POLY(VINYL ALCOHOL)-PECTIN CRYOGELS CONTAINING DYES AS TRACERS OF FOOD SPOILAGE

PIÑUEL LUCRECIA; MARTINEZ YANINA; BRECCIA JAVIER D.; CASTRO GUILLERMO R.

Congreso; 4th International Congress on Bioprocesses in Food Industries; 2010

Food safety is a challenge for increasing food trading in our global world. Successful application of international laws requires trustworthy tracers of food spoilage which must be easy to handle and cheap. Potential tracers could be used in quality control, amongst them surveillance of cool chains, changes of pH, detection of specific products of food degradation and foodborne pathogens. A common symptom in some food spoilage is a change of pH. Tracers of pH values can be used in "food labels" consisting on pH-indicator dyes entrapped into the polymer gels is a promising technology to monitoring food quality during transportation, distribution and storage. In the present work, combined poly(vinyl alcohol) (PVA) with pectin biopolymer were used to develop cryo-matrixes for immobilization of acid-base indicators. The matrix synthesis were developed by freeze-thawing cycles, to produce cryogel films with different composition and properties. Commercially available pH-dyes, a cationic dye (neutral red) and three anionic dyes (phenol red, bromothymol blue and indigo carmine) were selected on the basis of their different molecular structure and physico-chemical features. Cryogels (13.5 mg, and approximately 40 mm3) were incubated in 1.5 ml aqueous dyes solutions (0.015 % w/v) at 25 °C. Neutral red and phenol red were entrapped into the matrix at a reason of 85 and 30 mg dye per g of matrix respectively; while in the other dyes were found concentrations lower than 1.0 mg per g matrix. The release of neutral red from the matrix at 30 °C after 3 washing steps was only 0.11 % vs. 9.6 % for phenol red under the same experimental conditions. Increasing neutral red dye concentrations were placed in contact with the films and binding data fits non-linear Langmuir adsorption isotherm (R2 = 0.99). Binding capacity was 3.01 (± 0.01) x 10-5 mol of neutral red/g matrix and the binding constant was 3.3 (± 0.3) mM. The release of neutral red was undetectable at low temperature (5 °C) and was slightly raised with its increment. But increasing ionic strength showed a significant leakage from the matrix. These data are strongly suggesting electrostatic interactions between cationic neutral red dye and the negatively charged patches of pectin-PVA matrix, that might be the driving forces of dye binding.