1

Root, Tubers & BulbsCBA

PotatoTurnipGarlic

JicamaParsnipOnion

TaroSalsifyBeet

YamCeleriacRadish

SweetpotatoHorseradishCarrotsCassavaSunchokeRutabaga

Storage Temperatures Roots, Tubers and Bulbs

• Chilling insensitive roots: 0-5°C (32-41°F)

• Chilling sensitive roots: 10-15°C (50-59°F)

2

Washing Disinfecting Rapid coolingCut to 2 inch sectionsMechanical PeelingMechanical shapingDisinfection CoolingComputerized quality and color sortingVFS packaging

Processing Baby Peeled Carrots

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3

Baby carrots

“Baby” carrots

Carrot varieties

Carotene-uniformity of colorSugarFiber-texture

Longitudinal crackingis highly dependenton variety

4

Abrasion peeling of carrots leads to fragmented cell walls that dry out and result in “white blush”;can rehydrate carrots.

Diagrams from Saltveit, UC Davis

New equipmentautomatically peelsand then cuts the carrots;have less problem with“white blush”

White blush or chalking isMinimized at low temperature or with hygroscopic coatings

Carrots do not respond well toModified atmospheres

Free moisture in the bag favors Decay (5°C 1 month)

5

Carrot Flavor DefectsCarrot Flavor Defects• Harshness: Terpenes

– Variety– Growing conditions

• Bitterness: Isocoumarin– Postharvest defect– Ethylene exposure

Bitterness in CarrotsBitterness in Carrots

• Induced by ethylene• Threshold ~0.15 ppm C2H4 at 0-5°C• 70% of isocoumarin in the peel• Sliced carrots form 4X more isocoumarin• Physical damage increases isocoumarin• Other factors: temperature, age, variety

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Days at 5°C0 5 10 15 20 25 30

Isoc

oum

arin

(m

g.10

0 g-

1 )

0

20

40

60

80

100

120

Days at 5°C0 5 10 15 20 25 30

Air0.5 ppm

Whole Sliced

Wounding increases sensitivity to ethylene

Pulp of unpeeled 5 cm pieces is very sensitive to ethylene

Days at 5°C with 0.5 ppm C2H4

0 4 8 12 16 20

Isoc

oum

arin

(mg.

100

g-1 )

0

20

40

60

80

100

120"Baby"PiecesWhole

Pulp

7

8

Medium to firmSoft to mediumInterior Texture

Multiple layers of thick, dark skinThin, light colored skinExterior

Mildly pungent to strongMild to slightly pungentAroma

Varies from mild to very pungentSweet/mild to slightly pungent flavors

Sweetness

Odors will be absorbed by apples, celery and pears. Will absorb odors produced by apples and pears.

Odor Sensitivity

Hardier than other types.Highest freezing point

= 30.6°F or -0.8°C

Moderately sensitive.Highest freezing point

= 30.6°F or -0.8°C

Freezing Injury

Keep in a dry, well ventilated placeHumidity

Room temperature – Dry storageTemperature

30 days or lessRetail Shelf-life

30 –180 days30 – 60 daysStorage/Shelf-life

Designed specifically to withstand long periods of storage

Typically not stored, unless under controlled atmosphere

or refrigeration

Storing Ability

Fall/winter Storage Onions

Spring/summer Fresh Onions

Attributes

Onion Handling and Storage Attributes

http://www.onions-usa.org

9

Botrytis- gray moldAspergillus- black moldSunburnSenescence- translucency

Storage Temperature:0°C (32°F) 20°C (68°F)

Low RH (~65-70%)

• Sweet onions 5 µmol pyruvate/g FW• Supersweet

10

• Low temperature minimizes wound response

• Diced onions yellow, decay, soften and leak more than whole peeled onions

Storage Temperature

Res

pira

tion

(µL

CO

2. g

-1 h

-1)

0

1

2

3

4

5

6

7

8

9

10

11

12 Yellow Onion

IntactPeeledDiced

0°C 5°C 10°C

Impact of temperature andcontrolled atmosphereson quality of fresh-cut diced onions

RO=rolled (damaged)

32°F 41°F 50°F

45°F

41°F

36°F

11

Respiration of Onion Dices

Days

0 2 4 6 8 10 12 14

Res

pira

tion

(mL

CO

2/kg-

h)

0

5

10

15

20

25

0°C 32°F5°C 41°F5°C 41°F Rolled 10°C 50°F

9=ex

celle

nt, 1

=unu

seab

le

1

2

3

4

5

6

7

8

9 Visual Quality

1 =n

one,

5 =

seve

re

1

2

3

4

5

Days

0 5 10 15 20

1

2

3

4

5 Discoloration

Decay

Limit of Salability

0°C 32°F 5°C 41°F

10°C 50°F 5°C 41°F Rolled

Fresh-cut Onions (dices)Low temperature is essentialfor shelf-life and quality

Days

0 5 10 15 20

pyru

vate

µm

/g fr

esh

wt.

