postharvest handling leafy & related vegetablesucce.ucdavis.edu/files/datastore/234-2559.pdf ·...
TRANSCRIPT
6/19/2013
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Postharvest Handling Leafy & Related
Vegetables
Marita Cantwell, UC Davis
http://postharvest.ucdavis.edu
Postharvest Technology Short Course June 2013Ch. 34 Postharvest Technology Book
Causes of Quality & Postharvest Losses
Leafy & Related VegetablesLettucesSpinachCabbageChardBroccoliCeleryHerbsEndivesAsparagusGreen OnionsMushrooms
Water loss Mechanical damage Loss of chlorophyll and
other nutrients Respiration rates Microbial growth Sensitivity to ethylene
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Effect of Temperature on Deterioration
Temp. °F
Temp. °C Q10
Relative Velocity of Deterioration
Relative Shelf-life
Daily Loss (%)
32 0 -- 1.0 100 1
50 10 3.0 3.0 33 3
68 20 2.5 7.5 13 8
86 30 2.0 15.0 7 14
104 40 1.5 22.5 4 25
Q10 = rate of deterioration at T+10°rate of deterioration at T
Storage temperature
Day
s
(to
init
iate
yel
low
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
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3
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Cantwell, unpublished
• Head Size, floret uniformity
• Floret/Head Color
• Head Firmness, Stem Texture
• Water loss and firmness loss
• Decay susceptibility
• Discoloration cut ends
• Shelf-life
• Composition– % dry weight
– Sugars
– Vitamin C
– Pigments
– Glucosinolates (glucoraphanin)
– Antioxidant activity
Broccoli Quality and Variety Evaluations
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Loss of Broccoli Head Firmness is Correlated to Water Loss
% Weight loss
0 1 2 3 4 5 6 7
% F
irmn
ess
loss
0
10
20
30
40
50
60
y = 7.228x; R2 = 0.98
% Firmness loss vs % Weight loss
Broccoli held at 7.5C
% Weight loss
0 2 4 6 8 10 12
% F
irmne
ss lo
ss
0
20
40
60
80
y = 5.68x + 9.69R2 = 0.80
% Firmness loss vs % Weight loss
Broccoli held at 0, 5, 10, 15 and 20°C
This image cannot currently be displayed.
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.
ICELESS BROCCOLI Minimize delay from harvest to cooling Plastic liners with holes reduce water loss Keep it cold About 4% weight loss = soft head
Treatment Shelf‐life 5°C
1. Control 22.8
2. 30 min hydrate 23.1
3. 4 hr hydrate 21.0
4. 3% weight loss 26.7
5. 3% weight loss + 30 min hydrate 26.9
LSD.05 2.6
Days at 5°C
2 4 6 8 10 12 14 16 18 20
Res
pira
tion
rate
, µ
L/g-
h
8
10
12
14
16
18Control30 min hydrate4 hour hydrate3% weight loss3% wt. loss + 30 min hydrate Water loss and water
gain do have an effect on broccoli respiration rates and shelf‐life
cv IronmanMelo and Cantwell, 2012
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We
ight
loss
, %
0
2
4
6
8
10
12
14
16
18
LSD.05
A. % Weight loss, bags folded over
Days at 10°C (50°F)
0 2 4 6 8 10
Firm
ness
, N
for
ce t
o co
mpr
ess
0
10
20
30
40
50
60
70
80
90
100
LSD.05
B. Firmness, bags folded over
No Bag, waxed carton
Lettuce bag, folded over
Extend bag, folded over
New Peak Fresh bag, folded over
Smart bag, folded over
Broccoli weight lossand firmness losscan be minimized withplastic liners.
Simple perforated PElettuce or basil linersperform as well as more expensive plastic films.
Cantwell, UC Davis, 2009
Maturity at harvestProtect from water lossCool as soon as possible
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Leafy greengrower, SingaporeAug 2007
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 Leaf maturity:Size, weightLeaf openingUncurling of edgesColorWidth of midribLeaf thicknessLeaf wax
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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
Napa or Chinese cabbageBlack Speck Disorder
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Cultivar
1 2 3 4 5 6 7 8 9
Bla
ck s
pe
ck
ind
ex
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 the black speck disorder.
