The oxidative stability of phytosterols in canola, coconut, peanut, and soybean oils was examined under simulated frying conditions of 100, 150, and 180°C for 20 h. The degree of oxidative decomposition was assessed by the loss of phytosterols, accumulation of phytosterol oxides, and the change in fatty acid profiles. The phytosterol oxides produced in the oils were identified using mass spectroscopy. Oils with higher levels of polyunsaturated fatty acids showed greater amounts of sterol loss; however, the sterol loss was less complete than in the more saturated oils. A greater variety of sterol oxides was observed at the lower temperatures of 100 and 150°C compared to 180°C. This study demonstrates that under conditions similar to frying, there is a loss of phytosterols and polyunsaturated fatty acids. The accumulation of phytosterol oxides may be temperature-limited because of further breakdown into products not measurable by typical gas chromatography-mass spectrometry techniques.

No abstract

No abstract

The effect of sodium caseinate and whey protein concentrate on benzaldehyde, d-limonene, and citral flavor intensity was determined by quantitative descriptive analysis deviation from reference using a 12-member trained panel. The concentrations for the benzaldehyde, d-limonene, and citral flavor intensity references were 17.8, 53.0, and 19.8 ppm, respectively. The concentration for both protein references was .25%. Flavored protein solutions were held for 17 h at 6 degrees C and contained benzaldehyde (17.8 ppm), d-limonene (53 ppm), or citral (19.8 ppm) and 2.5% sucrose with 0, .125, .25, or .5% protein. Benzaldehyde flavor intensity declined as the whey protein concentrate concentration increased from 0 to .5%. There was no significant difference in benzaldehyde flavor intensity with casein compared with the reference. The d-limonene flavor intensity declined as the protein concentration increased. Panelists found no significant drop in citral flavor intensity with casein or whey protein. Decreased benzaldehyde and d-limonene flavor intensity in the presence of whey protein concentrate or casein may be due to nonpolar interactions (casein), interaction with nonpolar binding sites, cysteine-aldehyde condensation, or Schiff base formation (whey protein concentrate).

A freeze-dried whey powder was produced by microfiltration of Cheddar cheese whey. A 0.2-micron ceramic membrane in a stainless steel housing unit was used to concentrate components > 400 kDa present in the whey. The experimental whey powder, derived from Cheddar cheese whey, and a commercial whey powder were subjected to proximate analysis, lipid classes, phospholipid classes, and fatty acid compositional analyses. Commercial whey powder and commercial soybean lecithin were subjected to an alcohol fractionation procedure in an effort to alter the ratio of phosphatidyl choline to phosphatidyl ethanolamine and the functionality of dairy phospholipids. The fractionation procedure produced an alcohol-insoluble fraction containing 84% phosphatidyl ethanolamine, whereas the alcohol-soluble fraction resulted in a decrease in the phosphatidyl choline to phosphatidyl ethanolamine ratio. The commercial whey contained a higher ratio of phospholipids to neutral lipids compared with the experimental whey. The classes of phospholipids present within the two wheys were similar, whereas the experimental whey contained a phosphatidyl choline content twice that of the commercial whey, and the phospholipids composition of both wheys differed from the milk fat globule membrane. Comparison of the phospholipids and fatty acid composition of the wheys with the soy lecithin revealed that although the wheys were similar to each other, they differed from the soy lecithin in both the classes of phospholipids present and in the fatty acid composition. These compositional differences may influence the functionality of whey phospholipids.