Optimization of method for extraction of pectin from apple pomace

Abstract

Method for extraction of pectin from apple pomace-waste generated from apple juice processing industries for commercial adoption was optimized. Fresh pomace yielded 13.3% pectin on dry weight basis (dwb). Blanching of pomace (boiling at 95^oC for 5 minutes followed by cooling) and drying (at 50±2^oC) was found to be a necessary pretreatment before pectin extraction. Among different methods of pectin extraction and precipitation, extraction of apple pomace by using 0.05N HCl at 95^oC for one hour followed by precipitation in 95% ethanol was found optimum with pectin yield of 10.5% on dry weight basis. The resultant pectin was characterized by 59.1% anhydrogalacturonic acid content, 71.2% degree of esterification (DE) and 110 jelly grade. Water and Ammonium Oxalate-oxalic acid extractions on the other hand yielded very low 3.4 and 8.0% pectin, respectively. Sequential combination extractions, viz. water and acid or water and ammonium oxalate-oxalic acid though yielded slightly higher amount of pectin yet the addition of a unit operation along with comparatively low increase in pectin yield was found to limit their use for pectin extraction. Among precipitation methods, precipitation of extract in 95% ethanol resulted in higher pectin yield with comparable quality of the pectin obtained by using aluminium chloride precipitation. The cost of production of pectin calculated on the basis of input used and after adding labour and processing charges worked out to be Rs. 808.30 per kg. The standardized method of pectin extraction and precipitation can be used commercially by the processing industries for utilization of apple pomace.