Model of vegetable freshness perception using luminance cues

Freshness perception is a quality discrimination process that influences our consumer choice and eating behavior, especially of highly perishable products such as vegetables. Previous research used photographic stimuli to investigate the relationship between luminance distribution and freshness perception for a cabbage leaf (C. Arce-Lopera, Masuda, Kimura, et al., 2013) and a strawberry (Carlos Arce-Lopera, Masuda, Kimura, Wada, & Okajima, 2012). In this study, the luminance and chromatic information of the freshness degradation process of four different vegetables (cabbage, strawberry, carrot and spinach) was recorded in a temperature, humidity and light controlled environment. However, instead of a camera, a 2D luminance and chromaticity analyzer (TOPCON UA1000) was chosen as the measurement equipment. Then, using a color management system to guarantee the exact reproduction of the recorded luminance and chromatic data of the real objects, a color and a grayscale version of the stimuli was created. Subsequently, those pictures were randomly presented to subjects who had to rate their perceived freshness using a visual analog scale. The achromatic results did not differ from the chromatic ones suggesting that luminance information is sufficient to enable an accurate estimation of vegetable freshness. Additionally, the original images were digitally manipulated only by modifying their luminance distribution and keeping their color information intact. When the resulting images were presented, using the same psychophysical experimental setting, the results showed that the perceived freshness also changed concordantly with the changes on the asymmetry of the luminance distribution. Finally, a model for vegetable freshness perception that utilizes only luminance cues is presented.