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Changes in heme iron content in beef during wet heating. Consequences for human nutrition
Valérie Scislowski, Gilles Gandemer, Alain Kondjoyan
To cite this version:
Valérie Scislowski, Gilles Gandemer, Alain Kondjoyan. Changes in heme iron content in beef during wet heating. Consequences for human nutrition. 57. International Congress of Meat Science and Technology (ICOMST), Aug 2011, Ghent, Belgium. 714 p. �hal-02748502�
Changes in heme iron content in beef meat during wet heating.
Consequences for human nutrition
Scislowski V.1, Gandemer G. 2,3, Kondjoyan A.4
Adress : 1ADIV, 10 rue Jacqueline Auriol, ZAC des Gravanches, 63039 Clermont Ferrand, cedex 2, France ;
2Inra, Centre de Lille, 2 chaussée Brunehaut, Estrées Mons, 80203 Péronne, France ; 3Centre d’Information des Viande, Tour Mattei, 207 rue de bercy, 75587 Paris cedex 12, France ; 4Inra, UR370 QuaPA, 63122 St Genes
Champanelle, France.
Abstract : Meat heme iron (HI) is an excellent source of iron for human because its digestibility is far higher than that of non-heme iron (NHI).
However HI is partially converts into NHI through heme degradation by heat. Up to now, very little is known about the kinetics of this reaction. The aim of the present study was to determine the kinetics of HI conversion into NHI under various conditions of wet heating (from 50
°C to 120 °C, and from 0 to 300 min). This work was performed on both meat juice extracted by pressure and on beef meat. The results showed that HI conversion into NHI is low during the first ten min of heating in juice, then it increased with time and temperature from -3% at 60 °C to 93% at 120 °C for a 300 min heating. In meat, the conversion increased continuously. HI content in cooked meat is between 30-40% of its content in raw meat after 300 min whatever the temperature. Based on these results a model will be built to predict HI content in cooked meat under various cooking conditions.
This study showed that a significant proportion of HI of raw meat is converted into NHI in cooked meat. This reduces significantly the bioavailability of iron. This must be taken into account to evaluate the true iron supply through meat consumption. The model developed in this study is helpful to predict HI content in cooked products in various cooking modes used by the consumers and to a subsequent calculation of iron supply by the consumption of cooked meat portions.
In European countries, iron deficiency is a relatively common problem in public health (Monsen et al., 1978). It is recognized that this problem is of major concern for adult women because they lose significant amount of iron during menstruation.
More recently, poor iron status are often observed in some groups, namely vegetarians and low red meat
eaters. Meat could help to prevent iron deficiency because meat contains heme iron mainly as myoglobin which is absorbed in a higher proportion than non heme iron. Thus, the proportion of heme iron absorbed by humans is far higher than that of non heme iron (25-35% versus 5%). Among the most common meat species available in European countries, beef is the meat which has the highest amount of heme iron (Purchas et al., 2003).
However, a part of heme iron is converted in non heme iron during meat cooking. The level of this conversion depends on many parameters, including cooking conditions and others such as size of cuts (Lombardi-Bocca et al., 2002; Purchas et al., 2003).
In these studies, looses in heme iron varied from several percents up to 50%. However, data are too disparate to predict heme iron content of meat cooked in the wide diversity of cooking practices of consumers and manufacturers. This is crucial to estimate the iron bioavailability of cooked meats and the contribution of meat in covering dietary requirement of humans but also to deliver correct information to consumers and manufacturers. To achieve this goal, the only way is to build a model predicting heme iron conversion in non heme iron in a wide range of cooking conditions. The first step is to describe the kinetics of heme and non heme iron in meat under a wide range of temperature and time combinations covering those of cooking practices of consumers and manufacturers. The second step will be to couple this kinetics with a model predicting the temperature in each point of the meat cuts under various cooking conditions. This paper deals with the kinetics of the conversion of heme iron in non heme iron in beef meat according to a large variety of temperature and time of cooking.
Materials and methods
Kinetics of heme iron conversion in meat juice:
Juice was extracted from shank according to the method of Ardvidson et al. (1999). Juices were obtained through three successive steps of pressing:
3T for 1min, 5 T for 1min and 3 T for 15 sec.
Extracted juices accounted for 31% of meat weight and contained around 10% of dry matter. Juices are filtered and they freeze-dried. For kinetics determination, juices were restored in distillated water to a final density of 1.022. Kinetics of heme iron conversion in non heme iron were studied as follows: 50°C for 7, 20, 40 and 60 min, 60°C for 10, 20, 40 and 300 min, 80°C for 10, 20, 60, 180 and 300 min, 89°C for 10, 60, 180 and 300 min, 98°C for 10, 60, 180, 300 and 900 min, 120°C for 10, 60, 180 and 300 min.
Kinetics of heme iron conversion in meat juice:
Small pieces of meat (1x1x1cm) cut in Longissimus thoracis. Four pieces of meat were used for each point of the kinetics. One is used for following the evolution of the temperature in the samples and the three others for further analyses. Samples were placed in a plastic bag and immersed in a water bath at 60°C, 80°C or 95°C for 10, 30, 60, 180 and 300 min. At 120°C, samples were immersed for shorter times (1, 3, 5, 10 and 30 min). At the end of the cooking time, samples were quickly cold in a freezer until the internal temperate felt down to 4°C.
