Effects of measurement and preparation conditions on mechanical properties of dessert jellies containing konjac

Abstract

The effects of measurement and preparation conditions on the mechanical properties of so-called konjac jellies were investigated using agar jellies for comparison. Here, konjac jellies represent dessert jellies containing konjacbased materials as a constituent with other polysaccharides like κ-carrageenan and locust bean gum, whereas agar jellies contain only agar as a polysaccharide source. As mechanical properties, the apparent breaking stress and strain were determined by puncture tests. Both fracture parameters for konjac jellies were more sensitive to the measurement conditions, including size of the plunger relative to the container, table speed(deformation rate), trigger settings, and temperature than those for agar jellies. Moreover, these fracture parameters for konjac jellies were more sensitive to the preparation conditions, including swelling time of konjac mannan(as a constituent)and storage time of jellies, than those for agar jellies. These results indicate that more detailed conditions should be required for determination of the mechanical properties of konjac jellies when the test protocol is standardized or manualized in terms of data reproducibility and universality.