Influence of refrigerated adsorption dehumidified drying towards the retention of phenolic, flavonoid and antioxidant properties of small cardamom (Elettaria cardamomum): Performance comparison with convection, solar and fluidized bed dryer

Abstract

Cardamom, known by the botanical name Elettaria cardamomum, is a well-known spice which is increasingly used in the field of cosmetics and industrial applications in the form of dried powders and oil. However, usage of cardamom is limited by its moisture content (around 80% in wet basis) and for effective oil extraction and usage, cardamom needs to be dried to a moisture content of less than 10% (in wet basis) prior to usage. Solar driers are traditionally used for cardamom drying and fluidized bed driers and tray driers are also used for industrial-level large-scale drying. During drying, loss of bioactive like phenolics, flavonoids and antioxidants become inevitable. Under such a scenario, this study explores the performance of low-temperature, low-humidity dryers namely refrigeration adsorption dehumidified dryers (RADD), designed and developed by CSIR-NIIST, for retention of bioactives during drying. To assess and compare the RADD with traditional dryers, experiments were performed in a tray dryer, solar dryer and fluidized bed dryer and the results are compared with RADD. It was found that cardamom dried in RADD retained around 70–75% of total phenolic, flavonoid and anti-oxidant compounds, whereas retention in other conventional drying methods was in the range 35–60% only. Advanced analysis such as SEM, FTIR and GC-MS was also done to evaluate the morphological changes, functional group changes and difference in essential oil composition due to different drying methods. Considering the overall result it has been proved that RADD has several advantages over the conventional dryers (due to low temperature and low humidity inside RADD) and thus can be used for drying cardamom which will promise good quality cardamom with maximum retention or preservation of all the bioactives. Thus, RADD is found to be a promising alternative for fluidized bed dryers and also it performs better than other conventional drying methods.