One of the most technologically important and widely
studied aspects of food colloid research is concerned with
the gelation of proteins, especially milk proteins. The article
by van Vliet et al. (pp. 298–304) describes recent developments in understanding the rheology and structure of milk
protein gels in terms of the underlying molecular and
colloidal interactions. Casein gels are commonly produced
by enzyme action (renneting) and acidification, separately or
in combination. It is now becoming increasingly recognized
that a casein gel, once formed, cannot be modelled as a
simple aggregated particle gel; the polymeric character of
the building blocks of the network has to be properly taken
into account. Whey protein gels can be made by thermal or
high-pressure treatments, and also by various types of cold
gelation processes involving limited heating at low ionic
strength, acidification and/or addition of divalent cations. In
an acid-induced gel made from a mixture of whey protein
and casein, the structural and rheological properties are
affected, after heating, by both the whey protein associated
with the casein particles and the whey protein aggregates
dispersed in the continuous medium. The relative significance of disulfide bonds to the properties of gels containing
whey proteins remains an active area of research. Genetic
manipulation ofh-lactoglobulin has recently demonstrated
the key role of the single cysteine residue 121 as the prime
catalyst of its heat-induced aggregation and gelation.
One of the most technologically important and widelystudied aspects of food colloid research is concerned withthe gelation of proteins, especially milk proteins. The articleby van Vliet et al. (pp. 298–304) describes recent developments in understanding the rheology and structure of milkprotein gels in terms of the underlying molecular andcolloidal interactions. Casein gels are commonly producedby enzyme action (renneting) and acidification, separately orin combination. It is now becoming increasingly recognizedthat a casein gel, once formed, cannot be modelled as asimple aggregated particle gel; the polymeric character ofthe building blocks of the network has to be properly takeninto account. Whey protein gels can be made by thermal orhigh-pressure treatments, and also by various types of coldgelation processes involving limited heating at low ionicstrength, acidification and/or addition of divalent cations. Inan acid-induced gel made from a mixture of whey proteinand casein, the structural and rheological properties areaffected, after heating, by both the whey protein associatedwith the casein particles and the whey protein aggregatesdispersed in the continuous medium. The relative significance of disulfide bonds to the properties of gels containingwhey proteins remains an active area of research. Geneticmanipulation ofh-lactoglobulin has recently demonstratedthe key role of the single cysteine residue 121 as the primecatalyst of its heat-induced aggregation and gelation.
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