Fungal pigments from spalting fungi attenuating blue stain in Pinus spp.

• Pigments from spalting fungi were produced in liquid media.
• Pigments were impregnated in pine wood with different levels of blue sap-stain.
• Pigments penetrated and attenuated the presence of blue stain.
• Proposed treatment may be used to improve the commercial value of blue stained wood.

Fungal pigments from spalting fungi Scytalidium cuboideum (red), Scytalidium ganodermophthorum (yellow) and Chlorociboria aeruginosa (green), were used to attenuate the presence of blue sap-stain in Pinus spp. samples. Pigments, filtered from liquid cultures of spalting fungi, were vacuum impregnated into pine samples with three different levels of blue staining: 1 [0–50%], 2 [50–90%] and 3 [100%]. The CIE L*a*b* color difference at wood surfaces, before vs. after treatment, was quantified with a chroma meter and the internal color coverage in the core of the samples with digital images. Light microscopy was used to observe the penetration of pigment in the microstructure of blue stained pine samples. Results show that fungal pigments are suitable candidates to attenuate the appearance of blue stain on the wood surface. Pigments produced by S. cuboideum showed a higher color difference regardless of the blue stain level, but the highest color difference was obtained in samples with staining level 1. The percentage of internal color coverage of pigments was significantly higher for green and red pigments in staining levels 1 and 2. The proposed treatment may be used to improve the value of blue stained wood allowing its commercialization into the niche of environmentally friendly products.