Factors affecting fatty acid oxidation and the formation of odorous aldehydes during TMP production.

Application: Food products should never be tainted by the paper used as packaging. It is important to understand the aspects of thermomechanical pulping that could affect foods wrapped in it.

Volatile compounds that originated from wood may taint food packaged in paper and paperboard products. Unsaturated wood fatty acids may form odorous aldehydes by autoxidation. Factors that affect the formation of odorous aldehydes during TMP production include storage time and temperature, wood species, dithionite bleaching, EDTA treatment, and the presence of lime in the pulp.

In this study, the author compared the contents of odorous aldehydes and fatty acids in dithionite-bleached TMP made from spruce, pine, and a mixture of the two. Overall, dithionite bleaching reduced the formation of odorous aldehydes. Although less effective than hydrogen peroxide as a bleaching agent, dithionite may be better as a bleaching agent for TMP intended for packaging foods.

In regard to other factors, the aldehyde concentration was higher in pulps that contained lime than in pulps with no lime. Pine TMP is lower than spruce TMP in the amount of odorous aldehydes formed, and EDTA-treated pulps are lower than untreated pulps in odorous aldehydes. The formation of odorous aldehydes increases when TMP is stored, more so at a higher storage temperature (20[degrees]C) than at a lower temperature (12[degrees]C).

Karin Oyaas is with the Norwegian Pulp and Paper Research Institute, N-7491 Trondheim, Norway. Email Oyaas at [e-mail].