Stability of microencapsulated volatiles during high-temperature short-time (HTST) extrusion

PhD Student: Sri Yuliani
Supervisors: Dr. Rulande Rutgers, Dr. Bhesh Bhandari and Dr. Andrew Whittaker

The stability of flavour during extrusion is very important. The extrusion process can cause loss of pre-extrusion added flavour compounds due to thermal degradation, oxidation, polymerisation and reaction with food components. In addition, the flavours are flashed off with the steam during expansion of the extrudate. Because of the inherent problems, flavours are mostly added after a product has been extruded. However, this post-addition flavour suffers from numerous inherent problems, such as the need for high dosage levels, uneven distribution, oxidation of flavours applied at the surface, insolubility of some flavours in the chosen base medium, and need for an addition of fat to bind the flavour to the product.

The use of microencapsulated flavour flavours through effective microencapsulation techniques can improve flavour retention during extrusion. Therefore the innovation of microencapsulation methods for optimised flavour retention and the understanding of flavour loss during processing is very important. The aim of this research is to determine the effect food extrusion process conditions on microencapsulated volatiles. In this research, the effectiveness of two different microcapsules will be compared: one encapsulated with b-cyclodextrin and other using a novel technique protein precipitation with sodium caseinate. The effect of mode of introduction of flavours into the extrusion process also will be studied: prior to extrusion or direct injection into the extruder barrel. A mathematical expression will be developed to allow the prediction of flavour loss as a function of processing parameters such as volatility, temperature, shear rate, and microcapsule characteristics.