MYCOFLORA OF STORED LOCUS BEANS (Parkia biglobosa ) PURCHASED FROM USELU MARKET
Stored locust bean samples were purchased from Uselu market and analysed for their fungal load and physicochemical properties such as moisture content, pH value and titratable acidity. Enumeration of the total fungal species was carried out by pour plate technique using appropriate medium, potato dextrose agar (PDA) with antimicrobial agents (streptomycin), incorporated to inhibit bacteria growth. The fungal isolates were identified using cultural and morphological characterization. Moisture content determination was done by drying to constant weight in oven at 103°C, the pH value was determined using a pH meter while titratable acidity was by acid-base reaction using 0.1N sodium hydroxide (NaOH) solution. The total fungi count on potato dextrose agar was 2.0x10-8 from Uselu market. The moisture content was 18.9%, the pH value 6.1 and titratable acidity 0.61ml of 0.1N, NaOH. The species of fungi isolated and identified at the end of the analysis were Fusarium sp, Aspergillus flavus, Penicillium sp, Saccharomyces sp and Aspergillus niger. The identification was based of morpohological characteristics. These fungal colonization and contamination of stored locust bean cause inedibility, reduce market value and depletion of its nutrients. Hence, adequate drying of crops, prevention of moisture re-absorption and the general improvement of storage facilities at all levels of production is recommended as a safe guard against fungi deterioration of locust bean.
The seed of locust beans (Parkiabiglobosa) plant found growing in the Savannah Africa provides one of the popular seasonings in African diet. The nutritious and delicious food spice is popularly called “ogiri” in Igbo, “iru” in Yoruba and “dawadawa” in Hausa in Nigeria. It is heavily consumed in Nigeria, Ghana, Sierre Leone and Togo (Odunfa, 1985). It serves as source of protein for most of the people whose protein intake is low due to high cost of animal protein sources.
The African locust bean tree, Parkiabiglobosaare perennial trees legumes which belongs to the sub-family mimosoideae and family leguminosae (now family fabaceae). They grow in the Savannah region of West Africa up to the southern edge of the Sahel zone 13°N (Campbell-Platte, 1980). The plant occurs in a wide range of Natural Savannah woodlands and ithas the capacity to withstand drought conditions because of its deep tap root system (Nwadiaroet al., 2015). A matured locust bean tree (20-30years) can bear about a ton and above harvested fruits. From experience, the tree can start to bear fruits from 5-7 years after planting (Musa, 1991). The African locust bean tree grows to about 20m in height and has bark evergreen pinnate leaves. Its fruit is a brown leathery pod of about 10-30cm long and contains gummy pulps of an agreeable sweet taste, in which lie a number of seeds. It is important indigenous multipurpose fruit tree. Parkiabiglobosa tree plays vital ecological roles in recycling of nutrients from deep soil, by holding soil particles to prevent soil erosion with the aid of its roots. It also provides shade where it is found (Campbell-Platte, 1980). This tree is protected by peasant farmers and rural dwellers for its many benefits. Its wood is a source of fuel energy. It helps to enrich the soils nutrient.
The most important use of African locust bean is found in its seed which is a legume, although it has other food and non-food uses especially the seeds which serve as a source of useful ingredients for consumption (Campbell-Platte, 1980). It has been reported that the locust bean is rich protein, carbohydrate, soluble sugars and ascorbic acid. The cotyledon is very nutritious, has less fibre and ash content. The oil content is suitable for consumption since it contains very low acid and iodine contents. The oil has very high saponification and hence would be useful in the soap industry (Alabiet al., 2005). It has also been reported that the husks and pods are good for livestock (Douglass, 1996; Obiazoba, 1998). The locust bean tree is also important in medicinal practices in treatment of aliments such as bronchitis, pneumonia, malaria, diarrhoea and as poison for sore eyes (Farombi, 2003).
Although microorganisms of all groups including bacteria, protozoa, algae, viruses, fungi together with insects and rodents play significant role in food deterioration, the most active and more versatile organisms that affect locust bean seeds and its products causing spoilage when stored are species of bacteria and fungi (Omafuvbeet al., 2000). They can occur on growing crops as well as harvested commodities leading to damage ranging from rancidity, odour and flavour changes and germ layer destruction (Cutler, 1991). In a study to identify the bacterial and fungal flora of deteriorated and maggot infested samples of fermented locust bean seeds, the isolated fungal species were identified as Aspergillusniger, Aspergillusflavus, Penicillium, Rhizopus and Candidaspecies. Parkiabiglobosa seeds are subject to degradation induced by diverse organisms including fungi which are among the most active microorganisms in these processes (Popoola and Akueshi, 1985). Microorganisms associated with fermented locust bean seeds have been widely studied (Odunfa, 1981; Ikenebomehet al., 1986; Odunfa and Oyewole, 1986; Ogbadu and Okagbue, 1988). Bacilli and Staphylococci were observed to dominate the fermentation together with a number of fungal species causing deterioration of this especially in storage in Northern Nigeria.
