Acrylamide in Baking Products: A Review Article

540 Food Bioprocess Technol (2011) 4:530–543precursors might be a good index for evaluating processconditions involved in acrylamide formation during themanufacture of cereal products. For instance, determinationof furosine (∈-N-(furoyl-methyl)-L-lysine) and HMF hasbeen used as an indicator to evaluate the heat effectsinduced during the manufacture of cereal products such assliced bread toasting (Ramírez-Jiménez et al. 2000; Henleet al. 1995; Ramirez-Jimenez 1998).Furosine amino acid is formed during the hydrolysis ofAmadori compounds, including fructosyl-lysine, lactulosyllysineand maltulosyl-lysine, produced by the reaction of∈-amino groups of lysine with glucose, lactose and maltose,respectively (Erbersdobler and Hupe 1991). HMF is anintermediate product in Maillard reaction and is also formedfrom the degradation of sugars at high temperatures(Ramírez-Jiménez et al. 2000; Kroh 1994; Berg and VanBoekel 1994; Morales et al. 1997).Ramírez-Jiménez et al. (2000) used furosine and HMFdeterminations as indicators of browning reactions in breadto evaluate their usefulness in process control. Theyreported a linear correlation between HMF and colourindex in different commercial breads, but no linearcorrelation was found between furosine/HMF and furosine/bakingtemperature. They found that when the watercontent of the bread samples was lower, a smaller extensionof the browning reaction happened and a lower colour wasobserved, as can be verified by the higher furosine content(early stage indicator) and the lower HMF value. In thecrust, higher baking times produced a greater extension ofthe Maillard reaction and, therefore, a degradation offurosine. The study of toasted sliced bread showed thatfurosine levels began to descend after the first 10 min of thetoasting process (Ramírez-Jiménez et al. 2000). From theabove results, it may be concluded that negative correlationsexist between furosine and colour index and betweenfurosine and acrylamide formation. Therefore, when furosinecontent begins to decrease in bread crust, acrylamidecan be expected to start forming. This might be a usefulindicator for evaluating the effects of baking conditions onacrylamide formation.As regards HMF, it is shown that there should be a linearcorrelation between HMF and acrylamide content in breadso that HMF determination can be recommended as aquality control measure instead of acrylamide determination,which is much more difficult and expensive.Ruiz et al. (2004) identified the three browningindicators, namely furosine, HMF and glucosylisomaltol,to be used as a complex indicator of utility for monitoringthe processing of pre-baked bread. They reported nodetectable furosine in raw dough. However, they observedthat the early stages of Maillard reaction were favouredduring the pre-baking process (14–15 min at 175 °C) sothat furosine increased in content throughout the processwhilst colour did not change when compared with theoriginal dough and no HMF could be detected in thepre-baked bread. Therefore, no acrylamide formationcould be expected. They also reported that furosinecontinued to increase after baking for 14 min at 220 °C,but declined after 30 min. This is while the HMFcontent increased for all baking times. Their results areconsistent with those by other authors (Ramírez-Jiménezet al. 2000; Ramirez-Jimenez 2001).It can be concluded that furosine and HMF might be theuseful indicators for the estimation of acrylamide formationduring the bread baking process.ConclusionAcrylamide is a non-volatile compound which is classifiedas “potentially carcinogenic to humans”. Man can bedirectly exposed to it by consuming heat-treated foods richin carbohydrates, such as baked foods, or indirectly throughcertain packaging materials. The recent risk characterizationof acrylamide concludes that the evidence of acrylamideposing a cancer risk for humans has been strengthened.Therefore, reducing the acrylamide formed in baked foodsis still a major concern.This paper provides an overview of acrylamideformation during the bread making process. Even thoughbaking is by evidence an important step during whichacrylamide is formed, several other parameters such asformulation, flour quality, fermentation conditions amongothers play their roles in its formation. The followinggeneralizations may be drawn from the literature cited inthis review:There is a strong positive correlation between bakingtemperature and time and acrylamide formation, whilstreplacement of reducing sugars with sucrose and the use offlours with a lower asparagine content (in recipe) maydecrease the acrylamide content of baked foods. On theother hand, reduced pH in some recipes such as cookies hasan opposite effect.Chemical indicators such as furosine and HMF may beused for controlling the acrylamide content in pre-bakedand fully baked products, respectively.Finally, it is possible to reduce the acrylamide contentwhilst retaining the sensory quality by either introducingsteam in traditional baking or by using new alternativebaking techniques. The experimental works showed that itis possible to reduce acrylamide content by 40% in whitebread by applying steam during the final 5 min of bakingwith no significant changes in the sensory quality. Also,using infrared radiation heating makes it possible to reducethe acrylamide level in flat bread cakes by 60% withretained sensory properties.