Changes in colour and sugar content in rose hips (Rosa dumalis L. and R-rubiginosa L.) during ripening

Rose hips constitute a recently domesticated small fruit crop. In the last few years, interest in this crop has increased considerably due to its nutritive and health promoting values. Changes in CIE colour co-ordinates L*, a* and b*, glucose, fructose and sucrose contents, fruit weight, percentages of fruit flesh and dry matter, and degrees Brix values were determined during the ripening period in two species, Rosa dumalis and R. rubiginosa. In both species, colour changes during ripening were characterised by a large increase in a* (redness) for the first three harvest dates, whereas L* and b* (yellowness) decreased during the whole study (rose hips became darker and less yellow). Glucose was the major sugar, followed by fructose, both increasing significantly in R. rubiginosa until the beginning of October. By contrast, a maximum was reached by mid-September for R. dumalis. degrees Brix values increased in both species during the first 3 weeks of September, then levelled-out. In both species, changes in calculated hue (visible colour) were related to changes in total sugar content and degrees Brix value. It should, therefore, be possible to use colour as an indicator of optimum harvesting time.