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Title: ON-LINE SFE/ENZYMATIC HYDROLYSIS OF VITAMIN A ESTERS - A NEW SIMPLIFIED APPROACH FOR THE DETERMINATION OF VITAMIN A AND E IN FOOD

Author
item TURNER, CHARLOTTA - LUND UNIVERSITY, SWEDEN
item King, Jerry
item MATHIASSON, LENNART - LUND UNIVERISTY, SWEDEN

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: A knowledge of the vitamin composition of foods that the consumer ingests is critical for the maintenance of health. The analysis of vitamins in foodstuffs is complicated due to the many components in the sample matrix aside from the vitamins. Such analysis requires many steps and has traditionally relied on the use of organic solvents and multi-step procedures that are labor intensive to produce the final analytical results. In this study, a method has been developed that eliminates the need for organic solvents which have an adverse effect on the environment and the health of the analysts. High pressure carbon dioxide is used as the substitute extraction solvent and removes the vitamins from various food matrices (milk, meat, baby food) very effectively. Conversion of the vitamins to a more detectable form is facilitated by using an environmentally benign catalyst called an enzyme. This desired conversion can also be accomplished in the high pressure medium noted above, thereby creating an analytical method that accomplishes several integrated steps on automated instrumentation that can be run overnight. This improvement in technique supplements methodology developed for vitamin analysis that has been certified among nations in the European Union and the United States, thereby providing for the future an analytical method that can be used between nations in certifying the vitamin content of a variety of foods.

Technical Abstract: An on-line supercritical fluid extraction (SFE)/enzymatic hydrolysis procedure using immobilized lipase has been developed for the determination of vitamin A in dairy and meat products. Several lipases were tried, of which Novozyme 435 (Candida antarctica type B) showed the highest activity towards retinyl palmitate. There was no observed activity with alpha tocopheryl-acetate. Several parameters such as pressure, temperature, modifiers, flow rate, extraction time and water content were investigated for the purpose of obtaining high vitamin A recovery in milk powder. Retinyl esters were found to be quantitatively converted to all-trans-retinol, after analyzing collected extracts by RP-HPLC with UV and fluorescence detection without additional sample clean-up. The procedure applied to other food items, such as infant formula, minced pork, beef meat, and low and high fat liver paste, gave reliable values of vitamin A, as well as of vitamin E, determined as tocopherols, or tocopherols plus unchanged alpha-tocopheryl-acetate when present. The described method is much faster and more automated than conventional methods based on liquid-liquid extraction, or SFE using off-line saponification, for vitamin A and E determination. Results obtained with the new method did not differ significantly from those obtained with the other two methods mentioned above.