Variation in ganglioside content of bovine dairy products.

摘要

Methods for crude extraction of gangliosides from dairy products were compared, and ganglioside contents of dairy products were determined following purification of crude extracts by TLC. Quantification of gangliosides involved spectroscopic analysis of the sialic acid content using resorcinol-HCl staining of TLC plates. 4 extraction protocols were tested using powdered buttermilks: a modified Folch-like extraction; removal of neutral lipids with acetone followed by modified Folch-like extraction; reconstitution of dried buttermilk followed by dialysis to remove protein, and lyophilization prior to modified Folch-like extraction; and dialysis of reconstituted dried buttermilk followed by lyophilization, resuspension and successive extraction with chloroform/methanol. Ganglioside contents of sweet and cultured buttermilk were highly variable (250-750 and 165-467 nmol sialic acid/g dry wt., respectively) the chloroform/methanol extraction method giving the most consistent results. Gangliosidecontents of sweet buttermilk, cultured buttermilk and yoghurt were: 21.3 plus/minus 4.5, 12.6 plus/minus 2.0 and 17.6 plus/minus 4.7 nmol sialic acid/g dry wt., respectively, on the basis of a single extraction. Over 2 separate extractions, gangliosidecontents were 2.2 and 2.0 nmol sialic acid/g dry wt. in milk, and 0.4 and 0.1 nmol sialic acid/g dry wt. in skim milk. Results are discussed in terms of milk fat contents of these dairy products.