Effects of addition of phenolic compounds on the acid gelation of milk

Tannic acid (0.1-1%, w/w) and gallic acid (0.3-1%, w/w) were added to skim milk prior to acidification with GDL. The acid gelation of tannic and gallic acid fortified milk had a faster gelation time in comparison with the control gel without phenolic compounds. The addition of tannic acid and gallic acid (up to 0.8%) to the milk resulted in a higher storage modulus (G'), decrease in the water mobility (T-2 time) and had no significant effect on the syneresis index (SI). However, the inclusion of 1% gallic acid resulted in a significant decrease in G', a significant increase in the SI and a wider T-2 distribution. Lowering the temperature of the gels from 30 to 5 degrees C caused the G' for the gels with gallic and tannic acid to increase significantly in comparison with the control, possibly due to increased hydrogen bonding in the presence of phenolic compounds. (C) 2010 Elsevier Ltd. All rights reserved.