A composition for reducing undesirable odors emitted by hydrocarbonaceous materials is provided. The composition contains at least one aldehyde-containing compound and, optionally, one or more ketone-containing compound and/or a carrier. The composition is free of ester-containing compounds. In at least one exemplary embodiment, the composition contains one or more aldehyde-containing compounds and a liquid carrier. The aldehyde-containing compound(s) has a molecular weight greater than 100 daltons and may be chosen from vanillin or cinnamaldehyde. The ketone-containing compound(s) has a molecular weight greater than 100 daltons, and in exemplary embodiments, from about 120 to about 1,000 daltons. Undesirable odors from hot asphalt are reduced by the composition without adversely affecting the physical and performance properties of the asphalt or decreasing the flash point of the asphalt. The composition may be added to asphalt in a molten or semi-molten form to reduce or eliminate unpleasant odors and form a low odor asphalt.