Scientific Study

Phytosterols in commercially grown Runner; Virginia; and Spanish peanuts (n = 221) from 2005 and 2006 were quantified by a combination of acid hydrolysis and alkaline saponification steps followed by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry analysis of the trimethylsilyl derivatives. Delta(5)-Avenasterol; which partially degrades during acid hydrolysis; was quantified after alkaline saponification plus direct analysis of the steryl glucosides isolated by solid-phase extraction. beta-Sitosterol; Delta(5)-avenasterol; campesterol; and stigmasterol were identified in peanut lipid extracts as the dominant sterols by retention time mapping and mass spectra with recoveries approximately 99%. Clerosterol; Delta(5;24(25))-stigmastadienol; Delta(7)-sitosterol + cycloartenol; and one unidentified sterol were also present but at low levels. Free and esterified phytosterols accounted for approximately 80% of the total sterols determined; the remainder was attributed to steryl glucosides. The total sterol level in Spanish market type peanuts (144.1 +/- 5.3 mg/100 g) was significantly greater than both Runners (127.5 +/- 6.3 mg/100 g) and Virginias (129.3 +/- 6.9 mg/100 g) (P < 0.05). Tamspan 90 (146.9 mg/100 g) followed by OLIN (138.5 mg/100 g) showed the highest total sterol content among the cultivars examined. Cultivar effects were strongly significant (P < 0.001) for all phytosterols; whereas production year effects were strongly significant (P < 0.001) for Delta(5)-avenasterol; Delta(5;24(25))-stigmastadienol; and the combined quantities of Delta(7)-sitosterol + cycloartenol; which coeluted. Cultivar x year interactions were strongly significant (P < 0.001) in all sterols except for Delta(7)-sitosterol + cycloartenol (P < 0.01). Total phytosterol contents were markedly higher than those reported in the existing literature for Runner and Virginia type peanuts; partially attributed to the inclusion of steryl glucosides in the analysis.