Characterizing the gloss properties of hydrocolloid films

Hydrocolloid films were prepared by two methods, namely dehydration of thin layers of gels and of gum solutions. Gelatin gel films containing greater amounts of dry matter than all other prepared films provided by far the highest gloss values. Increase in gelatin concentration in the gels resulted in an increase in the mean gloss of the dry films in a linear fashion. Roughness measurements and scanning electron microscope (SEM) micrographs indicated that the gelatin films possessed very smooth surfaces. Similar to gelatin, increase in concentration of gellan resulted in an increase in gloss of resultant films. In direct contrast, mean gloss of both agar and agarose gel films decreased with increasing gel concentration. These trends may be due to the increase in roughness of films with increasing gel concentration, which in the case of agar was also noticeable in the SEM micrographs. Xanthan films provided the most glossy appearance of those prepared by drying of gum solutions, followed closely by alginate. Both exhibited the same trend of mean gloss increasing with gum concentration, similar to gelatin. In both instances, this behaviour could not be related to roughness, which also increased with gum concentration.