Strawberry quality as a function of the 'high pressure fast cooling' design

Oso Grande strawberries were picked, wrapped with polyvinyl chloride film, and finally cooled by 'high pressure fast cooling' units with slight differences in design in terms of number of fans functioning and ventilation spacer widths. The effect on strawberry quality of these cooling cells was evaluated compared to room-cooled fruits, and when compared to quality parameter values at fruit gathering. Quality evaluations 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 cooling, after 3 days at 2 degrees C simulating refrigerated transport, and after 4 days at 17 degrees C storage (shelf-life). Reducing (by half) the ventilation spacer (V cell), resulted in a 20% higher air speed and a 20% faster cooling than control units (N cell), while units using 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, showed a different quality pattern compared to fruits from N and F cells, with 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 cooled by the N or F cells. In these cells, fruit colour remained practically unchanged along the different commercial stages including the long shelf-life period. (C) 1998 Elsevier Science Ltd. All rights reserved.