⦁ This study is aimed at DETECTING THE FUNGI SPECIES INVOLVED IN PARKIABIGLOBOSASPOILAGE.
1.2 SPECIFIC OBJECTIVES
⦁ To isolate and identify fungi associated with locust beans (Parkiabiglobosa).
⦁ To determine the pH, moisture content and titratable acidity of locust beans.
5.0 DISCUSSION AND CONCLUSION
Five fungal isolates were identified in this study. These include Fusariumsp, Aspergillusflavus, Penicilliumsp, Saccharomycessp and Aspergillusniger.
The total mean viable fungal count in the sample is 2.0x10-8 from Uselu market. These fungi species isolated and identified in this study corroborate those implicated by Garren (1996) and Sullivan (1984) that locust bean seeds are highly susceptible to disease, as they act as a surce of stored nutrients for fungi such as identified in this study. The presence of Fusariumsp, Aspergillusflavus, Penicilliumsp, Saccharomycessp and Aspergillusniger might be due to improper handling during production, harvest, storage or processing.
The moisture content of the locust bean sample is 18.79%. The low moisture content of the samples will discourage the proliferation of the microbial isolates. Increase in the moisture content may be due to different storage and processing method. The pHvalues of the locust bean seeds from Uselu market is 6.1while the titratable acidity from Uselu market is 0.61ml.
The occurrence of fungal isolates could indicate that handling and storage processes by the seller in the market may greatly affect the level of microbial load. The presence of Apergillus species in the sample indicates the possible contamination by aflatoxin, a carcinogenic compound that has been implicated in a number of human and animal ailment.
Most of the fungi isolates including genera of Aspergillus and Penicillium have been implicated in post-harvest rot of some fruits and vegetables in storage (Adaskaveget al., 2002; Fagbohun and Lawal, 2011). Fusarium spp. is a well-known pathogenic fungus Anwar et al. (1996) and their isolation from deteriorating samples indicates that they were seed-borne and must have followed the seeds right from the field. Their presence in the sampled seed can cause up to 30% reduction in yield of the locust bean seeds. Isolation of these fungal species has health implications as some of them produce mycotoxins, carcinogenic agents (Campbell Platte, 1980) which are elaborated into food substance. These mycotoxins are heat stable, and are dangerous to the system when ingested even in very minute concentration. Aspergillus species has been reported as an opportunistic pathogens, causing asthma and otomycosis in compromised individuals (Austwick, 1965).
Aspergillus species are worldwide in distribution and have been isolated from various habitats including stored foodstuffs. Aspergillushas been reported as one of the predominantly isolated microbial species in Nigeria (Ogaraku, 2010).
Aspergillusand Penicilliumcause discolouration, and mouldy smell of locust bean seeds during storage. Sharma and Vir (1986) reported Aspergillus species as the cause of rotting in numerous food products including fruits and vegetables, thereby causing huge economic losses due to spoilage.
The identification provided evidence that pathogenic fungi enter and proliferate within locally processed foods. Thus, these fungal colonization and contamination of stored locust bean could cause inedibility, reduce market and depletion of its nutrients. This is however dependent on the moisture content and several environmental factors such as temperature and relative humidity of the harvested locust bean prior to storage.
In conclusion, the seeds of locust bean plant are very important source of nutrients especially proteins that could alleviate malnutrition among different sections of Nigerian population and beyond. The seed is a readily source of protein for most of the people whose protein intake is low due to high costs of animal protein sources. The study has shown that the colonization of locust bean seeds by storage fungi had a significant impact in reducing the nutritional worth of the seeds. This situation can be improved by taking some measures including; drying of the seeds properly to reduce the moisture content which encourages microbial growth and spoilage. Oerkeand Dehne (2004) reported that the present of little moisture permit the growth of fungi such as Aspergillusand Pencilliumspecies.
Therefore, locust bean seed which are stored before sale or use should be kept dry and soil debris should be removed completely from the harvested locust bean so as to avoid soil dwelling microbes.
Secondly, Farmers, traders and consumers should maintain sanity in the storage facilities which will go a long way to prolong the shelf life of the seeds. Considering the previous works on fungal deterioration of agricultural produce including locust bean seeds, the farm products are generally susceptible to fungal attack mostly because of the relative humidity and moisture which is always high in the storage areas.
Hence, adequate drying of crops, prevention of moisture re-absorption and the general improvement of storage facilities at all levels of production is recommended as a safe guard against fungi deterioration of locust bean..