A feasibility study on the drying of fig extract (The relation between the key operating parameters of a pilot scale spray dryer and product specifications)

In this study, fig extract with 14% total soluble solids (TSS) prepared from dry figs, supplemented with 50% of TSS by a mixture of maltodextrin (MD) : pectin(P) (in ratios of 70:0, 56:14, and 49:21 g/ kg feed) as drying aid, was dried in a pilot scale two fluid nozzle spray dryer operating with a mixed air/feed flow system. A total of 27 experiments were conducted (in triplicate) at inlet air temperatures of 150, 170, and 190°C, and air flow rates 400, 440, and 480 m3/h, with the feed rate, feed temperature, and compressed air flow for the atomizer kept constant. Analysis of the data revealed that due to the high amount of glucose and fructose in extract (almost 8 g per 100 g of extract) resulting in low Tg, no measurable quantity of suitable powder could be obtained if amount of the drying aid is less than 50% of the TSS (i.e. 70g drying aid per kg feed with 14% TSS). The moisture content of the powder was affected by the inlet or outlet air temperatures, air flow rate and MD:P ratio. Powder bulk density decreased from 0.38 to 0.44 g/cm3 as inlet air temperature decreased from 150 to 190oC whereas the MD:P ratio and air flow rate were not as effective in changing powder bulk density. The best powders were obtained when the inlet air temperature was 170oC

کلیدواژه ها:

Fig ، spray drying ، drying aid ، powder properties