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Chromatographic Sterol Analysis As Applied to the Investigation of Milk Fat and Other Oils and Fats

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Chromatographic Sterol Analysis As Applied to the Investigation of Milk Fat and Other Oils and Fats CHROMATOGRAPHIC STEROL ANALYSIS AS APPLIED TO THE INVESTIGATION OF MILK FAT AND OTHER OILS AND FATS ACADEMISCH PROEFSCHRIFT TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE WISKUNDE EN NATUURWETENSCHAPPEN AAN DE UNIVERSITEIT VAN AMSTERDAM, OP GEZAG VAN DE RECTOR MAGNIFICUS DR. J. KOK, HOOGLERAAR IN DE FACULTEIT DER WISKUNDE EN NATUURWETENSCHAPPEN IN HET OPENBAAR TE VERDEDIGEN IN DE AULA DER UNIVERSITEIT (TIJDELIJK IN DE LUTHERSE KERK, INGANG SINGEL 411, HOEK SPUl) OP WOENSDAG 23 OKTOBER 1963, DES NAMIDDAGS TE 16 UUR DOOR JAN WILLEM COPIUS PEEREBOOM GEBOREN TE 'S-GRAVENHAGE qP CENTRUM VOOR LANDBOUWPUBLIKATIES EN LANDBOUWDOCUMENTATIE WAGENINGEN 1963 1"%-! .••: i PROMOTOR:PROF .DR .W .VA NTONGERE N Es ist nichtgenug zu wissen Manmuss auch anwenden Es ist nichtgenug zu wollen Manmuss auch tun. GOETHE Bij de voltooiing van dit proefschrift betuig ik in de eerste plaats gaarne mijn dank aan alle hoogleraren en lectoren, die tot mijn wetenschappelijke vorming hebben bijgedragen. Hooggeleerde WIBAUT, naar U gaat mijn dank uit voor het inzicht in de organische chemie, dat ik van U mocht ontvangen. Van mijn blijvende belangstelling voor klassieke onderwerpen uit de organische chemie als de sterolchemie, mogen vele gedeelten van dit proefschrift getuigen. Hooggeleerde VAN TONGEREN, Hooggeschatte Promotor, met gevoelens van grote erkentelijkheid richt ik mij tot U om dank te zeggen voor het onderricht in de ana­ lytische chemie en voor de grote steun, die ik bij de bewerking van dit proefschrift van U mocht ondervinden. Het geduld waarmede U steeds weer talloze onvolkomen­ heden in de Engelse tekst signaleerde, heeft mijn grote bewondering. Het onderzoek werd in zijn geheel uitgevoerd op het RIJKSZUIVELSTATION. Gaarne wil ik hierbij mijn dank betuigen aan mijn collegae en medewerkers van het RIJKSZUIVELSTATION, die op enigerlei wijze hebben bijgedragen aan het tot stand komen van dit proefschrift. Ir. B. M. KROL ben ik erkentelijk voor het vervaar­ digen der foto's. Zeer speciale dank ben ik verschuldigd aan Ir. J. B. Roos voor de waardevolle discussies en stimulerende kritiek betreffende „sterolanalyse". Het aantal malen dat in dit proefschrift wordt verwezen naar publikaties en rapporten van zijn hand, moge getuigen van mijn waardering voor het werk dat hij op dit gebied heeft verricht. Mej. H. W. BEEKESdan k ik voor de toegewijde assistentie en bekwame experimentele vaardigheid, die van zo grote waarde zijn geweest bij de uitvoering van het onderzoek. De directeur van het RIJKSZUIVELSTATION, Dr. J. G. VAN GINKEL, ben ik erkentelijk voor zijn toestemming dit onderzoek te mogen publiceren en voor de vele faciliteiten, die hij mij tijdens de bewerking van dit proefschrift heeft verleend. DRUK: N.V. NOORD-NEDERLANDSE DRUKKERIJ - MEPPEL Deze dissertatie verschijnt tevens als Nr. 69.8 in de reeks Verslagen van Landbouwkundige Onder­ zoekingen CONTENTS 1 CLASSICAL ANALYTICAL METHODS FOR NATURAL STEROLS, APPLIED TO FAT ANALYSIS 1 1.1 Fat analysis based upon characteristic values 1 1.1.1 Fatty acid values and special applications 2 1.1.2 Glyceride (fat) analysis 3 1.1.3 Guide (fat) analysis 4 1.2 The principal naturally occurring sterols 6 1.3 Sterol values in fat analysis 12 1.4 Application of the sterol content to fat analysis (sterol value a) ... 