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DEVELOPMENT OF SENSITIVE ANALYTICAL METHODS FOR IDENTIFYING GAMMA IRRADIATED DRIED FRUITS AND NUTS

Ahmad, Anwar (1998) DEVELOPMENT OF SENSITIVE ANALYTICAL METHODS FOR IDENTIFYING GAMMA IRRADIATED DRIED FRUITS AND NUTS. PhD thesis, University of the Punjab, Lahore.

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Abstract

Different analytical techniques, label dosimeters (flexible/rigid), radiation indicators and selected Physico-chemical methods, were employed to identify and/or verify the absorbed dose in gamma irradiated dried fruits and plant nuts. Bulk density of various samples was also measured and it was observed that the values varied depending upon the package size, type and the nature of the fruit or nut. The bulk density was generally higher in dried fruits (0.59-1.00 g cm-3) than in plant nuts (0.62- 0.80g cm-3). As for the analytical tests, thermoluminescence (TL) measurements taken at 80-320°C exhibited clearly linear relationship between radiation dose and the TL values (r=0.97-0.99) indicating dose dependent differences between treated (0.5-1.5 kGy) and untreated samples. The maximum peak heights were observed at 200 °C in each dried fruit/nut. The chemiluminescence (CL) values of the irradiated (0.5-1.5 kGy) dried fruits/nuts and non edible parts, on as-such basis and in certain cases moisture-free, fat-free, ash (mineral matter), were analyzed. The data indicated irregular and inconsistent patterns in each case. Electron spin resonance (ESR) spectroscopy also displayed profound differences in peak heights between irradiated and un-irradiated test samples except the raisin where no peak was observed both in the irradiated and control samples. Gas chromatographic analysis of the ether extracted lipids from p1ant nuts revealed only minor changes in their five acid profi1e upon irradiation treatment. In the case of amino acids analysis although radiation treatment produced marginal and large changes, increase in the content of tyrosine at the expense of phenylalanine was particularly notab1e. In the physico-chemical tests, the data showed decreasing trend in pH with corresponding increase in free and total acidity on irradiation of all the fruit/nut samples. The peroxide value, anisidine value and free fatty acid values in the solvent extracted p1ant nut oils were found to increase with irradiation treatment. The iodine values, a quality parameter which is less affected by environmental parameters, of plant nut oils exhibited consistent decreasing trend with increasing radiation treatment. Similarly there was a regular decreasing pattern in the viscosity of different samples upon irradiation. Among the label dosimeters, the flexible polyethylene (PE) materials were not found suitable in the dose range of 0.1-3.0 kGy. However, the samples of clear PMMA, in the thickness range of 4-10 mm gave almost a linear response in relation to the irradiation doses and the optical response was stable almost for 6 months at ambient storage (15-35 oC RH 55-80%) in all the thicknesses especially 8-10 mm strips. As for the Sterin indicator, an ISP product from USA, their subjective evaluation revealed that these indicators are reliable for and above the designated doses (125 Gy and 300 Gy) of ionising radiation; however, they were also affected by the doses lower than their threshold values. The yellow PMMA dosimeter (YL-PMMA) developed in China was useful in the range of 125-1000 Gy of gamma radiation.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Gamma Irradiation, Dried Fruits, Nuts, Apricot, Date, Raisin, Almond, Peanut, Pinenut, Walnut
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:338
Deposited By:Mr Ghulam Murtaza
Deposited On:26 Jun 2006
Last Modified:04 Oct 2007 21:00

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