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, ….) ALIMENTATION AGRICULTURE ENVIRONNEMENT
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
ďƒ˜ 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. ALIMENTATION AGRICULTURE ENVIRONNEMENT
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) ALIMENTATION AGRICULTURE ENVIRONNEMENT
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
Âľg/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
Âľg/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 ALIMENTATION AGRICULTURE ENVIRONNEMENT
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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