13 1.4.1 Gravimetric methods 13 1.4.2 Other procedures 16 1.4.3 Applications 19 1.5 Melting point of the sterol acetates as a characteristic value (sterol value m) 20 1.5.1 Procedures 20 1.5.2 Melting point diagrams 23 1.5.3 Reliability of BÖMER'S phytosterol acetate test 25 1.6 Cholesterol percentage as a characteristic of sterol mixtures (sterol value c) 31 1.6.1 Detection of vegetable fat in animal fat and vice versa 31 1.6.2 Detection of cholesterol from the melting point diagram 33 1.6.3 Other procedures 34 2 THE CHROMATOGRAPHIC SEPARATION OF STEROLS 38 2.1 Adsorption chromatography 38 2.2 Paperchromatography 39 2.3 Experimental procedures 45 2.3.1 Preparation of the sterol mixture 45 2.3.2 Procedure of paperchromatography 47 2.4 Quantitative evaluation of the paperchromatographic analysis .... 48 2.4.1 Quantitative evaluation by planimetry 49 2.4.2 Densitometrie evaluation 50 3 A STUDY OF THE SYSTEM: PARAFFIN/ACETIC ACID-WATER (84 : 16) 52 3.1 Principles of paperchromatography 52 3.1.1 Fundamental equations 52 IX 3.1.2 Applications of the RM concept 56 3.1.3 The occurrence of critical pairs 57 3.2 Experimental conditions in the system: paraffin/acetic acid-water (84:16) 58 3.2.1 Influence of external circumstances 58 3.2.2 Features of the partition process 60 3.3 Correlations between structure and RM values 62 3.3.1 RFan d RM values of a group of sterols 62 3.3.2 Critical pairs of sterols 66 3.3.3 Calculation of A RM values 68 3.4 Applications of the correlation between structure and RMvalues.. 72 3.4.1 Rules concerning the correlation and ARMvalue s 72 3.4.2 Identification of unknown sterols 73 3.4.3 Influence of different steric configurations 78 4 APPLICATIONS OF THE CHROMATOGRAPHIC STEROL SEPARATION TOTH E ANALYSIS OF FAT MIXTURES 81 4.1 Analysis of mixtures of animal and vegetable fats 81 4.1.1 Analysis of animal fats 81 4.1.2 Analysis of vegetable fats 82 4.2 Composition of the sterol mixture 83 4.3 Probable structure of the third-band phytosterols 86 4.4 Detection of cholesterol in mixtures with third-band phytosterols. 90 4.4.1 With the normal paperchromatographic procedure 90 4.4.2 Further examination of questionable samples 92 5 THIN-LAYER CHROMATOGRAPHY OF STEROLS 94 5.1 Introduction 94 5.2 Normal thin-layer chromatography of sterols 96 5.3 Reversed-phasethin-laye rchromatograph y ofsterol san d sterolacetate s 99 5.3.1 Separation of sterol acetates 100 5.3.2 Separation of sterols 102 5.4 Some applications 104 5.5 Separation of sterol acetate bromides 106 5.5.1 Bromine containing systems 106 5.5.2 Experimental procedure 108 5.5.3 Semi-quantitative evaluations 108 6 BEHAVIOUR OF SOME ABERRANT PHYTOSTEROL TYPES IN CONNECTION WITH THEIR POSSIBLE STRUCTURE 110 6.1 Failure of the original phytosterol acetate test of BOMER HO 6.1.1 Special behaviour of pumpkin phytosterols 110 6.1.2 Phytosterols of shea nut fat