1

2

3

4

5

6

7

8

9

10

11

12

0°C 5°C

10°C 5°C Rolled

Pungency

Fresh-cut Onions (dices)Low temperature is essentialfor shelf-life and quality

12

• Respiration increases exponentially with increased temperature

• At 10°C, chopping doubles respiration rate

• At 0°C, wound response is minimizedTemperature

Res

pira

tion

rate

(µL

CO

2.g-

1 h-1

)

0

20

40

60

80

100

120

140

Intact

Chopped, Manual Chopped, Commercial

Green Onions

0°C32°F

5°C41°F

10°C50°F

15°C59°F

20°C68°F

13

9=ex

celle

nt, 1

=unu

seab

le

123456789

123456789

A ir2 % O 20 .2 % O 2a ir+ 7 .5 % C O 22 % O 2 + 7 .5 % C O 20 .2 % O 2 + 7 .5 % C O 2a ir+ 1 5 % C O 2

0 7 1 4 2 1

123456789

123456789

D a y s a t 5 o C 0 7 1 4 2 1

123456789

123456789

In ta c t

C u t

H e a t tre a te d + C u t

Visual quality and CA storageVisual quality and CA storage

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Garlic Bulb Storage

• Well cured• Relative humidity 60-70% (reduce molds, rooting)• -1°C to 0°C (30°-32°F) long-term• 20°-30°C (68-86°F) 1-2 months• 5°-18°C (41°-65°F) favor sprout growth• Odor easily transferred to other products

Considerations for Maintaining the Quality of Fresh Peeled Garlic

Respiration rates; mechanical injuryStorage temperaturesControlled atmospheresControl of sprout/root growth

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Average Respiration Rates (µL CO2/g-h)

40.629.318.110°C (50°F)

21.217.410.65°C (41°F)

Compressed Compressed Air PeeledAir Peeled

Manually Manually PeeledPeeled

Unpeeled Unpeeled ClovesCloves

0

10

20

30

40

50

Days0 2 4 6 8 10 12 14 16 18 20

Res

pira

tion

(μl C

O2/

g-h)

0

10

20

30

40

50

5ºC (41°F)

Unpeeled Manually peeled Compressed air peeled

10ºC (50°F)

Res

pira

tion

(μl C

O2/

g-h)

Careful peeling causes a substantialincrease in respiration rates.

Mechanical compressed air peeling doubles respiration rates.

0°C32°F

Commercially Peeled Garlic Stored 9 Days

5°C41°F

10°C50°F

15°C59°F

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♦Controlled atmospheres with10% CO2 helped maintainvisual quality of peeled garlicat 5°C (41°F) and 10°C (50°F).

♦ High CO2 atmospheres retarded discoloration and decay

1% O2 + 10% CO2Remainder N2

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Heat treatments controlSprout growth and Root growth

Cantwell, Kang, Hong, 2000; stored at 10°C

Spro

ut R

atio

(>1.

0 =

emer

ging

)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Weeks at 10°C (50°F)

0 1 2 3 4 5

1=no

ne, 3

=3-5

, 5=1

1-15

, and

7=>

20m

m

1

2

3

4

5

6

A. Sprout growth

B. Root growth20°C (68°F) 60 min 50°C (122°F) 10min 50°C (122°F) 20 min 55°C (131°F) 10 min 60°C (140°F) 2.5 min 45°C (113°F) 60 min

•• AlliinAlliin is the main precursor to important flavor and potentially biological active sulfur-compounds in garlic.

•• AllicinAllicin is the main thiosulfinate produced: provides flavor and pungency and is bioactive.

Garlic Composition

Alliin and allicin concentrations vary by:Garlic varietyIrrigation and fertilization practicesStorage conditions and duration

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Maintaining Quality of Peeled GarlicMaintaining Quality of Peeled Garlic

• Reduce mechanical injury at peeling• Store at low temperature, ~0°C (32°F)• Use modified atmospheres with 5-10% CO2• Heat shock treatments retard sprout/root growth

• Selection of varieties with specific qualities, high or low pungency, long dormancy, resistance to bruising and mechanical injury

• Treatments to remove “crowns” during peeling

Many root crops are chilling sensitive: Jicama as example

Potato stored 4-5 mo. 2°C

19

Jicama: Discoloration is problematiconly at high temperaturesRaw material quality, starch-sugarSurface drying

