Optimization of process parameters for cryogenic grinding of dried ginger

Abstract

The processing of spices requires additional care because they are sensitive to atmospheric parameters like temperature and light. The exposure to temperature during any of the processing stage may lead to their quality deterioration in terms of colour, volatile oil, volatile oil constituents, oleoresin content etc. The grinding of spices at cryogenic temperatures helps in retaining the heat sensitive components in the spices. This study envisages on the cryogenic grinding of dried ginger in order to optimize the grinding conditions, considering the important quality characteristics and compared the cryoground powder with the conventionally ground ginger. The physical properties which affect the grinding process directly or indirectly were also determined. The experiments on cryogenic grinding have been carried out for different feed rates and grinding temperature and the best combination was determined in terms of product quality as well as grinding characteristics. The optimized feed rate and temperature were 35 kg/h and -130±5 o C. The lower temperature in the grinding zone solidifies the moisture and oil components in the raw material and makes it brittle, which facilitates the grinding easy and faster thus leads to less energy consumption. The extreme cold condition prevents the volatile oil loss and lead to their higher retention. The comparison of cryoground powder with the powder obtained by conventional method has shown that cryogenic grinding prevented the essential oil and oleoresin loss of ginger considerably and retained its constituents. The colour of cryoground ginger powder was superior and the particle size was finer. The time of grinding and specific energy consumption was found lower in cryogenic grinding. The packaging studies on ginger powder showed that laminated aluminum foil is suitable for long term storage.