examination of the effect of domestic cooking on acrylamide levels in food rachel burch leatherhead...

EXAMINATION OF THE EFFECT OF DOMESTIC COOKING ON

ACRYLAMIDE LEVELS IN FOOD

Rachel Burch

Leatherhead Food International

Objectives

• To compile a list of foods relevant to home cooking that are high in asparagine, taking into account levels of consumption

• To examine the effect of cooking on acrylamide levels of less complex foods (i.e. vegetables)

• To examine varietal effects in potatoes

Total quantities (grams) of vegetables and vegetable products consumed in 7 days

(consumers only)

Type of foodTotal quantities (grams) consumed

in 7 days

Mean Median % consumers

Green beans 108 90 22

Leafy green vegetables 152 108 53

Carrots – not raw 106 85 56

Tomatoes – not raw 131 85 24

Other vegetables 226 170 80

Potatoes

Potato chips 348 270 71

Other fried/roast potatoes and products 203 175 42

Potato products – not fried 146 120 6

Other potatoes and potato dishes 469 396 84

NDNS data, 2002

Asparagine and glutamine levels

Asparagine mg/100g fresh weight

Glutamine mg/100g fresh weight

Carrots 25-110 37-123

Tomatoes 16.6

Onions 33-55

Cauliflower 7 40

Mushrooms 12-17

Broccoli 7 16

Green bean pods 187 5

Kale 16 107

Spinach 6 39

Potatoes 133 94

Task 3a

• Potatoes cooked from fresh and from frozen– Baked, boiled, roast, saute, microwave “baked” from

fresh– Boiled, roast, saute from frozen

• Onions cooked from fresh and from frozen– Boiled, baked, fried from fresh and frozen

Task 3a – Potatoes

Potatoes

0500

1000150020002500

Raw

Boi

led

Sau

te

Roa

st

Bak

ed (

insk

in)

Mic

row

aved

(in s

kin)

Sau

te f

rom

froz

en

Roa

st f

rom

froz

en

Cooking type

Ac

ryla

mid

e

mg

/kg

Task 3a – Onions

Onions

0100200300400500600

Raw Boiled Fried Baked Friedfrom

frozen

Bakedfrom

frozenCooking method

Acr

ylam

ide

m g/k

g

Task 3c – Cyclic re-use of frying oils

• Five different oil types• Five cookings in each oil

– Initial cookings to same colour, to determine fry time for each oil. Subsequent cookings for the same length of time

– Oil temperature 190ºC (except lard: 175ºC)

Use of different cooking oils

0

50

100

150

200

250

300

350

400

450

500

Lard Corn oil Rapeseed Vegetable Sunflow er

Oil type

m

Re-use of cooking oils

0

100

200

300

400

500

600

700

1 2 3 4 5

Fry number

Acr

ylam

ide

mg

/kg

Corn oil A

Corn oil B

Rapeseed A

Rapeseed B

Re-use of cooking oils - conclusions

• Preliminary data suggests:– Some differences in acrylamide levels in chips

cooked in different oils– Some indication that acrylamide levels increase in

chips cooked in re-used rapeseed oils

Task 3d – Effect of pre-treatment

• Chips– Washing, storing in water for 30 mins, storing in

water for 2 hours– Samples prepared in triplicate, chips cooked for

same length of time

• Roast potatoes– Washing, storing in water for 30 mins, storing in

water for 2 hours, par-boiling– Samples prepared in triplicate, cooked for same

length of time except for par-boiled

Task 3d – Effect of pre-treatment - Chips

potato pre-treatments - chips

0200400600800

1000

none washing 30 minwater

2 hr water

pre-treatment

Ac

ryla

mid

e m

g/k

g

Chips – correlation with colour

green red

0

100

200

300

400

500

600

700

800

900

0 1 2 3 4 5 6 7 8 9

C ol our (a val ue)

m No pre- treatment

Washed

Soaked 30 min

Soaked 2 hours

Chips – correlation with colour

L Value

Dark Light

0

100

200

300

400

500

600

700

800

900

0 10 20 30 40 50 60 70

C olour ( L value)

m

No pre- treatment

Washed

30 min soak

2 hour soak

Pre-treatment – Chips – glucose removed

Glucose - chips

0.00

0.20

0.40

0.60

washed 30min soak 2 hour soak

treatment type

glu

co

se

re

mo

ve

d g

/kg

Task 3d – Effect of pre-treatment – roast potatoes

potato pre-treatments - roast

0

200

400

600

800

no pre-treat

washing water 30min

water 2hr

par-boil

pre-treatment

ac

ryla

mid

e m

g/k

g

Pre-treatment – roast potatoes – glucose removed

0.000

0.200

0.400

0.600

0.800

washed 30 minsoak

2 hoursoak

Par-boiled

Pre-treatment

glu

cose

rem

ove

d

g/k

g

Effect of variety - chips

Chips

0

500

1000

1500

2000

King Edward Desiree Maris Piper

Variety

Ac

ryla

mid

e m

g/k

g

Effect of variety – Roast potatoes

Roast Potatoes

0

200400

600

King Edward Desiree Maris Piper

Variety

Ac

ryla

mid

e

mg

/kg

Effect of variety – baked potatoes

Baked potatoes

0

100200

300

marfona cara estima

Variety

Ac

ryla

mid

e

mg

/kg

Conclusions – factors affecting acrylamide formation in domestic

cooking• Type of cooking– Acrylamide formed in roasted, sautéed, oven baked

potatoes, higher levels found in potatoes cooked after freezing

– Not formed in boiled or microwaved potatoes– Formed in fried onions, onions baked from frozen– Not formed in onions baked from fresh, or boiled

• Pre-treatments– Soaking for two hours, or par-boiling led to greatest

reductions– Indication that some pre-treatments affect fat

content

Conclusions – factors affecting acrylamide formation in domestic

cooking• Chip colour correlates to acrylamide levels,

roast potato colour does not– Roast potatoes were not of uniform size and shape

• Variety– Some varieties result in higher acrylamide levels

relative to other varieties cooked using the same method