CHARACTERIZATION OF PECTIC SUBSTANCES FROM 2 POTATO CULTIVARS WITH DIFFERENT SENSITIVITIES TO PREWARMING

Potato cultivars Chieftain and Kennebec were prewarmed at 70-degrees-C for 15 min. prior to heating at 100-degrees-C for 18 min. in a water bath. Chieftain exhibited a large increase in fracturability upon trea tment while Kennebec showed a smaller increase. Pectic substances of t he two cultivars were sequentially extracted in water, sodium hexameta phosphate (0.5%), hydrochloric acid (0.05 M, 50-degrees-C), and sodium hydroxide (0.05 M, 5-degrees-C). The largest fraction isolated from b oth cultivars consisted of hydroxide-soluble pectic substances, and wa s followed by the acid-soluble fraction. Chieftain contained significa ntly greater amounts of the hydroxide-soluble fraction than Kennebec. Ion exchange chromatography revealed that the extracted pectic substan ces from the two major fractions consisted of a charged pectin chain w ith attached neutral sugars. Gel filtration chromatography revealed wi de molecular size distributions for the isolated pectic substances. Pe ctic neutral sugar content for the hydroxide-soluble fraction (50% of total pectic substances) was greater for Chieftain than for Kennebec.