Oxidative stability of foods and beverages

Oxidative stability of olive oil via quantitative EPR analysis.
The oxidative stability is a major problem in food related industries and is affected by a number of factors, such as oxygen, temperature, presence of metals and light. For example, extra virgin olive oil (EVOO) oxidation is of particular interest due to the complexity of its distribution channels around the world and the fact that it is an individually packaged product (its final quality reflects either positively or negatively on the producer). The resistance of EVOO to oxidation is related to the high levels of monounsaturated triacylglycerols and the presence of natural phenolic antioxidants. EPR is a useful tool to detect free radicals and to determine the level of free radical formation in olive oil during forced oxidation at different temperatures. Application of EPR to foods can reveal important information about radical reactions that may be responsible for food qualities and deterioration.

EPR spectrum detected after addition of spin trap (DMPO) to an olive oil sample at 40 C. Experimental spectrum was simulated and each of the three radical components is presented as separate simulation
Concentrations of peroxyl, alkoxyl, alkyl DMPO-radical adducts, and the oxidized form of DMPO obtained in olive oil during oxidation at 40 C

Antioxidant capacity

DPPH scavenging assay to measure antioxidant activity in beverages.
Antioxidants play an important role as health protecting factor. Scientific evidence suggests that antioxidants reduce the risk for chronic diseases including cancer and heart disease. DPPH (2, 2-Diphenyl-1-picrylhydrazyl) is a free radical that is widely used to test the ability of compounds to act as free radical scavengers or hydrogen donors and to evaluate antioxidant activity. The DPPH assay method is based on the reduction of DPPH by antioxidants and is a rapid and simple method to measure antioxidant capacity of food and beverages.

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EPR industry antioxidant
Antioxidant activity in wine and tea samples determined by the DPPH scavenging assay

Radiation dosimetry

Alanine radical detected by EPR corresponds to the irradiation dose.
Alanine forms a very stable free radical when subjected to ionizing radiation. The alanine free radical yields an EPR signal that is dose dependent, yet is independent of the dose rate, energy type, and is relatively insensitive to temperature and humidity. Thus, alanine dosimetry is equally suited to gamma, e-beam, or x-ray irradiation facilities.

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EPR signal of Alanine radical and the reference marker

Pharmaceutical analysis

Lactose radicals in the tablet filler causes enhanced degradation of the active pharmaceutical ingrediants (APIs)
EPR spectroscopy has a wide variety of applications within the analysis of pharmaceutical compounds. These include photodegradation and oxidation of APIs, the effects of sterilization techniques such as irradiation, interactions between APIs and excipients, etc. Excipients can initiate, propagate or participate in radical chemistry interactions which may compromise the effectiveness of a medication and studied by EPR. Lactose radicals originating from lactose monohydrate, used as a filler in the tablets, react with the API causing an enhanced degradation.


Food science and beverages

Ionizing radiation of poultry and fruits creates very distinctive EPR spectra.
Food irradiation is used to reduce the health risk associated with food-borne pathogens and to prolong shelf life. In fact, ionizing radiation inhibits the division of microorganisms and creates radiolytic products as well as free radicals. In a dry environment these radicals are very stable. For example, irradiated poultry bones or fruits may contain a substantial amount of stable radicals which can be easily detected by EPR.

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EPR spectrum of irradiated chicken bone
EPR spectrum of irradiated mango

Polymer research

Polyethylene radicals detected by EPR can predict premature failure of implants.
Ultra-high molecular weight polyethylene (UHMWPE) has been used as standard lining material in orthopedic implant industry. Oxidative degradation of the polymer caused by free radical formation can lead to premature aging and wear of the material and implant, causing a painful inflammation. EMXnano is capable of detecting and quantifying polyethylene radicals providing reliable and accurate measurements.

EPR spectra of two different polyethylene radicals
Data courtesy of Dr. Gavin Braithwaite, Cambridge Polymer Group

Diamond quality evaluation

EPR can detect the N3 and single substitution nitrogen centers in diamonds.
It is an unambiguous technique for quantifying nitrogen centers and hence provide a tool for color grading. It can also be used to distinguish between synthetic and natural diamonds.

Room temperature EPR spectra of diamonds with different grades (colors)