Postharvest Handling Update Cool Season Vegetables

Marita Cantwell, UC Davismicantwell@ucdavis.edu

http://postharvest.ucdavis.edu

UCCE Vegetable Pest Management and Postharvest IssuesSanta Maria, June 9, 2010

http://postharvest.ucdavis.edu

Produce Facts• Harvest indices• Quality indices• Temperature and RH• Freezing point/damage• Respiration rates• Ethylene production• Effects of ethylene• Effects of modified

atmospheres• Physiological disorders• Postharvest diseases• Mechanical injury• PHOTOS

140FruitsVegetablesFlowers

Causes of Quality & Postharvest LossesLeafy Vegetables

LettucesSpinachCabbageChardBroccoliCeleryHerbsEndivesAsparagusGreen Onions

♦ Water loss♦ Mechanical damage♦ Loss of chlorophyll and

other nutrients♦ Respiration rates♦ Microbial growth♦ Sensitivity to ethylene

Fresh Produce Deterioration

• Metabolic changes: – respiration, ethylene,

– texture, aroma, etc.

• Growth and development• Transpiration• Mechanical injury• Physiological disorders• Decay; microbial growth

Temperature Affects All Causes of Deterioration

Postharvest Handling Update Cool Season Vegetables

• Broccoli– Iced to iceless product; firmness and water loss

• Specialty Brassicas– Compare postharvest performance to broccoli

• Fresh-cut and modified atmospheres– Response of broccoli and sugar snap peas

• Cauliflower --needs postharvest work• Cabbage Quality and Temperature• Lettuce Varieties

– Fresh-cut performance

Storage temperature

Day

s (

to in

itiat

e ye

llow

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 appearanceGreen floretsTender stemNo discolorationNo breakageNo decayNo off-odors

mg/

100

g FW

0

5

10

15

20

25

mg/

100g

FW

0

1

2

3

4

Days0 5 10 15 20 25

mg/

100

g FW

05

10152025303540

Days0 5 10 15 20 25

mg/

100

gFW

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Cantwell, unpublished

Days

0 2 4 6 8 10 12 14 16 18

Col

or s

core

, 5=d

ark

gree

n, 1

=yel

low

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

Chl

orop

hyll,

mg/

g FW

0.3

0.4

0.5

0.6

0.7

0.8

0C Control 0C 1-MCP 5C Control 5C 1-MCP 10C Control 10C 1-MCP

A. Chlorophyll

LSD.05

Days

0 5 10 15

Suga

r, m

g/g

FW

3

4

5

6

7

8B. Sugar

LSD.05

Vita

min

C, m

g/10

0g F

W

40

80

120

160

200

240

280

0C Control 0C 1-MCP 5C Control 5C 1-MCP 10C Control 10C 1-MCP

A. Vitamin C (AA + DHA)

LSD.05

Days

0 5 10 15

Glu

cora

phin

in, µ

mol

e/g

DW

5

6

7

8

9

10

11

12

13

14

15B. Glucoraphinin

LSD.05

Broccoli and Temperature and 1-MCP (no ethylene exposure)

Glucoraphin produces Sulforaphane – potent Phase 2 Enzyme Inducer, inhibit cancer

Specialty Brassicas Comparative StudyGai-lanChoi-sumBroccoli raab, rapiniBroccolini

Florets Stem Tissue

ComponentInitial 5C,

8d10C8d

Initial 5C8d

10C8d

Total sugars, mg/gFW 5.2 4.5 3.7 17.4 14.4 12.0

Ammonia, µmole/100gFW 1.1 1.4 2.3 0.5 1.0 1.1

Antioxidant activitymg Trolox/100g FW

117 100 92 47 43 32

Vitamin C, mg/100g FW 235 176 112 87 86 88

M. Cefola, G. Hong, M. Cantwell, R. Paiva e G. Colelli. 2009

Marketable qualityCompositional qualityResponse to TemperatureResponse to atmospheres

Broccoli raab

0

200

400

600

800

1000

1200

1400

1600

0°C 5°C 10°C

AM

MONIA

INCREASE %

25

27

29

31

33

35

37

39

TOTAL

GS A

CTIV

ITY

AMMONIA INCREASE GS TOT

6 days, data of Eghle Catalano, 2007

Changes in ammonia and GS activity in Spinach

Days

0 2 4 6 8 10 12 14 16 18

mg/

g fr

esh

wei

ght

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

Ammonia concentration

Changes in ammonia in spinachat 4 temperatures over 18 days

µmol

e/10

0g F

W

0

50

100

150

200

250

300

350

400

450 A. Ethanol

µmol

e/10

0g F

W

0

10

20

30

40

50

60

70

80

90 B. Acetaldehyde

Days at 5°C

0 3 6 9 12 15 18

µg/g

FW

0

10

20

30

40

50

60

70

80

Days at 5°C

0 3 6 9 12 15 18

g/g

FW

45

50

55

60

65

70C. Ammonia D. Sugars

LSD.05

3%O2+7%CO23%O2+12%CO23%O2+18%CO210%O2+12%CO2

Air

3%O2+7%CO23%O2+12%CO23%O2+18%CO210%O2+12%CO2

AirTest #2

18 days at 5°C (41°F)

