Effect of extrusion parameters on flavour retention, functional and physical properties of mixtures of starch and d‐limonene encapsulated in milk protein

Abstract

SummaryThe purpose of this research was to investigate the retention of flavour volatiles encapsulated in water‐insoluble systems during high temperature–short time extrusion process. A protein precipitation method was used to produce water‐insoluble capsules encapsulating limonene, and the capsules were added to the extruder feed material (cornstarch). A twin‐screw extruder was used to evaluate the effect of capsule level of addition (0–5%), barrel temperature (125–145 °C) and screw speed (145–175 r.p.m.) on extruder parameters (torque, die pressure, specific mechanical energy, residence time distribution) and extrudate properties [flavour retention, texture, colour, density, expansion, water absorption index, water solubility index (WSI)]. Capsule level had a significant effect on extrusion conditions, flavour retention and extrudate physical properties. Flavour retention increased with the increase in capsule level from 0% to 2.5%, reached a maximum value at capsule level of 2.5% and decreased when the capsule level increased from 2.5% to 5%. The die pressure, torque, expansion ratio, hardness and WSI exhibited the opposite effect with the presence of capsules.