Abstract
The gelling properties of an acidified mixed gel consisting of alkali- or acid-treated gelatin (3%) and a denatured whey protein isolate (WPI 6 %) were investigated. Compared with the WPI gel alone, the mixed gel adjusted to pH 5.5 was more resistant to syneresis and its rupture value was higher, regardless of the type of gelatin. The value for the apparent rupture stress of the mixed gel with either type of gelatin was a maximum at pH 4.5, while the mixed gel incorporating the acid-treated gelatin showed a second peak at pH 3.5. The mixed gel at around pH 6 with orange juice added had a low value of apparent rupture stress and a high value of apparent rupture strain. The mixed gel at around pH 4.7 with lemon juice added had a high value of apparent rupture stress and a low value of apparent rupture strain. The mixed gel consisting of WPI and alkali-treated gelatin with 5 % orange juice added had a small amount of free water and its structure was characterized by a dense network formed by WPI strands filled with membranous gelatin.
