Evaluating multiple texture properties of gelatines by combining a new 3D printed tool and a universal testing machine

Introduction Strength of gelatine is employed by producers and end-users as a key quality indicator. The standard method to define gelatine strength is the Bloom test. However, further information is helpful and required by companies to meet consumers' appeals. We developed a new probe designed ad hoc for a universal testing machine by 3D printing to determine more properties on the same gelatine sample. Material and Methods Probes utilized in mechanical test were designed using the solid modelling software SolidWorks 12. Additive manufacturing models were realized by rapid prototyping technique with the 3D printer Object 30 and the Objet VeroWhitePlus 835 acrylic resin. Mechanical tests were performed on standard gelatines using a Zwick/Roell Z050 universal testing machine. Results A cylindrical-shaped tool and a concentric piston were combined for a fracture/compression test. A device for the classical Bloom test was 3D printed to find a correlation parameter. One part of the probe allowed sampling a cylindrical specimen of gelatine directly from the cup (Bloom-like test), required for the subsequent compression-extrusion test, and acquiring information correlated to gel strength. The probe employed in the Bloom-like test, filled with a cylindrical gelatine portion, was overturned. Then, the concentric piston compressed the cylindrical gelatine portion sampled. Jellied mass flowed out through rectangular slots and was collected on the plate of the probe. Discussion In the Bloom's test, the plunger penetrated into the gelatine up to a depth of 4mm, without cracking the sample. The maximum value of force recorded (the resistance to penetration) was translated as the Bloom degree. In the Bloom-like test a fracture stress, a drop of the force and a subsequent increase up to the bottom of the cup were detected. Remarkably, for all the gelatines, the new probe must penetrate the average depth of 1.40mm ± 0.01 to achieve the corresponding Bloom degree. Furthermore, in the Bloom-like test, the maximum force registered was correlated with the resistance to cut of the sample. In the compression-extrusion test, the mean value of the force necessary to extrude the samples was calculated and correlated to the homogeneity of the jellies with different strength.