13 January 2017
Journal of the Science of Food and Agriculture. 97 - 2, pp. 564 - 571. 2017.
Marlene Costaa, Sonia Losada-Barreiro*ab, Fátima Paiva-Martinsa, Carlos Bravo-Díazb
Autor affilations:
*Corresponding authors
aREQUIMTE-LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007, Portugal
bDpt. Química Física, Facultad de Química, Universidad de Vigo, Vigo-Pontevedra, Spain
E-mail: sonia@uvigo.es
Abstract
BACKGROUND:
The relationships between the hydrophilic-lipophilic balance (HLB) of antioxidants (AOs) and their distributions and efficiencies in emulsions are not fully understood. Recent reports indicate that, for series of homologous antioxidants of different hydrophobicity, the variation of their efficiency with the HLB of the AO increases with the alkyl chain length up to a maximum (C3 -C8ester) followed by a decrease (cut-off effect).
RESULTS:
We determined the distributions of a series of caffeic acid derivatives in intact soybean emulsions by employing a specifically designed chemical probe located in the interfacial region of the emulsion. We also determined the AO efficiencies in the very same emulsions. We demonstrate that the variation of the percentage of AO in the interfacial region of soybean oil-in-water emulsions with the AO HLB parallels that of their antioxidant efficiency.
CONCLUSION:
The results provide physical evidence that the variations in the efficiency of homologous series of antioxidants in emulsions are the result of differences in their distribution. The results confirm that, with other things being equal, there is a direct relationship between the percentage of AO in the interfacial region of the emulsions and their efficiency, providing a natural explanation, based on molecular properties, of the cut-off effect.
