The effect of the melting of the collagen-like gelatin aggregates on the stability against aggregation of the bovine casein micelles |
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Authors: | J Lefebvre Y Antonov |
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Institution: | (1) I.N.R.A., Centre de Recherche Agro-Alimentaires Laboratoire de Physico-Chimie des Macromolecules. BP 1627, 44316 Nantes Cedex 03, France, FR;(2) N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences Kosigin Str, 4. 117977 Moscow GSP-1 Russia e-mail: serg-ant@mtu-net.ru, RU |
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Abstract: | The effect of the melting of the collagen-like acid and alkaline gelatin aggregates on the stability against aggregation
of bovine casein micelles was investigated by turbidimetry, DSC and circular dichroism in the wide range of biopolymers concentrations,
gelatin/casein ratio (R) in initial mixture (R=0.03–20), pH (4.9–6.7), ionic strength (I=10−3 to 1.0/NaCl/), and temperature (10°–70 °C), using glucono-δ-lactone (GL) as acidifier. At low ionic strength (10−3/milk salts/) and neutral pH interaction between gelatin molecules and casein micelles is suppressed significantly above 36 °C.
The melting of the collagen-like acidic gelatin above this temperature shifts the pH at which the complex formation is maximal
to the acidic range. The cause may be that some of the functional ionized groups of gelatin molecules are inaccessible due
to the conformational changes. The presence of gelatin B molecules had no effect on the aggregation stability of micellar
casein in the range 0.03<R<20. At very high total protein concentration (above 10%) depletion flocculation of casein micelles
was observed. The reason for the very high stability of casein micelles in this case cannot be explained by volume exclusion.
Received: 28 March 2000 Accepted: 5 October 2000 |
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Keywords: | Bovine casein micelles Gelatin Interactions Depletion flocculation |
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