Comparison of reflectance of sunburned fruit among 3 apple cultivars

摘要

There exist some differences of reflectance between sunburned and normal fruit as well as among various cultivars. The reflectance of 'Redchief' is higher than that of 'Jonagold' and 'Gala' in all combinations except necrotic/'Gala'. Regardless of wavelengths, the maximum reflectance with 3 cultivars shows consistently in the following descending order: necrosis > browning > normal. It was found that the chart shape of browning and normal fruit was completely different from that of the necrotic, because there located a marked valley near the wavelength of 675 nm, which can be used as an ideal index to distinguish different types of sunburned fruit With three cultivars, the wavebands of normal, browning and necrotic fruit were 748.45-751.69, 803.38-822.07 and 925.15-937.88 nm, respectively. Thus it is possible to classify them by measuring the maximum values of reflectance at wavelengths 750-950 nm.