10 - Quality Evaluation of Citrus Fruits

Abstract

This chapter describes machine vision inspection of citrus fruits. Machines are capable of sorting fruit by size and weight, but consumers value more quality attributes, such as the appearance of the fruit, its taste (which is related to the sugar-to-acid ratio), and the high vitamin content. Furthermore, packing houses need to detect rotten fruit to avoid the spread of fungal infections and blemishes that can be a focus of future infections, causing undesired loses of quality. In the last 20 years, research and development on machine vision inspection has been focused on the measurement of size and shape, color sorting, and detection of blemishes with great success. Current commercial machines are able to obtain these objectives with an adequate processing speed of close to 15 fruits per line. The next step is the possibility of identifying the defects and sorting the fruit according to potential negative effects. This objective has been partially solved in commercial machines, but more effort is required to improve their precision and processing speed. Internal quality of fruit is also essential for consumers, but this cannot be assessed with current machines. Efforts have been directed towards the estimation of sugar and acid content, detection of seeds, internal physiological disorders, fungal infections, and presence of insects, but current machines are unable to achieve this objective online and thus results are still at the laboratory level.