J. Fichtali

Production of Maillard reaction flavour precursors by extrusion processing

Abstract In-situ generation of Maillard reaction flavours by extrusion was investigated using a model system consisting of 15% (w/w) glucose, 5% (w/w) tryptophan and 80% (w/w) inert microcrystalline cellulose under preselected conditions of temperature, moisture, screw speed and feed rate. Samples were analyzed by HPLC for Amadori product, hydroxymethyl furfural and maltol. The effects of the extrusion parameters on product formation were assessed by the generalized distance approach to derive individual and compromise optima and their associated extrusion conditions. Product yields were similar to those obtained by aqueous refluxing, but their rate of formation was ∼8 times faster. The results indicate that a controlled continuous production of Maillard reaction flavour precursors by extrusion is possible.

Performance evaluation of acid casein neutralization process by twin-screw extrusion

The performance of an extrusion process designed to convert acid casein to sodium caseinate was evaluated relative to screw speed, temperature and feed rate; their effects on mixing, conveying, specific energy consumption (SEC), pressure, product temperature and end product physicochemical characteristics were considered. The effect of the process variables were assessed in terms of resulting residence time distribution (RTD) and associated parameters, and compared to theoretical models in an attempt to describe the flow behavior in the extruder. The process variables did not have a significant effect on physicochemical properties, however, they strongly affected RTD patterns, SEC, pressure generated and product temperature. A detailed analysis of the process is presented, indicating that the twin-screw extruder reactor is well described by a plug flow/perfect mixing model. The process produced a well mixed homogeneous product of comparable quality to conventionally manufactured caseinate and the performance analysis carried out provides a solid basis for the further optimization of such a process.

Acid coagulation of skimmilk powder by extrusion processing

Abstract Using the extruder as a continuous reactor, skimmilk powder was mixed with acid to produce an acid-coagulated product. The extrusion process was studied by response surface methodology to determine the influence of the extrusion parameters on selected extrudate physico-chemical responses including total and soluble protein, non protein nitrogen (NPN), lactose, and pH. Analysis of the high heat skimmilk powder extrudates showed that total and soluble protein, NPN and lactose were not affected by any of the extrusion parameters, while pH was significantly affected by moisture and screw speed. When medium heat skimmilk powder was used, total protein and lactose levels were significantly affected by temperature. The final pH values of extrudates from both powders were significantly affected by moisture or acid level, however polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulphate(SDS)-PAGE electrophoresis of the extruded product did not show any alteration in the caseins of the original skimmilk powders. Extrusion processing appears to be a potential means of preparing an acid-coagulated product from skimmilk powder as a preliminary step to the production of sodium caseinate.