By means of two alternative methods lipid and protein hydroperoxides (HP) were determined by fluo... more By means of two alternative methods lipid and protein hydroperoxides (HP) were determined by fluorometry using the diphenyl-1-pyrenylphosphine (DPPP) probe. It has been shown that the formation of the fluorescence was influenced by the type of solvent and HP whereas the presence in the media of antioxidants such tocopherol and butylated hydroxytoluene had no effect. The combination of the chloroform:methanol (2:1, v/v) solvent mixture that is widely used for lipid extraction was combined with suitable solvents to develop a method with the maximum performance in determining HP in lipid extracts. Using a variety of lipids and lipid extracts, the final method proposed agreed well with the thiocyanate method for HP determination. In addition, the DPPP method was very sensitive, precise, accurate, free of interferences and specific for the determination of lipid soluble HP. DPPP can be also used to measure HP soluble in hydroalcoholic media. This alternative procedure showed a similar performance to its lipid soluble equivalent and was able to measure hydrogen peroxide promoted peroxidation of bovine serum albumin and water soluble HP in protein extracts. With the addition of triphenylphosphine the hydroalcoholic method is specific for the determination of protein HP.
Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To unders... more Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To understand the mechanisms and differentiate between the prooxidant and antioxidant potential of oxymyoglobin (OxyMb) and metmyoglobin (MetMb), their prooxidant activity, iron content, solubility, free radical scavenging activity, and iron binding capacity were determined as a function of thermal processing. The ability of native and heat denatured OxyMb and MetMb to promote the oxidation of muscle microsomes was different. MetMb promoted lipid oxidation in both its native and denatured states. Conversely, OxyMb became antioxidative when the protein was heated to temperatures g75°C
Hemoglobin (Hb) has been proposed to be a major pro-oxidant in raw and cooked meats. To understan... more Hemoglobin (Hb) has been proposed to be a major pro-oxidant in raw and cooked meats. To understand the mechanisms and differentiate between the pro-oxidant and antioxidant potential of oxyhemoglobin (OxyHb) and methemoglobin (MetHb), their pro-oxidant activity, protein solubility, radical scavenging capacity, iron content and contribution of non-chelatable iron on lipid oxidation were determined as a function of thermal treatments. The ability of native OxyHb and MetHb to promote lipid oxidation was similar and higher than their corresponding OxyHb or MetHb heated at 68 and 90°C but not different from those at 45°C. The pro-oxidant activity of MetHb heated at 68 and 90°C were similar whereas the pro-oxidant activity of OxyHb heated at 68°C was higher than that heated at 90°C. The decreased pro-oxidant activity of heat-denatured Hb was associated with a decrease in the solubility of heme iron while free iron showed little impact on the lipid oxidation.
Journal of agricultural and food chemistry, Jan 2, 2015
This research strove to understand the relationships between physical structure and oxidative sta... more This research strove to understand the relationships between physical structure and oxidative stability in crackers since mechanisms of lipid oxidation are poorly understood in low-moisture foods. Confocal microscopy showed that lipids formed a continuous matrix surrounding starch granules, and starch-lipid, lipid-air, and protein-lipid interfaces were observed. Unlike bulk oils, meats, and emulsions, lipid hydroperoxides exhibited greater stability in low-moisture crackers as hexanal formation was delayed >20 d. Iron, added at 10 times the concentrations normally found in enriched flour, did not increase oxidation rates compared to the control. EDTA may reduce endogenous iron activity but not as greatly as in other matrices. Addition of fatty acids up to 1.0% of total lipid weight did not statistically affect lipid oxidation lag phases. The unique structure of low-moisture foods clearly affects their resistance to metal-promoted lipid oxidation.
By means of two alternative methods lipid and protein hydroperoxides (HP) were determined by fluo... more By means of two alternative methods lipid and protein hydroperoxides (HP) were determined by fluorometry using the diphenyl-1-pyrenylphosphine (DPPP) probe. It has been shown that the formation of the fluorescence was influenced by the type of solvent and HP whereas the presence in the media of antioxidants such tocopherol and butylated hydroxytoluene had no effect. The combination of the chloroform:methanol (2:1, v/v) solvent mixture that is widely used for lipid extraction was combined with suitable solvents to develop a method with the maximum performance in determining HP in lipid extracts. Using a variety of lipids and lipid extracts, the final method proposed agreed well with the thiocyanate method for HP determination. In addition, the DPPP method was very sensitive, precise, accurate, free of interferences and specific for the determination of lipid soluble HP. DPPP can be also used to measure HP soluble in hydroalcoholic media. This alternative procedure showed a similar performance to its lipid soluble equivalent and was able to measure hydrogen peroxide promoted peroxidation of bovine serum albumin and water soluble HP in protein extracts. With the addition of triphenylphosphine the hydroalcoholic method is specific for the determination of protein HP.
Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To unders... more Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To understand the mechanisms and differentiate between the prooxidant and antioxidant potential of oxymyoglobin (OxyMb) and metmyoglobin (MetMb), their prooxidant activity, iron content, solubility, free radical scavenging activity, and iron binding capacity were determined as a function of thermal processing. The ability of native and heat denatured OxyMb and MetMb to promote the oxidation of muscle microsomes was different. MetMb promoted lipid oxidation in both its native and denatured states. Conversely, OxyMb became antioxidative when the protein was heated to temperatures g75°C
Hemoglobin (Hb) has been proposed to be a major pro-oxidant in raw and cooked meats. To understan... more Hemoglobin (Hb) has been proposed to be a major pro-oxidant in raw and cooked meats. To understand the mechanisms and differentiate between the pro-oxidant and antioxidant potential of oxyhemoglobin (OxyHb) and methemoglobin (MetHb), their pro-oxidant activity, protein solubility, radical scavenging capacity, iron content and contribution of non-chelatable iron on lipid oxidation were determined as a function of thermal treatments. The ability of native OxyHb and MetHb to promote lipid oxidation was similar and higher than their corresponding OxyHb or MetHb heated at 68 and 90°C but not different from those at 45°C. The pro-oxidant activity of MetHb heated at 68 and 90°C were similar whereas the pro-oxidant activity of OxyHb heated at 68°C was higher than that heated at 90°C. The decreased pro-oxidant activity of heat-denatured Hb was associated with a decrease in the solubility of heme iron while free iron showed little impact on the lipid oxidation.
Journal of agricultural and food chemistry, Jan 2, 2015
This research strove to understand the relationships between physical structure and oxidative sta... more This research strove to understand the relationships between physical structure and oxidative stability in crackers since mechanisms of lipid oxidation are poorly understood in low-moisture foods. Confocal microscopy showed that lipids formed a continuous matrix surrounding starch granules, and starch-lipid, lipid-air, and protein-lipid interfaces were observed. Unlike bulk oils, meats, and emulsions, lipid hydroperoxides exhibited greater stability in low-moisture crackers as hexanal formation was delayed >20 d. Iron, added at 10 times the concentrations normally found in enriched flour, did not increase oxidation rates compared to the control. EDTA may reduce endogenous iron activity but not as greatly as in other matrices. Addition of fatty acids up to 1.0% of total lipid weight did not statistically affect lipid oxidation lag phases. The unique structure of low-moisture foods clearly affects their resistance to metal-promoted lipid oxidation.
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Papers by Eric Decker