Use of Evaporative Water Cooling (EWC) in grinding chili

Size reduction is one of the steps in processes where the raw materials are converted into final products. When considering spices, size reduction must be performed carefully because of the loss of aroma due to temperature increase during milling. These problems are encountered with conventional grinding of chili. Therefore, grinding under reduced temperature by means of water vapor was tested as a novel application. A pin mill with 5hp motor was used to grind chili with water mixing during milling in which water is considered as the coolant. The temperature of the conventionally ground and evaporative water cooled ground chili were 58 ± 2.65 ⁰C and 36 ± 1.5 ⁰C respectively and the corresponding amounts of heat removed by water vapor were 29.33 kJ and 186.50 kJ. The moisture content of conventionally ground chili and evaporative water cooled ground chili with water spraying were 9.06 ± 0.41 and 9.65 ± 0.23 percent on wet basis and the corresponding color values were 49.19 ± 0.99 (L*), 17.35 ± 1.62 (a*), 23.38 ± 1.29 (b*) and 47.52 ± 1.74 (L*), 18.38 ± 0.14 (a*),26.93 ± 0.68 (b*). Retention of capsicum oleoresin in two grinding methods; conventional and EWC are 0.0217± 1.27 and 0.0129 ± 1.00 mg/ml respectively. The results proved that the use of water vapor is applicable as the coolant in size reduction confirming reducing temperature rise during grinding, controlling the color weakening after grinding, preferable final moisture content with higher oleoresin retention than that of conventional grinding.