Download RTF (Rich Text Format)

16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/view/projects/conference.html
Potential Risk of Acrylamide Formation in Different Cultivars of
Amaranth and Quinoa
Graeff, S.1,, Stockmann, F.1,, Weber, A. 1, Berhane, B. 1, Mbeng, K.J. 1, Rohitrattana, R.
1
, Salazar, P. 1, Shoko, P. 1, Kaul, H.-P.2, Claupein, W. 1,
Key words: asparagine, acrylamide, pseudocereals, cultivar, food products
Abstract
Acrylamide (AA), a potential human carcinogen, is formed in strongly heated
carbohydrate-rich food as a part of the Maillard-reaction. The amino acid asparagine
(Asn) and reducing sugars are considered to be the main precursors for AA formation.
So far, research in AA has mainly focused on potato and cereal products, indicating
the relevance of species, cultivars, amount of N fertilizer, and climatic conditions.
Potential additional sources of acrylamide in food products might be pseudocereal
grains (e.g. amaranth, quinoa). As amaranth and quinoa are often cultivated as cash
crops in organic production systems, the aim of this study was to investigate the
potential of acrylamide formation in different amaranth and quinoa cultivars. Grain
samples were collected from field trials in Germany and Austria consisting of 6
amaranth and 3 quinoa cultivars. The results indicated significant differences in the
potential for acrylamide formation of quinoa cultivars and also slight differences
between tested amaranth cultivars. It is obvious that the selection of cultivars with a
low AA formation potential would offer a suitable strategy for the minimization of AA in
foodstuffs.
Introduction
In April 2002, the Swedish National Food Administration announced that certain food
products contain high amounts of acrylamide. As affected food products mainly
carbohydrate-rich foods, such as potatoes or cereal products, were mentioned
(Mottram et al., 2002). These findings attracted world-wide attention, especially as
acrylamide is classified as “probably carcinogenic to humans” (IARC, 1994). Since the
announcement in 2002, considerable progress has been made in basic
understanding, and several aspects of acrylamide research have been addressed,
such as methods of analysis, occurrence, formation, chemistry, toxicology, and
potential health risk in the human diet. So far, most studies on acrylamide have been
carried out on fried potatoes to understand the critical factors that may control or
reduce acrylamide formation. Results clearly indicated that the amount of acrylamide
increased with frying and baking temperature (Tareke et al., 2002). From the results
gained so far, it can be concluded that the contamination of foods with acrylamide
originates from a reaction of asparagine with carbohydrates at high temperatures as
part of the Maillard-reaction. Based on these findings, many studies have been carried
out, and have found ways to minimize the levels of acrylamide in heated products.
From the current standard of knowledge, minimization can be accomplished either by
1
Institute of Crop Production and Grassland Research, Universität Hohenheim, Fruwirthstr. 23,
70599 Stuttgart, Germany, E-Mail [email protected], Internet www.uni-hohenheim.de
2
Institute of Agronomy and Plant Breeding, BOKU-University of Natural Resources and Applied
Life Sciences, Vienna, Gregor-Mendel-Str. 33, 1180 Wien, Austria
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/view/projects/conference.html
modifying the processing parameters such as pH, temperature, and time of heating, or
by elucidating the mechanistic path-ways of acrylamide formation and eliminating
precursors or intermediates.
