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Isolation of Seed-Borne Mycoflora from Cashew Nuts Vended in Selected Markets in Awka

Okigbo, R.N., *Ezebo, R.O. and Obieze, I.V.

Department of Botany Faculty of Bioscience, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Anambra State, Nigeria

*Correspondence: esau_056@yahoo.com; Phone No:+2348060044563

ABSTRACT

This study investigated the mycoflora associated with Cashew nuts sold in Awka markets. Samples of Cashew nuts were purchased from local markets (Eke-Awka, Amaenyi and Good-Will). Samples were analysed for the moisture contents and the presence of fungi by adopting dilution plating method. Data were analysed using Analysis of Variance (ANOVA) via Statistical Analysis System (SAS) of Version 9.1. Means of treatment were compared using Duncan’s Multiple Range Test (DMRT) at p<0.05. The results of the study revealed thatSix fungal species were isolated which included Fusarium oxysporum, Aspergillus niger, A. flavus, A. fumigatus, Penicillium oxalicum and Mucor species. The results showed that Eke-Awka Market recorded the highest percentage moisture content of 6.8%, which was followed by Amaenyi Market with a percentage moisture content of 6.6%, while least was Goodwill Market with moisture content of 4.1%. The presence of fungi in stored food commodity deteriorates the nutritive value and secrete toxins injurious to human health. The occurrence of pathogenic fungi on cashew nuts could be avoided or diminished if proper farming, harvesting and storage methods were adopted.

Keywords: Isolation, Mycoflora, Cashew, Nut, Market, Awka

INTRODUCTION

The cashew plant, Anacardium occidentale L., is a tropical evergreen, perennial tree with a darkish-green leathery foliage, crooked branches and very irregular crown, a small to medium sized tree belonging to the family Anacardiaceae [1]. For over 400 years after introduction, cashew trees were exploited mainly for apple and no commercial value was attached to the nuts [2]. The first commercial cashew planting in Nigeria was in the mid 1950 at Ogbe, Oji, Udi and Mbala by the defunct Eastern Nigeria Development Corporation (ENDC) and Iwo, Eruwa and Upper Ogun by the defunct Western Nigeria Development Corporation (WNDC) [3]. The cashew nut liquid as a by-product of processing cashew is mostly composed of anacardic acids [4] which have been used effectively against tooth abscesses due to their lethality to a wide range of gram-positive bacteria [5]. The nut oil from cashew seeds is used topically as an anti-fungal agent, also for healing cracked heels as opined by [5]. [6], reported that consuming nuts at least four times a week resulted in a 37% reduced risk of coronary heart disease compared to those who never or seldom ate nuts. The cashew nut is a popular snack often eaten on its own and approximately 75% of their fat is unsaturated fatty acids which includes health [7]. In relation to the seed-borne mycoflora of cashew nut, fungi play a significant role in deteriorating the nutritive value of the nut by utilizing the nutrient for their growth. Plant based edible stuffs are very susceptible to fungal contamination [8]. Fungi are found in different food commodities including nuts and other parts of the plants and these results to economic losses on cashew nuts [9]. Several environmental factors like humidity and temperature during storage of these nuts influence the infestation by fungi and aflatoxin production [10].Contamination of foodstuffs by aflatoxins has created serious concerns on food safety in Africa and especially Nigeria [11]. Mycotoxins are diverse group of secondary metabolites produced by molds which contaminate foods and have toxic effects on the health of humans and animals. Aspergillus spp, Penicillium spp, Rhizopus spp and Mucor spp are the most frequent species recovered from non-disinfected cashew nuts [12]. Fungi grow to produce secondary metabolites under favorable chemical, physiological and environmental conditions, especially when temperature and moisture are suitable [13]; [14]; [15]. Mycotoxicoses are becoming increasingly implicated in human and animal pathology [16]. However, the mycotoxigenic Aspergillus, Penicillium and Fusarium are responsible for secretion of different metabolic toxic compounds [17]; [18] and could be considered the most serious fungal genera that contaminate cashew nuts [19]. [20], summarily stated that a proper study of mycoflora of cashew nuts may improve and establish a new variety of seeds as a necessary immediate measure to increase the average cashew nut yield in Nigeria. Considering the significance of cashew in the livelihood, the effect of mycoflora will cause a significant yield reduction of cashew in Nigeria, hence this study therefore, investigated the mycoflora associated with cashew nuts (Anacardium occidentale L.) vended in selected Markets in Awka.

DISCUSSION

Cashew nut infection by pathogenic fungi has been reported in a number of studies and revealed a high risk due to contamination with mycotoxins [24]. It is a fact that plant based edible stuffs are very susceptible to fungal contamination [8]. From the results of this study, it was shown that six fungi were isolated which included F. oxysporium, A. niger, A. flavus, A. fumigatus, P. oxysporium and Mucor species. This finding is in line with reports of [25]. Most of the fungi were previously reported from cashew nuts in many parts of the world [26]; [24][27]; [25]. Incidence of these isolates depends on a number of factors including moisture content and storage time [26]. Low moisture levels limit mould growth after harvesting and during storage. The percentage moisture contents for the three sample locations revealed that Eke-Awka Market recorded highest moisture content of 6.8%, which was closely followed by Amaenyi Market with moisture content of 6.6%, while the least moisture content of 4.1% was noticed against Goodwill Market. This agrees with the preliminary study conducted by some authors that moisture content below 5.8% is approximately equivalent to 70% relative humidity. This is generally considered the maximum level for safe storage [28]. However, samples from Eke-Awka and Amaenyi had moisture contents above the limit and consequently were predisposed to more fungal growth and mycotoxin contamination (Table 6). Cashew nut is one of the few commodities that travel a long distance between times of harvest and when consumed [29] and these can lead to the initiation of these fungal activities thereby causing loses of commercial and nutritional values in the nuts and most importantly endanger the life of consumers by exposure to mycotoxins infestation. Aspergillus was represented by three species and showed the widest diversity among all isolated fungi which are A. niger, A. flavus, A. fumigatus, and followed by Mucor species, Fusarium and Penicillium. [30] stated that these fungal species are found common to the soil and different agricultural food commodities. The contamination of toxigenic fungi and aflatoxins may occur from the soil during growth or harvesting or from the environment during storage and sale which are conductive for fungal growth proliferation and aflatoxin contamination [31].

CONCLUSION AND RECOMMENDATION

This study demonstrated that cashew nuts vended in Awka are contaminated with several mycotoxigenic fungi which included F. oxysporum, A. niger, A. flavus, A. fumigatus, P. oxalicum and Mucor species. It is therefore, recommended that strict mycological hygiene measures should be established in cashew farming, harvesting and storage to minimize mycotoxin contamination and to discourage high humidity that favours the growth of these fungi.

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CITE AS: Okigbo, R.N., *Ezebo, R.O. and Obieze, I.V. (2023). Isolation of Seed-Borne Mycoflora from Cashew Nuts Vended in Selected Markets in Awka. IDOSR JOURNAL OF APPLIED SCIENCES 8(3) 140-146. https://doi.org/10.59298/IDOSR/2023/10.2.1420

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