Powder is an important form of nutraceutical and food product transport. The reasons for having product in powder form are predominantly for two reasons: (i) to extend the shelf-life (drying effect deactivates micro-organisms’ metabolisms) thus preserving product quality, and (ii) reducing product bulkiness hence enabling more economical handling along the supply chain. Powder formation is conventionally done via spray dryer where the bio-active ingredients begin as solutions. Pressure, air-atomiser or rotary nozzles inside the spray dryers turn solutions into tiny droplets. Tiny droplets have high surface area per unit volume thus enabling high mass and high heat transfers for very short drying time in the order of seconds. As drying time is very short before bioactive compounds leave the spray dryer, the thermal degradation (as a result of high air drying temperature) of bioactive compound is actually negligible (akin to running a finger through a candle-lit flame). Product that is dried fast also reduces the oxidation rate of nutraceutical and food products.
The standard design of spray dryers used in Malaysia’s nutraceutical and food sector tend to experience 20-30% loss of bio-active ingredients through powder elutriation via exhaust air exit duct and/or excessive powder sticking onto the chamber walls. Powder sticking onto the chamber walls is usually washed off with water at the end of a batch process cycle and collected as a solution, only to be spray dried in the next batch. Such practice decreases the quality of bio-active ingredients due to excessive processing and prolonged exposure to temperature in excess of ambient conditions. The overall operating cost also increases due to the energy needed for repeated water vaporisation of the recycled bio-active ingredients.
There is a however scope for improvement for spray dryer performance in Malaysia to reduce the loss to around ~5% or less. This will however require the understanding of the processing nuances: (i) between counter-current and/or co-current processes, (ii) a combination of various gas-solid separation techniques, (iii) acoustic recovery, and (iv) controlling for solid concentrations.
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