Acrylamide in Baking Products: A Review Article

538 Food Bioprocess Technol (2011) 4:530–543information obtained from such experiments, baking conditionswere defined to achieve similar crust colour withvarious baking techniques. It was obvious that theacrylamide content in bread crust could be reduced usingalternative baking technologies. Reduced levels wereobtained with both infrared radiation and air jet impingementbaking.Preliminary experiments were also performed to studythe flavour of breads baked by these new technologies. Aclose relationship was found to hold between the presenceof a large number of volatiles, especially those volatile andodorous compounds that are known to be formed viabrowning reactions in the bread crust like Streckeraldehydes and alkyl pyrazine, and the formation ofacrylamide for the baking methods studied. Obviously, thebaking method that produced low amounts of acrylamide inthese experiments also tended to result in low contents ofimportant flavour substances.IR baking has been further focussed on to evaluate howit can be optimized with regard to acrylamide minimizationand sensory product quality. Crust colour, acrylamide,flavour compounds and sensory characteristics were investigatedas a function of baking time under various bakingconditions. One important finding from these experimentswas that, with IR baking, it is possible to obtain a sensoryprofile almost identical to that of conventionally bakedbread, but with considerably lower acrylamide content. Areduction of acrylamide content by 60% could be shown(HEATOX Project 2007).Effects of Precursors and Reaction ConditionsThe influence of the composition of food and thermalconditions of the process are the main factors that interactwith acrylamide formation (Berg and Van Boekel 1994;Morales et al. 1997; Gökmen et al. 2007; Gökmen and Acar1999; Gökmen and Şenyuva 2006). Since reduction ofacrylamide content is a major concern of baking producers,Gökmen et al. (2007) studied the effects of dough formulaand baking conditions on acrylamide formation in cerealproducts (cookies) (Fig. 5). They investigated the type andconcentrations of sugars and pH levels along with theeffects of six different formulae and measured hydroxymethylfurfural(HMF) as a chemical indicator and as anacrylamide precursor to assess the quality of thermallyprocessed food products. They reported that the amount ofsucrose in the recipe was less effective on the yield ofacrylamide than glucose because increasing amounts ofsucrose from 10 to 35 g in the recipe almost doubled theamount of acrylamide formed during baking. This is whilereplacing sucrose with glucose in the recipe resulted in adrastic increase in the amount of acrylamide formationupon baking at 205 °C for 11 min (74.1 ± 5.60 ng/g ofacrylamide in cookies). The reason for this, they claimed, isthat the hydrolysis of sucrose might be very limited underthese baking conditions (baking for 11 min at 205 °C).Reduction of acrylamide formation by a factor of 50% ormore using sucrose instead of reducing sugars (e.g.glucose) confirms earlier findings by other researchers(Amrein et al. 2004; Graf et al. 2006; Vass et al. 2004).Some authors have also reported that a reducing sugar isneeded to form acrylamide from asparagine (Mottram et al.2002; Stadler et al. 2002; Yaylayan et al. 2003). Sugarseems to be the most important ingredient in the doughformula for acrylamide formation because the free asparagineis relatively low in wheat flour (0.15–0.40 g/kg;Surdyk et al. 2004; Noti et al. 2003). Rather than sugar,organic acids added to baking powders as an acidic salt toreduce pH decrease the amount of acrylamide formedduring baking (Surdyk et al. 2004; Rydberg et al. 2003;Jung et al. 2003; Kita et al. 2005). However, when reducingsugars are used in place of sucrose, the reduced pHincreases the amount of acrylamide by 1.8 times in cookiesunder the same baking conditions. This is probably due tothe excessive hydrolysis of sucrose (Gökmen et al. 2007).Finally, they showed that the kinetics of acrylamideformation significantly differed between the recipes comprisingsucrose (with a lower initial rate of formation) andthose with glucose (with a rapidly increasing rate offormation). These results are comparable with thosereported by Summa et al. (2006) who confirmed a linearincrease in acrylamide concentration of cookies for therecipe comprising glucose, but a lower initial rate ofacrylamide formation within a baking time of 15 min withthe recipe using sucrose instead of glucose.Even though acrylamide concentration increases duringfrying and baking, addition of different additives, such asrosemary, amino acids or protein, reduces the level ofacrylamide. Also, reduced pH dramatically reduces acrylamidecontent during frying and baking (Tareke et al. 2002;Becalski et al. 2003; Brathen et al. 2005; Grob et al. 2003;Rydberg et al. 2003; Jung et al. 2003).It has been found that in baking products, addition ofasparagine dramatically increases the amount of acrylamide,but no effect of glucose addition is observed. However,the increase in acrylamide content occurs only with lowerconcentrations of asparagine, whilst at higher concentrations,a decrease is observed in acrylamide content. Thisindicates that one acrylamide elimination mechanism mightbe its reaction with excess amounts of amino acids.Rydberg et al. (2003) reported that addition of amino acidsor protein-rich ingredients reduced the amount of acrylamide.No similar decrease at high concentrations was foundfor glucose, indicating that reaction of acrylamide withcarbohydrates is insignificant in the removal of acrylamide(Brathen et al. 2005).