title: Determining the gelation temperature of β-lactoglobulin using in situ microscopic imaging.
abstract: Evolution of microstructure during heat-induced gelation of β-lactoglobulin (β-LG) was investigated in situ using confocal laser scanning microscopy at various gel-preparation conditions: pH=2, 5, and 7; protein content=5, 10, and 15%; and salt (NaCl) content=0, 0.1, and 0.3 M. The number and area of evolving β-LG clusters were observed as a function of time and temperature and the data were fitted to a log-normal model and sigmoid model, respectively. The gelation temperature (Tgel) of the β-LG system was determined from both the number (Tgel/N) and total area (Tgel/A) of β-LG clusters versus temperature data. The range of Tgel/N and Tgel/A values for all the cases was 68 to 87°C. The effect of pH was the most dominant on Tgel/N and Tgel/A, whereas the effects of β-LG and salt contents were also statistically significant. Therefore, the combined effect of protein concentration, pH, and salt content is critical to determine the overall gel microstructure and Tgel. The Tgel/N and Tgel/A generally agreed well with Tgel determined by dynamic rheometry (Tgel/R). The correlations between Tgel/N and Tgel/A versus Tgel/R were 0.85 and 0.72, respectively. In addition, Tgel/N and Tgel/A values compared well with Tgel/R values reported in the literature. Based on these results, Tgel/N determined via in situ microscopy appears to be a fairly good representative of the traditionally measured gelation temperature, Tgel/R.
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Gwanak-Gu, Seoul 151-921, Republic of Korea.
authors.forename: Hee-Dong
authors.initials: HD
authors.lastname: Woo
authors.forename: Tae-Wha
authors.initials: TW
authors.lastname: Moon
authors.forename: Sundaram
authors.initials: S
authors.lastname: Gunasekaran
authors.forename: Sanghoon
authors.initials: S
authors.lastname: Ko
mesh_terms: D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000737:chemistry* / Q000648:ultrastructure; D018613:Microscopy, Confocal; D013696:Temperature
chemical_list: D005782:Gels; D007782:Lactoglobulins
keywords: confocal laser scanning microscopy; gelation temperature; microstructure; β-lactoglobulin