EFFECT OF IONIZING RADIATION ON SOME MACRO- AND MICRONUTRIENTS OF SOME NIGERIAN SPICES

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Date
1992-10
Authors
ONYENEKWE, PAUL CHIDOZIE
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Abstract
The effect of gamma irradiation on the microflora of some Nigerian spices were investigated to determine the irradiation dosage required to produce commercially sterile spices without adversely changing their seasoning qualities. Whole and ground forms of red chilli pepper (Capsicum frutescens) coriander (Coriandrum sativum), ginger (Zingiber officinale) rhizomes and Ashanti pepper (Piper guineense) berries with initial microbial load of 104 to 1U7 colony forming units per gram (CFU/g) were subjected to 0, 2.5, 5.0, 7.5 and 10.0 kGy doses of gamma rays from 60Co source. Samples were analysed monthly for a period of nine months. The microbial load decreased by at least two log cycles as a result of irradiation with 5.0 kGy irrespective of spice and form. A dose of 7.5 kGy eliminated the fungal population, while sterilization was achieved with 10 kGy. Storage time enhanced the effect of the 7.5 kGy dose on the bacterial population. The effect of irradiation on the oleoresin content of the spices differed from one spice to the other. Oleoresin content of capsicum was significantly (P < 0.05) increased from 25.45 to 31.61% whereas marginal decrease (7.4 and 9.93%) in oleoresin level of ginger for the whole and ground forms respectively was observed. The sensitivity of Ashanti pepper to irradiation was very similar to that of ginger. Coriander oleoresin level was not affected by the treatment. The observed effect on ginger and Ashanti pepper was overcome with time. The essential oil content of the ground ginger sample significantly (P < 0.05) decreased from 2.39 to 1.89% (v/w) while that of the whole decreased from 2.40 to 2.18% (v/w). Form had a negative effect on the volatile oil content of ginger and Ashanti pepper as shown by GC-MS analysis of the oils. Like the oleoresin, the pungent principles of the spices showed varied sensitivity to radiation treatment. There was dose-dependent decrease in the pungent principles contents of ginger (gingerol) and Ashanti pepper (piperine) whereas capsiacin, the pungent principle of capsicum was radioresistant. No appreciable change was observed with respect to the total available carbohydrate, proteins, moisture and ash contents. Irradiation caused a dose dependent decrease in sucrose level and slight increases in total lipid and reducing sugars at varying levels. Irradiation of the spices with 10 kGy dose of gamma radiation completely eliminated the microflora and did not significantly (P > 0.05) affect the nutrient composition. The form of irradiated sample was observed to play a significant rofe,. Decontamination of capsicum, coriander, ginger and Ashanti pepper using gamma radiation should therefore be carried out with whole rather than the ground spice
Description
A DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA, IN PARTIAL FULFILLMENT FOR THE AWARD OF A DOCTOR OF PHILOSOPHY DEGREE IN BIOCHEMISTRY Department of Biochemistry Ahmadu Bello University Zaria, Nigeria October, 1992
Keywords
IONIZING,, RADIATION,, MACRO- AND MICRONUTRIENTS,, NIGERIAN SPICES
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