Relationship of colour and other quality parameters of sweet cherry during development and ripening

Sweet cherry fruits ( Prunus avium cv. Vera, Carmen, Linda and Krupnoplodnaja) were harvested in different ripeness stages after anthesis 39, 42, 49, 56 days (Carmen); 37, 40, 47, 52, 59 days (Krupnoplodnaja); 32, 36, 44, 53, 58 days (Linda); 38, 42, 50, 52, 57 days (Vera). The colour, total soluble solids, dry matter content, β-galactosidase and polygalacturonase activity were determined. The dry matter content and total soluble solids content (Brixo) increased during development. The L* values significantly decreased as a function of ripening while a* values increased up to 3 rd harvest, then they decreased, b* values continuously decreased as a function of development. The a*/b* values linearly increased as a function of development, indicating reddening of fruits. Hue angle (ho) increased rapidly between harvest one and two. The measured (a*, b*, L*) and calculated parameters (ho, a*/b*, chroma) well represented the colour development of sweet cherries. Linear and strong correlation was found between a*/b*, L* values and the Brixo, exponential correlation was found between ho, chroma and Brixo. Activity of β-galactosidase was different among cultivars and as a function of development. The two maximums might β-galactosidase isoenzymes. The role of PG (polygalacturonase) could not be explained clearly enough, further investigations are needed to find the exact role of the enzyme in the cell wall metabolism of sweet cherry