Structural analysis of sodium caseinate acid gels by image digital processing

COSTA, JUAN PABLO; CASTELLINI, HORACIO; RISSO, PATRICIA; RIQUELME, BIBIANA

Biocell

Instituto de Histología y Embriología ?Dr. Mario H. Burgos? (IHEM-CONICET)

Año: 2010 vol. 34

Sodium caseinate (NaCAS) is a very useful ingredient in food industry because of its nutritional and functional properties. Acidification produces a gel structure as a result of the dissociation and aggregation of caseinic fractions. Formation of these protein gels can be made by the slow reduction of pH, by the addition of gluconodelta-lactone (GDL). Depending on its concentration and temperature, hydrolisis speed of GDL can affect the grade of hardness and elasticity of the formed gel. In this work, is assessed the formation and structure of NaCAS gels (3%) induced by different GDL/NaCAS ratio (0,35; 0,5; 0,7 y 1,0) at 35°C, by means of a digital processing of the images obtained in an inverted opticalmicroscope with an adapted digital camera (Canon Powershot A640). Images were normalized to a grey scale before transformation and then turned to an entire numerical format of 8 bits. In its numerical representation, the Shannon entropy, softness, gray scale variance and uniformity were studied as an estimation of the texture of the images obtained. The entropy, softness and variance decrease with the added GDL quantity, but the uniformity increases. Results confirm that texture depends on gelification speed, which is directly related to the amount of added GDL. This image digital analysis technique using a conventional microscopy is, therefore, suitable and very useful for the texture analysis of NaCAS acid gels formed by different GDL ratios.