Development of a ball back extrusion technique for texture analysis of fluid food.

Textural properties of a food not only influence consumers' sensory preference of the product but also more importantly influence the strategy of food oral manipulation. Availability of reliable instrumental techniques has always been sought by food industry for proper assessment of food texture both in lab and online quality control. In this work a set of ball back extrusion (BBE) geometries with various ball/cup diameters (38/40, 35/40, 31.5/40, 24.5/28, all in mm) have been assessed as a fixture of a standard texture analyzer for flowability and consistency test of fluid foods. The feasibility of the new design has been tested against plate back extrusion (PBE), a current standard, for a set of fluid food materials (3 near Newtonians and 2 non-Newtonians). Pressing force and apparent maximum stress were used to quantify the flowability of fluid materials. It was observed that both techniques were able to reflect the rheological nature of the samples and were able to distinguish flowability for both Newtonian and Non-Newtonian fluids. However, the new design shows advantages against the plate back extrusion with much improved stability. Results show that BBE could replace the conventional plate-back extrusion to evaluate the flow properties of fluid foods in an industrial environment. The geometries of 35/40 or 24.5/28 ball/cup diameters (aspect ratio 0.875) were shown to give most satisfactory performance. The device is specifically suitable for texture classification of fluid foods for dysphagia management.