Effect of acid type and concentration on the yield, purity, and esterification degree of pectin extracted from durian rinds

Abstract

This current research aimed to investigate the effect of acid type and concentration on the yield, anhydrouronic acid content (AUA), and esterification degree (DE) of durian rind pectin by using three types of mineral acids (hydrochloric, sulphuric, and nitric acids) and three types of organic acids (citric, tartaric, and acetic acids) at five different concentration (0.0001, 0.001, 0.01, 0.1, and 1.0 M). The pectin yield (0.93–10.23%), AUA (41.64–80.58%), and DE (0.43–25.69%) were pronouncedly affected by the acid type and concentration during extraction. The results were affected by the strong-weak and protic nature of the acids. The pectin yield and DE decreased at higher acid concentrations (0.1, 1.0 M), with mineral acids giving a more significant effect. Additionally, mineral acids were more effective in extracting pectin with greater purity (AUA > 65%). In contrast, organic acids-extracted pectins had AUA < 65%, indicating poor purity. All pectins extracted were low-methoxyl pectin (LMP) with DE < 50%. Based on the results, mineral acids appeared to be more suitable for durian rind pectin extraction than organic acids due to their good yield and purity of LMP. The FTIR spectra showed that durian rind pectins were rich in homogalacturonan content. 0.001 M H2SO4 could be a promising extractant for commercial LMP production (DE = 20.11%) from durian rind, considering its satisfying yield (9.13%) and purity (AUA = 66.72%), in which the LMP could be a potential thickener and stabilizer for low-calorie foods and beverages.