Effect of soil tillage and a fungicide application on the accumulation of free asparagine on wheat flours and the risk of acrylamide formation in baked goods

Free asparagine (ASN) is the main precursor of acrylamide (AA), a probable human carcinogenic process contaminant in cereal-based bakery products. This study has assessed the combined effects of soil tillage, minimum tillage (MT) vs conventional tillage (CT), and a chemical disease control fungicide application (F) vs an untreated control (NF) on the accumulation of ASN in wholegrain and refined flour. MT_NF showed the highest ASN levels in wholegrain flour from multiple wheat genotypes and different agronomic years, whereas on average a MT_F treatment reduced ASN by 37%, CT_NF by 22% and CT_F by 48%. The AA levels measured in the wholemeal biscuits mirrored the initial ASN concentrations. Biscuits produced under MT_F accumulated 18% less AA than MT_NF, while those from CT_NF and CT_F showed 14% and 22% lower AA levels than MT_NF, respectively. The observed differences in the ASN concentration were mostly associated with the effects of the applied crop practices on the thousand kernel weight (TKW). The severity of Fusarium head blight was reduced by both the CT and F treatments, leading to heavier kernels due to enhanced starch accumulation, and lowering the ASN concentration per unit weight. This dilution effect accounted for more than 50% of the observed variation of ASN concentration in the wholegrain flour. The observation that the application of F slightly reduced ASN, compared with NF, in the refined flours of the MT treatment, without a corresponding change in the starch content, suggests an additional physiological response of the plant to the applied crop practices. Overall, agronomic practices that ensure an appropriate grain filling can dilute ASN in whole kernels and reduce the AA content of wheat-based products.