Variation of carotenoids, total phenolics and antioxidant activity levels in ananas comosus from different counties in Kenya with duration of storage
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Date
2015-11
Authors
Obumba, Maxwell Ouma
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Epidemiological studies have repeatedly shown the apparent association between high
fruit intake and lower incidence of chronic degenerative diseases. The chemo protective
properties of fruits have been partly attributed to the antioxidants including phenolic
compounds and carotenoids. Despite numerous reports of commonly available tropical
fruits on their antioxidants and antioxidant activity, no information is available for the
smooth cayenne, a common variety of Ananas comosus grown in Kenya. The concern on
the perishability of the fruit also calls for investigation on the variation of the levels of
antioxidants with duration of storage. The antioxidant activity, carotenoid content (lutein,
beta-carotene and lycopene) and total phenolic content of fruit samples of smooth
cayenne sourced from five Counties were studied. Samples were obtained from Kiambu,
Homabay, Kilifi, Kericho and Nyamira and analysed for 7 days of storage under room
temperature (21°C-25°C). The carotenoids were determined using high performance
liquid chromatography method, Folin-Ciocalteu reagent used to measure total phenolic
content and expressed as gallic acid equivalents. The in vitro antioxidant activity was
assessed by DPPH Assay and expressed as ICso. One way ANOV A was employed for
statistical data analysis. The levels of beta-carotene and lycopene were below detection
limit in all samples while lutein levels ranged between 107.52±1.25 )..I.g/IOOgand
233.55±5.77)..1.g/100g.The antioxidant capacity ranged between 45.00 ug/l Oug and 88.15
)..I.g/IOOgwhile total phenolic content ranged from 82.64±0.28 ~lg/lOOgto 164.64±0.28
)..I.g1O/ Og, expressed as gallic acid equivalents. The Kilifi sample showed the highest
radical scavenging activity with ICso value of 45.00±1.13)..1.g/100gwhile the Nyamira
sample showed the highest content of phenolic compounds (160.79±0.28 to
164.64±0.28). Findings not only showed that levels of lutein, phenolics and antioxidant
activity differed significantly among samples but there also was generally a significant
increase in the levels of lutein and total phenolic content during storage from day 1 to 7
(p<0.05), indicating the effect of storage on the nutritional value of the fruit. Findings
pointed out that storage beyond the fourth day had no significant change in the
antioxidant activity of samples from Homabay, Kilifi, Kericho and Nyamira. There were
notable strong positive correlations between total phenolic content and the antioxidant
activity (r> 0.875) attributing the phenolic compounds to the antioxidant activity. The
findings indicated that the smooth cayenne variety of Ananas comosus contains sufficient
levels of lutein and phenolic compounds that increase with fruit storage and would be of
nutritional value. The fruit should therefore be promoted for consumption with a
particular focus on reducing incidences of chronic degenerative diseases.
Description
A thesis submitted in partial fulfillment of the requirements for the award of the
degree of Master of Science (Chemistry) in the school of Pure and Applied Sciences
of Kenyatta University. November, 2015