Writing recently in the International Journal of Cancer, the scientific team from the Institute of Food Technology at Hohenheim University, Stuttgart, said that recent studies have revealed different acrylamide formation mechanisms.
The team claim to have discovered pyrolytic acrylamide formations in purified wheat gluten and gluten-supplemented wheat bread rolls.
In the German study, gluten was recovered from wheat flour by water extraction. Starch, reducing sugars and amino acids were removed using -amylase and NaCl solutions and were completely absent in the purified gluten fraction.
The gluten was dry heated at temperatures ranging from 160 to 240°C for 8 to 12 min and analysed for acrylamide and cinnamic amide using liquid chromatography-tandem mass spectrometry.
The team reported that acrylamide could be detected up to 3997 microgrammes per kg gluten dry weight. Cinnamic amide was detected and unambiguously identified in the gluten samples, thus confirming the proposed formation of acrylamide from proteins.
Acrylamide is a carcinogen that is created when starchy foods are baked, roasted, fried or toasted. It first hit the headlines in 2002, when scientists at the Swedish Food Administration first reported unexpectedly high levels of acrylamide, found to cause cancer in laboratory rats, in carbohydrate-rich foods.
Since the Swedish discovery a global effort has been underway to amass data about this chemical. More than 200 research projects have been initiated around the world, and their findings co-ordinated by national governments, the EU and the United Nations.
Such coordination has done much to calm consumer and industry fears. Recently, the Scientific Committee of the European Food Safety Authority (EFSA) said that the adoption of what it called a "harmonised and transparent scientific" approach would make it easier for food firms to avoid dangerous substances.
But what makes the German team's study interesting is the manner in which they claim acrylamide was formed. After gluten was added to bread roll dough, protein pyrolysis to form acrylamide in the complex food matrix was assessed.
Contents of asparagine and reducing sugars were diminished due to the addition of the gluten.
In contrast to the expectation with respect to the well-established common formation mechanism of acrylamide, it increased from 53.4 to 63.9 g/kg (+20 per cent), which was in good correlation with the higher proportion of gluten. As demonstrated by the t-test, the increase in acrylamide was significant when comparing 0 and 15 per cent gluten addition.
Additionally, cinnamic amide could be found in crusts of bread rolls.The scientists claim that this provides evidence of pyrolytic formation of acrylamide from wheat gluten.