Effect of genotype, growing environment, and fertilization treatment on free asparagine concentration in western Canadian wheat

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Xie, Yi
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The Maillard reaction, that involves a free amino acid – asparagine (ASN), as its main precursor, results in the formation of acrylamide in bakery products, such as bread. Acrylamide is known as a neurotoxin and a class 2A carcinogen to humans. Therefore, it is critical to understand how free ASN concentration in western Canadian wheat is influenced by wheat genotype, growing environment, and agronomic practices. Such an understanding allows strategies for controlling acrylamide in bread to be proposed. It is also important that quantification of free ASN for both research and industry occurs, and so a rapid test that allows accurate quantification of free ASN concentration becomes necessary. Free ASN concentration in whole-wheat flour was measured using an ultrahigh performance liquid chromatography (UPLC) with a Photodiode Array Detector (PDA). The whole-wheat flour was milled from eight western Canadian wheat genotypes that were grown in three locations over two years, and that were subjected to four agronomic practices (two nitrogen levels combined with two sulfur levels). A rapid enzymatic test for asparagine concentration was validated against two established techniques using whole-wheat flour from a sub-sample set that consisted of all genotypes from all location-years with only one fertilizer treatment. For a preliminary study of bread acrylamide’s relationship to wheat free ASN, six whole-wheat breads made from flour with low, medium, and high concentrations of free ASN were selected. From the free ASN study, it was found that environment, genotype, and their interaction were the main influencing factors on free ASN concentration in wheat, whereas fertilization had a minimal effect (varied 521–557 µg g-1 free ASN in wheat). The new rapid enzymatic test was reliable and user-friendly. A gratifying result was that the acrylamide concentration in the whole-wheat breads made with western Canadian wheat were all below 10 ng g-1. In conclusion, free ASN in Canadian wheat can be controlled with a careful selection of wheat genotype and nitrogen fertilization levels. In addition, the rapid enzymatic method is recommended for simple laboratory environments where free ASN analysis can be conducted at low cost.
Free asparagine, Canadian wheat, Genotype, Agronomic practices, Growing environment, Analytical method