Texture Analysis of Milk Protein Gels using Digital Image Analysis

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 through the addition of glucono-delta-lactone (GDL). Depending on its concentration and temperature, hydrolysis speed of GDL can affect the grade of hardness and elasticity of the formed gel. This study evaluated the effect on the formation and structure of protein gels induced by different relations of GDL through analysis of digital images obtained in an inverted conventional microscope and a confocal microscope. The entropy, smoothness and variance decrease with the added GDL quantity, but the uniformity increases. Results confirm that the texture depends on gelification speed, which is directly related to the amount of added GDL. This digital image analysis technique using conventional or confocal microscopy is, therefore, suitable and very useful for the texture analysis of acid gels formed by different GDL/NaCAS rates.