Comprehensive VOC profiling of an apple germplasm collection by PTR-ToF-MS

Fruit quality is generally represented by several components, among which aroma plays a fundamental role in determining the overall appreciation. To generate a comprehensive data inventory of aroma compounds in apple, a large collection represented by 190 apple accessions was characterized by a proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) instrument, a valid alternative to a gas chromatography-mass spectrometry (GS-MS) apparatus. The analytical performance of this instrument allowed to profile volatile organic compound (VOC) spectra of a portion of apple fruit flesh in a short time and efficient manner. Based on the VOC composition, the collection resulted grouped into six main clusters, mainly determined by ester and alcohols. These two VOC categories were also further exploited for the definition of an Alcohols/Esters index, which can be considered as a novel fruit quality descriptor useful for a further and more exhaustive characterization of several apple accessions. The distribution of these compounds and the possible further use of these information are discussed.