No abstract

Summary Galicia (N.W. Spain) produces 60% of Spanish kiwifruit (Actinidia deliciosa) and 5–20% of these are ‘destrío’ fruits, which do not reach market size and the appropriate form. These rejected fruits can be processed into products, thus increasing their added value. The processing of kiwifruit always includes a peeling operation, which can be performed by different systems. The most suitable conditions for caustic peeling and thermal peeling were established. Then, the two peeling systems were compared with manual peeling with the aim of selecting the best system to remove the peel of the ‘destrío’ kiwifruit. The fruits, once harvested, were stored in a cold chamber at 0 °C. Before processing or marketing kiwifruits, it is necessary to remove them from storage in cold chamber and storage at room temperature. In this study, different storage times at room temperature before peeling kiwifruits were also tested. The best system for peeling the kiwifruit was thermal peeling as this system resulted in the lowest weight loss and preserved the green colour characteristic of the kiwifruit. The best time for peeling the kiwifruit was after 8 days of storage at room temperature, after being removed from the cold chamber.

Producers of kiwifruit can often be affected by the economic loss generated by culled fruit; thus, the processing of kiwifruit in syrup was proposed as a way to both increase profits and also lower losses for these producers. First, a series of experiments with consumers was successively planned and performed in order to establish the optimal conditions for the final product depending on how the kiwifruit were cut (halves, quarters or slices), the soluble solids concentration (light syrup, syrup, heavy syrup or extra heavy syrup) and the type of sugar (white or brown). Once the processing conditions of the product were selected (sliced kiwi and extra heavy syrup with white sugars), we verified that consumers liked it and that this acceptance was also reflected in their intention to buy the product. Therefore, the process was applied to elaborate both an organic and a conventional version of kiwifruit in syrup. The effect of processing (both organic and conventional) on the physicochemical characteristics of the raw material (both organic and conventional) was studied. All variables, except b*, C*, glucose, fructose and a w , were significantly modified by processing. Organic kiwifruit has less soluble solids, sugars and total acidity than conventional fruit but a higher pH. These small differences were maintained in the organic kiwifruit in syrup when it was compared to conventional product; however, the difference in the sensory characteristics (as measured by a panel of trained tasters) was not great enough to be detected. Both products were stable over time.