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Contaminación fúngica toxigénica de las bebidas a base de cacao: una
posible preocupación de salud pública en un país tropical
Toxigenic fungal contamination of cocoa-based beverages: A possible
public health concern in a tropical country
Resumen
Las enfermedades transmitidas por los alimentos y su deterioro microbiano son el resultado de la incapacidad de regular o controlar
los microorganismos en una o más etapas de la cadena alimentaria, desde la producción de la materia prima hasta el consumo
del producto nal. Este estudio se realizó para detectar algunas bebidas a base de cacao que se venden en Nigeria, con el n
de determinar el estado micológico y aatoxínico de dichos alimentos. Setenta y nueve (79) muestras de diferentes marcas de
bebidas de cacao recogidas de diferentes mercados en la ciudad de Benín (Nigeria), se evaluaron mediante la estimación de la
carga de hongos; utilizando el método de recuento de placa estándar y el nivel de aatoxina B1 (AFB1) por extracción de columna
de gel de sílice de inmunoanidad y cromatografía de capa na con detección espectrofotométrica. Las colonias de moho aisladas
de las muestras se identicaron mediante métodos micológicos estándar como Aspergillus avus, Aspergillus niger y Aspergillus
fumigatus. La muestra de bebidas Zamis registró el mayor recuento de hongos de 5500 ufc /g, nivel de AFB1 de 40,6 ± 3,2 μg/kg y
contenido de humedad de 4,00%; mientras que la muestra de bebidas Peak registró el menor recuento de hongos de 500 ufc /g, el
nivel de AFB1 de 5,3 ± 2,5 μg/kg y el contenido de humedad del 1.00%. AFB1 no se detectó en muestras de bebidas de Ovaltine
y Benco. Los géneros más frecuentes de moho en todas las muestras fue A. avus, con una incidencia de 63,3%. Las bebidas
con bolsita de cacao que se venden en la metrópolis de Benin conllevan un riesgo potencial para la salud. Por lo tanto, una mejor
manipulación a través del procesamiento, la conservación y el almacenamiento de los alimentos puede minimizar las aatoxinas
en los alimentos y garantizar una calidad sostenible del suministro de alimentos. Estos hallazgos sugieren la necesidad de una
atención urgente a las posibles implicaciones para la salud pública.
Palabras Clave: Aatoxina B1; bebida cacao; mohos; salud pública.
Abstract
Food safety is a call for concern nowadays. Food borne disease and microbial spoilage of food result from the failure of or inability
to control microorganisms at one or more stages of food chain, from raw material production to consumption of the nal product.
This study was undertaken to screen some cocoa-based beverages sold in Nigeria in order to ascertain the mycological and
aatoxin status of such foods. Seventy-nine (79) samples of different brand of cocoa beverages collected from different markets
in Benin City, Nigeria was evaluated by estimating the fungal load; using standard plate count method, and aatoxin B1(AFB1)
level by immunoafnity silica gel column extraction and thin layer chromatography with spectrophotometric detection. Colonies
of mould isolated from the samples were identied by standard mycological methods as Aspergillus avus, Aspergillus niger and
Aspergillus fumigatus. Zamis beverage sample recorded the highest fungal count of 5500 cfu/g, AFB1 level of 40.6 ± 3.2 µg/kg
and moisture content of 4,00%; while Peak beverage sample recorded the least fungal count of 500 cfu/g, AFB1 level of 5.3 ± 2.5
µg/kg and 1.00% moisture content. AFB1 was not detected in Ovaltine and Benco beverage samples. The most frequent genera
of moulds in all samples was A. avus, having an incidence of 63.3%. Sachet cocoa-based beverages sold in Benin metropolis
carry potential health hazard. Thus, improved handling through food processing, preservation and storage can minimize aatoxins
in foodstuffs and ensure sustainable quality of food supply. This ndings suggest needs for urgent attention to the possible public
health implications.
Keywords: Aatoxin B1; cocoa beverages; moulds; Public health.
Chinwe-Christy, Isitua
*1
; Isaiah-Nnanna, Ibeh
2
; Tony- Ifeanyi, Ojiezeh
3
(Recibido: Febrero - 2018, Aceptado: Marzo - 2018)
1
Department of Biological Sciences, Microbiology Unit, College of Sciences, Afe Babalola University Ado-Ekiti, KM 8.5, Afe
Babalola Way, P.M.B. 5454, Ekiti State, Nigeria. Email:christykings@yahoo.com, isituacc@abuad.edu.ng
2
Department of Medical Laboratory Sciences, School of Basic Medical Sciences, College of Medicine, University of Benin,
P.M.B. 1154, Benin City, Edo State, Nigeria.