A B C D E 3+7 3+12 3+18 10+12 Air

DAMAGING

Air=Best quality

Iceless BroccoliTemperature-yellowingMoisture loss-softening

• 0°C with very high humidity• MA: 5-8% O2 + 7-10% CO2

Broccoli Storage Conditions

Table 1. Broccoli head firmness and compactness scoring and the relationship to firmness measurements on texture analyzer. This table based on preliminary 2009 data.

Subjective score

Description Objective firmnessN compression

force*

5 Heads hard, very tight and firm 65-100N

4 Heads firm, a few outer florets may be loosened 50-80

3 Heads moderately firm, with some florets loosened** 40-60

2 Heads moderately soft, with most florets loosened 25-40

1 Heads soft, with extensive loosening of florets 10-25

*Heads compressed with a flat disc to a depth of 7.5 mm**A score of 3 is likely the limit of marketability at retail.

Days at 7.5°C

0 1 2 3 4

% W

eigh

t los

s

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

irmne

ss lo

ss

0

10

20

30

40

50

60

70

80

90

100

Curve 1 original firmness technique Curve 2, modified technique, mark

B. % Firmness Loss

Minimize delay from harvest to cooling Use plastic liners to reduce water loss Keep it cold

2.5°C (36°F) 5°C (41°F) 7.5°C (45°F)

14 days air

14 days 5°C (41°F)

5% O2 5% O2 + 7.5% CO2 5% O2 + 15% CO2

14d 5°C

Quality ProblemsGrayingLoss of fluidOff-odor

Air 1%O2 +15% CO2

RESEARCH TO DO• Evaluate the performance of cultivars for

quality of fresh market and fresh-cut product • Evaluate the impact of initial postharvest

handling on the shelf-life and quality of fresh-cut cauliflower florets.

• Evaluate the impact of production conditions (seasonablity, fertilization, irrigation) on the quality and shelf-life of cauliflower florets

Cauliflower Qualitycolor is cream whitefreedom from mechanical injuryfreedom from decayoverall attractive appearanceno 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

Days

1 2 3 4 5 6

Res

pira

tion

(µL

CO

2/g-h

)

0

20

40

60

80

100

120

140 0°C (32°F)5°C (41°F)10°C (50°F) 15°C (59°F) 20°C (68°F)

A. Heads

Days

1 2 3 4 5 6

B. Florets

Napa or Chinese cabbageBlack Speck Disorder

Cultivar

1 2 3 4 5 6 7 8 9

Bla

ck s

peck

inde

x

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 Cabbage

Cabbage Quality and TemperatureCDFA WIC Stores Small Farm Program ProjectShermain Hardesty, Lucia Kaiser, and Advisors

• Retail handling—good to poor conditions• Impact on marketability and nutritional value—

conditions to retain 80% original nutrition• Vitamin C, Antioxidant Activity, Carotenoids • Wide range of temperatures (0-29°C; 32-84°F)• Cabbage performs well over temp range—should be

available in all WIC stores

Fresh-cut LettucesVarieties of Iceberg, Romaine and Crosses

• Performance as fresh-cut product– Visual quality score – Discoloration – Decay

• Respiration rates

• Phenolics and phenolic enzymes (PAL, PPO)

• Composition – Number leaves per head– % dry weight– Sugars– Chlorophyll and carotenoids– Vitamin C– Ammonia

Discoloration Rating Scale for Romaine

1 3

4 5

2

Tota

l sug

ars

(mg/

g fw

t.)

0

5

10

15

0 days7 days

HeartInner

Young Midsize Full sizeOuter

Leaf Position

Total sugars

LSD.05

Leaf Position

Tota

l asc

orbi

c ac

id (m

g/10

0g fw

t.)

0

10

20

30

40 0 days7 days

LSD.05

Vitamin C (Total Ascorbic Acid)

HeartInner

Young Midsize Full sizeOuter

Romainelettuce

Variety

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

Rus

set S

potti

ng S

core

1=no

ne, 9

=sev

ere

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

Is Temperature a Quality Issue or a Food Safety Issue?

Prevention of Contamination is most important Time and Temperature are Amplifiers of Risk

Slide from Trevor Suslow, UC Davis

1) Harvest at correct maturity2) Reduce physical handling3) Protect product from sun4) Keep packingline simple and

clean; ensure good worker hygiene5) Select, classify, and pack carefully6) Align cartons, strap pallet7) Cool as soon as possible8) Know market and product requirements9) Coordinate efficient & rapid handling10)Train and compensate workers adequately

10 Basic Postharvest Principles