The production of a free flowing fruit juice powder by spray drying requires an appropriate carrier. Materials such as maltodextrins are commercially used as a drying aid because of their higher glass transition temperature (Tg) but the juice powder is not pure, potentially has decreased nutrition and organoleptic properties. Alternatively, fibre-rich by-products from fruit-vegetable processing might be suitable as a drying support. Carrot fibre was prepared from the fibre by-product of juice extraction by freeze drying and milling. It was compared with maltodextrin as a carrier for the spray drying of fructose and apple juice with added malic acid.

The Tg (from a DCS) of carrot fibre mixtures was found to be lower (80-93°C) than corresponding maltodextrin mixtures (114-125°C) but the powder was more easily formed and less sticky with carrot fibre. Increasing concentrations of malic acid in mixtures of fructose + carrot fibre resulted in lower Tg. Spray drying of apple juice concentrate (75% total solids) was possible with 30% added carrot fibre powder but at least 50% maltodextrin was required to produce a powder. The addition of carrot fibre to 50% maltodextrin + apple juice concentrate did not improve the yields. Using 50% carrier the yield when using carrot fibre was 65% but only 7% when using maltodextrin. The results indicate that spray drying of fruit juice and carrot fibre would be feasible in a larger drying, but they cast doubt on the use of Tg as an indicator for ease of drying.