Analytical methods: Analyses were done on three replicates for each kinetic point. Dry matter (DM) of samples was determinate according the normalized method (AFNOR ). Heme iron was quantified according to the method of hornsey (1956) and non heme iron was determinate using ferrozine as described by Ahn et al. (1993). Results were expressed as µg/g DM of meat or µg/mL of juice.
Results and discussion
Juice heating. Heme iron decreased during the heating process whatever the temperature above
50°C. The higher was the temperature, the faster was the decrease and the lower was the reminding heme iron at the end of heating (Figure1). Thus, the proportion of heme iron remained high after 300 min at 60 °C (97% of initial amount in raw meat) but dropped down to a very low level after 300 min at 120 at 120 °C (7% of the initial amount in raw meat). This kinetics recovered several mechanisms.
During the first minutes of heating when the temperature remains below 60-70°C, myoglobin remained in its initial state. When the temperature rose above 70°C, the globin of myoglobin was denaturized and heme iron become insoluble (Results not shown). At higher temperature, heme was destroyed and iron released as non heme iron (Figure 2). This is clearly illustrated on figure 2 where the decreased in heme iron during heating at 120°C was concomitant with an increase in non heme iron. These results confirm with those previously published (Purchas et al., 2003). It is assumed that the processes involve in heme iron conversion in non heme iron in juice are similar to those happening in meat because myoglobin is also in soluble form in water inside of meat.
Meat heating. Longissimus thoracis contained 2.54 mg/g of total iron, 1.58 mg were heme iron which represents 71% of total iron. These results are close to those previously published which showed that heme iron in beef is comprised between 60-80% of total iron (Purchas et al., 2003, Carpenter et Clark, 1995). As described for juice, heme iron decreased in meat during heating (Figure 3). This decrease remained low at 60°C and was about 66% of the initial amount in raw meat at 95 °C. At 120 °C, the heme iron amount dropped down very fast to reach one third of the initial amount in raw meat in 10 min. In contrast, the amount of non heme iron increased at all the temperatures and times studies.
These results are consistent with those previously published (Purchas et al., 2003; Garcia et al., 1996;
Han et al., 1993). The decrease of heme iron amount starts by a decrease in heme iron soluble fraction (Results not shown). Then, when the temperature increases in meat a part of heme iron is converted in
non heme iron fraction because of oxidative cleavage of prophyrin ring of heme. This causes a release of ionic iron which explains the increase in soluble non heme iron. Further, a part of non heme iron became insoluble as shown by the increase in this fraction during heating (results not shown). A first order reaction model appears to fit well with the kinetics of heme iron decay in meat during heating. Coupling this kinetics with a model which calculates temperature at each point of meat cut during heating could allow predicting heme iron recovered at the end of cooking process in a wide range of conditions. The work is in progress in the lab based on the model developed by Ollic et al.
(2011) to predict cooking looses from various meats during heating.
Nutritional implications: The present paper demonstrates that a part of heme iron is converted in non heme iron during cooking. The level of losses depends on cooking mode. We estimate that the heme iron content of cooked meat is close to that of raw meat when cooked on a grill and remains low when roasted in an oven (less than 10%). Only long time cooking modes (stewed and braised cooking) markedly decrease heme iron content of meat (-30- 40%).This strongly impairs the bioavailability of iron in meat and must be taken into account to estimate properly the amount of iron supplies by a cooked meat. Anyway, meat, mainly beef red meat, remains an interesting source of iron for consumers with a poor iron status. This heme iron reduction in meat during cooking could be also regarded as a positive fact considering some public heath aspects.
Thus, heme iron is postulated to be involved in colorectal cancer (Corpet, 2011). Consequently, the reduction of the amount of heme iron during cooking must be taken into account to evaluate the
putative implication of this molecule in colorectal cancer risk. This underlines that it is essential to improve our knowledge on iron content and bioavailability in cooked meat to provide accurate nutritional information to consumers and nutritionists.
Conclusion: This paper described the kinetics of heme iron conversion in non heme iron. This is the first step for building a model calculating the heme iron content of meat as according to the cooking method and the size of meat cuts. This will permit to improve the estimation of iron availability of meat and to give a better estimation of meat contribution to daily iron supply.
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Figure 2 : Conversion of heme iron (HI) in non heme iron (NHI) during juice heating at 120°C Figure 1 : Changes in heme iron content in juice
during heating at temperatures from 50 to 120°C
Figure 3 : Changes in heme iron and non heme iron during meat heating at 60, 80, 95 and 120 °C
0 2 4 6 8 10 12 14 16
0 200 400 600 800
µg/mL juice
Heating time (min)
Heme iron
50 60 80
89 98 120
0.0 5.0 10.0 15.0 20.0
0 100 200 300
µg/mL juice
Cooking time (min) 120°C
HI NHI
0 20 40 60 80 100
0 50 100 150 200 250 300
µg/g dry matter
Heating time (min)
Heme iron
60 80 95 120
0 20 40 60 80 100
0 50 100 150 200 250 300
µg/g dry matter
Heating time (min)
Non heme iron
60 80 95 120
