title: Effect of heat treatment of rennet skim milk induced coagulation on the rheological properties and molecular structure determined by synchronous fluorescence spectroscopy and turbiscan.
abstract: Heat treatment applied to milk induces denaturation of whey proteins, leading to a complex mixture of whey protein and whey protein coated casein micelles. The present paper investigates the effects of heat treatment (60 and 80°C during 20min) and rennet-induced coagulation temperature (30 and 40°C) determined by rheology, synchronous fluorescence spectroscopy (SFS) and turbiscan measurements. The gelation times determined by rheology and SFS increased with the increase of heat treatment applied to milk. The rise in temperature induced a decrease in the maximum curd firming rate and an increase in the viscosity of the investigated milk samples. The principal component analysis (PCA) applied, separately, to the SF and turbiscan spectra showed a clear discrimination between: (i) raw milks and heated milks; and (ii) milks renneted at 30°C from those renneted at 40°C. The results showed the ability of SFS as a rapid and non-destructive technique for the: (i) monitoring network structure and molecular interaction during the coagulation process; and (ii) determination of gelation time of rennet-induced coagulation of studied milk samples.
authors.affiliation: Gembloux Agro-Bio Tech, University of Liège, Laboratory of Food Science and Formulation, Passage des Déportés, 2, B-5030 Gembloux, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Blecker
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Habib-Jiwan
authors.forename: Romdhane
authors.initials: R
authors.lastname: Karoui
mesh_terms: D000818:Animals; D012085:Chymosin / Q000737:chemistry*; D005511:Food Handling; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D011487:Protein Conformation; D055550:Protein Stability; D012212:Rheology; D013050:Spectrometry, Fluorescence / Q000379:methods*; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D000067816:Whey Proteins; C025350:rennet; D012085:Chymosin