Increase In Lipid Oxidation Products Research Articles

Changes in key aroma-active compounds and sensory characteristics of sunflower oils induced by seed roasting.

This study investigated the changes in aroma composition and perception of sunflower oils induced by seed roasting using sensory-oriented flavor analysis. Volatile compounds were extracted by solvent-assisted flavor evaporation and headspace solid-phase microextraction. Odorants were characterized by gas chromatography-olfactometry-mass spectrometry and aroma extract dilution analysis. The cold-pressed and roasted sunflower oils contained 13 and 50 odorants, respectively, with the flavor dilution factors between 1 and 256. Fifty-six odorants were newly identified in sunflower oils. Quantification of 26 important odorants by the external standard method revealed apparent changes induced by seed roasting in loss of terpenes, formation of Maillard reaction products, and the increase in lipid oxidation products. The most important odorants (odor active values, OAVs=1-1857) in the cold-pressed sunflower oil included α-pinene (11,145µg/kg), β-pinene (4068µg/kg), linalool (56µg/kg), hexanal (541µg/kg), octanal (125µg/kg), α-phellandrene (36µg/kg), and (E)-2-octenal (69µg/kg), contributing to the raw sunflower seed, woody, green, earthy, and sweet aromas of the oil. The most important contributors (OAVs=1-884) to the roasted, smoky, and burnt aromas of the roasted sunflower oil were 2- and 3-methylbutanal (6726 and 714µg/kg), 2,6-dimethylpyrazine (2329µg/kg), 2,5-dimethylpyrazine (12,228µg/kg), 2,3-dimethylpyrazine (238µg/kg), 2,3-pentanedione (1456µg/kg), 2-pentylfuran (1332µg/kg), 2,3-dimethyl-5-ethylpyrazine (213µg/kg), and 1-pentanol (693µg/kg). Aroma recombination of the key odorants in odorless sunflower oil adequately mimicked the general aroma profiles of sunflower oils. This study provides an important foundation for understanding the relationship between oil processing and aroma molecules of sunflower oils. PRACTICAL APPLICATION: The clear changes observed in the composition and concentrations of key aroma compounds explained the changes in sensory characteristics of sunflower seed oils induced by seed roasting on a molecular basis. Characterizing the key aroma-active composition of sunflower oil and investigating its relationship with oil processing could provide important practical applications for the sunflower oil industry in flavor regulation, quality control, product development, and process optimization.

Short communication: Flavor and flavor stability of cheese, rennet, and acid wheys

Dried whey ingredients are valuable food ingredients but potential whey sources are underutilized. Previous work has established flavor and flavor stability differences in Cheddar and Mozzarella wheys, but little work has compared these whey sources to acid or rennet wheys. The objective of this study was to characterize and compare flavor and flavor stability among cheese, rennet, and acid wheys. Full-fat and fat-free Cheddar, rennet and acid casein, cottage cheese, and Greek yogurt fluid wheys were manufactured in triplicate. Wheys were fat separated and pasteurized followed by compositional analyses and storage at 4°C for 48 h. Volatile compound analysis and descriptive sensory analysis were evaluated on all liquid wheys initially and after 24 and 48 h. Greek yogurt whey contained almost no true protein nitrogen (0.02% wt/vol) whereas other wheys contained 0.58%±0.4% (wt/vol) true protein nitrogen. Solids and fat content were not different between wheys, with the exception of Greek yogurt whey, which was also lower in solids content than the other wheys (5.6 vs. 6.5% wt/vol, respectively). Fresh wheys displayed sweet aromatic and cooked milk flavors. Cheddar wheys were distinguished by diacetyl/buttery flavors, and acid wheys (acid casein, cottage cheese, and Greek yogurt) by sour aromatic flavor. Acid casein whey had a distinct soapy flavor, and acid and Greek yogurt wheys had distinct potato flavor. Both cultured acid wheys contained acetaldehyde flavor. Cardboard flavor increased and sweet aromatic and buttery flavors decreased with storage in all wheys. Volatile compound profiles were also distinct among wheys and changed with storage, consistent with sensory results. Lipid oxidation aldehydes increased in all wheys with storage time. Fat-free Cheddar was more stable than full-fat Cheddar over 48h of storage. Uncultured rennet casein whey was the most stable whey, as exhibited by the lowest increase in lipid oxidation products over time. These results provide baseline information for the viability of processing underutilized wheys into value-added ingredients.

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

AbstractThe effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at −20 and −30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of −20 °C compared with samples stored at −30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at −20 than −30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both −20 and −30 °C but was greater at −20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at −20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish.© 2002 Society of Chemical Industry

Metabolic response of skeletal muscle to ischemia.

To evaluate the temporal relationship and potential correlation between intramuscular phosphagen levels, lipid oxidation, and extent of muscle injury, a canine gracilis muscle model was used to study the consequences of a global ischemic episode for up to 7 h duration with reperfusion for 4 h. In this model the contralateral gracilis muscle was prepared identically to the test side but was not subjected to ischemia and thus served as a control. Blood flow, oxygen consumption, and lactate and glycerol release were measured before and after 2- and 7-h ischemic stress periods. The intramuscular metabolites, glycogen, lactate, phosphocreatine, and ATP, as well as free fatty acid conjugated dienes, were measured before, during, and after the ischemic insult. A 2-h ischemic insult resulted in minimal ultrastructural damage and complete regeneration of intramuscular phosphagens and glycogen on reperfusion with complete normalization of lipid oxidation products. In contrast, a 7-h ischemic insult resulted in profound injury at the ultrastructural level with an inability to restore intramuscular phosphagens and glycogen on reperfusion. This severe muscle injury correlated with a 2.5-fold increase in lipid oxidation products (free fatty acid conjugated dienes) and a decline in ATP levels below 5 mumol/g dry wt on reperfusion. Our results emphasize the prolonged glycolytic activity of skeletal muscle during global ischemia and document the increased production of oxygen free radical-mediated lipid oxidation products in irreversibly injured muscle.