Changes in heme iron content
in beef meat during wet heating
Consequences for human nutrition
Scislowski V., Gandemer G., Kondjoyan A.
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What we know about heme iron
Positive aspects
 Beef meat is an important source of iron mainly as heme iron
(3-4 mg/100 g meat, 70-75% as heme iron)
 Heme iron is an excellent source of iron for Human for at least 2
reasons :
1. Its bio-disponibility is far higher than that of non-heme iron (25-35% vs 2-5%)
2. Its intestinal absorption is independent of other components of the diet
 Consequently, beef meat can contribute to improve iron status of
some human groups under sub-deficiency (low meat consumers, adult
women, ….)
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What we know about heme iron and human health
Less positive aspects
 Heme iron is suspected to increase colorectal cancer risk through 2
main ways:
1. Heme iron catalyses lipid oxidation producing some components involved
in cancer propagation
2. Heme iron favors N-nitroso-compounds formation in stomach and colon
 Consequently, nutritionists recommend to reduce red meat
consumption (less than 500 g/week)
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What we know about heme iron and cooking
 Meat is mainly eaten after cooking
 Cooking partially converts heme iron into non heme iron
 The level of heme iron conversion depends on many parameters
(cut size, cooking mode, individual practices…)
 Data available are too disparate to predict heme iron content in
cooked meat in various conditions
 Consequently, we need a global approach through modeling of heme
iron conversion into non heme iron in meat during cooking.
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Aim of the work
To built a model for predicting iron content in cooked meat
covering the wide diversity of cooking practices
Strategy
1- To establish the kinetics of heme and non heme iron in
meat juice and meat under a wide range of temperature and
time combinations
2 – to built a model to predict heme iron content in meat in
most of cooking conditions used in practice
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Samples
 Meat juice :
1. Extracted under high pressure (several Tons) (Ardvidson et al., 1999)
2. Freeze-dried and stored at -80 °C
3. Restore in distillated water
4. Heated in a bath from 50 to 120° C and for 7 to 300 min
 Beef meat : Longissimus thoracis
1. Cut in small cubes or slices
2. Heated in a bath from 60 to 120° C and for 1 to 300 min
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Analytical methods
 Heme iron : Hornsey et al. (1956)
 Non-heme iron : using ferrozine – Ahn et al. (1993)
Results were expressed as µg/g dry matter for meat or /mL for juice
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Changes in heme iron content of juice
as related to température and time
Heme iron
50
60
80
89
98
120
16
14
µg/mL juice
12
10
8
6
4
2
0
0
200
400
600
Heating time (min)
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800
Time course of the conversion
of heme iron in non heme iron at 120°C in juice
Heating temperature: 120°C
HI
NHI
µg/mL juice
20,0
15,0
10,0
5,0
0,0
0
50
100
150
200
Cooking time (min)
250
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300
Changes in heme iron content of meat
as related to temperature and time
µg/g dry matter
Heme iron
90
80
70
60
50
40
30
20
10
0
60
80
95
120
0
50
100
150
200
Heating time (min)
250
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300
Changes in non-heme iron content of meat
as related to temperature and time
Non heme iron
100
µg/g dry matter
80
60
60
80
95
120
40
20
0
0
50
100
150
200
Heating time (min)
250
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300
Model for the prediction of heme iron in juice
according to time and temperature
dC
 kCn
dt
  Ea 
k  k 0 exp

 RT 
•
•
•
•
•
•
C is heme iron concentration
n is reaction order
t is time
k is the constant of the kinetics
k follows the Arrhenius law
Ea is the activation energy
• This model is that used to modelize protein denaturation
during cooking
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Calculation of the main parameters of the model
• n=1
• k0 = 79775 s-1
• Ea = 64715 J mole-1
• Mean error = 0.56 µg/mL less than 4% of
initial content in juice
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Comparison of calculated and measured values
for heme iron content in juice
as related to temperature and time
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Thank you for your attention
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