 0.97
Romaine y = 0.64x + 0.43 R2 = 0.94
Mushroom y = 1.48x + 0.21, R2 = 0.98
Strawberry
Broccoli
Romaine lettuce
Mushroom
Weight loss in relation to VPD in 4 products
Belgian Endive-keep cold and away from light
Celery heartsTrimmed, washed and packagedMobile processing unitChlorine rinseDrain and package in perforated bag
With permission from T&A, June 2007
Harvesting equipment for fennelD’Arrigo Brothers, Castroville CA
Belgium: Hortiplan, mobile gully system
Production Conditions: Quality Implications
China: nutrient film technique
China: row covers lettuces
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