Whey proteins modify the phase transition of milk fat globule phospholipids

Abstract

-The phospholipids extracted from milk fat globule membranes were composed of three major classes, phosphatidylethanolamines (37.2 %), phosphatidylcholines (30.0 %), sphingomyelin (28.2 %), and two minor classes, phosphatidylinositols (2.0 %) and phosphatidylserines (2.6 %). The thermogram showed that the extracted phospholipids presented a single wide-phase transition centered at 18.3 oc. The effects of temperature on the phase behaviour of milk phospholipids in the presence of~-Iactoglobulin and a-Iactalbumin have been studied at pH 4.0 and 7.0 (with or without calcium) using Fourier transform infrared spectroscopy. Principal component analysis carried out on the spectra in the 3 000-2 800 cm-i region showed that the binding of the whey proteins to the phospholipids modified the Iipid phase transition in different ways, depending on the in-solution protein. © Inra/Elsevier, Paris milk 1 phospholipid 1 protein 1 interaction 1 phase behaviour 1 infrared Résumé -L'arrangement des phospholipides extraits des globules gras du lait est modifié par la présence de la~-lactoglobuline et de l'a-lactalbumine. Les phospholipides extraits de la membrane du globule gras comprennent des phosphatidylethanolamines (37,2 %), des phosphatidylcholines (30,0 %), des sphingomyélines (28,2 %), des phosphatidylsérines (2,6 %) et des phosphatidylinositols (2,0 %). Le thermogramme des phospholipides du lait présente un pic large avec une seule transition de phase à 18,3 oc. L'effet de la température sur l'arrangement des phospholipides extraits des globules gras du lait en présence de la~-Iactoglobuline et de l'a-lactalbumine a été étudié par spectroscopie moyen infrarouge à pH 4,0 et 7,0 (en présence ou en absence de calcium). L'analyse en composantes principales réalisée sur les spectres correspondant à la région 3000-2800 cm-i montre qu'aux deux pH étudiés, l'arrangement des phospholipides est modifié suite à leurs interactions avec les protéines du lactosérum. © Inra/Elsevier, Paris lait 1 phospholipide 1 protéine 1 interaction 1 transition de phase 1 infrarouge * Correspondence and reprints at present address: ENIT A -Clermont-Ferrand, Marmilhat, 63370 Lempdes, France. dufourrs'gentiane.enitac.fr ifier protein of the lactose synthase complex in the mammary cell. The secondary structure of this protein yields 45 % of a-helix and 5 % of p-sheet [1]. Ptitsyn [31] showed that oe-lactalbumin has a 'molten globule state' conformation at low pH. This conformational state may facilitate the insertion of proteins in membranes [18,19,24].Studies of lipid-protein interaction in reconstituted model systems have been an active topic for a numbers of years [9,17,25,27,36,39].These studies provide basic information about the molecular organization of biological membranes. Biophysical studies on model membranes such as liposomes have also been quite successful in characterizing the organization and dynamics of a lipid matrix. The development of Fourier transform infrared (FTIR) spectroscopy in recent years affords the possibility of ob...

Relations Between Spectral and Physicochemical Properties of Cheese, Milk, and Whey Examined Using Multidimensional Analysis

“…4). As previously reported (Dufour et al 1999(Dufour et al , 2000, the differences in the A CH2 /A CH3 ratios are related to the lengths of the fatty acid chains, i.e., the value of A CH2 /A CH3 ratio increases with the increase in the length of fatty acid chains. In addition, there are relation between the lengths of fattyacid chain in triglycerides and the viscosity of fats.…”

“…The two spectral patterns were similar showing an opposition between positive bands located at about 2,923 and 2,852 cm −1 (corresponding to CH 2 bands) and negative bands at about 2,946 and 2,883 cm −1 (corresponding to CH 3 bands). It is well known that the bands between 3,000 and 2,800 cm −1 associated with C-H stretching modes are sensitive to the physical state (liquid or solid) and nature (fatty-acid chain length) of lipids (Dufour et al 1999(Dufour et al , 2000. These spectral patterns indicated that the ratios of absorbance A CH2 /A CH3 were larger for samples on the positive side of common component q 1 than for samples on the negative side of this common component (Fig.…”

The potential of combined infrared and fluorescence spectroscopies as a method of determination of the geographic origin of Emmental cheeses

“…Spectral patterns are similar to spectra and may be used to derive structural information at molecular level (Dufour, Subirade, Loupil, & Riaublanc, 1999). The spectral pattern 2 associated with PC2 (data not shown), presented a positive peak at 325 nm and a negative peak at 365 nm.The spectral pattern 3 associated with PC3 exhibited a positive peak at 340 nm and two negative peaks at 325 and 370 nm.…”

Monitoring the identity and the structure of soft cheeses by fluorescence spectroscopy

“…They reveal the characteristic wavelengths for which large differences are observed in the spectra. They are similar to spectra and can be used to derive structural information at the molecular level [13,25]. Figure 5 shows the spectral patterns 1 and 2 associated with the principal components 1 and 2.…”