IMPORTANCE OF COOKING TEMPERATURE AND PANCREATIC AMYLASE IN DETERMINATION OF DIETARY FIBER IN DRIED LEGUMES

Total dietary fiber (TDF) was measured in large lima, roman, black tur tle, light red kidney, white navy, pinto, black-eyed, and soya beans a nd in chick peas by the Mongeau rapid method (A), the Prosky method (B ), and the Lee method (C), When the samples were soaked and cooked acc ording to package instructions (gentle boiling, 95 degrees C), TDF val ues by method A were all within 19.7-22.1%, except for black-eyed bean s (9.9%) and chick peas (11.3%) (g/100 g, cooked dry matter), For larg e lima beans (20.0-21.3%) and soya beans (19.2-19.7%), TDF values by m ethods A, B, and C were in agreement, For 7 samples, however, TDF valu es were up to 81% higher by method B (17.4-34.7%) and up to 122% highe r by method C (21.1-39.8%) than those by method A (P less than or equa l to 0.01), For 6 legumes, TDF values by method C were 15-28% higher ( P less than or equal to 0.013) than by method B, White navy beans were analyzed also after different cooking conditions, varying from no coo king to autoclaving for 15 min at 120 degrees C, TDF values by method A were independent from cooking conditions and remained between 20.2 a nd 22.4%, For navy beans cooked at 95 degrees C, TDF values by method B (up to 34.7 +/- 1.4%) and C (up to 39.8 +/- 0.3%) were unpredictable , but autoclaving at 120 degrees C reduced them to about 22%, Incorpor ation of a pancreatic amylase in methods B and C consistently decrease d the aforementioned analytical discrepancies, as did the absence of c ooking, Only autoclaving (for at least 15 min at 120 degrees C) fully restored agreement among methods A-C.