LOW-TEMPERATURE BLANCHING EFFECTS ON CHEMISTRY, FIRMNESS AND STRUCTURE OF CANNED GREEN BEANS AND CARROTS

Green beans and carrots were canned using extended blanching at 64-65 degrees C and added calcium and/or acid. Firmer products resulted from all treatments but lowered pH was most effective. Blanched green bean s were firmer with lower pectin esterification, indicating pectin meth yl esterase activity. Green beans and carrots treated with calcium and /or acid and then cooked were firmer than controls. Acid exhibited a f irming effect, perhaps by loosening tissue, while calcium reduced the influence of heat. Instrumental bioyield values correlated with sensor y results of canned green beans; bioyield may result from a scleriform ic layer. Microscopy showed firmer beans had intact middle lamellae wh ile softer samples contained separated cells. These data suggest that the treatments rendered pectates in the middle lamella less heat labil e.