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Orange terpenes, carvacrol and tocopherol were used as model substances for flavours, essential oils and lipophilic liquid (bio)-active ingredients (AI). They were encapsulated via a batch mixing process in various carbohydrate matrices containing maltodextrin and sucrose. Plasticizing properties of the AIs, independently from their concentration (4.5–8.8%), on the matrices were not obtained. Furthermore the AIs did not affect the solid state properties, especially the crystalline content, of the carbohydrate matrix. An AI retention between 6% and 100% correlated inversely with the vapour pressure of the pure AI. At a mixing time of 5 min a vapour pressure of higher than 70 kPa led to a almost completely loss of the AI. The AI retention and the solid state of the matrices were not affected by applying different cooling conditions. These results can be used to adjust the parameters of an extrusion process to receive high AI retention.

Until now extrusion is not applied for pharmaceutical encapsulation processes, whereas extrusion is widely used for encapsulation of flavours within food applications. Based on previous mixing studies, a hot melt counter-rotating extrusion process for encapsulation of liquid active pharmaceutical ingredients (APIs) was investigated. The mixing ratio of maltodextrin to sucrose as matrix material was adapted in first extrusion trials. Then the number of die holes was investigated to decrease expansion and agglutination of extrudates to a minimum. At a screw speed of 180 min−1 the product temperature was decreased below 142 °C, resulting in extrudates of cylindrical shape with a crystalline content of 9–16%. Volatile orange terpenes and the nonvolatile α-tocopherol were chosen as model APIs. Design of experiments were performed to investigate the influences of barrel temperature, powder feed rate, and API content on the API retentions. A maximum of 9.2% α-tocopherol was encapsulated, while the orange terpene encapsulation rate decreased to 6.0% due to evaporation after leaving the die. During 12 weeks of storage re-crystallization of sucrose occurred; however, the encapsulated orange terpene amount remained unchanged.

Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients’ glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.