3
Department of Medical Laboratory Sciences, College of Medical and Health Sciences, Afe Babalola University Ado-Ekiti, KM
8.5, Afe Babalola Way, P.M.B. 5454, Ekiti State, Nigeria
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INTRODUCTION
In recent years food and feed safety has been a major
concern of nations especially as more knowledge
is gathered on the occurrence of natural toxins in
food stuffs, fertilizers, animal feed and edible plant
materials. World Health Organization (WHO) has
characterized naturally occurring toxins as signicant
sources of food borne illnesses (1), while the Food
and Agriculture Organization (FAO) has estimated
that fungal toxins alone contaminate about 25% of
agricultural products worldwide resulting in great
losses for farmers (2) (3).
Food safety is usually determined by the absence or
presence of pathogenic organisms, or their toxins,
and the number of pathogens, with their expected or
destructive agents (4). The level of spoilage microbes
reects the microbial quality, wholesomeness,
of a food product as well as the effectiveness of
measures used to control or destroy such microbes
(5). Food borne disease and microbial spoilage of
food result from the failure of or inability to control
microorganisms at one or more stages of food chain,
from raw material production to consumption of the
nal product (6). Specically, the microbiological tools
are used to assess the safety of food, adherence to
good manufacturing practices (GMPs), the keeping
quality (shelf life) of certain perishable foods and
the utility (suitability) of a food or ingredient for a
particular purpose (7).
In Nigeria, like other tropical and sub-tropical regions
of the world, aatoxicosis is a public health problem
and control of aatoxin contamination requires
thorough risk assessment, monitoring, quality
control and empirical data (8). Aatoxin problem
is global; however, it is more serious in tropical
countries of the world where relative humidity is
high and temperatures conducive for the growth
and production of aatoxin by moulds. Aatoxin are
potent carcinogens that are produced as secondary
metabolites of strains of Aspergillus parasiticus
and Aspergillus avus that grow on important food
crops such as groundnuts, maize, cocoa and other
oilseeds (9).
The consumption of cocoa-based beverages is
fast gaining ground in Nigeria due to its nutritional
and health benets. Its production has been an
increasing trend in Nigeria without much concern for
whether or not they meet the microbiological criteria
for food safety and public health consequences
(10). Cocoa powder has a reduced water activity
that may not constitute suitable substrate for the
growth of microbes, but if not handled in hygienic
form before consumption can result in the production
of pathogenic organisms or production of toxic
metabolites that can cause serious health problems
(10).
Moulds are frequently found in cocoa beans and
it is not uncommon to nd mycotoxin-producing
moulds and occasionally low levels of mycotoxins
in cocoa (11). Beside Aspergillus being among
the fungus genera, it has also been implicated in
mycotoxicosis because it produces toxic metabolite
called mycotoxins in food. Some of the species of
this genus that have been severally reported in
mycotoxicosis includes Aspergillus avus, which
produces aatoxin that causes cancer of the liver,
Aspergillus ochraceous and Aspergillus niger which
produce ochratoxin that is nephrotoxic (4).
In view of this, there is need to determine the
mycological safety of the cocoa based beverages
we consume as health drink so as to stem down the
occurrences of mycotoxin associated diseases in our
community. Also, regardless of the wide consumption
of these group of food by Nigerians, little or no data
are available as regards mycotoxin levels in the
commodities; the need for this study.
In this research, we screened some sachet cocoa
beverages retailed in Benin metropolis, Edo State,
Nigeria for aatoxin B1 levels and fungal load with
the aim of providing preliminary useful data on the
aatoxin status of these foods consumed in many
homes and to enlighten the manufacturers and
consumers on the need for proper food processing,
handling and storage.
MATERIALS AND METHODS
Collection of samples
Seventy-nine (79) samples of different brands of the
beverages (Zamis, Domo, Milo, Cowbell, Richoco,
Ovaltine, Bournvita, Spectra, Benco and Peak
chocolate) were obtained from four different markets
(Uselu Market, New-Benin Market, Oba Market and
Zoro supermarkets) in Benin City (Nigeria). The
samples were obtained at two-week intervals for
24 weeks to obtain a good representation. Samples
were analysed mycologically within 24 h of collection.
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Evaluation of mycoora
The evaluation of fungi was carried out using dilution
plating method and the direct plating technique (12).