Black speck index = black speck score multiplied by % extension.
Black Speck Disorder on Chinese Cabbage
Cauliflower Quality• Color is cream white• Freedom from mechanical injury• Freedom from decay• No discoloration on cut edges
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Cauliflower Decay/Discoloration (in relation to storage temperature)
Marita Cantwell
Cauliflower and Modified Atmospheres
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Constituent (fresh wt. basis) Romaine Iceberg
Chlorophyll (mg/100 g) 21.5 5.1
Carotenoids (mg/100 g) 5.9 1.6
Sugar (mg/g) 20.4 20.0
Vitamin C (mg/100 g) 23.9 7.5
Phenolics (A320) 0.44 0.22
Opportunities related to more nutritious lettuces
Cantwell and Ermen 2006
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 lettuces.
From M. Cantwell, UC Davis 1998
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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
19800V
ital
Hea
t (B
TU
/to
n-d
ay)
Temperature and Respiration RateOxygen and Respiration Rate
ImmatureMatureOvermature
No. leavesWeightFirmness% GreenSweetnessBitternessPhenolics
Lettuce Maturity
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Russet SpottingEthylene-induced Disorder on Lettuces
Large differencesamong varietiesin 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
Ru
sse
t Spo
ttin
g S
core
1=
none
, 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
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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 StainCO2 >3%
Lettuce disorders• Brown stain—CO2• Pink rib –overmature heads• Heart leaf injury– O2/CO2
Pink ribHeart Discoloration
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Symptoms of Freezing in Lettuce
Normal Frozen
Romaine
Freeze Injury
Lettuce Storage Conditions
• 0°C (32°F) but freezing point is -0.2°C (31.5°F)
• Shelf-life:– 0°C (32°F): >4 weeks
– 5°F (41°F): ~3 weeks
• High relative humidity, avoid free moisture
• Controlled atmospheres– Low O2 beneficial, CO2 >3% damaging
• Ethylene sensitive
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Simple packaging to reduce water loss.Need to cool product before packaging (room or hydrocool)or used vented packaging and vacuum cool (romaine lettuces)
Spinach Quality Parameters
• Green and uniform color
• Minimum breakage
• No dirt ; Clean
• No decay
• Composition– nitrates, oxalates
• Shelf-life
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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
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Water uptake by undamaged spinach leaves
% water uptake (3 min 20°C)
Cultivar 1st group* 2nd group**
AM harvest
Whale 1.7 1.9
PS 1037 1.6 2.0
Space 1.6 2.3
Average 1.6 2.1
PM harvest
Whale 2.8 1.7
PS 1037 2.6 2.0
Space 2.2 3.4
Average 2.6 2.4
Spinach plants dug up with roots, placed in polyethylene bags inside coolers and transported to lab where held overnight* or 3.5 days** at 2.5°C. Leaves of commercial size cut for testing. Spinach in moving water at 20°C for 3 min.
Spinach Damage Increases Water Absorption in Wash Flume
20°C water 3 min
0
1
2
3
4
5
6
7
8
No damage 1 Cut 4 Cuts
Young LeavesOlder Leaves
% weight increase
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1 2 3 4 5
Color score L* Chroma Hue Chlorophyllmg/g FW
Carotenoidsmg/g FW
1 39.2 18.1 129.5 1.49 0.29
2 40.7 21.6 126.6 1.17 0.26
3 45.0 27.5 123.4 0.75 0.18
4 47.6 31.3 121.4 0.50 0.16
5 59.8 44.6 110.9 0.22 0.10
Color values measured in upper right hand corner of each leaf; data average 4-6 leaves per category
Yellowing Rating Scale for Spinach
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: Commerical washed and baggedproduct stored at 4 temperatures
Cantwell, UC Davis
BUT….Target Temp.0ºC (32ºF)
Impact of Temperature on Quality Changes
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Quality categories (leaf damage)
for commercial packaged spinach
Category number and name Category Description
1 No damage Intact leaves with no or only minor damage
2 Slight damage Intact or near intact* leaves with 1 notable damaged area (tear, fracture)
3 Moderate damage Intact or near intact* leaves with several damaged areas
4 Severe damage Partial leaves and partial leaves with numerous damaged areas
5 Leaf Pieces Leaf pieces comprised of <25% of leaf area
*Near intact refers to leaves cut at the base with mechanical harvester
Typical defects (% damaged leaves) in spinach from commercially processed and packaged
product.Defect level Food Service Retail
None or slight 34.7 33.7
Moderate damage
47.9 50.5
Severe damage 13.1 14.3
Leaf Pieces 4.3 1.4
cv Space; data average 4 bags (for foodservice packaging, 30% of bag was evaluated; product was prepared on same line.
