Main compounds responsible for off-odour of strawberries infected by Phytophthora cactorum

Volatile compounds present in strawberries infected with Phytophthora cactorum, especially those responsible for the characteristic off-odour of such fruits were the subject of this study.

Six strawberry varieties (Redgauntlet, Selva, Korona, Tenira, Real, Pegasus) inoculated with P. cactorum strain (PC-5), isolated from naturally infected fruit and one variety inoculated with 15 strains of P. cactorum in the laboratory were analysed. All the samples had a distinct, to a various degree, off-odour reminiscent of watercolour paint with phenolic notes. Volatile compounds were isolated by solid phase microextraction and simultaneous distillation extraction methods. To detect compounds responsible for the characteristic off-odour, gas chromatography-olfactometry was used. Two compounds were found to be responsible for the characteristic off-odour of strawberries infected by P. cactorum: 4-ethyl phenol and 4-ethyl-2-metoxy phenol (4-ethyl guaiacol). The content of these compounds in infected varieties ranged from 1.12 to 22.56 mg kg(-1) and 0.14-1.05 mg kg(-1) respectively. Other volatile compounds, not detected in noninoculated sound strawberries, were also identified: camphene, 1-octene-3-ol, 3-octanone, o-cymene, phenyl methanol, cis-linaloloxide, nonanal, phenyl ethyl alcohol, 2-undecanone and alpha-muurolene.

Volatile compounds responsible for the characteristic off-odour of strawberries infected with P. cactorum were identified. Also compounds produced as a result of P. cactorum growth on strawberry fruit were characterized.