Fungi Associated with Dried Tomato Chips Marketed in Sokoto Metropolis

Food spoilage is a multifarious process and excessive quantities of foods are lost as a result of microbial spoilage even with contemporary preservation practices. The high water activity in tomato makes it more vulnerable to spoilage by fungi. The fungi produce mycotoxins and if consumed, poses threats to immune-compromised individuals. This study is consequently conducted to isolate and identify the fungi associated with dried tomato chips marketed in Sokoto Metropolis, in Sokoto State, Nigeria. The fungi isolated were Aspergillus niger, A. fumigatus, A. flavus, A. oryzae, Rhizopus stolonifer, and Scopularis Candida. Isolates of A. oryzae has the highest percentage of occurrence (40%), followed by A. niger, and S. candida with (16%) respectively. A. flavus has the least percentage of occurrences (4%). Proper handling and adequate storage facilities must be employed to prolong the shelve life of tomato fruits. There is utmost need to devise means of minimizing contamination to meet the global standard of preservation practices. Keyword: Fungi, Dried Tomato Chips, Market Sample and Sokoto INTRODUCTION Tomatoes (Solanum lycopersicum L.) are unarguably significant in the human diet as they provide color, flavor, and essential vitamins and minerals needed for good health [1, 2]. The cultivation of tomato has a potential of improving the livelihood of many smallholder farmers that live in the rural and peri-urban settlers by generating job opportunities and serving as a source of income [3]. However, despite these benefits, tomatoes are not only perishable but seasonal and easily become spoilt a few days after harvest. Perishability of the fruit is one of the major threats affecting its storage. Sugri [4] reported that 10 – 20% losses might occur due to delay in transportation. Hence, called for sun-drying as a means of preservation. According to Abdulmalik [5], dried tomato chips are commonly produced by direct sun-drying in the open. Although this technique is easy and cheaply carried out, the end product is contaminated with filth and sand; thus, posing threats to immune-compromised individuals. Spoilage of tomatoes are those adverse alterations in the quality (appearance, smell, taste, and texture) of the fruit which are induced mainly by the action of physical and biological factors. According to Ghosh [6], fungi are the major causes of spoilage in tomatoes than bacteria. In the same vein, Etebu [7] reported A. niger, A. phoenicis, Absidia spp, Penicillium spp, Geotrichum spp, Trichoderma spp, Mucor spp, Alternaria alternata, Fusarium oxysporum, F. moniliformis, Rhizopus stolonifer, and Phytophthora spp as the major fungi affecting tomatoes. Spoilage of tomatoes induced by fungal infection has been reported to be recognized as a source of possible health threat to both humans and animals. This is because they produce mycotoxins, which upon ingestion or inhalation are capable of causing mycotoxicoses [8]. The infections by mycotoxins are diverse; they rapidly diffuse and contaminate all parts of the fruit, rendering them flabby for consumption. Curtailing these threats requires the water activity of the tomato fruit to be reduced by drying; and is one of the oldest and the most common forms of food preservation [9]. There exist various reports on their spoilage organisms in the African perspectives and the globe entirely, but there is ashortage of information on mycoflora in dried tomato chips in a developing city such as Sokoto, Nigeria. As such, there is need to assess the fungi associated with their spoilage. Thus, this study isolates, characterized, and identified the fungi associated with dried tomato chips marketed in Sokoto metropolis. MATERIALS AND METHODS Study Area This study was carried out in Sokoto metropolis of the Sokoto state. The State geographically lies along longitude 110 30 to 130 50 East and latitudes 4o to 61 North and covers a total land mass of 26,648.48 square kilometers. Sokoto State shares boundary with Kebbi State to the south, Zamfara State to the east and the Republic of Niger to the north. The State has an estimated population of about 4,742,459 people as of 2015 with 95.9 persons per square kilometer, and 3% growth rate annually based on 2006 population census [10]. Occupation of the city inhabitants includes farming, trading; commerce, with a reasonable proportion of the population working in private and public sectors [11, 12] Collection of samples Healthy and sun-dried tomato chips were randomly selected from five different markets, namely; Kofar Rini, Marina, Tsohuwar Kasuwa, Unguwar Rogo, and Kasuwar Dankure located in Sokoto State, Nigeria. The tomato chips were put into sterile bags and properly labeled and taken to mycology laboratory for microbial analysis. Isolation of fungi Dilution plating method was the technique used for isolation of fungi in this study. According to Jarvis [13], this is the most common procedure used for examining feed and foodstuffs. About 1gr of the sample was sterilized with ethanol and mixed with 10ml of sterile distilled water. The mixture was thoroughly shaken,and 1 ml of suspension was pipetted into the sterile test tube containing