INCREASE IN THE CONTENT OF LOW-MOLECULAR CARBOHYDRATES AT LUMBER SURFACES DURING DRYING AND CORRELATIONS WITH NITROGEN-CONTENT, YELLOWING AND MOLD GROWTH

In this study a quantitative analysis of the low molecular carbohydrat es (predominantly sucrose, fructose and glucose) in a series of lumber samples of Pinus sylvestris and Picea abies taken at various distance s from the surface has been made. The increase of nitrogenous compound s towards the surface had been shown in a previous study. Several of t he lumber samples showed a marked sugar accumulation at the surface, w hich correlated quite well with a corresponding nitrogen accumulation. In one case, the total amount of the three sugars was as high as 4.9% of the dry matter content in the 0-1 mm layer. It was of special inte rest to note that samples with high nitrogen and sugar contents also h ad a yellow surface colour, which probably formed during the drying pr ocess by the well-known Maillard reaction - a complex of reactions occ urring when sugars and amino acids, peptides and proteins are heat-tre ated together. Growth of the mould fungus Penicillium brevicompactum w as well correlated with the content of nitrogen and low molecular carb ohydrates in adjacent samples. The initial colonization was somewhat d elayed in material from the outermost sapwood zone despite high nutrie nt contents indicating effects of antifungal compounds from the bark o r toxic Maillard reaction products effective against germination. Grow th of Aspergillus versicolor was likewise most elaborate on samples wi th the highest nitrogen and soluble carbohydrate content but the resul ts also indicate a sensitivity to antifungal compounds present.