Optimization of pectin extraction from banana peels with citric acid by using response surface methodology

• Pectins were extracted from banana peels with citric acid.
• A central composite design was used, with 3 variables: pH, temperature, and time.
• Harsh temperature and pH enhanced yield, but decreased degree of methoxylation.
• The optimum conditions were defined as 87 °C, 160 min, pH 2.0.

A central composite design was used to determine effects of pH (2.0–4.5), extraction temperature (70–90 °C) and time (120–240 min) on the yield, degree of methoxylation (DM) and galacturonic acid content (GA) of pectins extracted from banana peels with citric acid. Changes in composition during the main steps of pectin extraction were followed by Fourier transform infrared (FTIR) spectroscopy. FTIR was also used to determine DM and GA of pectins. Harsh temperature and pH conditions enhanced the extraction yield, but decreased DM. GA presented a maximum value at 83 °C, 190 min, and pH 2.7. The yield of galacturonic acid (YGA), which took into account both the extraction yield and the pectin purity, was improved by higher temperature and lower pH values. The optimum extraction conditions, defined as those resulting in a maximum YGA while keeping DM at a minimum of 51%, were: 87 °C, 160 min, pH 2.0.