Pectin hydrogels ph stability as affected by methacrylic grafting to low methoxyl pectin structure

Abstract

Pectin hydrogels have interesting; properties for pharmaceutical and food industries; nevertheless, pH sensitivity is one major drawback. The aim of this research was to evaluate the effect of methacrylate grafting on the structure of low methoxy citrus pectin (P), its gelling ability and pH sensitivity. 1% (w/v) P in phosphate buffer (pH 7) solution was mixed with methacrylic anhydride (1:2) (MP). FT-IR epectra (1737, 1617 and 949 cm-1) suggested an efficient grafting. MP gels had larger pores and were 2.46 times stronger than P gels. Gellation of 3% (w/v) pectin dispersions with 10 mM CaCl2 were photocrosslinked with 10% (w/v) Irgacure 2959 (265 nm UV). Bovine serum albumin (BSA) was incorporated into gels by diffusion and diffusion coefficient (Dm) was calculated. At pH 1.5, BSA release from P gels was complete after 1 h of exposure, instead, 5% of BSA was released from MP gels after 7 h of exposure and a Dm value of 2.08×10-7 ± 1.2 × 10-8 cm2·-s-1 was inferred. At neutral pH, P and MP gels dissolved into medium tested. Grafting pectins with methacrylic group s and combining photocrosslinking and ionic gelation allowed getting MP gels that overcome acidic pit sensitivity and improved the controlled retease capacity.