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The inactivation of the enzymes polyphenoloxidase (PPO) and peroxidase (POD) and color loss with steam blanching, was studied. The yacon roots were washed and peeled, cut into 1.75 Ϯ 0.35-mm slices, and placed in wire baskets inside an autoclave generating steam at a temperature of 100C for 1, 2, 4, 6, 8 and 10 min. The best condition was with a time of 4 min, where it was possible to reduce the activity of POD and PPO by 84.62 and 83.76%, respectively, with losses of inulin, glucose and fructose of 30.69, 39.40 and 15.82%, respectively. Total color difference and browning index values changed when compared with original color of yacon roots. These changes were higher during the first 2 min and, after this time, these parameters did not change significantly. Principal component analysis of steam blanching times in yacon too revealed no significant differences starting from 4 min of blanching. PRACTICAL APPLICATIONSBlanching is a unit operation that is used in order to achieve inactivation of enzymes that produce the browning. This procedure is used as a pretreatment before pasteurization, sterilization, refrigeration and freezing. Either steam or hot water can be used to blanch food. However, prolonged hot water blanching results in considerable loss of soluble sugars because of leaching. Blanching can also be used to deactivate enzymes that cause depolymerizing of polysaccharides such an inulin. This fructan has prebiotic properties and is a dietary fiber. The aim of the present work was to study the deactivation of enzymes that produce changes of color using steam in yacon roots.

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