Photoprotection of Vitamins in Skimmed Milk by Aqueous Soluble Lycopene - Gum Arabic Microcapsule

M.A. MONTENEGRO; I.L. NUNES; A.Z. MERCADANTE; C.D. BORSARELLI

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

American Chemical Society

Lugar: Columbus, USA; Año: 2007 vol. 55 p. 323 - 329

0021-8561

Riboflavin (Rf)-mediated photosensitized degradation of vitamins A and D3 in skimmed milk under illumination with white fluorescence lamp was studied by using HPLC technique. The photosensitized degradation of both vitamins followed first-order kinetics, and the temperature effect on the observed photodegradation rate constant allowed the determination of activation energy Ea as being 4 and 16 kcal/mol for vitamins A and D3, respectively. The addition of lycopene microencapsulated by spray-drying with gum arabic-sucrose (8:2) mixture (MIC) produced a reduction of ca. 45% in the photosensitized degradation rate of both vitamins. Front-face fluorescence experiments showed the same photoprotection factor in the degradation of Rf itself, indicating that the photodegradation mechanism involved Rf-mediated reactive species, such as the excited triplet state of Rf, e.g. 3Rf* and/or singlet molecular oxygen, 1O2. The interaction of both 3Rf* and 1O2 with MIC was evaluated in aqueous solutions by using laser-induced time-resolved absorption or emission spectroscopy, and the contribution of inner-filter effect in the presence of MIC in skimmed milk was evaluated by diffuse reflectance spectroscopy. The main operating mechanism of photoprotection is due to the deactivation of 3Rf* by the proteic component of gum arabic, thus gum arabic based microcapsules could be used to improve the photostability of milk during its storage and/or processing under light.