Microwave-assisted extraction of pectin from pineapple peel

Abstract

Pineapple peel has the potential to become one of the sources for pectin production due to the high content of pectin in its dietary fibre composition. Pectin is used as food thickener, emulsifier, stabiliser and gelling agent in food industry. The conventional extraction process with long operating hours at high temperature has been identified to cause thermal degradation of pectin molecules. Microwave technology application in pectin extraction has shown high potential to expedite the extraction process and produce higher yield. Therefore, this research was intended to investigate the effect of various factors (irradiation time, pH, temperature, microwave power and solid-to-solvent (S/S) ratio) of microwave-assisted extraction (MAE) on the pineapple peel pectin (PPP) yield. Pectin extracted was then analysed for its dry weight yield percentage and degree of esterification (DE). It was shown that the pectin yield was significantly affected by pH, S/S ratio and microwave power. From this study, no significant effect of irradiation time was observed from 2.5 min until 20 min to the yield of pectin, thus longer time of extraction is not necessary in MAE. The highest yield of PPP obtained was in the range of 2.27 to 2.79% w/w at pH 2.0 and S/S ratio of 1:20. The result of DE (63.93 ± 0.30%) indicated that PPP is categorized in high methoxyl pectin (HMP) pectin type because the DE values were greater than 50%. This study showed that MAE is highly potential for extraction of high yield of PPP.