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g/g
fres
h w
eigh
t
0 .0
0.5
1.0
1.5
2.0LSD.05 = 0.32A. Am m onium
mg
/g fr
esh
wei
ght
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 and carotenoid concentrations in spinach after 0 and 21 days in air at 5C (41F). Data averaged from
11spinach cultivars (Cantwell, 2001)
0
200
400
600
800
1000
1200
1400
1600
0°C 5°C 10°CAMMONIA
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
Days at 7.5°C (45°F)
0 3 6 9 12
µm
ole
/g f
resh
wt.
0
10
20
30
40Ammonia
Air5% O2 5%O2 + 5%CO25%O2 + 15%CO2 Air + 15%CO2
Ammonia increases are associated with senescence and stress (storage time and temperature, modified atmospheres) in spinach and other green leafy vegetables.
5 + 5%
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Controlled or modified atmospheres appear to maintain visual quality of spinach but may also cause darkening of the leaves
O2 +CO2
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 et al
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
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• Young and mature spinach leaves respond similarly to storage conditions
• Young leaves have less physical damage• Excessive N fertilization results in weaker leaves• Low temperatures are essential for adequate
shelf-life– 0°C (32°F): 3 weeks– 5°C (41°F): 2 weeks
• Modified atmospheres, keep CO2 at 5% or less• High CO2 atmospheres stressful to spinach
Spinach Storage
2-3°C (34-36°F) best temperature; Asparagus is slightly chill sensitiveCA with high CO2 is beneficial
Asparagus
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Asparagus
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
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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
ality
sco
re
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
Storage Conditions for Fresh Herbs
• 0°C (32°F) but freezing point is -0.2°C (31.5°F)– Shelf-life at 0°C (32°F): 3-4 weeks– Shelf-life at 5°C (41°F): 2-3 weeks - Shelf-life based on aroma quality: 1-2 week- Exception: chilling sensitive basil 12.5°C (55°F) best
• High relative humidity, protective packaging, but avoid free moisture condensation
• Modified atmospheres can be beneficial
• Ethylene sensitive: yellowing, abscission, epinasty
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9=e
xce
llen
t, 1=
unu
sab
le
1
2
3
4
5
6
7
8
9A. Visual Quality CILANTRO
1=
gree
n, 5
=ye
llow
1
2
3
4
Days
0 2 4 6 8 10 12 14
1=
none
, 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
1 2 3 4 5
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 mg/g FW
1.77 1.61 0.85 0.60 0.40
Carotenoidsmg/g FW
0.28 0.25 0.17 0.12 0.06
Paulenas and Cantwell, UC Davis, 2008
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???
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Days
1 2 3 4 5 6 7 8 9
C
hil
lin
g S
core
0=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
Cantwell, UC Davis, July, 2006
Shiso, a basil relative, is alsochilling sensitive
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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
We
igh
t lo
ss,
% p
er d
ay
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
“Cold and Dry”
Bacterial growth: temperature and moisture
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Belgian Endive-keep cold and away from light
Belgium: Hortiplan, mobile gully system
Production Conditions and Quality Implications
China: nutrient film technique
China: row covers lettuces
Harvesting mache, Turin, Italy, 2011