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