Chemistry Reference
In-Depth Information
acrylamide levels in sliced potato chips.
41
Varying blanching regimes with respect to both
time and temperature and introducing longer soaking treatments have been shown to reduce
acrylamide by simply washing out the precursors.
22, 38, 39
In coffee, no significant mitigation opportunities have yet been identified.
22
Acrylamide
formation starts rapidly at the beginning of the coffee roasting, reaching a maximum level
approximately halfway through the roasting cycle, at which point acrylamide levels start
decreasing due to breakdown or depletion. Final levels in roasted coffee beans are approx-
imately 20-30% of the initial maximum level. Consequently, darker roasting tends to give
lower acrylamide levels. Also storing of packed, roasted coffee decreases acrylamide levels
significantly. However, both freshness and degree of roasting are important quality param-
eters, meaning that mitigation based on these parameters is far from optimal. Trials on
alternative roasting technologies are still in the exploratory phase.
22
A drawback to some of the current acrylamide-reducing technologies is that these will not
only affect acrylamide levels but also potentially impact final product characteristics, such as
colour, texture and flavour, due to a general reduction in Maillard reactions.
23
Additionally,
health or nutritional implications should be considered, for example loss of minerals and
vitamins during intensive blanching of potatoes, and increased fat uptake upon frying at lower
temperatures and longer times. For cereal products, replacement of ammonium bicarbonate
with sodium bicarbonate will reduce acrylamide values, but at the same time increase sodium
intake. Also, the use of refined flour instead of whole grain flour may reduce acrylamide
levels, but will provide a less desirable product due to the lower fibre content.
22, 23
An alternative approach to a general reduction of Maillard reactions is to focus on removal
or reduction in the level of the specific precursor, asparagine. This can be done by controlling
raw materials and is furthermore the scope of various plant-breeding programmes. Another
option is to apply the enzyme asparaginase, which catalyzes the hydrolysis of asparagine to
aspartic acid and ammonia. This enzyme reduces the level of free asparagine while leaving
other amino acids unaffected.
Initially, tests in simple chemical model systems containing only asparagine and glucose
or fructose showed that asparaginase could significantly reduce acrylamide formation in
these systems.
12, 42
Subsequently, asparaginase has been tested in laboratory models of a
variety of cereal food and potato-based food products. The resulting acrylamide reductions
have ranged from 50% to 90%, suggesting that asparaginases could potentially be used to
make a broad impact on dietary acrylamide exposure.
12,42-48
However, since commercial
asparaginase products have only very recently become available at pricing and production
scales appropriate to the food industry, asparaginase application technology is still very new.
Published data are therefore limited and full-scale industrial experience scarce.
In coffee or other roasted products, a few patent publications have included treatments
in which using asparaginase leads to a reduction of acrylamide formation during roasting.
US patent 7 220 440
49
describes a process where asparagine is extracted from green beans
using water. The extract containing solubles and asparagine is treated with an asparaginase
and returned to the beans before roasting. In WO 2005/004620,
50
a process where cocoa
beans are treated in an asparaginase solution before roasting is described. In both cases, an
acrylamide reduction exceeding 10% is obtained.
This chapter will give an introduction to asparaginases, followed by a review of acrylamide
reduction achieved by applying asparaginase to cereal and potato-based products and coffee.
Advantages and potential limitations of using asparaginase will be illustrated and necessary
considerations for enzyme application will be highlighted. Data shown and discussed are
derived mainly from Novozymes laboratory testing.
