Trans-Hydroxy, Trans-Epoxy, and Erythro-dihydroxy Fatty Acids Increase during Deep-Frying.

Deep-frying of food is a common cooking technique causing thermal oxidation of fatty acids (FA). Here, we investigated for the first time the formation of hydroxy-, epoxy- and dihydroxy-FA derived from oleic, linoleic (LA), and α-linolenic acid (ALA) during frying. Potato chips were fried in high-oleic sunflower oil for 4 × 5 cycles on 2 days, and the oil was comprehensively analyzed by liquid chromatography-tandem mass spectrometry. During frying, the E,Z-9- and E,Z-13-hydroperoxy-LA and -ALA concentrations decrease while their corresponding hydroxy-FA remain constant. The concentrations of both E,E-9-/13-hydroperoxy-LA and E,E-9-/13-hydroxy-LA increase with the frying cycles, which is also found for the concentration of trans-epoxy-FA. The increase in trans-epoxy-FA is more pronounced than that of the corresponding cis-epoxy-FA, exceeding their concentrations on the second day of frying. This selective change in the cis-/trans-epoxy-FA ratio is also observed for their hydrolysis products: concentrations of erythro-dihydroxy-FA, derived from trans-epoxy-FA, increase during frying stronger than threo-dihydroxy-FA derived from cis-epoxy-FA. Based on these data, we suggest that the ratio of E,E-/E,Z-hydroxy-FA, in combination with the cis-/trans-epoxy-FA ratio, as well as the threo-/erythro-dihydroxy-FA ratio are promising new parameters to evaluate the heating of edible oils and to characterize the status of frying oils.

Relevance of ß-Glucan Molecular Properties on Its Suitability as Health Promoting Bread Ingredient.

The fate of ß-glucan (BG) health promoting properties during food production is crucial, but not predictable yet. Therefore, high molar mass BG (hBG) and control BG (cBG) were extracted from two barley varieties, characterized and added to wheat breads at levels of 3% and 6%. Bread quality criteria, carbohydrate contents and BG content and structural properties were determined. Additionally, breads were subjected to an in vitro digestion. The BG content in the chyme, molar mass, molar ratio, viscosity and bile acid retention were determined. The hBG and the cBG decreased loaf volume and increased crumb hardness with increasing BG content. The reduction in BG content during bread making was similar for hBG and cBG, but the molar mass of cBG decreased to a greater extent. As a result, only 10% of cBG entering in vitro digestion were found in the chyme afterwards, while 40% of the ingested hBG were detected. Molar mass reduction was much more severe for cBG compared to hBG. The use of hBG showed higher viscosity and better bile acid retention, indicating cholesterol lowering properties, compared to similar or higher amounts of cBG. These results provide valuable knowledge on the criteria to select BG-rich raw materials for ideal health promoting properties.