Use of mild heat pre-treatments for quality retention of freshcut 'Rocha' pear

The effect of mild heat pre-treatments on quality of fresh-cut 'Rocha' pear (Pyrus communis L.) was evaluated by response surface methodology (RSM) in different time/temperature combinations. Susceptibility to cut surface discoloration and changes in firmness, total soluble solids content (SSC) and pH of cut pears (quarters) were the measured dependent variables. The models developed for L*, a*, firmness and pH appeared adequate (R-2 > 0.72). RSM results also showed a significant lack of fit (P > 0.05), for b* and SSC models. Firmness of the 'Rocha' pear quarters was preserved in the range of the mild heat pre-treatments used (36-42 degreesC). An increase in firmness from an initial value of 27.2 to 70 N was observed whenever treatment temperature was greater than 45 degreesC. Treatment time did not have a significant (P > 0.05) effect on firmness. To preserve the two significant colour parameters (L* and a*), treatments should be conducted in the range 36-45 degreesC with treatment times greater than 40 min. Mild heat pretreatments produced an increase in pH values from 4.5 in raw material to 5.8 for samples exposed to high treatment intensities. In order to preserve the pH values, the best-suited conditions are those corresponding to treatments at temperatures lower than 45 degreesC for less than 150 min. Mild heat pre-treatments (35-45 degreesC for 40-150 min) were effective in avoiding the cut surface browning and preserving or increasing firmness of 'Rocha' pear quarters. When pre-treated fruit were stored for 7 days at 2 degreesC, no significant changes were detected in colour parameters, pH and SSC. However, firmness decreased approximately 30% from the 4th to the 7th day. (C) 2003 Elsevier B.V. All rights reserved.