Potato Internal Color

1 2 3 4 5

20

Defects1. Skinning2. Internal deterioration3. Cut edge discoloration

1.210.50.30.86.02.29.3LSD.05

5.30--5.00.543.515.739.011 Aug22 Jul

4.704.33.90.629.917.738.86 Aug22 Jul5.603.03.22.160.215.243.51 Aug22 Jul

6.352.72.12.566.115.534.627 Jul22 Jul

6.001.52.04.1102.615.230.022 Jul22 Jul

4.906.24.70.546.214.321.46 Aug17 Jul

6.304.43.91.859.114.123.41 Aug17 Jul7.252.82.21.265.914.621.527 Jul17 Jul

6.751.12.03.387.513.222.522 Jul17 Jul6.751.22.14.1132.613.821.717 Jul17 Jul

RespirationµL CO2/g-h

Torquelb-inch

Skin Score

% wt loss (5d 7.5°C)

Sugar,mg/g DW

% dry wt.

Ave. wt. g/potato

Harvest Date

Kill Date

Quality characteristics of ‘Morning Gold’ potatoesharvested at different times and at different plant kill dates.

Cantwell and Carlson, Tule Lake, CA, 2002

“Salad Potatoes”

21

Days stored

0 7 14 21 28

Suga

r (m

g/g

dry

wt.)

100

200

300

400

500

600

700A. cv. Penta

(data averaged over 5 atmospheres)

5°C 41°F

10°C 50°F

Days stored

0 7 14 21 28

5°C 41°F10°C 50°F

B. cv. Cherry Red

Storage of “new potatoes” at 5°C (41°F) in air results in significant increases in sugar concentrations, while sugarlevels do not increase much at 10°C (50°F).

Tule Lake potatoes, 2001

Per

cent

0

3

6

9

12

15

18

21

24 Carbon dioxideCryovac Bag

Days stored

0 3 6 9 12 15 18

Per

cent

0

2

4

6

8

10

12

Days stored

0 3 6 9 12 15 18

OxygenThick Polybag

OxygenCryovac bag

Carbon dioxide Thick Polybag

2.5°C 36°F5°C 41°F7.5°C 45°F

2.5°C 36°F5°C 41°F7.5°C 45°F

The 2 bags testedcreated very different atmospheres.

Storage temperatures from 2.5-7.5°C (36-45°F) did not greatly affect gas concentrations

MA Test #1, Tule Lake, “new potato” cv. Penta

22

Days stored

0 6 12 18

Suga

r (m

g/g

dry

wt)

50

60

70

80

90

100

110

120

130 Sugar ContentThick Polybag

Days stored

0 6 12 18

Sugar ContentCryovac Bag

2.5°C 36°F

5°C 41°F

7.5°C 45°F

Sugars increased more in potatoes stored in the bag that provided higher O2 and lower CO2 concentrations.

MA Test #1, Tule Lake, “new potato” cv. Penta

Fresh-peeled and cut Potatoes

Raw material quality

Washing and peeling, slicing (sharp)abrasion, steam, caustic

Focus on control of browningCultivars vary widelyCitric, ascorbic acid Bisulfites not allowedhttp://hort.cabweb.org/Postharv/Laurila.htm

Temperatures and atmospheresColdMA: high CO2 + N2

23

Toxic glycoalkaloid formation isclosely associated with greening

Control greening & glycoalkaloids:• No Light- opaque packaging• Low Temperature• Short Duration

Potato variety

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

mg

per

100

g fr

esh

wei

ght

0

1

2

3

4

5

6

7

8

9

10

11 1 Satina 2 Crispin 3 Moly 4 Yukon Gold 5 Red LaSoda 6 Cal Red 7 Ruby Red 8 Adora 9 White Rose10 Cal White11 Morning Gold12 Durango

24

Glycoalkaloids vs Chlorophyll Content

TGA

(mg/

100g

FW

)

0

5

10

15

20

25

30

35TGA vs Chlorophyll

CalRedy = 6.45x +10.97R2 =0.997

CalWhitey = 4.25x +8.28R2 =0.936

0.0 0.5 1.0 1.5 2.0 2.5 3.0 Chlorophyll (mg/100g FW)

CalRed

Durango VC1015

A94381

5.44.53.5Yukon Gold (w/w)10.04.42.4Satina (w/y)12.15.93.8Latona (w/y)26.79.94.7CalWhite (w/w)7.05.64.3VC1015 (r/y)9.96.64.8Durango (r/w)29.421.68.0CalRed (r/w)6.63.02.1A94381 (r/y)

9d light9d dark0 timeCultivar (color)

Average TGA Concentrations (mg/100g FW)

Satina Yukon Gold

LatonaCalWhite6 days20°CDark LLight R