The role of yeast in reducing acrylamide in bread, biscuit, and cracker doughs may be underappreciated, suggests a new study from the UK.
An evaluation of the different approaches available to bakers showed that, while techniques such as adding extra amino acids and calcium showed some benefit, the role of yeast exceeded expectations.
"The effect of yeast in real bakery processes is more wide ranging than has been hitherto appreciated," wrote lead author Peter Sadd in the Journal of Agricultural and Food Chemistry.
"It has a protective effect giving lower levels of acrylamide in the final food than would be expected from the levels of precursors in the recipe ingredients."
The work of Sadd and co-workers from RHM Technology in High Wycombe is important because it used realistic conditions at the pilot-plant scale.
Acrylamide is a potential 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.
Despite being a carcinogen in the laboratory, many epidemiological studies have reported that everyday exposure to acrylamide in food is too low to be of concern.
This has not stopped industry from exploring ways of removing or reducing the formation of the compound. Successful areas of study have focused predominantly on the precursors to acrylamide, mainly asparagine.
Approaches include converting asparagine into an impotent form using an enzyme or yeast, binding asparagine to make it inaccessible, adding amino acids, changing the pH to alter the reaction products, cutting heating temperatures and times, and removing compounds from the recipe that may promote acrylamide formation.
The new study indicates that the food application dictates which approach will be successful and highlights that some, like adding calcium as a binding agent, simply do not work in bakery.
Sadd and co-workers evaluated the different approaches in bread, biscuit, and cracker dough systems. They found that in doughs, extending the yeast fermentation could reduce asparagine levels and, thereby acrylamide levels.
The effects of yeast were unexpected, they said. "Recipe or process changes that affect yeast may have unexpected effects on final acrylamide levels as the yeast acts as a filter/amplifier for acrylamide precursors: it may consume asparagine, and reducing sugars can be either released or consumed depending on circumstances."
Adding calcium in the chloride or carbonate form also led to acrylamide reductions. "Hence, the fortification of flour with calcium carbonate, over and above its natural mineral content, has an additional benefit," they said.
"However, some other possible methods of adding calcium to bakery doughs, for example, via the permitted preservative calcium propionate, were not beneficial," they added.
The team found that products that of employed chemical raising agents, "ammonium salt replacement should be the priority, and best practice should avoid allowing biscuit doughs to age".
Moreover, while calcium "looks promising" the potential interactions with other ingredients are not known, they said, and should be investigated further.
Playing with the pH of the product was an option, but the practical benefits are limited, added Sadd and co-workers, since this would promote other undesirable products, such as 3-monochloropropane-1,2-diol (3-MCPD).
"Fortunately, changes to process conditions to reduce acrylamide such as reducing oven temperatures or baking times will not promote 3-MCPD," they added.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf7037482
"Effectiveness of Methods for Reducing Acrylamide in Bakery Products"
Authors: P.A. Sadd, C.G. Hamlet, L. Liang