A High-throughput Color Measurement System for Evaluating Flesh Browning in Apples

The development of new high-quality apple (Malus ×domestica) cultivars that are resistant to flesh browning is needed to expand the use of apples in the food service and catering industry. However, conventional methods for evaluating apple flesh browning can be both time-consuming and costly, thereby rendering such methods unsuitable for breeding programs that must characterize a large number of product samples. Therefore, it is necessary to develop new, simple, and inexpensive methods. The aim was to develop a method for simultaneously measuring the color values of 42 apple samples using a digital camera. The processing time per sample was reduced to less than one-tenth of that of the conventional method. The measurement dispersion [sd of the color difference between two colors ( Δ E * ab ) ] of this system was less than 0.08, equivalent to the nominal value of a general colorimeter. Time-series analysis of six apple cultivars using this method showed that the calculated browning index values correlated well with the degree of browning judged by human perception. Further, the measurement data showed that the CIE L* a* b* value trends associated with browning in reddish- and watercored-flesh samples, was different from the corresponding trends in yellowish-flesh samples. This work reports the development of a high-throughput analytical system of apple browning and provides cautionary notes for evaluating reddish- and watercored-flesh browning, which should be measured on a different basis from that used for normal-flesh browning.