Ernst Albrecht Weber

Impact of Nitrogen and Sulfur Supply on the Potential of Acrylamide Formation in Organically and Conventionally Winter Wheat

In a two-year field trial, the effect of nitrogen (N) and sulfur (S) fertilization was 11 investigated on grain yield, grain quality parameters, formation of acrylamide (AA), and the 12 precursor free asparagine (Asn) in organically and conventionally produced winter wheat cultivars. 13 In both production systems, different types, amounts, and temporal distributions of N were tested. 14 While the effect of S fertilizer types and amounts on free Asn was only tested in the conventional 15 farming system. 16 Within both cropping systems, grain yield and baking quality were significantly influenced by N 17 treatment while the effect on free Asn was only minor. Especially within the organic farming system, 18 increasing N fertilization levels did not increase free Asn significantly. A slight trend of increasing 19 free Asn levels with an intensified N supply was observed, especially in the presence of crude 20 protein contents of 14 % or higher. But only N amounts of 180 kg N ha-1 or higher increased the 21 probability of high free Asn contents considerably, while N supply below that amount led to free 22 Asn values similar to the unfertilized controls. The results indicated that good baking quality can 23 be achieved without significantly increasing free Asn levels. 24 In addition, cultivars affected the levels of free Asn significantly. Compared to cv. “Bussard” and 25 “Naturastar”, cv. “Capo” exhibited the lowest AA formation potential at an N supply of 180 kg N 26 ha-1 while simultaneously reaching a crude protein content > 15 % (conventional) and > 12 % 27 (organic). Thus, it seems that cultivars differ in their ability to store and incorporate free Asn into 28 proteins. 29 Over all trials, a correlation of free Asn and AA was shown by R2 = 0.77, while a relation of free Asn 30 and protein was only R2 = 0.36. Thus, lowering free Asn by adjusting N treatments should not 31 necessarily affect baking quality. 32 S nutrition within conventional farming did not change free Asn amount or crude protein 33 significantly, probably due to the fact that soil was not sulfate-deficient. 34 In summary, it was evident that free Asn amounts in wheat varied widely both within cultivars and 35 between cropping systems. In order to clearly unravel genotypic differences and their interaction 36 with environmental factors and especially N fertilization, further research is needed. 37

Acrylamide Formation Potential of Organically and Conventionally Grown Cereals

As bakery products contribute considerably to the daily intake of the carcinogen acting substance acrylamide (AA), the aim of this study was to evaluate the impact of the cropping system (conventional vs. organic farming) on AA precursor levels of free asparagine (Asn) across different cultivars of the cereal species, namely winter wheat (Triticum aestivum), winter spelt (Triticum aestivum ssp. spelta) and winter rye (Secale cereale) with simultaneous consideration of gained grain yields and flour qualities. For this purpose, orthogonal field trials were established at two sites in Southwest Germany over two growing seasons (2006-2007 and 2007-2008). The results indicated a significant impact of the cropping system on free Asn contents. Across all species, free Asn contents in the flour were 26 % lower under organic compared to conventional farming. The impact of the cropping system on individual cultivars was obvious with a maximum reduction in free Asn contents of 50 % (e.g. for cultivars Ludwig, Privileg, Capo) if organically produced. For spelt, a significant impact of the cropping system was only found in 2008 with a reduction in free Asn of up to 25 % if organically produced. Across both cropping systems, cultivar Franckenkorn reached the lowest levels of free Asn. For rye, a significant impact of the cropping system was observed only in 2007 with 33 % higher Asn amounts in the conventional cropping system. Independent of the cropping system, rye reached the highest levels of free Asn followed by wheat and spelt. Across both cropping systems, species and cultivars, the amount of free Asn correlated with the AA content in heated flour with R2=0.63***. Furthermore, the results indicated that lower AA contents in bakery products can be achieved by proper selection of species (e.g. 66 % lower if rye is replaced by wheat) and cultivars. With an appropriate choice of the cultivar, a reduction of up to 65 % was possible within wheat, along with a reduction of 44 % within spelt and 12.5 % within rye. In summary, the results indicated that organically produced wheat especially offers the opportunity to significantly lower the AA potential of bread and bread rolls by the choice of raw materials low in free Asn.