Evaporation as a Method for Obtaining Plant Concentrates

Abstract

Low-pressure vacuum evaporation is an effective way to obtain dry concentrates. However, some factors may affect its efficiency and speed. This article introduces the effect of technological factors on the evaporation process in a rotary evaporator. The research objective was to select the optimal mode to obtain concentrates and extracts from plant materials. The experimental studies involved standard research methods and a BUCHI Rotavapor laboratory rotary evaporator (BUCHI, Switzerland). The research featured a water-alcohol extract of wild blueberries and an enzymatic hydrolysate of grain sorghum (durra), obtained by biotechnological treatment with amylolytic enzyme preparations. The optimal evaporation mode included the following values: the volume of the evaporation flask was 1 L; the wall thickness of the flask was 1.8 mm; the angle of inclination was 25°; the rotation speed was 280 rpm; the temperature heating bath was 50–60°C; the steam temperature in the evaporator was 30–40°C. For condensation, the temperature of the refrigerant in the condenser was 10–20°C. The experiment yielded a concentrate of blue-violet blueberries with 70–72% solids. The content of polyphenolic compounds was 1.86 times as high as in the original water-alcohol extract while that of anthocyanins was 1.4 times as high. The enzymatic hydrolysate of grain sorghum yielded a condensed sugar syrup with 78–80% solids and 91–92% reducing sugars in terms of glucose equivalent. The research provided optimal modes of evaporation for extracts and enzymatic hydrolysates from plant raw materials in a rotary evaporator. The plant concentrates had a high content of solids and maintained the sensory properties of the raw material.