Delayed Light Emission as a Means of Automatic Color Sorting of Persimmons (1)

DLE Fundamental Characteristics of Persimmon Fruits

Abstract

The delayed light emission (DLE) characteristics of chlorophyll of persimmons (Fuyu fruits) were investigated for the purpose of providing data for the automation of sorting process. The following results were obtained:
1. The DLE intensity of persimmons had a property of dark recovery which changed due to the exiting light intensity (Fig. 2).
2. The effects of fundamental factors such as exciting period, exciting light intensity and fruit temperature upon the DLE intensity were investigated (Fig. 3, 4, 5). From the results obtained, the exciting conditions for obtaining the maxmum DLE intensity were as follows:
Dark period for dark recovery; above 15min
Exciting illuminance; above 2800lx
Exciting period; 1 to 3 sec
Fruit temperature; 22 to 32°C
3. Delayed light of persimmon fruit was emitted from the chlorophyll in the peel tissue. The flesh was considered to aid the chlorophyll in the peel to be excited by the diffuse reflection within the part of the flesh (Fig. 6, 7).
4. The bloom covering the fruit surface, which could cause peel color to be misclassified, had little effect on the DLE intensity of persimmon (Table 2).
5. The DLE intensity of persimmon had a linear relation with the chlorophyll content. A specially high correlation was observed with the content of chlorophyll a and total chlorophyll (Fig. 8, 9, 10).