Determination of microbial quality and quantity of stored cinnamon quills
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Date
2015
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Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Since Cinnamon is one of the major spicecrops in Sri Lanka, maintenance of the quality of the
processed cinnamon is very important. Microbial infection of processed cinnamon quills makes
lowquality final product leading the product less demandedand high post-harvest losses. The
prevailing solution for the microbial infection is fumigation of sulfur and it is not acceptable in
many countries due to its harmful effects for consumer health. Therefore identification of
common types of microbes on quills and determination offavourable conditions for microbial
growth is very important to apply effective control measures.
Methodology
Experiments were conducted to identify the particular types of fungi that thrive on cinnamon
quills and the effect of moisture content, relative humidity, temperature and the storage period to
the microbial growth. Cinnamon quills were collected from three different placesjust after
processing. The moisture contents of the samples were measured in three days interval using
gravimetricmethod. Average relative humidity and ambient temperature were also recorded each
period. In quantification process, the number of colony forming units of fungi and bacteria in
cinnamon quills were counted separately using colony counter.1g of powdered sample of
cinnamon was dissolved in 10ml of distilled sterilized water and 200μl of the solution was
poured in to the culture plates. It was allowed to incubate under the room temperature for about
three days and colony count of fungi and bacteria were taken.The culture plates with microbial
colonies were allowed to incubate further to obtain pure cultures of fungi by frequent sub
culturing. Colony characteristics were observed with the time.The pure cultures of fungi were
used to prepare slide cultures for microscopic identification highlighting the distinguishing
characteristics (Funder, 1953; Cappuccino and Sherman 1996).
Results and Discussion
According to the morphological and microscopic observations, Rhizopus sp., Penicillium sp.,
Aspergillus niger, Aspergillus flavus were the most common types of fungi encountered on
cinnamon quills. In addition to those types Trichoderma sp. was appeared in the samples taken
from one farmer place. It may be happened when peeled cinnamon had been kept in ground for
drying and due to bad sanitary conditions in processing place.
Rhizopus sp. was rapidly growing white coloured fungus with cottony and fuzzy aerial
mycelium. The color of the colony was white initially and turned grey to yellowish brown with
time. It was grown as filamentous, branching coenocytichypha without cross-walls. Sporangia
were developed on the long stalks raised as groups from nodes directly above the rhizoids.
Unicellular ovoid, hyaline and striated sporangiospores were produced by Rhizopus species and
they were grown as root like rhizoids initiallyand finally grown as large mycelium. Penicillium
colonies were initially appeared in white colourand become blue green, gray green and then gray
in colour respectively. It was grown as a thallus with typical characteristic of a highly branched
network of multinucleate, septate, and usually colorless.Many-branched conidia sprout on the
mycelia, bearing individually constricted conidiospores. Aspergillus flavus colonies were
initially appeared in yellowish whitecolour and changed to olive green, dark green and brownish
green respectively.Hyphae grew as a thread-like structure and they were septate and hyaline. The
asexual spores,conidispores, produced in conidia were rough and dark.Aspergillus niger colonies
were initially white and become brownish with white reverse and brownish black colour
respectively covering the entire plate.Morphology of Aspergillus niger showed large, globose,
dark brown conidial heads, which become radiate. Conidiophores are smooth-walled, hyaline or
turning dark towards the vesicle. Conidial heads are biseriatewith the phialides, often septate.
Conidia are globose, dark brown and rough-walled.Trichoderma colonies were wooly and the
initialcolor is white. As the conidia are formed, yellow-green patches become visible making
concentric rings.Conidiosphores were erect, smooth and penicillately branched. Globose conidia
were developed on philides produced in the opposite direction in each point.
At the beginning the fungal infections of stored cinnamon were very low due to lack of enough
inoculums, even though preferable higher moisture contents for fungal growth were retained in
stored cinnamon quills. Next 10 days rapid increments of fungal colony forming units were
observed because preferable moisture contents were retained further in cinnamon quills. Fungal
infection was increased at 10 to 20 days also, but in negative rate due to desirable moisture
contents were still remained in the cinnamon quills. Moisture content in the cinnamon quills
were below 20 % after 20 to 30 days after processing and in this period fungal contaminations
were gradually declined. When the moisture content was reached below 12% in storage
cinnamon, fungal infection was at a minimum level. If the moisture level is reduced to below
12% in storage cinnamon as soon as possible, fungal infection can be controlled efficiently.
The most interesting phenomenon was the symbiotic relationship between fungal growth and
bacterial growth (Figure1).There was very strong significant positive correlation between fungal
and bacterial infections (r = 0.912, p = 0.0001). Bacterial contamination never had been occurred
without fungal infection. Bacterial colonies were appeared in the culture plates used to have the
fungal colonies separately, even though those were treated with antibiotics to retard the bacterial
growth.When fungal infection is terminated by managing moisture content, the bacterial
infection is automatically reduced
Description
Keywords
Export Agriculture, Agriculture, Spices, Crop Production, Pepper