Determining Tissue Damage of Fresh-cut Vegetables Using Imaging Technology

A method of quantitatively measuring tissue damage during fresh-cut vegetable processing was developed based on optical imaging technology. Images of damaged and undamaged tissues were acquired through a digital imaging system. The damaged areas were recognized and quantified using an Image-Pro Plus software program based on color differences of the damaged and undamaged tissues. In order to improve color differences between the damaged and undamaged tissue, the samples were stained with a 0.3% catechol solution to accelerate the browning reaction. This method was applied to determine the tissue damage of fresh-cut baby spinach (Spinacia oleracea) and iceberg lettuce (Lactuca sativa) during the centrifuge drying process. Significant differences were found among drying speeds and locations of the samples in the centrifuge drying baskets. By reducing centrifuge speed, a significant reduction in tissue damage of fresh-cut baby spinach and iceberg lettuce was obtained, especially on those located along the periphery of the centrifuge drying baskets. INTRODUCTION The fresh-cut fruit and vegetable industry has been rapidly expanding during the past decade, due to freshness and the high nutrition that fresh-cut produce offers, as well as convenience to consumers (Hodge 1995; Watada et al., 1996; Bauer, 1997). However, tissue damage incurred during fresh-cut processing causes rapid quality deterioration and shortens shelf life (Guerzoni et al., 1996; Watada et al., 1996). In addition to the cutting damage, centrifuge drying has been recognized as a major damaging point (Hodges et al., 2000). Centrifuge drying has been widely used in the fresh-cut vegetable industry to remove the excess surface water after washing. The impact of centrifuge drying on product quality and shelf life is two-fold: the inadequate drying that may result in fast quality deterioration and microbial growth, and the excessive drying that may cause severe tissue damage resulting in shortened shelf life and decreased production yield. It is therefore important to optimize the centrifuge drying speed and time to obtain sufficient drying while minimizing tissue damage. To do so, it is necessary to develop an easy-touse method to quantitatively and objectively determine tissue damage during the centrifuge drying process. Imaging processing technology has been used successfully in the food and agriculture industries in applications such as corn kernel damage evaluation (Steenoek et al., 2001; Liu and Paulsen, 2002), tomato ripening assessment (Polder et al., 2002), and defect sorting (Tao, 2000; Wen and Tao, 2000; Kim et al., 2001; Mehl et al., 2002). The main objectives of this study were 1) to develop an imaging system and methodology allowing quantitative measurement of tissue damage, and 2) to determine tissue damage of fresh-cut baby spinach and iceberg lettuce during centrifuge drying process. Proc. XXVI IHC – Issues and Advances in Postharvest Hort.