Comparison of Hydration Behavior of Bovine and Caprine Caseins As Determined by Oxygen-17 Nuclear Magnetic Resonance:  Temperature Dependence of Colloidal Stability

Abstract

Oxygen-17 nuclear magnetic resonance (NMR) transverse relaxation rates for bovine and caprine casein micelles at various temperatures were analyzed by nonlinear regression analysis and a protein activity model. The dependence of the NMR transverse relaxation rates was markedly nonlinear due to interactions between protein molecules. Temperature dependences of the hydration parameters of the bovine and caprine casein micelles were in accordance with the hypothesis that hydrophobic interactions are the predominant forces responsible for the self-association of the caseins. Relaxation differences between reconstituted micelles of bovine and caprine caseins strongly suggest that important structural dissimilarities exist between these milk proteins that are due to differences in the ratios of R s1 -to β-casein. A higher degree of hydration, characteristic of a more open and looser structure, is observed for caprine casein micelles high in R s1 -casein at 21 and 37 °C. The observed hydration behavior of bovine casein micelles at all three temperatures is consistent with the hydration values determined previously by deuterium NMR studies of bovine casein micelles in D 2 O containing 1,4-piperazinediethanesulfonic acid. The correspondence between the deuterium and oxygen-17 results suggests that both experiments detect exchangeable water "trapped" within the casein micelles. The dependence of the second virial coefficient B 0 on temperature was different for bovine and caprine casein micelles, suggesting the importance of "net" electrostatic charges of these milk proteins in their interactions with calcium and water.

Preliminary Investigation on the Characterization of Durum Wheat Flours Coming from Some Areas of South Italy by Means of 1H High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance

“…Other examples concerning the evaluation of the adulteration of edible oils (Zamora et al, 1994;Husain et al, 1993;Wollenberg et al, 1990;Gunstone et al, 1993) are based upon the use of 1 H or 13 C NMR spectra. Finally, the literature also reports a few papers regarding the analysis of other foods (Belton et al, 1993) such as milk (Mine, 1997;Gutierrez et al, 1996;Wahlgren et al, 1995) and meat (Renou, 1995). This work is related to a research program devoted to the study of the possible applications of high-resolution NMR spectroscopy to investigating typical Apulia agricultural products and those of nearby regions of southern Italy.…”

κ-Carrageenan Interaction with Bovine and Caprine Caseins As Shown by Sedimentation and Nuclear Magnetic Resonance Spectroscopic Techniques

“…The virial coefficients are a measure of the various molecular interactions (Tanford, 1963;Pessen and Kumosinski, 1985). The application of virial coefficients to the nonideality of macromolecules in solution is discussed by Richards (1980), Kumosinski and Pessen (1982), Bates (1982), Kumosinski et al (1987), Myers-Betts and Baianu (1990), Kakalis et al (1990), and Mora-Gutierrez et al (1995, 1996a.…”

“…The virial coefficients are a measure of the various intermolecular interactions (Tanford, 1963;Pessen and Kumosinski, 1985). The B0 virial coefficient reflects the repulsive or attractive forces arising from the net protein charge Z, the protein excluded volume, and a preferential interaction term (Mora-Gutierrez et al, 1995, 1996a,b, 1997.…”

Oxygen-17 Nuclear Magnetic Resonance Studies of Bovine and Caprine Casein Hydration and Activity in Deuterated Sugar Solutions

“…One approach toward evaluating the determinants of protein stability induced by the addition of sucrose and lactose to milk is to examine the effects of these molecules on the hydration properties of casein. In previous work (Mora-Gutierrez et al, 1995, 1996a, we have evaluated the effects of salt and pH/pD on the interactions of water with caseins by oxygen-17 NMR relaxation techniques. In this work, the response of oxygen-17 NMR relaxation rates of D 2 O to the presence of lactose, sucrose, bovine casein, and two caprine caseins differing in their content of the R s1 -casein component at pD 7.20 and 21 °C will be evaluated.…”

“…The virial coefficients are a measure of the various molecular interactions (Tanford, 1963;Pessen and Kumosinski, 1985). The application of virial coefficients to the nonideality of macromolecules in solution is discussed by Richards (1980), Kumosinski and Pessen (1982), Bates (1982), Kumosinski et al (1987), Myers-Betts and, Kakalis et al (1990a), and Mora-Gutierrez et al (1995, 1996a.…”