and Mowrah fat 112 6.1.3 Zl7-sterol mixtures 116 6.2 Structure of the pumpkin oil phytosterols 119 6.2.1 Characteristics of pumpkin oil 119 6.2.2 Paperchromatography 119 6.2.3 U.V. spectrophotometry 120 6.2.4 T.L.C. bromine system 120 6.2.5 Colour reactions 120 6.2.6 Melting point and optical rotation 122 6.2.7 Infrared and N.M.R. spectra 123 6.2.8 Thin-layer chromatography 126 7 CALCULATIONS ON THE BASIS OF STEROL VALUES 129 7.1 Identification of the type of admixed animal fat 129 7.2 Analysis of a cottonseed oil sample 131 7.3 Analysis of a palm oil sample 132 7.4 Analysis of a second palm oil sample 133 7.5 Detection of cocoa extraction fat in pure cocoa butter 134 SUMMARY 139 SAMENVATTING 141 REFERENCES 143 Chapter 1 143 Chapter 2-7 151 XI 6.1.1 Special behaviour of pumpkin phytosterols 110 6.1.2 Phytosterols of shea nut fat and Mowrah fat 112 6.1.3 zl7-sterol mixtures 116 6.2 Structure of the pumpkin oil phytosterols 119 6.2.1 Characteristics of pumpkin oil 119 6.2.2 Paperchromatography 119 6.2.3 U.V. spectrophotometry 120 6.2.4 T.L.C. bromine system 120 6.2.5 Colour reactions 120 6.2.6 Melting point and optical rotation 122 6.2.7 Infrared and N.M.R. spectra 123 6.2.8 Thin-layer chromatography 126 7 CALCULATIONS ON THE BASIS OF STEROL VALUES 129 7.1 Identification of the type of admixed animal fat 129 7.2 Analysis of a cottonseed oil sample 131 7.3 Analysis of a palm oil sample 132 7.4 Analysis of a second palm oil sample 133 7.5 Detection of cocoa extraction fat in pure cocoa butter 134 SUMMARY 139 SAMENVATTING 141 REFERENCES 143 Chapter 1 143 Chapter 2-7 151 XI The author wasawarde d the degree of Doctor of Science, Universityo fAmsterdam , The Netherlands,o na thesi s with the same title and contents, on 23st October 1963. 1 CLASSICAL ANALYTICAL METHODS FOR NATURAL STEROLS, APPLIED TO FAT ANALYSIS 1.1 FAT ANALYSIS BASED UPON CHARACTERISTIC VALUES As a consequence of the very complex composition of natural fats the analytical chemistry of lipoids forms a distinct field with special problems. Besides multifarious types of triglycerides as quantitatively most important fraction, a minor part consists of an enormous variety of other lipoid substances: monoglycerides, triglycerides, phosphatides,tocopherols ,sterols ,stero lesters ,hydrocarbons ,carotenoid san dtrace s of several other compounds. The triglycerides forming the main fraction of the fat consist ofa glycerolmolecul eesterifie d withthre efatt y acids.Th etriglycerid e fraction largely varies in composition, numerous combinations of the fatty acid constituents in their molecules being conceivable. Evidently, the great number of possible tri­ glycerides still further enhances the complexity of this type of analysis. One of the purposes of fat chemistry is the determination of all these individual types oflipoid si na fat , but inth epas tappropiat e analytical techniques werelacking . At the end of the nineteenth century a complete analysis of a natural fat thus was by no means possible. Nevertheless, fat analysis had to differentiate between the various types of oils and fats and to determine the proportion of the constituents of commercially available fat mixtures.
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