Kinetics of the renneting reaction followed by measurement of turbidity as a function of wavelength

Abstract

In order to describe the kinetics of rennet coagulation, measurements of turbidity as a function of wavelength were used to determine the weight-average degree of polymerization, x¯w, during renneting of milk at three different concentrations of enzyme and three concentrations of casein, including the normal casein concentration of milk. The change of x¯w as a function of time was described using Von Smoluchowski's equation, testing a number of expressions for the aggregation rate constant, kij. The best description was achieved when kij was taken as a function of an energy barrier against aggregation that was diminished by the proteolysis of κ-casein. The initial value of the energy barrier partly depended on the casein concentration, and had a value >25 kBT at normal casein concentration, where kB is Boltzmann's constant and T the absolute temperature. When the proteolysis of κ-casein was complete, the energy barrier was reduced to 11 kBT and was independent of casein concentration.

Non-destructive control in cheese processing: Modelling texture evolution in the milk curdling phase by laser backscattering imaging

“…Within image analysis procedures, the laser-backscattering imaging characterizes the extinction of light transmittance across a changing magnitude measured in a given matrix. This principle has already been used to monitoring curdling process but in a classical optical turbidimetry approach (Lomholt et al, 1998) which presented limitations such as a dilute sample of milk is necessary. Laser-backscattering imaging follows that principle, but applying a more powerful light source, imaging analysis and data mining techniques for studding the diffraction patterns generated because milk matrix-light interactions.…”

Characterisation of whey drainage kinetics during soft cheese manufacture in relation with the physicochemical and technological factors, pH at renneting, casein concentration and ionic strength of milk

“…The caseinomacropeptide (CMP) part of κ casein and also the mineral equilibria between casein micelles and the diffusible phase play a prominent part in micelle stability [8,12,13]. The release of CMP from κ casein by rennet, and the solubilisation of the colloidal calcium phosphate by starter acidification of milk [5,6,15,18] allow a decrease of the stabilizing energetic barrier between casein micelles [21], allowing thereby a closer contact between micelles leading to the formation of a solid network entrapping the aqueous phase.…”

Hydrolysis of β-casein by the cell-envelope-located PI-type protease of Lactococcus lactis: A modelling approach

“…The role of micelles on hydrolysis has also been discussed in various studies on hydrolysis of k-casein by chymosin (van Hooydonk et al, 1984;Hyslop, 2003;Lomholt & Qvist, 1997;Lomholt et al, 1998;Saputra et al, 1994). In such cases, k-casein was present in micelles, complex structures containing all types of caseins.…”