Image analysis of blush coverage extent and measures of categorical blush intensity in 'Honeycrisp' apples.

摘要

Coverage extent and intensity of apple blush are important factors in the evaluation of apple fruit quality for some cultivars. Blush coverage extent and intensity were analysed in the cultivar Honeycrisp to: define categories of marketable blush in terms relating to device-independent colour measurements; assess relationships among a modified anthocyanin index (AI_m) calculated from spectral measurements, colorimetry (CO) and human judgment of apple blush intensity; assess the efficacy of digital image analysis (DIA) of colour-calibrated digital photography as a tool to measure blush coverage extent; and explore differences between human judgment of blush coverage extent and DIA. AI_m and CO were both effective in providing statistical categorical separation among 5 classes of apple blush in Honeycrisp: non-blush, slight non-marketable blush, minimum quality marketable blush, clear marketable blush and outstanding blush as judged by human participants. The boundary between blush and non-blush was judged to be a hue angle <49.0 +or- 3.1 h_ab in CIELAB L*C_ab*h_ab colour space and an AI_m value >4.3 +or- 1.3 at alpha < 0.05. DIA was less sensitive and did not show statistically significant differences between clear marketable blush and outstanding marketable blush, although its use to distinguish the other categories was successful. All methods of analysis resulted in high agreement with respect to the blushon-blush boundary (Cohen's kappa >= 0.897).