Optimisation of the drying temperature of star anise by low-temperature drying technique combined with microwave

Abstract

The purpose of this study is to optimise the drying temperature of star anise fruit using the low-temperature drying technique combined with microwaves on a heat pump combined with microwave drying system so that the drying time is shortest and the essential oil is highest. The raw materials used for the research are fresh anise harvested in Van Quan district, Lang Son province in August 2021. Experimentally, the effects of drying temperatures at the levels: 30, 35, 40, 45, 50 and 55^oC have been determined on drying time and essential oil content in dried anise fruit (moisture content of anise fruit after drying ≤10%). Research results have determined that the optimal temperature for drying anise fruits using the low-temperature drying technique combined with microwaves is 48.7±1^oC, drying time is 530±5 minutes, and the essential oil content in dried star anise fruits reaches 9.9 ml/100 g. These experimental research results have provided a scientific basis for the essential oil content of Lang Son star anise fruit, and technical parameters for drying star anise fruit using lowtemperature drying techniques combined with microwaves, helping the production and processing of anise on an industrial scale, increasing the value of goods and serving export purposes.