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

Abstract

AbstractThe effects of α‐ and β‐cyclodextrin (CD) on the oxidative stability of linoleic acid (LA) at 35°C were studied by measuring headspace oxygen depletion in airtight 35‐mL serum bottles. LA was encapsulated in α‐CD or β‐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 µmole/L·h. The rates of oxygen depletion for LA, encapsulated at a 1:1 mole ratio (mole CD/moles LA) in α‐CD and β‐CD, were 13.8 and 111 µmoles/L·h, respectively. When LA was encapsulated in α‐CD and β‐CD at a 2:1 mole ratio (moles CD/moles LA), the rates of oxygen depletion were 0.573 and 53.9 µmoles/L·h, respectively. Although α‐CD protected LA from reaction with oxygen at both ratios, the rate of oxygen depletion by LA encapsulated in β‐CD at a 1:1 mole ratio was not statistically different from the control. β‐CD protected LA from reaction with oxygen at a 2:1 mole ratio. 1H nuclear magnetic resonance spectra of the complexes formed from 1:1 mole ratios of LA and CD indicated that LA was encapsulated in α‐CD or β‐CD.