ACRYLAMIDE IN HEATED FOODS
In April 2002, a report by the Swedish Authorities on the presence of acrylamide (2-propenamide) in a wide range of fried and oven-cooked foods [4] attracted worldwide attention, due to the fact that acrylamide is classified as probably carcinogenic to humans (Group 2A) by the IARC [10]. Acrylamide is formed in food as a result of cooking practices, many of which have been used by mankind for many centuries. Initial surveys have shown that relatively high concentrations of acrylamide are found in high-carbohydrate foodstuffs such as potato chips, French fries, pan-fried potato products, and crisp bread [2]. The main pathway of acrylamide formation in foods is linked to the Maillard reaction and, in particular, the amino acid asparagine [13–15].
Presence of acrylamide in common heated foods is considered as an important food safety problem by international authorities. Acrylamide exposure varies depending upon the population’s eating habits, and the way the foods are processed and prepared.
Generally, fried potato products, bakery products, and roasted coffee appear as the most important food categories that contribute most to acrylamide exposure. The levels of acrylamide in heat-processed foods depend on certain recipe factors and thermal-
processing conditions. The initial concentrations of precursors and processing temperatures are known to affect the rate of acrylamide formation in foods [16–20].
During baking or frying of foods, the evaporation of water, being an important barrier to internal energy increase, limits the amounts of acrylamide formed. However, greater energy input to the food at higher temperatures causes faster drying, and hence the temperature and moisture levels favor the formation of acrylamide to set in early during the process [19]. Time–temperature history differs in different locations of food as a result of simultaneous heat and mass transfer. Temperature rises much faster on the surface than the interior parts of food during heating under conventional conditions [21]. This makes the surface of foods more risky part from the viewpoint of chemical reactions leading to undesired toxic compounds. It has been reported that acrylamide formation takes place mainly at the surface and in near-surface regions, because during heating, the conditions in this part of foods become favourable [19]. This causes a large difference between the acrylamide concentrations of the surface and the core regions of food.
For optimization, it seems very useful to find a relationship between time and temperature to evaluate potential risks and benefits of the thermal process. Greenwood et al. [24] have first published a technique, which they used to study the destruction of thiamin in cured pork luncheon meat compared with microbial destruction. This evaluation allows determining the only acceptable combinations of time and temperature that fall within the area of “cooked sterile,” all other combinations of time and temperature being unacceptable [25]. As we recently exemplified, similar evaluation can be applied to baked, fried, and roasted foods taking into account the formation of thermal-process contaminants and development of acceptable sensory properties [22]. In such case, the appropriate combinations of time and temperature would fall within the area “non-risky acceptable” [1,23].