firmness, toughness, adhesiveness
A major jam and jelly manufacturer asked Texture Technologies Corp to develop a test method for the firmness and consistency of their fruit preserves. Their previous methods involved manual manipulation and visual observations by an expert panel of individuals, however, neither method was quantitative and each involved too much training. Quantifying the firmness of fruit preserves has always been difficult. The number, size, shape and distribution of fruit pieces are usually randomly distributed within each jar’s gel matrix (fruit juice, pectin, sugar and acid). While it is easy to quantify the firmness of the clear jellies or the matrix with standard gel measurement techniques (gel compression or depression, or gel rupture) those techniques are useless for quantifying the firmness of the fruit particulates themselves. It is possible to test unprocessed fruit pieces in bulk (e.g. with a kramer shear cell) but the results may not correlate with endproduct firmness. Firmness is often affected by the production process, the duration it has been in the matrix, and the matrix composition. It is also possible to screen the pieces from the matrix in order to quantify the fruit, although the separation process is awkward and inefficient and often damages the fruit pieces. The optimal method should test the fruit while suspended in the matrix. We used the TA-65 Multiple Puncture Probe to conduct the tests directly into the jars of preserves.