Application of electron paramagnetic resonance (EPR) spectroscopy for control of irradiated food

Abstract

Four groups of foodstuffs were irradiated in a ""Co source with doses from 0.3 to 10 kGy and subsequently measured by EPR spectrometry at room temperature in air: (1) poultry bones and fins, scales and bones of carp, (2) seeds of selected fruits, (3) dehydrated mushrooms, and (4) a selected set of spices and herbs. Qualitative and, in some cases, quantitative data related to the absorbed dose of radiation were collected. In the irradiated bones from poultry and carp an asymmetric singlet (gl = 2.0030. g,, = 1.9973; AH,,, = 0.85 mT) was detected which was stable at room temperature and was similar to that previously found in irradiated mammalian bones. Another stable EPR signal = 2.0024. AHpp = 0.56 mT) was found in the fins and scales of carp which was about five times more intense in fins than in scales. In pips of pears irradiated with a dose of 3 kGy, a signal which was about twice as intense as the endogenous signal was recorded. A multicomponent EPR signal derived from the stones of dates differed from the endogenous signal even when a low dose (0.5 kGy) was applied. A multicomponent EPR signal is also observed in dried mushrooms irradiated with a dose of 3 kGy. In white mustard, paprika and chilli no native EPR signal exists and a radiationinduced stable EPR signal can still be observed after a period of 3 months. The radiation-induced EPR signal in black pepper was highly sensitive to moisture and disappeared, yet the native signal survived. The pilot experiments performed with irradiated stones of cherries, plums, lemons. apple pips, raspberries, cranberries, red currants, blackcurrants. gooseberries and tomatoes showed the induction o f short-lived EPR signals of no practical use for the control of food irradiation.

Comparison of the Effect of X-ray and Electron Beam Irradiation on Some Selected Spices

“…These signals decrease considerably during the first week after irradiation and then remain relatively stable (15). Therefore, the EPR measurements were performed during the second week after irradiation, when the signals have become relatively stable but are still strong enough to allow an optimal comparison between the two types of irradiation.…”

Aspects of detection of irradiated foods by EPR spectroscopy

“…The following classes of foodstuffs were examined: pork, beef, poultry, fish, egg shell, seeds of raw and dried fruits, assortment of spices and herbs, dried vegetables and mushrooms, dehydrate gelatin, macaroni, flavour additives. With all of them positive results of the detection of irradiation have been achieved [4][5][6]. We participated from 1989 to 1994 in ADMIT (Analytical Detection Methods for Irradiation Treatment of Foods) Programme co-ordinated by Joint FAO/IAEA Division in co-operation with WHO [7] and were actively involved in a number of international intercomparison studies on irradiated foodstuffs organized by CEC, ADMIT, MAFF [8].…”

“…For the estimation of the absolute spin concentration we used CuSO4 6112 0 single crystals weighing 10 -3-10 -Z g each. The accuracy of weighing was 0.0005 g. The integrated EPR spectra of Cu" containing single crystals of cupric sulfate properly positioned inside the resonant cavity were compared with those registered with the reference samples which was the irradiated compact bone (bovine) powder carefully washed and defatted with ethyl alcohol and ethyl ether mixture of the average grain size about 200 gm (sieve selected fraction 100-300 gm) [4]. The reference bone samples were irradiated with the dose of 35 kGy and stored with the admission of air during one month.…”

“…The examples of applying the method of the estimation of dose with the use of bone powder are the dose dependence study of the EPR signals in bones, fish bones and dates to prove their radiation origin [4] and the evaluation of dose in chicken bones excised from carcasses exposed to low, medium and high doses of gamma rays in blind tests. The accuracy of dose determination was in this case at the level of about 20% [14].…”

“…It is quite often that increasing water content suppressed drastically the intensity of radiation induced EPR signals in foods making the application of the method doubtful [4].…”