To date, research in acrylamide has mainly focused on potato products (Weisshaar &
Gutsche, 2002) and cereals (Weber et al., 2007) indicating the relevance of cultivar,
amount of fertilizer, and climatic conditions. Current studies show that, due to
customary consumption habits in Europe, bakery products might contribute to about
25 % of total acrylamide intake. A potential additional source of acrylamide in cereal
food products might be popped or toasted cereal or pseudocereal grains, e.g. popped
amaranth (Amaranthus spp.) or quinoa (Chenopodium quinoa) flakes in breakfast
cereals, due to the heat application for popping, toasting or roasting. It has been
shown that popping or cooking can increase the contents of aspartic acid in amaranth
grain (Gamel et al., 2005). However, no studies on acrylamide in amaranth or quinoa
products are available so far. Amaranth and quinoa grain are high in fibre, calcium,
and iron content and have a relatively high concentration of other minerals as well,
including magnesium, phosphorus, copper, and manganese. Moreover, grain
amaranth and quinoa have higher amounts of protein (14-18 %) than many other
cereal grains and have significantly higher lysine contents. Because they are glutenfree, amaranth and quinoa are also popular with consumers who have wheat and
gluten allergies. Recent advancements on the potential of grain amaranth and quinoa
as a cash crop and as healthy anti-allergic alternative to cereal foodstuffs have led to
consider the expansion of these crops especially in organic production systems. As
the largest amaranth and quinoa grain consumer is the health food industry, where
organic and transitional productions carry a market premium, it seems to be essential
to investigate the potential of AA formation in amaranth and quinoa.
Hence, the goal of this study was i) to evaluate the potential of amaranth and quinoa
to form acrylamide, ii) to investigate potential differences of AA formation in multiple
cultivars of amaranth and quinoa. Grain samples were collected from field trials in
Germany and Austria consisting of 6 amaranth and 3 quinoa cultivars.
Materials and methods
Grain samples of amaranth were collected from field trials in Austria and Germany.
Field experiments were conducted on the experimental farm of the BOKU-University
at Gross-Enzersdorf in Eastern Austria (48° 12’ N; 16° 33’ E) during the growing
seasons of 2004 and 2005. The amaranth genotypes Amaranthus cruentus cv. Amar
(Mexican type), Amaranthus hypochondriacus I and Amaranthus hypochondriacus II
(both crossbred lines) were grown under semi-arid conditions of 9.8°C mean annual
temperature and 546 mm mean annual precipitation in a split plot design. The soil type
was classified as a chernozem of alluvial origin which is rich in calcareous sediments.
Since there was a high amount of soil nitrogen available, no N-fertilizer was applied. In
Germany in 2003, the amaranth cultivars K343, Pastewny, and Bärnkraft and the
quinoa cultivars Faro, Tango, and 407 were cultivated at the experimental station
Ihinger Hof (48° 44’ N; 8° 56’ E) of the University of Hohenheim, Stuttgart, Germany
on a loess derived soil with oat as previous crop. Mean annual temperature was 8.1°C
and mean annual precipitation was 693 mm. Target nitrogen amounts were 80 kg N
ha-1 for amaranth and 120 kg N ha-1 for quinoa.
Grain samples were analyzed for free amino acid content by using 2 g of flour mixed
with 8 ml of 45 % ethanol for 30 min at room temperature. After sequential
centrifugation for 10 min at room temperature and 4000 rpm followed by 10 min at
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/view/projects/conference.html
10 °C and 14000 rpm, the supernatant was filtered through a 0.2 µm syringe filter and
filled in vials. Amino acid analysis was performed using HPLC components
manufactured by Merck–Hitachi. The fluorescence intensity of the effluent was
measured at the excit and emission maxima of 263 and 313 nm were measured.
Determination of the sum of reducing sugars was made by using the method of Luff
Schoorl (Matissek et al. 1992). AA formation potential was determined according to
Weber et al. (2007). SigmaStat version 2.0 was used to compare the amount of
precursor factors and of AA formation potential in different cultivars and locations
(ANOVA, Tukey). Linear regression analysis was used to determine the correlation
between AA contents and precursor factors.
Results and discussion
-1
AA [ng g ]
AA (ng/100g)
Figure 1 indicates the AA formation potential of tested amaranth cultivars and
genotypes, respectively. AA formation potential ranged by between 320 and 492 ng
g-1. No significant difference in AA formation potential was found between the tested
cultivars and genotypes. Analysis of the supposed precursors reducing sugars and
Asn content indicated a similar capacity of sugar as well as Asn assimilation of all
tested cultivars and genotypes.
significant differences were observed between the
AA potential No
in amaranth
tested years, or between the locations.
