Development of a high methoxyl-pectin edible film for retention of L-(+)-ascorbic acid.

PEREZ, CAROLINA DAIANA; DE'NOBILI, MARIA DOLORES; GERSCHENSON, LIA NOEMI; ROJAS, ANA M.

Honolulu, Hawaii

Congreso; Pacifichem 2010 -; 2010

American Chemical Society, Canadian Society for Chemistry, Chemical Society of Japan, New Zealand Institute of Chemistry, Royal Australian Chemical Institute, Korean Chemical Society and Chinese Chemical Society.

An edible film to carry L-(+)-ascorbic acid (AA) was formulated for natural antioxidant food protection. Considering previous works where films based on the ?rigid? structure of gellan (deacylated form) or on a mixture of acylated-deacylated (more ?disordered?) gellan were used for network development, pectin was herein chosen by considering that the alternating presence of ?disorder? (hairy) regions together with ordered (homogalacturonan) ones, could sufficiently immobilize water for better AA retention and lower browning. High methoxyl (DM = 73%) pectin (HMP) of commercial origin was firstly investigated. AA stability and browning were studied during film storage at 33.3, 57.7 or 75.2% RH and 25 ºC, having been found again their dependence on water mobility determined through 1H-NMR analysis, as well as the correlation between browning development and AA degradation. Network characteristics and glycerol (plasticizer) interactions were analyzed through X-ray diffraction and FTIR, as well as through uniaxial tensile assay. From all results obtained it was hypothesized that browning development in solid-like systems may be directly related to the water molecules more closely adsorbed on the hydroxyl-polymeric (active) surfaces. HMP-film microstructure produced the best immobilization of water molecules excepting at 75.2% RH, where it showed lower AA stability than acylated-deacylated gellan film. It is suggested that disordered (hairy) amorphous regions (14% molar base) of this HMP network may not be adequately counterbalanced by the more transient junction zones constituted by alternating hydrophilic (water) and hydrophobic (methyl ester) interactions, also disturbed by glycerol molecules, for accomplishing enough water immobilization in the whole network at 75.2% RH. The distribution pattern of hairy regions and methyl esterification may be also a key factor in the microstructural characteristics (and water immobilization) of film networks obtained from pectins.