Tests with eight commercially available plant sterol-containing ingredients showed that, under oxidizing conditions, only a very small quantity of oxidation products were produced, report researchers from the University of Valencia and the Hero Institute for Nutrition.
“From the results obtained (low rate of oxidation) in the ingredients tested, we can conclude that the plant sterols remain stable in these ingredients,” wrote the researchers in the Journal of Agricultural and Food Chemistry.
Numerous clinical trials in controlled settings have reported that daily consumption of 1.5 to 3 grams of phytosterols/-stanols from foods can reduce total cholesterol levels by eight to 17 per cent, representing a significant reduction in the risk of cardiovascular disease.
According to a recent market research conducted by Frost & Sullivan, phytosterols are the most heart health targeted and benefited from approved health claims in many markets (as well as recently approval from the European Food Safety Authority).
Despite a wealth of studies supporting the efficacy, the Spanish researchers behind the new study state that, as far as they are concerned, “only one study has been published on the evaluation of the oxidation of phytosterols in different vegetable oils added as microcrystalline phytosterols suspensions prepared from wood-based fractions”.
In order to test the stability towards oxidation, the researchers employed gas chromatographic (GC) technique with mass-spectrometric detection to identify the specific types of plant sterols present in certain sterol-containing ingredients, and then GC with a flame ionization detector (GC-FID) to quantify the phytosterols.
Eight commercially available phytosterol-containing ingredients were tested, with the sterols present in esterified or free form, and derived from pine, soybean, rapeseed, soybean, corn, and sunflower oils in one of three physical forms: Powder, oil paste, or liquid emulsion. Sterols were tested in their original state and then after thermo-oxidation.
Results showed that the most prevalent sterol was beta-sitosterol, and that under oxidizing conditions this produced a range of so-called plant sterol oxidation products (POPs). However, oxidation of beta-sitosterol was limited to between 10 to 50 micrograms per 100 g of beta-sitosterol.
“In view of this low rate of oxidation in the ingredients tested, it can be concluded that the plant sterols remain stable in these ingredients,” wrote the researchers.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, ASAP Article, doi: 10.1021/jf1044102
“Stability of Plant Sterols in Ingredients Used in Functional Foods”
Authors: M. Gonzalez-Larena, G. Garcia-Llatas, M.C. Vidal, L.M. Sanchez-Siles, R. Barbera, M.J. Lagarda