High performing VOC phenomics to improve fruit quality

Fruit quality can be defined by the achievement of four key factors: appearance, flavor, texture and nutritional properties. Among them, flavor directly impacts the consumers appreciation, therefore the fruit marketability. Although the importance of these factors can hardly be underestimated, breeding efforts have historically been oriented to improve mostly fruit appearance and storability. However, often, selection for yield, fruit size, color, and shelf life properties had unintended negative consequences on other fruit quality traits, such as taste and aroma [1]. Defining and quantifying these quality components, in relation with distinct segments of the production chain, needs comprehensive investigations and a tight synergy of analytical approaches, with a particular focus on rapid and non-invasive methods. Understanding the stability of each quality trait during different storage and growing conditions may allow a better definition of future breeding strategies aimed, for example, at the selection of accessions suitable to improve distinct markets. The monitoring of volatile organic compounds (VOCs) produced by fruits and vegetables needs analytical techniques that are capable of dealing with challenging issues: i) the need of separating and quantifying VOCs in complex gas mixtures, ii) the need to detect concentrations that may span a large range, from trace levels to parts per million and iii) the need to track concentrations that rapidly change over time. Because of these experimental constraints, the ideal methodology for VOC monitoring should be highly selective, with high sensitivity and dynamic range, and with high time resolution [2]. Non-chromatographic techniques, based on direct injection mass spectrometric (DIMS) VOC assessment, are receiving great interest mainly i) because of their capacity to carry out rapid, high-throughput measurement of large sample sets without affecting samples and without interfering with the VOC production process and ii) because the possibility of rapid process monitoring. Besides its technological performances (e.g., sensitivity and selectivity), advanced DIMS is also increasingly being used because of its stability since the mass/charge ratio does not vary with the experimental conditions. However, the greatest difficulty arising in DIMS, due to the lack of chromatographic separation, is the need to identify hundreds of compounds produced by fruits. The fruit breeding research activity at the Foundation E. Mach, based on genomics, sensory and conventional characterization tools, has been recently complemented with advanced DIMS phenotyping tools, such as PTR-ToF-MS, and with tailored pre- and post-harvest studies aimed to simulate the entire fruit production chain. This synergism of novel analytical approaches is fully applied into the breeding activities of blueberry, raspberry, strawberry, and apple in order to develop new cultivars characterized by both prolonged storability and high perceived quality. Moreover, this research approach was valuable to deeply investigate and step forward in the comprehension of the genetic and physiological aspects controlling fruit quality. These studies, for instance, allowed to determine the possible interaction between genetic variability and fruit ripening stages on the aroma development of different fruit species during cold conservation at different atmospheric condition, to develop several genetic and molecular markers [3-6]. This knowledge would enable, in a close future, for a more precise selection of the most favorable new accessions distinguished by superior fruit quality. In this presentation we will report several experimental trials about the four analytical approaches, based on PTR-MS technology, suitable to fully investigate the complexity of fruit and vegetable aroma: i) non destructive VOC assessment; ii) automated analysis of frozen tissue; iii) dynamic destructive analysis; iv) monitoring of processes. In our opinion these proposed methodologies can be applied, with slight modification, on every kind of fruit or vegetable