Infusion pasteurization of milk: Influence on the viscosity and casein micelle size

Milk is normally heat treated in order to obtain safe dairy products with an elongated shelf life as compared to raw milk. New methods, such as infusion pasteurization, for heat treatment of milk are currently being developed. This provides an opportunity for treating milk in a manner that creates different or improved functional properties compared to traditional indirect pasteurization. Infusion pasteurization has a time-temperature profile characterized by very rapid heating to relatively high temperatures, short holding times and very rapid cooling, which may lead to products with different properties as compared to products subjected to the standard low pasteurization at 72°C for 15s. Infusion pasteurization was performed on raw milk with two different holding times (0.1s and 0.7s) and for each holding time samples were drawn at three different temperatures (80°C, 100°C, and 120°C). Samples were compared to raw milk and to milk from the same batch subjected to a standard pasteurization at 72°C for 15s. The size of the casein micelles and the viscosity were measured in skimmed milk samples, using dynamic light scattering and capillary viscometri, respectively. The results showed a broadening of the size distributions of the casein micelles as the temperature of the infusion pasteurization increased from 80°C to 120°C with no marked difference between the two holding times. The viscosity also increased with increasing intensity of the infusion pasteurization treatment. Little or no difference was seen between the raw milk, the standard pasteurization and the infusion treatments at 80°C regarding both casein micelle size and viscosity. The observed changes in the investigated physical properties of the infusion pasteurization treated milk indicate that this novel pasteurization process might result in milk with altered functionality when used in the production of dairy products. This is currently under investigation

Infusion pasteurization of whole milk and skim milk: Influence on viscosity and particle size

Infusion pasteurization was performed on both whole milk and skim milk and at different temperatures in the range 72°C-120°C. The skim milk was prepared at a commercial dairy and had been heated to approx. 60°C during the separation process. The whole milk was skimmed by centrifugation prior to the analyses. In the analyses, the infusion pasteurized samples were compared to a standard low pasteurization on the same batches of milk and samples of the raw milks. Particle sizes were analyzed using dynamic light scattering, and the viscosity of the samples were measured with a capillary viscometer. The viscosity measurements showed no significant changes in viscosity after infusion pasteurization of skim milk, nor did the particle sizes change. On the other hand, when whole milk was infusion pasteurized an increase in viscosity of the skim milk fraction was seen as treatment temperature increased, and an increase in the z-average diameter of particles and broadening of the size distributions was observed. These observations were quite surprising and might be the result of influence of several different processes during and after infusion pasteurization

Infusion pasteurization of skim milk: Effects of different time-temperature combinations

Infusion pasteurization technology was used in different time-temperature combinations for heat treatment of skim milk and compared to untreated skim milk and a standard pasteurization treatment. Aerobic count of microorganisms and activity of alkaline phosphatase showed that all infusion-pasteurized samples had received proper pasteurization. There were no difference in the size of casein micelles, but differences were seen in activity of the enzyme xanthine oxidase. The results indicate possible differences in properties of infusion-pasteurized skim milk compared to standard pasteurized skim milk

Permanental processes from products of complex and quaternionic induced Ginibre ensembles

We consider products of independent random matrices taken from the induced Ginibre ensemble with complex or quaternion elements. The joint densities for the complex eigenvalues of the product matrix can be written down exactly for a product of any fixed number of matrices and any finite matrix size. We show that the squared absolute values of the eigenvalues form a permanental process, generalising the results of Kostlan and Rider for single matrices to products of complex and quaternionic matrices. Based on these findings, we can first write down exact results and asymptotic expansions for the so-called hole probabilities, that a disc centered at the origin is void of eigenvalues. Second, we compute the asymptotic expansion for the opposite problem, that a large fraction of complex eigenvalues occupies a disc of fixed radius centered at the origin; this is known as the overcrowding problem. While the expressions for finite matrix size depend on the parameters of the induced ensembles, the asymptotic results agree to leading order with previous results for products of square Ginibre matrices.Comment: 47 pages, v2: typos corrected, 1 reference added, published versio