Oxidative stability and nuclear magnetic resonance analyses of linoleic acid encapsulated in cyclodextrins

The effects of alpha-and beta-cyclodextrin (CD) on the oxidative stability of linoleic acid (LA) at 35 degrees C were studied by measuring headspace oxygen depletion in airtight 35-mL serum bottles. LA was encapsulated in alpha-CD or beta-CD in an aqueous solution during homogenization at 8000 rpm for 1 min and then dried under vacuum for 60 h at room temperature. Headspace oxygen was measured by thermal conductivity gas chromatography. The rate of oxygen depletion for the control, which contained LA only, was 93.8 mu mole/L.h. The rates of oxygen depletion for LA, encapsulated at a 1:1 mole ratio (mote CD/moles LA) in alpha-CD and beta-CD, were 13.8 and 111 mu moles/L.h, respectively. When LA was encapsulated in alpha-CD and beta-CD at a 2:1 mole ratio (moles CD/moles LA), the rates of oxygen depletion were 0.573 and 53.9 mu moles/L.h, respectively. Although alpha-CD protected LA from reaction with oxygen at both ratios, the rate of oxygen depletion by LA encapsulated in beta-CD at a 1:1 mole ratio was not statistically different from the control. beta-CD protected LA from reaction with oxygen at a 2:1 mole ratio. H-1 nuclear magnetic resonance spectra of the complexes formed from 1:1 mote ratios of LA and CD indicated that LA was encapsulated in alpha-CD or beta-CD.