Study on grinding of black pepper and effect of low feed temperature on product quality

Abstract

The effect of feed temperature on grinding of black pepper (Piper nigrum) in a hammer millwas studied at Coimbatore (Tamil Nadu). Variation in temperature was attained by keepingblack pepper in a refrigerator maintained at 4°C (low temperature sample) to attain a feedtemperature of 7.9 to 21.2°C and by mixing with dry ice at different ratios (ultra lowtemperature sample) to get temperatures from -3.33 to 12.86°C. On the basis of volatile oilcontent, oleoresin, piperine and volatile components, a feed temperature of -3.33 to -1.25°Cwas optimized.  The volatile oil content of the product indicated an increase of about 17%retention of oil for ultra low temperature and 15% for low temperature compared to theambient condition (control). Gas chromatographic analysis of the oil showed higher retentionof monoterpenes under ultra low temperature condition compared to ambient and lowtemperature conditions of grinding. An increase of 1% to 3% moisture was observed for theultra low temperature sample for a feed temperature of -3.33 to -1.25°C, which helped toincrease 2% to 3% oleoresin yield. The volume surface mean diameter of black pepper powdershowed an increasing trend of 0.15 mm to 0.18 mm with an increase in feed temperature from-3.33 to 12.86°C for ultra low temperature sample. The specific energy consumption variedfrom 24.79 to 46.62 kJ(kg°C)–1 with increase in grinding temperature.