Black raspberry (Rubus occidentalis) and purple raspberry (R. idaeus x occidentalis) are fruits known for their pleasant and distinctive flavors. However, unlike their more popular cousin red raspberry (R. idaeus), little is known about what defines the characteristic aromas of black and purple raspberry. Using SPME-GCMS, the chemical compounds in the headspace of pureed black raspberry (4 genotypes), purple raspberry (5 genotypes), and red raspberry (2 genotypes) were collected and identified through a combination of gas chromatography and mass spectrometry. Chemical concentrations were calculated by integrating the area under the chromatogram curve, and calibrated with an internal standard of 2-octanol. By utilizing a random forest model, chemicals that were the most important for distinguishing fruit types (red vs. black vs. purple) were determined. Of the top 30 chemicals, 12 chemicals were described on Flavornet as detectable by a human nose in gas chromatography-olfactometry (GC-O), and the typical aroma described. Those 12 chemicals were then evaluated individually for significant differences across types (red, black, and purple raspberry). Among the chemicals that differed significantly across species were D-Carvone (caraway aroma), 1,3,8-p-Menthatriene (turpentine aroma); β-Ionone (violet, flower, raspberry, and seaweed aromas); α-Ionone (violet aroma); 2-Hexenol (leaf, green, wine, and fruit aromas); and α-Terpineol (oil, anise, and mint aromas). These results have implications for breeding new black and purple cultivars with the expected characteristic flavor. This instrumental approach also allows for tracking these aromas in breeding populations when utilizing interspecific hybridization to broaden the black raspberry germplasm in breeding.
