Impact of lipase and lipoxygenase activity on the aroma profile of whole wheat bread.

Whole wheat flour is prone to lipid oxidation during storage and during the breadmaking process that can negatively impact the flavor profile. The impact of flour enzymatic lipid oxidation on aroma formation in whole wheat bread was investigated. Bread was made from two types of flour, a lipase/lipoxygenase knock-out and the corresponding wild-sibling control, stored at -40 °C (nonaged) and 37 °C (aged) for 8 weeks. Descriptive sensory analysis identified five key aroma attributes of the bread samples: fermented/yeasty, cardboard, fruity, roasty, and bran. A comprehensive gas chromatography-olfactometry analysis allowed the identification and quantification of twenty-nine odor compounds at levels above the odor threshold values. The knock-out of lipase and lipoxygenase activities led to a reduction in lipid oxidation compounds, which was associated with a decrease in cardboard-like off-flavors. Additionally, the knock-out samples reported an increased intensity for fermented/yeasty and fruity attributes related to the high concentrations of 2-phenyl ethanol, ethyl hexanoate, and ethyl heptanoate, as compared to the wild-sibling control samples. Finally, descriptive analysis of aroma recombination models corroborated the analytical findings, showing similar changes in aroma profiles as compared to the differences observed in the bread samples. This study highlights the significant role of enzymatic lipid oxidation in shaping the aroma of whole wheat bread and provides insights into modifying aroma profiles through enzymatic control.