The antioxidant activity of several anthocyanins was tested in vitro on human low-density lipoproteins (LDL) and on a lecithin−liposome system. Samples were incubated at 37 °C, and the extent of oxidation was measured by determining the formation of conjugated diene and hexanal. The inhibition of oxidation increased with concentration of the antioxidant. In the LDL system, when the oxidation was catalyzed with 10 μM copper, malvidin was the best oxidation inhibitor, followed by delphinidin, cyanidin, and pelargonin. When the oxidation was catalyzed with 80 μM copper, the order of antioxidant activity changed and decreased in the following order at all concentrations tested:  delphinidin, cyanidin, malvidin, and pelargonin. In the liposome system, catalyzed with either 3 or 10 μM copper, malvidin was the best inhibitor of both conjugated diene and hexanal formation. At 3 μM copper, delphinidin, cyanidin, and pelargonin showed prooxidant activity. At 10 μM copper, pelargonin followed malvidin in antioxidant potency, and cyanidin and delphinidin were prooxidants. Several antioxidant mechanisms may explain the effect of anthocyanins, including hydrogen donation, metal chelation, and protein binding. Keywords: Anthocyanin; antioxidant evaluation; LDL oxidation; liposome oxidation; natural antioxidants

The effect of bovine serum albumin (BSA) was investigated on the antioxidant activity of phenolic compounds, grape extracts, and red wines in a lecithin−liposome system oxidized at 37 °C with copper. In the absence of BSA, the phenolic compounds inhibited hydroperoxide formation in decreasing order:  ferulic acid, epicatechin, catechin, rutin, malvidin, caffeic acid, quercetin, and propyl gallate. Hexanal formation was inhibited in the following decreasing order:  ferulic acid, epicatechin, catechin, malvidin, caffeic acid, quercetin, rutin, and propyl gallate. Gallic acid and delphinidin promoted hydroperoxide and hexanal formation. In the presence of 20% BSA, liposome oxidation was much slower. Ferulic acid followed by malvidin and rutin were the most efficient in inhibiting lipid and protein oxidation. Two grape extracts and two red wines inhibited hydroperoxide and hexanal formation more efficiently without BSA. With BSA, the red wines were more active than the grape extracts in inhibiting lipid oxidation but were not different in inhibiting protein carbonyls. Keywords: Liposome oxidation; proteins; phenolic compounds; antioxidants; flavonoids; lecithin; liposome; hydroperoxides; hexanal; tryptophan; lysine; protein carbonyls; fluorescence

Lactoferrin is an iron transport protein present in human milk at an average concentration of 1.4 mg/mL. Commercially modified infant formulas based on cow's milk contain much lower amounts of lactoferrin (0.1 mg/mL lactoferrin) and soy based formulas have none. In addition to its role in iron transport, lactoferrin has bacteriostatic and bactericidal activities. Infant formulas are supplemented with relatively large amounts of iron (up to 12 mg/L). The effect of various concentrations of added lactoferrin and supplemental iron on lipid oxidation was tested in two different infant formulas. The extent of oxidation in the formulas as a function of time was determined by formation of hydroperoxides, production of hexanal, and fluorescence. On the basis of all three of these determinations, lactoferrin acted as an antioxidant in the absence and presence of different concentrations of supplemented iron. Lactoferrin inhibited oxidation in a concentration-dependent manner even at concentrations beyond its capacity to bind iron at its two high affinity binding sites. Lactoferrin can be used, therefore, as a dual purpose additive in infant formulas and similar food products for its antioxidant and its antimicrobial properties.

Oxidation in fish during thermal processing was studied by determining volatile production with a static headspace gas chromatographic system. Different processing temperatures and periods were evaluated to simulate conditions of fish industrial treatments. The major volatiles formed included acetaldehyde, propanal, heptane, 2-ethylfuran, pentanal, and hexanal. Changes in volatile composition were studied for different processing times and temperatures. The method for volatile analyses to determine oxidation in fish muscle was tested by correlation with peroxide value, conjugated diene, and thiobarbituric acid indices. Significant single and multivariate regressions were found between the time of thermal treatment and volatiles produced, showing that the amount of 2-ethylfuran was the best predictor of oxidative stability in fish.Paper no. J8854 in JAOCS 76, 231-236 (February 1999).