Sensory and instrumental textural characteristics of acid milk gels

Abstract

Texture is a group of physical properties that derives from the structure of food and the way its constituent ingredients interact. Understanding the textural properties of a food product can be achieved by examination of its rheological behaviour and microstructure, so long as they can be related to the perception of texture by consumers. In this research, skim milks acidified with glucono-δ-lactone (GDL) and representing a range of textures were assessed using descriptive sensory analysis (non-oral) and instrumental techniques to investigate the correlation between the two types of data. All sensory attributes could be used to discriminate between the gel samples. Heat treatment of the milks prior to acidification appears to be the main factor producing the textural differences between acid milk gels, with solids content (10–20%) as a secondary factor. Sensory differences were in agreement with differences revealed using instrumental techniques. Confocal laser scanning micrographs supported the sensory results and showed that gels made from unheated milk had large protein clusters with big pores, while gels from heated milks had a more defined, branched structure with smaller pores. The effect of solids content on the microstructure of the gels could be seen mostly by the degree of interconnectivity between clusters of protein. Correlation analysis revealed that, with the exception of surface water (whey separation) and smoothness, all other sensory descriptors could be satisfactorily modelled with the instrumental information available, with canonical R2 above 85%.