Optimization of microwave extraction metod of pectin from lemon and orange peels and characterization of producted pectin

In this study, optimization of pectin production by microwave assisted extraction (MAE) from lemon and orange peel, which are juice industry residues, was investigated. Some properties of obtained pectins were compared to pectins extracted by traditional acid extraction (TAE). Yield, degree of esterification (DE) and galacturonic acid (Gal) content of pectins produced under different conditions were determined. MAE conditions were determined with response surface method (RSM) and central composite design (CCD) was used. In the study, citric acid solution with a pH of 1.5, 2.0, 2.5 for orange peels and hydrochloric acid solution with a pH of 1.5, 2.5, 3.5 for lemon peels were used. Microwave power 120, 360, 600 W and irridation time 5, 10, 15 min were selected. In addition, pectins produced under optimal conditions were used in model gel preparation, texture and color properties of gels were studied. The optimum conditions for the maximum yield (19.18%), DE (61.52%), and Gal (45.21 g/100g) of lemon peel pectin were obtained at pH 1.5, microwave power of 600 W and irradiation time of 9 min. The optimum conditions for the maximum yield (19.05%), DE (69.12%), and Gal (31.55 g/100g) of orange peel pectin were obtained at pH 1.5, microwave power of 600 W and irradiation time of 15 min. FTIR analysis was performed and the structures of pectins extracted with MAE, TAE and commercial orange pectin were found similar. It was determined that the model gel formed from pectins produced under optimal conditions with MAE has better textural properties than the model gel formed from pectin produced under the condition (pH 1.5) where the highest efficiency is achieved with TAE. It was found that the textural properties of model gels produced from lemon at pH 3.2 obtained by MAE were better than those of gels produced from orange pectin. MAE is recommended for use in industry because of providing high yields and shorter extraction times.