Effect of Heat Treatments On the Quality of Fresh Cut ‘Ryan Sun' Peaches

Currently, consumers demand a high appearance and safety quality of fresh cut fruit without using chemical treatments. For that reason, new friendly environmental alternatives are being studied to delay enzymatic browning and firmness losses in order to prolong the shelf life of fresh cut peach. The effect of mild heat treatments on the quality of fresh cut ‘Ryan sun‘ peach (melting flesh) was evaluated on whole fruit stored at 0 ºC until processing. Then, they were submitted to immersions in water at 50 ºC for 6, 15 and 30 min. Also an immersion at same conditions for 30 sec was used in peeled and cut fruit (wedge shape). As a control, intact fruits were immersed in cold water (5 ºC). After the treatments, around 250 g of cut fruit were packed in polyethylene trays (0.5 L capacity) covered with a permeable plastic film  and stored at 5 ºC up to 8 d. The microbial growth (mesophilic aerobic and enterobateria bacteria), changes in color (L* value), firmness, respiration rate (expressed as mg CO₂ kg^-1 h^-1) and appearance were evaluated for 8 d at 5 ºC. Treated intact fruit at 50 ºC for 15 min (T15) before cutting showed a high delay of the enzymatic browning and higher flesh firmness than the other treatments, specially after 4 d Respiration rates were similar to control for immersions at 6 and 15 min. However, the rates were higher in treatments with 30 min and 30 sec for intact and cut fruit, respectively. The highest firmness values of 2 kg_f were shown by T15. In addition, this treatment kept the color (L* values) between 62 to 66 along the storage period. Mesophilic counts were below or close the maximun levels allowed by Chilean Legislation after 8 days at 5 ºC for all treatments.

 Keywords: Minimally processed; enzymatic browning; shelf life; sensorial quality, postharvest

 Acknowlegement: This study and the grant for Dr. Obando were supported by FONDEF (Chile) D07i1026 and Fondecyt 3100074, respectively.