Extraction of pectin from grapefruit peel by using microwave technique

Grapefruit peel is an agricultural waste of grapefruit juice production and exists abundantly in the worldwide. One of the most important utilization way of grapefruit peels is production of pectin from the peels. The aim of this study was to investigate the effects of different extraction parameters on microwave assisted extraction (MAE) of pectin from grapefruit peel and to optimize the extraction conditions to obtain maximum yield and quality of pectin. Response surface methodology (RSM) was applied to model and optimize extraction conditions: time (7-25 min), temperature (85-125 °C) and water:peel ratio (7:1-13:1, wt:wt). The best fitting quadratic model was determined by regression and backward elimination. The optimum extraction conditions were found to be extraction time 20 min, temperature 98˚C and water:peel ratio 10:1 (wt:wt). The predicted highest pectin yield was found as 21.31 % at these conditions. Properties of MAE pectins, obtained at the optimum conditions, was also compared with conventional extracted pectin. As a result; higher pectin yield (21.09%), lighter color, higher viscosity (10 cP), lower ash content (2.8%), lower moisture content (2.01%), higher degree of esterification (85.76%) and galacturonic acid content (78.37%) were obtained in MAE than that of conventional extraction. The overall results showed that MAE technique is more efficient than conventional extraction.