Suitability of Inulin a Carrier for Spray-dried Green Honeybush Extracts Confirmed at ARC (Stellenbosch)

CAPTION : Prof. Dalene de Beer, Specialist Researcher (ARC) of the Plant Bioactives Group, Post-Harvest and Wine Technology Division, ARC Infruitec-Nietvoorbij with the Buchi Mini Spray Drier used for lab-scale spray-drying of extracts with various carriers to evaluate the retention of phenolic compounds during spray-drying honeybush tea.

The South African honeybush tea, prepared from various Cyclopia spp., is popular due to its sensory profile, as well as health-promoting benefits such as anti-cancer, anti-diabetic and phytoestrogen activities. Green honeybush, prepared without the traditional high-temperature “fermentation” step, produces a herbal tea with higher content of the polyphenols associated with these health-promoting benefits. Inulin, a prebiotic fibre, can be used as a suitable carrier for spray-dried green honeybush, thus enabling it to maintain its healthy properties. Spray-drying of a green Cyclopia subternata extract were tested on a lab-scale at the Agricultural Research Council (Infruitec campus, Stellenbosch) using the Buchi Mini SprayDryer B-290.

Debbie Shaw from Labotec spoke to Prof. Dalene de Beer, one of the principal researchers who collaborated on this study. The study evaluated the retention of phenolic compounds during spray-drying of an anti-diabetic green C. subternata extract and physiochemical characteristics of spray-dried powders using different carriers. Inulin, the low kilojoule alternative to corn syrup solids, used extensively in the food industry, is a naturally occurring carbohydrate present in more than 36000 species of plants. Microencapsulation of a green C. subternata extract with inulin by spray-drying was found to provide a stable low-kilojoule powder, suitable for formulation of single-serve beverage mixtures that can be used by diabetics.

Spray-drying using the Buchi B-290 is a speedy, time saving and gentle method to obtain powder directly from a solution, and in a single stage, manufacture microcapsules. As the extract solution is subjected to high temperature for a very short time, degradation due to heat is minimised. Microencapsulation of the honeybush extract with inulin was possible as the extract and inulin were shown to be compatible. The study also showed for the first time that benzophenones remained stable during spray-drying, while xanthones (mangiferin and isomangiferin) and other polyphenols were also stable. These compounds are linked to the health-promoting properties of honeybush, e.g. anti-cancer, anti-diabetic and phytoestrogen properties. More research is necessary to develop an anti-diabetic nutraceutical from green C. subternata extract. In future such extracts may possibly reduce dependence on traditional drugs to control and prevent type II diabetes.

In a follow-up study optimising the spray-drying conditions for a green rooibos extract, the Plant Bioactives Group also made use of the Buchi Dehumidifier B-296 for inlet air conditioning of the drying air. The Dehumidifier B-296 is the ideal accessory to condition the drying air in order to reduce the moisture content of the resulting powders. It ensures process stability and performance. An additional accessory called the Inert Loop B-295, can be used to work safely with organic solvents while spray-drying.