Structure characterisation by means of rheological and NMR experiments as a first necessary approach to study the L-(+)-ascorbic acid diffusion from pectin and pectin/alginate films to agar hydrogels that mimic food materials.

DE'NOBILI M. D.; ROJAS AM; ABRAMI M.; LAPASIN R.; GRASSI M.

JOURNAL OF FOOD ENGINEERING

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015 vol. 165 p. 82 - 92

0260-8774

Pectin (P) and pectin-alginate (PAL) edible films, developed for antioxidant preservation, were placed on agar cylinders, mimicking food materials, in order to understand the release of L-(+)-ascorbic acid (AA) from the films. To improve the release properties of polymeric systems, it is crucial to describe and understand the macro- and microscopic properties of the matrices. Rheological studies performed within linear and non linear frames permitted to select, among different polymer concentrations (0.50?2.00% w/w), a 2.00% w/w agar gel as food model as this system shows the higher pure elastic contribution. Rheological and Low Field NMR (LFNMR) tests performed on 0.50?2.00% w/w agar gels as well as on P- and PAL-films after exposure (up to 6 hours) to 2.00%-agar gels, showed that in spite of the higher glycerol (plasticizer) content, P-network is characterized by more numerous calcium-junction zones than PAL-matrix. The determined average network mesh size ( ) for both of P- and PAL-films did not significantly change during 6 h of contact with 2.00%-agar gel. However, due to a higher swelling degree, PAL-film leads to higher value and water mobility inside the polymeric network. These results are of paramount importance as ? ? is the main parameter affecting the release kinetics of AA from film networks to agar gels and also the diffusion of AA into the agar gel or food.