Ultrastructure and Interactions of Soy Lecithin Dispersions in Milk Systems

Buchheim, W.; Wiechen, A.; Prokopek, D.; Funke, Andreas

doi:10.1007/978-1-4757-1364-0_21

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“…Gelation is such a process as any particles, casein micelles, in the milk are attracted to each other in a gelation process. It has been determined by many workers [9][10][11][12][13][14][15]19] that increased pressure encourages the casein micelles to fragment into smaller units, which would gel then more easily [5,8]. Studies carried out on b-lactoglobulin at 500 bar [17,18] demonstrate, that at moderate pressures these globular proteins partly denature.…”

Section: Resultsmentioning

confidence: 96%

Gelation of Milk Protein Concentrates Induced by Moderate Hydrostatic Pressures

Briscoe

Luckham

Staeritz³

2002

High Pressure Research

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Gelation of aqueous milk protein concentrates made up of spray dried milk was monitored both at atmospheric pressure and at moderate pressures (up to 1000 bar) using rheological methods. A Paar Physica UDS 200 rheometer was used to measure the gelation time at atmospheric pressure as a function of the temperature for a protein concentration of 16% [w=w]. The temperature dependence of the gelation time is well approximated by the Ross-Murphy model, which was originally developed to describe the concentration dependence of the gelation time. Using a purpose built Haake High Pressure High Temperature Rheometer, the effects of moderate pressures upon the gelation of milk protein concentrates (13% [w=w] protein content) were investigated. It was found that the gelation time reduces significantly (by up to almost an order of magnitude), when pressures of up to 1000 bar were applied. These findings, combined with the work of others indicate that these pressures bring about two effects: (1) casein micelle dissociation and as a result facilitate reassociation of those smaller micelle fragments, and (2) denaturation of beta-lactoglobulin. However, the main contribution to enhanced gelation was attributed to the caseins. It is not clear if association of whey proteins with caseins occur at moderate pressures around 50 C. We have modelled the dependence of the rate of gelation on pressure by an Eyring reaction rate process type equation. The major contribution to enhanced gelation upon pressurisation was attributed to a disruption of hydrophobic groups and ionisation of charged groups caused by an increase in electrostrictionhowever, disruption of hydrogen bonds was suggested to contribute to a lesser but still important extent.

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