Chemical composition of seeds of four Bulgarian grape varieties

Abstract

The composition of grape seeds from two white dessert ('Bolgar' and 'Super ran Bolgar') and two red wine Bulgarian varieties ('Mavroud' and 'Shiroka melnishka loza') was investigated. The content of proteins was established by Kjeldhal method and was found to be 6.3 - 8.9%. The content of carbohydrates - calculated as the difference of mean values: 100 - (amount in percentage of oil, moisture, protein and ash) - was 65.5 - 70.9%. The content of oil - by extraction with n-hexane - was 11.6 - 16.5%. The content of phospholipids was determined spectrophotometrically after isolation by chromatographic methods and was found to be 0.6 - 0.9%, including phosphatidylcholine, phosphatidylinositol and phosphatidic acids. The sterol content determined by gas chromatography was 0.3 - 0.4% while ß-sitosterol (70.0 - 72.1%) and campesterol (18.5 - 19.9%) were the major components. In the phospholipids and sterol esters, saturated and monounsaturated fatty acids presented higher amount than the triacylglycerols. Fatty acids of sterol esters and phospholipids were determined by gas chromatography after isolation. The quantity of palmitic acid in the phospholipid fraction was 43.4 - 59.4%, the content of oleic acid was 9.0 - 14.0% and the content of linoleic acid was 10.0 - 24.5% while in the sterol esters, the predominant ones were mainly linoleic (40.7 - 53.8%), oleic (24.9 - 35.5%) and palmitic acids (13.0 - 16.7%). Linoleic (68.5 - 72.3%) and oleic acids (16.3 - 18.7%) were found to be the main components of the triacylglycerols. The tocopherol content varied from 67.7 mg kg-1 to 290.5 mg kg-1 where a-tocopherol (74.8 - 84.4%) was the predominant component.