PREPARATION AND

HANDLING FRESH-CUT

ROOT VEGETABLES

MERETE EDELENBOS

DEPT. OF FOOD SCIENCE

AARHUS UNIVERSITY

DENMARK

merete.edelenbos@food.au.dk

Production Handling and Storage

Processing and Packaging

Distribution and Market

Consumption

Preparation and handling fresh-cut root vegetables

Pre-harvest Post-harvest Processing Post-processing

CONTENT

Characteristics of root vegetables

The unit operation

Peeling and cutting

Washing

Pre-packaging treatments

Packaging

Research needs

Conclusions

Root vegetables are mostly underground storage organs containing soil

Roots Tubers

C

Root vegetables

True taproots Includes a swollen hypocotyl

Seed Termination of

root growth Dormancy Growth

Seed Sprouting and

flowering Re-growth

Harvest Cold storage

Nov Jan May March

Root vegetables

Root vegetables are biennial crops

Chemical constituents vary between cultivars

Root vegetables

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Purple

Haze

Soprano Yellow

Stone

Nottingham Tornado White Satin Mello Yello Nairobi Nebula Line 1 Bolero

ng

/g

fre

sh w

eig

ht

Genotype

Total terpene content in carrots

Adapted from Kreutzmann et al. 2008

Chioggia

Touchstone Golden

Sensory quality vary between cultivars Root vegetables

Taunus

Rocket

Pablo

f:

a:

t:

Mikkelsen 2012

CHARACTERISTICS OF ROOT VEGETABLES

Belong to many different plant families

Are biennial crops

Continue to grow after harvest

Can be stored for up to 12 months

Store mainly sugars

Vary considerably in quality depending on

family, species, cultivar and time of usage

The unit operation for root vegetables

Unit operation

Peeling Cutting ± Washing Centrifugat.

±Pre-packaging treatment

Packaging

An example with processing of carrot sticks Unit operation

‘Bolero’ carrots

Fine abrasion peeling + rinsing

Cutting

Centrifugation

‘Bolero’ carrots

Cutting

Centrifugation

Washing in tap water

Household box

with ventilation

‘Bolero’ carrots

Hand peeling

knife

Trimming

+ rinsing

Cutting into 2 x 2 mm sticks

Cool room overnight

Coarse fine

abrasion peeling

+ rinsing

Cold air cooling

on conveyer belt

Centrifugation

Packaging

Trimming

Household Factory A Factory B Factory C

Effect of processing on visual quality

Factory A

Unit operation

Trimming Peeling Cutting

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Factory C

5 mm

5 mm 5 cm

Fractures

log

CF

U/g

afte

r 1

day

in M

AP

at 5

o C

0

1

2

3

4

5

6

7

Factory A

Factory B

Factory C

Coliforms Lacticacid bacteria

Yeast& Mold

Effect of processing on microbial load

Unit operation

Effect of processing on sensory quality

Unit operation

Se

nso

ry s

co

res f

rom

lo

w t

o h

igh

0

2

4

6

8

10

12

14 Household

Factory A

Factory B

Factory C

c

a

b

a

c

a

b

ab

Orange colour Wet surface

0

2

4

6

8

10

12

14

a

aa

b

a

bb

c

Carrot flavour Sweetness Juiciness

aa a

b

pinene

Vo

lati

le c

on

ten

t (n

g/g

fre

sh w

eig

ht)

1

10

100

1000

Control (cut)

Cut

Cut+spin

Cut+wash+spin

terpinolene caryophyllene

Effect of processing on aroma volatiles and sensory quality

Edelenbos et al. (2010) Acta Hort 876

Washing to reduce total microbial load Washing

Storage days at 4 oC

0 2 4 6 8 10

Mic

rob

ial l

oad

(lo

g C

FU

/g)

0

1

2

3

4

5

6

7

8

9

Control

Pre-wash water

Pre-wash chlorine

Pre-wash ozone

Washed sticks chlorine

Adapted from Klaiber et al. 2004

Total sugars

Control/pre-wash 6.3%

Washed sticks 5.2%

Washing to reduce microbial load

A B C

A

C B

Washing

Phytochemicals in carrots

Polyacetylenes

Isocoumarins

Phenolic acids

Some phytochemicals are simply removed in the peeling process

Peeling

Effect of processing on polyacetylenes

Parsnip discs

Peeling

Knife hand

Fine abrasion machine

Coarse abrasion machine

Carrot discs

Effect of peeling on phenolic acids

‘White blush’ in root vegetables

Trimmed

5 cm

Factory C

Peeled

Cut

Factory A

Chitosan-based coating to overcome ‘white blush’