Decimal dilutions of the samples were carried out by
placing one gram (1.0 g) of the beverage powder into 9.0
ml of sterile distilled water. This was thoroughly shaken
and from the suspension, 1.0 ml was transferred to
another tube containing 9.0 ml of sterile distilled water
and thoroughly mixed again. This dilution procedure
was further repeated thrice so that there were series
of ve tubes giving a serial dilution of 10-1 to 10-5.
An aliquot of 1.0 ml was pipetted at each dilution into
sterile Petri dishes. Three of the plates were over-laid
with cooled molten potato dextrose agar (PDA). The
remaining three were over-laid with Harold agar. The
latter contained malt, 40 % sucrose and yeast extract
which makes it suitable for isolating osmophilic and
xerophilic moulds.
Each medium was supplemented with 0.60 μg/ml of
streptomycin sulphate to suppress bacterial growth.
The plates containing the beverage powder and melted
agar were swirled round to allow for thorough mixing of
aliquot and media. After the agar had gelled, the plates
were incubated at room temperature (28±2°C) for 5 to
7 days. The number of fungal colonies that appeared
in a plate was multiplied by the dilution factor to obtain
the number of colony forming units per gram (cfu/g)
of cocoa-based beverage. For direct plating on agar
media, 1.0 g of each sample was aseptically plated
on PDA and Harold agar. The plates were incubated
under room conditions (28±2°C) and examined after 7
days under a stereoscopic binocular microscope for the
presence of fungi.
Representative colonies of fungi that appeared on
agar plates were repeatedly sub-cultured on fresh
PDA until pure culture of each isolate was established.
Identication of fungi was by observing the growth habits
and morphological characteristics under a wild binocular
microscope. Wet mounts of hyphal/asexual structures
stained with lactophenol in cotton blue were viewed
under the compound microscope and identied with
reference to standard texts (13) (14). Characterization
of the fungi was done based on the colour of the colony,
appearance, conidiophore, mycelium, arrangement of
conidia on sterigmata. The pure culture of fungi got was
prepared on a clean glass slide and stained with cotton
blue in lactophenol. Observation was done under ×40
oil immersion objective lens.
Estimation of total fungal counts
The total fungal in the samples was estimated from the
decimal dilutions carried out. The incidence of mould
contamination using direct inoculation was expressed
as a percentage of the 79 samples examined.
Determination of pH and moisture content
The pH of each sample was analysed using the
pH meter. Moisture content of each sample was
determined using Automated Moisture Analyzer
(Sartorius MA 150, Germany) as described by the
(15). The method was based on loss of moisture upon
drying at 105oC.
Extraction and determination of aatoxin
The beverage samples were extracted with
chloroform, and the extract was concentrated in
vacuum. The dry material was transferred to 1-dram
vials with small amounts of chloroform. The solution
was evaporated to dryness under a stream of nitrogen.
The crude extract was cleaned up by silica gel column
(15). Aatoxins were dissolved in chloroform and
separated by thin layer chromatography on silica gel
60 plates using chloroform-methanol (97:3 v/v) as the
developing solvent. The spots of aatoxin B1 were
removed from the plates, eluted with methanol and
estimated spectrophotometrically with absorbance
read at 365nm (16).
Statistical Analysis
The data obtained were subjected to analyses using
the one-way analysis of variance (ANOVA) in SPSS
statistical package and statistical signicance was
a c c e p t e d a t 5 % p r o b a b i l i t y l e v e l o r l e s s .
RESULTS AND DISCUSSION
The total fungal counts and moisture content in the
samples varied from 0.5 x 103 to 5.5 x 103 cfu/g and
1.00 to 4.00 respectively with an average pH value
of 7.15 for all samples (Table 1). Altogether, 3 fungal
species belonging to Aspergillus mould (A. avus,
A. niger, A. fumigatus) were identied with A. avus
mainly isolated; having an incidence rate of 63.3%.
Aatoxin B1 levels was not detected in 2 samples
(Ovaltine and Benco) but identied and quantied in
8 of the samples analysed; with amount varying from
5.3µg/kg to 40.6µg/kg.
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Table 2 shows the allowable limits (4.0µg/kg) specied
by the European Commission (17) which is also
currently being used by the National Agency for Food
and Drug Administration and Control (NAFDAC), in
Nigeria. Zamis sample had the highest fungal count
and aatoxin B1 level which correlated directly (r =
0.91) with its moisture content amongst all sample
analysed. It has been demonstrated that most of these
food–borne fungi exhibit the potential to produce toxic
metabolites.
