## 1 Introduction  
Sweet cherries of the genus _Prunus avium_ (family _Rosaceae_) are non-climacteric stone fruit, mainly grown in temperate climate countries. They are an important crop in Greece, with an annual production of 45,000-60,000 tons (7%-8% of EU production). Greece ranks 12 in world cherry production [1]. Even though sweet cherry trees are cultivated all over Greece (the mainland and the islands), 65%-70% of the cherry production concentrates in northern Greece in the greater area of Imathia and Pella [1]. A ripe cherry fruit has bright shiny pale to deep red or even purple colour, usually with a thin skin. Due to their colour, aroma, taste and health beneficial antioxidant properties, cherries are greatly appreciated worldwide [2,3]. Among the classical sweet cherry cultivars grown in Greece, the Ferrovia cultivar gives a large, red, shiny skin, heart-shaped fruit of firm texture destined for fresh consumption. The cultivar originates from the area of Bari (Puglia, Italy) but has adapted very well in various geographical areas of Greece. Fruit ripens in early June. The fruit flesh is pink in colour, juicy, with a strong adherence to the stone. It has a very pleasant flavour of intermediate sweetness [4]. The Lapins cultivar also gives a very large, red, shiny skin, heart-shaped fruit of firm texture destined for fresh consumption. This cultivar was developed by [PERSON] at the Agricultural Research Station in Summerland, British Columbia in Canada. The fruit ripens in late May to early June. The fruit flesh is very juicy of dark red colour. Among the newer promising cultivars grown in Greece, the Skeena cherry cultivar gives a large, red, shiny skin, kidney-shaped fruit of very firm texture destined for fresh consumption. Finally, the Canada giant cultivar gives a large, red, shiny skin, heart-shaped fruit of firm texture to be consumed fresh. Both the Skeena and Canada giant cultivars were also developed in Summerland, Canada. Greece has the comparative advantage of early sweet cherry ripening by 10-15 days as compared to the rest of Europe, with the exception of Turkey. In terms of sensory quality, the main cherry attributes include skin colour, sweetness (sugar content), sourness (organic acid content), fruit firmness, fruit weight, and aroma even though the compounds contributing to fruit odour comprise a very small portion (0.01%-0.001%) of the fruit fresh weight (FW) [5]. Aroma is one of the most valued attributes of sweet cherries which may influence consumer acceptance of the fruit. On the other hand, the total soluble solids (TSS)/titratable acidity (TA) ratio, known as maturity index, directly affects the perception of sweetness and flavour and thus, consumer acceptance of the fruit [2]. Cherries are also a good source of phenolic compounds (_ca._ 150 mg GAE/kg FW) made up mainly of hydroxycinnamates, anthocyanins, flavan-3-ols and flavonoids [6]. Such compounds are responsible for the strong antioxidant activity of cherry fruit [7]. It has been reported that TSS and TA are closely related to the intensity of cherry flavour and consumer acceptability increases with high TSS and TA levels [2,8]. TA has also been reported to be dependent on cherry cultivar with levels of 0.4%-1.5%. It is well accepted that the aroma of fruit is the combined result of a complex mixture of esters, alcohols, aldehydes, organic acids, ketones, terpenoid compounds, _etc._[9]. Methods used to analyze such complex mixtures include static and dynamic head space analysis, supercritical CO\({}_{2}\) extraction, and solid phase micro extraction (SPME) in combination with gas chromatography/mass spectrometry (GC/MS) [3; 10; 11]. Among these, SPME has proven to be a simple, rapid, solvent-free and effective method to analyze fruit volatiles [5; 12]. In addition to the determination of volatiles, sugar and organic acid content, it is appropriate that these attributes be correlated to sensory evaluation attributes (taste, odour, colour and texture) to characterize the overall quality of sweet cherry fruit [13].