Pre-packaging

6 mm carrot sticks

Packaging to maintain the initial sensory profile Packaging

Edelenbos et al. (2010) Acta Hort 876 Storage time (days)

Ga

s c

om

po

siti

on

(%

)

0

1

2

3

4

5

Carrot odor (**)

Sour odor (***)

Carrot flavor (*)

Sweetness (ns)

Fermented/sour flavor**

Juiciness (ns)

Day 0 8 days in perf film 8 days in non-perf film

Packaging

Packaging to prolong shelf-life Swede cubes

a

cb

b

aa

b ba b b

a

Days

Sw

eetn

es

s f

ra l

ow

to

hig

h

0

1

2

3

4

5

6

7

8

9

10

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a

cb

b

aa

b ba b b

a

Days

To

tal su

gars (

g/1

00 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

Packaging

Effect of time, temperature and packaging on quality

a

cb

b

aa

b ba b b

a

Days

To

tal

su

gars

(g

/10

0 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

a

cb

b

aa

b ba b b

a

Days

To

tal su

gars

(g

/100 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

a

cb

b

aa

b ba b b

a

Days

To

tal

su

gars

(g

/10

0 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

Adapted from:

Sugars Sweetness

Sc

ore

fro

m lo

w t

o h

igh

Packaging

a

cb

b

aa

b ba b b

a

Whiteness

Days

Sc

ore

fra

lo

w t

o h

igh

0

1

2

3

4

5

6

7

8

9

10

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

ab

A

a a aaa

B B

AABAB

a

cb

b

aa

b ba b b

a

Days

To

tal

su

gars

(g

/10

0 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

a

cb

b

aa

b ba b b

a

Days

To

tal su

gars

(g

/100 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

a

cb

b

aa

b ba b b

a

Days

To

tal

su

gars

(g

/10

0 g

FW

)

4.5

5.0

5.5

6.0

6.5

7.0

5 d

10 d

5 oC

10 oC

MA1

MA2

MA2-5%

Temperature Packaging

Swede Turnip Swede Turnip Swede Turnip

a aa

b bb

b

AB

AB

AAB

Whiteness (the higher the score the less enzymatic browning)

Sc

ore

fro

m lo

w t

o h

igh

Effect of time, temperature and packaging on quality

PROCESSING OF ROOT VEGETABLES

Peeling Cutting ± Washing Centrifugat.

±Pre-packaging treatment

Packaging

Effects on:

•The physical properties

•Wounding & oxidation

•Vapor exchange

•Constituents & microbial load

•Leakage

•Enzymatic

browning

•Microbial load

•Moisture

retention

•Quality

retention

Variation in the unit operation

•Abrasion peeling

•Knife peeling

•Knife cutting,

slicing,

dicing &

shredding

•Chemical

treatments

•Physical

•treatments

•Gas

transmission

rates

•Edible coatings

RESEARCH NEEDS

Appropriateness of cultivars/colored

types/tissue age at processing.

Gentle processing/efficient

decontamination to maintain sensory

quality and safety.

Better methods to evaluate the direct

effects of processing on quality.

CONCLUSIONS

Root vegetables contain dietary fibers, sugars and

phytochemicals. Are low in vitamin C.

Peeling removes the protective skin so

microorganisms can enter. Specific phytochemicals

are removed.

‘White blush’ develops in wounded tissue due to

loss of moisture from the surface.

Harsh handling/abiotic stress enhance phenolic

metabolism.

CONCLUSIONS

Fresh-cut root vegetables are prone to:

- enzymatic browning in white/light-colored tissue

- white blush in dark-colored tissue

- loss of aroma and flavor especially in carrots,

parsnips, root parsley and celeriac if finely cut and

washed

- loss of sweet taste if finely cut and washed

- fermentation if oxygen get too low in the package

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