600
500
400
300
200
100
0
a
Amar
G1
a
A. hyp. I
G2
a
A. hyp. II
G3
a
Pastewny
a
Bärnkraft
Pastewny -1 Baernkraft
a
K343
K343
Figure 1. Acrylamide (AA) potential [ng g ] of investigated amaranth cultivars
and genotypes.
Varieties
In contrast to amaranth, tested quinoa cultivars (Figure 2) showed a statistically
significant difference (P = 0.002) in AA formation potential. AA formation potential
ranged between 495 and 990 ng g-1. Especially, the cultivar Faro showed a relatively
low AA formation potential together with a low Asn content when compared to the
other tested cultivars. On average, AA potentials of 451 ng g-1 were found in
amaranth, while quinoa indicated a slightly higher AA potential with an average of 613
ng g-1. These values are close to NOEL (no observable effect level) at 500 ng g-1,
suggested by the Federal Institute of Risk Assessment, Berlin. Thus, it indicates a risk
potential of AA formation in foodstuffs derived of amaranth and quinoa.
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/view/projects/conference.html
AA potential in Quinoa
1200
c
AA [ng g-1]
AA (ng/100g)
1000
800
a
600
b
400
200
0
407
Faro
Tango
Figure 2. Acrylamide (AA) Varieties
potential [ng g-1] of investigated quinoa cultivars.
Further, AA potential of both amaranth and quinoa was 2-3 times higher than in cereal
species and thus has to be evaluated in further studies, to estimate potential risks for
consumers. Further studies are also required to investigate the role of other amino
acids that are present in higher quantities such as aspartic acid, lysine, methionine
and glutamine.
Conclusions
This study investigated acrylamide precursor contents and the potential of acrylamide
formation in different amaranth and quinoa cultivars. The results indicated significant
differences in the potential for acrylamide formation of quinoa cultivars and slight
differences between the tested amaranth cultivars and genotypes. The results suggest
that the use of cultivars with low levels of free asparagine and thus a low AA formation
potential might be a feasible strategy to lower the risk of consuming acrylamide in
foodstuffs derived of the two products described in this paper. In conclusion, to foster
the expansion of amaranth and quinoa especially in organic production systems while
ensuring premium quality foodstuffs, the selection of cultivars low in free asparagine
seems to be an effective strategy.
References
Gamel, T.H., Linssen, J.P., Mesallem, A.S., Damir, A.A., Shekib, L.A. (2005): Effect of seed
treatments on the chemical composition and properties of two amaranth species: starch and
protein. Journal of the Science of Food and Agriculture 85(2):319-327.
IARC (1994): Monographs on the Evaluation of Carcinogen Risk to Humans, vol. 60, International
Agency for Research on Cancer, Lyon, p. 389.
Matissek, R., Schnepel, F.M., Steiner, G. (1992): Lebensmittelanalytik. 2nd ed., Springer, Berlin,
Mottram, D.S., Wedzicha, B.L., Dodson A.T. (2002): Acrylamide is formed in the Maillard
reaction,.Nature, 419:449.
Tareke, E., Rydberg, P., Karlsson P. (2002): Analysis of acrylamide, a carcinogen formed in
heated foodstuffs. J. Agric. Food Chem. 50:4998-5006.
Weber, A., Koller, W., Graeff, S., Hermann, W., Merkt N., Claupein W. (2007): Impact of nitrogen
amounts and timing on the potential of acrylamide formation in winter wheat. Field Crops
Research (accepted).
Weisshaar R., Gutsche B. (2002): Formation of acrylamide in heated potato products - model
experiments pointing to Asparagine as precursor. Deutsche Lebensmittelrundschau 98:11.