Optimization and quality evaluation of extracting lemon pectin by oxalic acid

Abstract

Objective： This study aimed to improve the yield and gelling property of lemon pectin. Methods: Oxalic acid was used to extract pectin from lemon residue. The factors of optimal ratio of solid-liquid, pH, extraction temperature and extraction time were optimized through single factor experiments and orthogonal experiments. The purity, degree of esterification and rheological properties of the extracted lemon pectin were analyzed. The differences of gelling property between the extracted lemon pectin and two kinds of commercial high methoxyl pectins (HMP-1, HMP-2) were compared. Results: The results showed that the yield of pectin extract was 22.83%, with total galacturonic acid of 76.06% and degree of esterification of 75.94%, when the ratio of solid-liquid was 1∶20 （g/mL）, extracting pectin at pH 2.2 and 95 ℃ for 75 min. The viscosity of the extracted lemon pectin was higher than HMP-1 and HMP-2. The calcium sensitivity was between HMP-1 and HMP-2, and the temperature sensitivity was similar to HMP-2. The sol-gel transformation of the extracted lemon pectin was found at 76.55 ℃ in the calcium ion environment. Conclusion: Lemon pectin extracted by oxalic acid has good rheological and gel properties, and can be potentially used as a stabilizer in acidic milk drinks.

Keywords

• lemon pectin
• oxalic acid extraction
• viscoelasticity
• calcium sensitivity
• gelation