STRAWBERRY QUALITY AS A FUNCTION OF THE HIGH-PRESSURE FAST COOLING DESIGN

Oso Grande strawberries were picked, wrapped with polyvinyl chloride f ilm, and finally cooled by 'high pressure fast cooling' units with sli ght differences in design in terms of number of fans functioning and v entilation spacer widths. The effect on strawberry quality of these co oling cells was evaluated compared to room-cooled fruits, and when com pared to quality parameter values at fruit gathering. Quality evaluati ons by means of determination of main sugars and organic acids, colour , firmness, total soluble solids, titrable acidity and pH assessments were carried out at different commercial stages, inmediately after coo ling, after 3 days at 2 degrees C simulating refrigerated transport, a nd after 4 days at 17 degrees C storage (shelf-life). Reducing (by hal f) the ventilation spacer (V cell), resulted in a 20% higher air speed and a 20% faster cooling than control units (N cell), while units usi ng half of the fans (F cell) showed a lower air speed (45%) and a 30% more time to cool down the product. These modifications also affected strawberry quality. Fruits from the fastest cooler cell, V cell, showe d a different quality pattern compared to fruits from N and F cells, w ith a higher sucrose inversion and less glucose and fructose contents. V cell-cooled strawberries presented a lower content of citric, malic and ascorbic acids during shelf-life. However, fruits cooled by the V cell showed the highest marketable fruit percentage, although with a decrease in red colour compared to fruit at gathering, and fruit coole d by the N or F cells. In these cells, fruit colour remained practical ly unchanged along the different commercial stages including the long shelf-life period. (C) 1998 Elsevier Science Ltd. All rights reserved.