EFFECT OF DRYING ON PECTIN MADE FROM LIME AND LEMON POMACE

ABSTRACTSamples of approximately 350 kg of commercially leached lime and lemon peel were dried in a pilot plant direct fired rotary dryer with inlet air temperatures of 370, 425 and 535°C, yielding dried pectin pomace with a final moisture content of 15–20, 8–12 and 3–7%, respectively. Pectin was extracted from laboratory leached, undried peel, each of the above dried samples, and commercially leached and dried samples. From fresh peel leached in the laboratory, we found a 65.6 and 55.9% yield of 150 grade pectin on a dry weight basis for lime and lemon, respectively. Drying lemon peel to final moistures of 15–20, 8–12 and 3–7% resulted in yields of 41.1, 41.1 and 25%, respectively. Dehydration of lime peel to 3–7% moisture decreased the yield to 37%. Similar losses were found in commercially dried pectin pomace. A separate experiment was conducted to evaluate the effect of drying on pectin yield from fresh, unleached lemon peel. Unleached peel was successfully dried by mixing 1 part unleached peel with 2.5 parts of dry leached peel. There was a slight loss in the percentage yield of pectin 23.3 and 21.8, but not much change in the jelly grade 230 and 232 between the dry leached and dry unleached peel, respectively.