There is sufcient evidence to conclude that naturally
occurring mixtures of aatoxins are carcinogenic to
animals and humans (18). Some mycotoxins are
tremorgenic i.e. cause novel neurotoxic effects;
muscular tremors in animals.
Tremorgens are produced mainly by species of
Aspergillus and Penicillium. Also, they have been known
to produce mycotoxins such as aatoxin, ochratoxins,
aatrem, aspergillic acid and aspertoxin. Mycotoxins
seem able to cause serious disease of the liver,
kidney and blood – forming organs in extremely low
quantities i.e. parts per billion. In addition, many
mycotoxins have been shown to impair immunity
against various pathogenic agents. This has been
demonstrated for aflatoxins, diacetoxyscripenol,
ochratoxin and rubratoxin (19) (20).
Again, in humans, mycotoxins have been
implicated in a form of encephalopathy observed
in Thailand and in a particular nephropathy rather
Table 1. Total fungal count per gram of beverage and
some physicochemical parameters
Beverage
sample
Fungal
count
(103cfu/g)
Moisture
content (%)
pH value
Zamis 5.5 4.00 7.02
Domo 5.0 2.00 7.04
Milo 4.5 2.70 7.60
Cowbell 4.5 1.23 7.08
Richoco 4.0 3.02 7.70
Ovaltine 4.0 1.00 7.01
Bournvita 2.5 3.00 6.98
Spectra 2.5 1.03 7.01
Benca 2.0 1.03 7.01
Peak 0.5 1.00 7.08
Beverage
sample
Total No of
sample
avus (%) A.niger (%)
AFB1 (µg/kg)
sA.fumigats (%)
A.fumigats (%)
A.fumigats
Zamis 10 8(10.1) 5(6.3) 7(8.9) 40.6(3.2)
Domo 10 4(5.1) 3(3.8) - 10.5(4.1)
Milo 10 6(7.6) 3(3.8) - 15.3(2.2)
Cowbell 9 8(10.1) 4(5.1) - 24.6(2.0)
Richoco 8 7(8.9) 3(3.8) 6(7.6) 24.6(2.0)
Ovaltine 8 2(2.5) 4(5.1) 4(5.1 -
Bournvita 8 7(8.9) 5(6.3) 4(5.1) 18.2(3.5)
Spectra 6 4(5.1) - - 13.2(2.8)
Benca 5 2(2.5) - - -
Peak 5 2(2.5) 5.3(2.5)
Overall total 79 5 0 ( 6 3 . 3 ) 27(34.2) 21 (26.7) 154.2(22.9)
frequently seen in the Balkans (14). Apart from
danger of food poisoning caused by these fungi,
they also utilize nutrients found in the food thereby
causing deterioration of such food. To improve the
quality of cocoa beverages and to prevent spoilage
at various water activity (aw), it was suggested by
Mossel and Shennan (21) that if the aw is below
0.65 and the product is maintained at this level
during storage, problems arising due to microbial
spoilage are rare, irrespective of the number of
contaminating organisms present. It was further
noted that aflatoxins production ceases or become
very low at aw below 0.85 However, high level
of contaminating organisms should be avoided,
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since they can survive for long periods and may
contaminate other foods or cause problems after
dehydration.
Pelczar et al., (22) also reported that the extent
of contamination will depend upon the initial
microbiological quality of the product and the
level of aseptic precaution used during handling.
Therefore, if the product is well handled, the level
of microbial content of the final product will be
minimal. Furthermore, the spectrum of the fungi
isolated is similar to those in the raw material. This
may be due to reinfection of the product during
cooling of the samples before they are packaged
into polyethylene bags because of the ubiquity of
these organisms.
A more recent and increasingly popular way of
preserving foods is the use of controlled storage
or modified atmosphere packaging (MAP). These
methods take advantage of combining the inhibitory
effect of low O2 levels and elevated CO2 levels
in any deterioration processes in foods as well as
preventing the microbial spoilage (23).
The results of our investigation demonstrate that
the aflatoxigenic fungus (Aspergillus) aided by
moisture and other factors is a common agent
of contamination of cocoa-based beverages
marketed in Benin City, Nigeria. However, not
all samples contain the B1 aflatoxin screened
for; but the levels of Aflatoxin B1 in most of the
food samples were generally above the maximum
allowable limits of NAFDAC. Reduction of aflatoxin
levels in food stuffs in Nigeria especially in cocoa-
based beverages should be a public health priority.
Values in parentheses for AFB1 levels are S.D. of
three replicates
Conflict of interest
The authors have declared no conflict of interest.
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