36E-96 |
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T. NGO, Dept. of Food Science & Technology, Oregon State Univ., 100 Weigand Hall, Corvallis, OR 97331-6602 and Y. Zhao. Chlorophyll degradation during thermal processing has been one of the major challenges in thermally processed green fruits and vegetables. Zinc ions have been studied to help retain green pigments and used for some canned green vegetables. The interest in developing peels-on processed green pears had prompted the investigation of retaining green pigment on the pears using zinc ions. Our objective was to evaluate the effects of surface pretreatment, presoaking, blanching and canning conditions on retaining green pigment on thermally processed peels-on green pears. Green Comice, d°ŻAnjou and Bartlett pears were subjected to surface pretreatment by removing surface wax layer and a part of the top cuticle layer of the pears. Pretreated whole fruits or chunks were presoaked in 1%, 2% or 5% zinc lactate (ZnL) solutions for 1 to 2 hr, or blanched at 94oC for over 8 min in 0.1% to 2% ZnL solutions. Pears were then canned at 94oC for 20 min in water or 1% ZnL solution. The pH of canning solution was adjusted to 3 or 6. Hunter color values of canned pears were measured. Results showed that surface pretreatment was essential to retain green pigment on the peels using ZnL. Adding ZnL in blanching or canning solutions was more effective than that in presoaking solutions. For all studied pear varieties, blanching un-presoaked brushed pears in 1% ZnL solution for over 13 min, followed by hot-filling and canning in water with or without pH adjustment yielded bright green peels-on products. The zinc residue in the final product was lower than FDA 75 ppm limit level. This study validated that use of zinc ions can effectively retain green pigments for canned pears. The development of peels-on canned green pears would contribute significantly to the pear industry by creating a new value-added pear product.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |