Effect of heating on the stability of grape and blueberry pomace procyanidins and total anthocyanins

Fruit by-products are rich sources of procyanidins and anthocyanins known for potential health benefits. Freeze dried blueberry pomace and grape pomace were heated in a forced air oven at 40, 60, 105, and 125 degrees C for 72, 48, 16, and 8 h respectively, to study the stability of procyanidins and total anthocyanins. Heating decreased procyanidin concentrations significantly (p < 0.05) in both blueberry and grape pomace, except when heated at 40 degrees C for 72 h. Reduction occurred when heated at 60 degrees C or above with no further reduction when heating temperature increased from 105 to 125 degrees C. Heating also affected total anthocyanin contents in both grape and blueberry pomace with no significant (p > 0.05) loss when heated at 40 degrees C. Total anthocyanin loss was highest at 125 degrees C for both blueberry (52%) and grape pomace (70%). Results suggested that while heating at lower temperatures for up to 3 days may not be detrimental, heating at higher temperatures for more than 8 h results in considerable loss of both the compounds. (C) 2010 Elsevier Ltd. All rights reserved.