Characterization of cranberry polyphenolics, alkyl gallates, metal chelators and beta-carotene as effectors of lipid oxidation in muscle food systems.

摘要

Antioxidants are added to muscle foods separately or in combination with metal chelators to retard the onset of lipid oxidation processes. Metal chelators can also accelerate metal-mediated lipid oxidation under certain conditions. The major objectives of this research were to characterize cranberry polyphenolics, alkyl gallates and metal chelators such as ethylenediaminetetraaceticacid (EDTA) and tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN) as effectors of lipid oxidation in muscle food systems. Another objective was to develop a non-invasive approach to monitor lipid oxidation in comminuted muscle.;Quercetin was identified as the compound responsible for most of the inhibitory activity of the chloroform extract prepared from cranberry juice powder. Quercetin was a more effective inhibitor of lipid oxidation compared to its glycoside possibly due to its higher ability to incorporate into the muscle membranes and scavenge free radicals at the lipid-water interface.;Propyl gallate significantly inhibited lipid oxidation in mechanically separated turkey (MST) compared to other gallates. The fact that propyl gallate inhibited lipid oxidation, but was not incorporated in the muscle membranes indicates that the availability of propyl gallate at the lipid-water interface or aqueous phase was responsible for its inhibitory properties in MST. Butyl alcohol and ethanol more effectively incorporated octyl and lauryl gallates into the membrane SMS B phase compared to ethyl acetate. Propyl gallate bound added hemoglobin to insoluble components of washed cod muscle more compared to octyl and lauryl gallates. This suggests a probable mechanism by which propyl gallate inhibited hemoglobin-mediated lipid oxidation in muscle tissue.;TPEN accelerated added iron and hemoglobin-mediated lipid oxidation in washed cod. Addition of iron-ethylenediaminetetraaceticacid (Fe-EDTA) inhibited lipid oxidation in washed cod. TPEN was found to deliver more iron into the membranes compared to EDTA. Thus partitioning of iron into the membranes may have facilitated greater interaction with the membrane lipids for lipid oxidation processes to occur in washed cod.;A novel approach for non-invasively monitoring lipid oxidation was developed using Raman spectroscopy with beta-carotene as an internal marker in MST. Loss of the Raman signal in MST containing endogenous or 20-50ppm added beta-carotene was highly correlated with the formation of thiobarbituric acid reactive substances (TBARS).