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