Patrick Boulenguer

Effect of the Addition of High Methoxy Pectin on the Rheology and Colloidal Stability of Acid Milk Drinks

The effect of high methoxy pectin on the behaviour of model acid milk drinks has been investigated using viscometry, laser diffraction size measurement and microelectrophoresis. The results of these different tests are interpreted using the theory of colloidal stability. With increasing pectin concentration, the behaviour changes from flocculated with few particles below 0.2µm diameter and shear thinning, time-dependent rheology to non-flocculated, many sub 0.2µm particles and low viscosity with Newtonian rheology. With even higher pectin concentrations, the acid milk drink remains non- flocculated, but with increasing viscosity and close to Newtonian rheology.

Continuous-flow fast atom bombardment-mass spectrometry of permethylated oligosaccharides: A comparative study of direct mixture analysis with packed capillary column liquid chromatography-fast atom bombardment-mass spectrometry

Conventional positive fast atom bombardment (FAB) and continuous-flow FAB analysis were carried out with permethylated lacto-N-tetraose. This latter method, a new approach, has been used to analyze a mixture of permethylated oligosaccharides by liquid chromatography-mass spectrometry (LC-MS) with a packed capillary fused-silica column and the continuous-flow probe as interface. Under these conditions, we found the continuous-flow probe to be superior to the conventional probe because its low matrix level increased the signal-to-noise ratio. The analysis of the mixture of permethylated oligosaccharide alditols obtained from hen ovomucoid by LC-MS using the continuous-flow probe as interface is described.

Enzymatic degradation of hybrid ι-/ν-carrageenan by Alteromonas fortis ι-carrageenase.

Hybrid iota-/nu-carrageenan was water-extracted from Eucheuma denticulatum and incubated with Alteromonas fortis iota-carrageenase. The degradation products were then separated by anion-exchange chromatography. The three most abundant fractions of hybrid iota-/nu-carrageenan oligosaccharides were purified and their structures were analyzed by NMR. The smallest hybrid was an octasaccharide with a iota-iota-nu-iota structure. The second fraction was composed of two decasaccharides with iota-iota-iota-nu-iota and iota-[iota/nu]-iota-iota structures. The third fraction was a mixture of dodecasaccharides which contained at least a iota-iota-iota-iota-nu-iota oligosaccharide. The carbon and proton NMR spectra of the octasaccharides were completely assigned, thereby completely attributing the nu-carrabiose moiety for the first time.

Complete assignment of 1H and 13C NMR spectra of standard neo-ι-carrabiose oligosaccharides.

Standard Eucheuma denticulatum iota-carrageenan was degraded with the Alteromonas fortis iota-carrageenase. The most abundant products, the neo-iota-carratetraose and neo-iota-carrahexaose were purified by permeation gel chromatography, and their corresponding (1)H and (13)C NMR spectra were fully assigned.

BINDING OF GALACTOMANNANS TO KAPPA-CARRAGEENAN AFTER COLD MIXING

Abstract The room temperature interaction between swollen carrageenan particles and solutions of carob, cassia, guar, and tara galactomannans has been studied. Analysis using gel permeation chromatography of the supernatant solution above the carrageenan particles demonstrated binding of all the galactomannans, except guar, to kappa-carrageenan. It was also demonstrated that carob galactomannan did not bind to iota-carrageenan. Binding after cold mixing saturates at high kappa-carrageenan/carob ratios, of the order of 80, unlike the interaction in mixtures after heating, which saturates at ratios close to 1. The existence of binding shows that the interaction between these two species is attractive, and thus suggests that the synergistic rheological interaction which occurs after heating is due to the formation of mixed junction zones.

Hybridity of carrageenans water- and alkali-extracted from Chondracanthus chamissoi, Mazzaella laminarioides, Sarcothalia crispata, and Sarcothalia radula

Carrageenans water- and alkali-extracted from Chondracanthus chamissoi, Mazzaella laminarioides, Sarcothalia crispata, and Sarcothalia radula were degraded by Pseudoalteromonas carrageenovora κ-carrageenase and Alteromonas fortis ι-carrageenase. The composition of the high molecular weight fraction (i.e., enzyme-resistant fraction) as well as the standard and hybrid oligosaccharide content highlighted differences between the species-specific carrageenans in terms of composition and distribution of the carrabiose moieties. Inspection of the distribution of μ- and ν-carrabiose, the biosynthetic precursors of κ- and ι-carrabiose, revealed their localization in κ-carrabiose- or ι-carrabiose-rich segments, respectively.

Acylgalactosylceramides in Developing Dysmyelinating Mutant Mice

Acylgalactosylceramides (AGC) from forebrains of normal and dysmyelinating (quaking and shiverer) mice were purified by Florisil column chromatography and preparative TLC. These procedures resolved the AGC on the basis of their Rf values into two main fractions which co‐nigrate with their homologs from rat forebrains. In control animals, AGC were detectable in mouse forebrains from the eighth postnatal day and reached maximal values within 20 days. The same developmental pattern was obtained in dysmyelinating shiverer mice but the AGC content was reduced to approximately 30% of control values. In quaking mutants, the AGC were hardly detected. They were also present in sciatic nerve of normal mice and to a lesser extent in trembler mice. Gas chromatography‐mass spectrometry analysis of both ester‐ and amide‐linked fatty acids isolated from AGC of normal and shiverer mice shows that the shiverer mutant AGC display a chemical structure similar to that of normal AGC. AGC constituents of control myelin are reduced by approximately 70% in shiverer myelin, indicating that these molecules can be considered as early markers of oligodendrocyte differentiation. The early arrest of myelinogenesis in the quaking animals and the near absence of AGC are in good agreement with this proposal. Moreover, the reduced amount of AGC in the trembler PNS indicates that AGC could also be early markers for differentiation of the Schwann cell.

Structure determination of the polymorphism of acylgalactosylceramide in rat brain by gas chromatography/mass spectrometry and proton magnetic resonance

This paper describes the structure of acylcerebrosides isolated from rat brains. Three fractions (acylglycosylceramides I, II, III) were resolved according to their decreasing RF values on TLC. GLC analysis of acylglycosylceramides II and III indicates that their ester-linked fatty acids are short and rather unsaturated, while amide-linked fatty acids are longer and hydroxylated. Sugar GLC analysis indicates that acylglycosylceramides II and III contain only galactose. To determine the substitution position of the acyl group on the galactose moiety, the free hydroxyl groups of acylglycosylceramide were protected with dihydropyran, deacylated and subjected to permethylation. The methylated galactoside acetates obtained after hydrolysis and reduction were then analyzed by gas chromatography/mass spectrometry. Acylglycosylceramides II and III turned out to be complex mixtures of 2-O-acyl-, 3-O-acyl-, 4-O-acyl- and 6-O-acylgalactosylceramides. Moreover, the abundance of alpha-methylgalactoside reveals the existence of unsubstituted galactose, suggesting that some ester-linked fatty acids could be esterified to the hydroxyl group of hydroxy fatty acids linked to sphingosine. NMR spectrometry was used to confirm this ester linkage. The key spectral feature of the fatty acid-galactose linkage (4.45 ppm) did move to 4.15 ppm after saponification of acylglycosylceramide II; on the other hand, acylglycosylceramide III contained only the spectral feature 4.15 ppm, corresponding to a high percentage of unsubstituted galactose and consistent with the presence in the molecule of a fatty acid esterified by the omega-OH group of the hydroxy fatty acid (3.95 ppm).