05-Postharvest Handling of Roots and Bulbs

8/14/2019 05-Postharvest Handling of Roots and Bulbs

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6.4

4.3

1.4

10.1

0.350.08

0.92

88.5

RawOnion

Suc, Glu, Fru5.0Sugars, total

Relatively low4.8Vitamin C

Total dietary0.9Fiber

Calculated bydifference

7.6Carbohydrate

K, Ca, P, Mg0.34 Ash0.08Fat

0.80Protein

91.2Water

Raw SweetOnion

Component(%)

USDA Database Composition of Generic Onions

http://www.nal.usda.gov/fnic/foodcomp/Data/ 2004

Other Important ConstituentsHealth Benefits, Phytonutrients, Nutraceuticals

Quercetin (flavonoid) Antioxidant activity--delay or slow the oxidative damage to cells Reduce/eliminate free radicals in the body, Inhibit low-density lipoprotein oxidation (heart disease), Protect and regenerate vitamin E (a powerful antioxidant)

Sulfur-containing compounds Allyl and diallyl sulfides and othersFlavor Reduce blood cholesterol levels Improve immune function

Lower blood sugar levels Increase production of enzymes that protect cells against

cancer-causing substances (carcinogens)

http://www.onions-usa.org/

Onions and Garlic


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Field packing of sweetwhite and red onions

Forced air curing of onion skins

Curing with natural ventilationunder shade cloth


4/13

Curing reduces moldgrowth during storage

30 days

Storage Conditions:0C (32F)

20C (68F)

Low RH (~65-70%)

0C = 32F25C = 77F

Botrytis Neck RotBotrytis allii, B. squamosa, B. cinerea

Symptoms usually appear after harvestInfections originate in the field.Develops best under cool & humid conditions (50 to 75F),

ControlGrow varieties known to store wellFollow production practices that promote crop storability.

Avoid excessive and late applications of nitrogen.Do not irrigate within 10 to 14 days of lifting onions.

Allow tops to dry approximately 1 week before topping.Harvest only when the crop is mature, and during dry weather.Good storage onions

at least three wrapper scalestight neck when dried

Provide good ventilation for curing onions before storage.

http://cru.cahe.wsu.edu/CEPublications/eb1359/eb1359.html


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Onion & Garlic Bulb Storage

Well cured Relative humidity 60-70% (reduce molds, rooting) 0C (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

Garlic harvest and curing

Chemical Composition &Postharvest Quality

USDA Garlic Germplasm CollectionRon Voss and Marita Cantwell

Percent Dry Matter and/or Soluble Solids

Alliin Content

Allicin Content and/or or total Thiosulfinates

Peeled clove quality/shelf-life

Sprouting


7/13

AlliinAlliin is the main precursor to important flavorand 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

Variation in CompositionGarlic Germplasm2004 data; 190 accessions

% Dry Weight

30 32 34 36 38 40 42 44

A c c e s s i o n n o .

0

20

40

60

80

100

120

140

160

180

Ca Early (39.2)

Ca Late (40.2)

% Dry Weight 2004 Data

Range = 30.0-44.5; Average = 38.3

% Dry Wt


Alliin (mg/g DW)

0 5 10 15 20 25


0

20

40

60

80

100

120

140

160

180

Ca Early (17.9)

Ca Late (20.6)

Alliin 2004 DataRange = 8.6-28.7

Average = 17.8

Alliin


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Thiosulfinates (m/g DW)

0 10 20 30 40 50 60 70 80 90 100 110


0

20

40

60

80

100

120

140

160

180

Ca Early (64.2)

Ca Late (73.4)

Thiosulfinates 2004 Data

Range = 29-114; Average = 72

Thiosulfinates

r e l a t i v e

t o c l o v e

l e n g

t h

0.00

0.25

0.50

0.75

1.00

1.25 A. Sprout growth

m m

0.0

0.5

1.0

1.5

2.0

F o r c e

i n N e w

t o n s

8

12

16

20

24

Months at 0-1C

0 1 2 3 4 5 6

%

3334353637383940414243444546

Months at 0-1C

0 1 2 3 4 5 6

m g / g

D W

10

15

20

25

30

35

Months at 0-1C

0 1 2 3 4 5 6

m g / g

D W

4

6

8

10

12

B. Root growth C. Clove firmness

D. % Dry weight E. Alliin F. Allicin

W6 17074W6 17260W6 1861W6 2308W6 383833W6 4264

LSD.05

Garlic Germplasm 2001: Changes during storage at 0-1C

Cantwell and Hong


9/13

Hot water dips retard sprout growth withoutreducing peeled garlic quality

Alliin and allicin slowly increase in storage andchanges are similar among cvs stored at 0-1C

Controlled atmospheres retard sprout growthand fructan changes, but reduce alliin andallicin concentrations

Garlic: Postharvest TestsGarlic: Postharvest TestsGarlic: Postharvest Tests

Carrots

0C for storage Very high humidity Packaging

Topped to reduce waterloss

Carrot varieties

Carotene-uniformity of color

Sugar Fiber-texture


10/13

Mechanical Harvest

Mechanical harvestof carrots

Longitudinal crackingis highly dependenton variety


11/13

Temperature

C r a c

k i n g

I n d e x

( T o t a l

% c a r r o t s c r a c

k e d / h e i g h

t w h e n

d r o p p e

d 2 , 3 , 4 a n

d 5 f e e t )

0

10

20

30

40

50

60

70

80

90

100

110

2.5C36F

12.5C(55F)

20C(68F)

Effect of Carrot Root Temperature on Cracking

Cultivar ImperatorDominatorCellobunch

Nantes

- Variety very Important- Carrot cracking increased by high N fertilization

Hartz and colleagues, UC Davis

Carrots requireDiameter &Length Sizing

After sizing,

Carrots are hydrocooled (left),Defects removed (below),and then packaged


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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 C 2H4 at 0-5C 70% of isocoumarin in the peel Sliced carrots form 4X more isocoumarin Physical damage increases isocoumarin Other factors: temperature, age, variety


13/13

Parsnips also become bitter withEthylene exposure

05-Postharvest Handling of Roots and Bulbs

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