Macromolecular integrity of egg yolk lipoproteins is an essential prerequisite towards retaining cake quality of Madeira cakes and fatless sponges. In Madeira cakes, the low density lipoprotein of yolk is the major determinant of yolk function. In fatless sponge‐cake making, it assists aeration and foaming. The high density yolk lipoprotein inhibits aeration but helps to retain air whipped in by other egg constituents. Implications of these findings are discussed in terms of possible modes of action of lipoproteins during cake making.
It is commonly accepted that phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, the three major phosphatide constituents of soya lecithin are insoluble in acetone, and that extraction of the soya lecithin with acetone dissolves out the triglyceride oil and leaves a precipitate of a mixture of these three phosphatides. Intimate molecular association between phosphatides and acetone appears to be responsible for this. This paper presents a mechanistic picture for this association, discusses the means for preventing this association, and thereby dissolving phosphatides into acetone. A prospect for dissolving phosphatidylethanolamine into acetone, preferentially over others from a mixture, is thus opened up. This is important since it has practical applications in industry. It has been exploited by the development of a process for the separation of phosphatidylcholine and phosphatidylinositol (mixture) from commercial soya lecithin. The process solves a long standing industrial problem for the preparation of phosphatidylethanolamine-free phosphatides.Verfahren zur Trennung Von Phosphatid-Gemishen: Herstellung Von phosphatidyläthanolaminfreien Phosphatiden aus Sojalecithin Es ist bekannt, daB Phosphatidylcholin, Phosphatidyläthanolamin und Phosphatidylinosit, die drei Hauptphosphatidbestandteile Von Sojalecithin, in Aceton unlöslich sind; bei der Extraktion Von Sojalecithin mit Aceton bleibt ein Ruckstand, der aus einer Mischung dieser drei Phosphatide besteht. Fur dieses Verhalten scheint eine molekulare Assoziation zwischen Phosphatiden und Aceton verantwortlich zu sein. In der vorliegenden Arbeit wird ein mechanistisches Bild fur diese Assoziation aufgezeigt; die Möglichkeiten zur Verhinderung der Assoziation und somit zum Lösen Von Phosphatiden in Aceton werden diskutiert. Es eröffnet sich damit die Aussicht, Phosphatidyläthanolamin mit Aceton bevorzugt aus einem Gemisch herauszulösen. Dies ist fur die Industrie Von praktischer Bedeutung. Das Verfahren ist bei der Entwicklung eines Prozesses fur die Abtrennung Von Phosphatidylcholin und Phosphatidylinosit aus handelsüblichem Sojalecithin erfolgreich angewendet worden. Der ProzeB löst das seit langem bestehende Problem der industriellen Herstellung Von phosphatidyläthanolaminfreien Phosphatiden.
Enzymatically modified yolk or yolk plasma and succinylated yolk plasma gave unacceptable Madeira cakes but good fatless sponges of reasonable cell structure although somewhat inferior to the control. Modified yolk plasma showed variable degrees of aggregation in response to various treatments but the overall integrity of lipoprotein structure was unaffected. It is thought that in addition to the macroscopic integrity of yolk lipoproteins, their interfacial molecular anatomy has a marked influence on baking performance in both Madeira cakes and fatless sponges.
Yolk plasma has been examined before and after (a) freeze-thaw gelation and (b) heat-setting at 62.5"C for aggregation states by gel filtration and electron microscopy and for its performance in standard Madeira cake baking. Frozen and thawed plasma consists predominantly of large aggregated species of lipoprotein particles. Heat set plasma has a lower degree of aggregation than frozen and thawed samples. I t is richer in aggregated species than untreated plasma. The aggregation state is not readily reversed by egg white andfor sucrose The degree of aggregation does not appear to affect the baking performance of plasma. Implications of this finding are discussed in terms of possible relationship of lipoprotein size distribution to baking function.
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