Qualitative and Quantitative Analysis of Sphingomyelin in Whey Protein
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Date
2005-06
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The Ohio State University
Abstract
Sphingolipids are a group of phospholipids found in eukaryotic cells and are especially prevalent in plasma membranes and related cell membranes. Sphinogmyelin (SM) is the predominant membrane sphingolipid and can be hydrolyzed to form ceramides and sphingosines which are involved in numerous cellular processes such as apoptosis, cell cycle progression, and cell differentiation. Recent research suggests that SMs may play an important role in the development and/or prevention of chronic disease. Dietary sources of SM include milk, eggs and soybeans, although their exact concentration in food has not been well characterized.
The present research examines the sphingolipid content of whey protein concentrates (WPC) and isolates (WPI). Whey protein, commonly the byproduct of cheese and dairy manufacturing, is a pure, natural, high quality protein from cow's milk. The fat produced as a byproduct of whey processing contains about 20% phospholipids. The present study examines the SM content of several WPC and WPI samples. We hypothesize that the SM content of the whey protein samples will be proportional to their total lipid content.
WPC and WPI were extracted, fractionated and analyzed for SM content. A total of five samples were analyzed, three whey protein concentrates and two whey protein isolates. Ten gram samples of each sample were extracted by solid phase extraction (SPE) and further separated using ion exchange methods. SM content was analyzed by thin-layer chromatography and quantified using a standard curve generated using pure SM.
WPCs containing 14.5, 15 and 17.5% total lipids had SM contents of 0.0137, 0.0193 and 0.0114% SM respectively. Conversely, WPIs containing 0.3% had significantly different SM contents (0.0015 and 0.019%). Statistically significant patterns were not found when comparing lipid content and SM of whey protein samples. Therefore, the hypothesis that the SM content of whey protein samples is proportional to total lipid content was not supported. The WPCs had relatively similar SM content regardless of fat content. These findings may be due to the inability to control for some experimental error, including humidity conditions during extraction and separation of SM. In addition, processing methods, and/or interfering components in samples (e.g. protein) may account for these results.
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Keywords
sphingomyelin, whey protein