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Fat-soluble vitamins in cow milk commercialized in Portugal
S. Freitas, C. Coelho, H.M.M. Ramalho, S. Casal and M.B.P.P. Oliveira
REQUIMTE/ Serviço de Bromatologia, Faculdade de Farmácia da Universidade do Porto, Rua
Aníbal Cunha nº 164, 4099-030 Porto, PORTUGAL
Cow milk and dairy products have a long tradition in human nutrition. From the first day of our
life until elderly, the milk accompanies us step by step, bringing many benefits to our
development. Milk and milk products are nutritious food items containing numerous nutrients
(proteins, essential fatty acids, conjugated linoleic acid, omega-3 fatty acids, short- and
medium chain fatty acids, vitamins, minerals, other bioactive compounds) that promote
positive health effects. Milk consumption varies considerably between different countries.
According to the INE, National Institute of Statistics, the consumption of milk and dairy
products in Portugal has a positive development in recent decades, and this food group
registered the highest per capita growth (+41%) from 2005 to 2008.
The objective of the present work was to compare chemically different milk brands
commercialized in Portugal in terms of fat-soluble vitamins. The evaluated compounds
included vitamin A, D (D2, D3 and proD3), E and pro-A (β-carotene). A liquid-liquid
extraction method was optimized for this purpose. All the studies were carried out in the
presence of BHT (antioxidant) and adequate internal standards. The chromatographic
conditions were also adjusted, with the more effective resolution being achieved using a
gradient of acetonitrile/water/ethyl acetate on a C18 reversed phase. The detection was carried
out simultaneously by UV (diode-array) and fluorescence (λex= 290 nm; λem= 330nm).
When comparing milk brands with the same labelled fat content, all vitamins were present,
with exception of vitamin A acetate, which is only present in fortified foods. Vitamin E was
the major compound among the lipossoluble vitamins. These results are important because
milks with the same fat content are not always associated with the same amount of lipossoluble
vitamins, a relevant information regarding their nutritional quality.
Acknowledgments
Heryka Ramalho is grateful to AlBan Office for a Ph.D. grant (E07D401312BR). S. Freitas and C.
Coelho thank the University of Porto for the financial support through the programme Investigação
Científica na pré-graduação 2009 (Project PP II- Componentes na fracção azotada do leite. Influência
na qualidade e implicações na saúde do consumidor).
438 3 rd meeting of young researchers at UP