Microorganisms Associated With the Spoilage of Sweet Potato


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MARCH, 2023



Microorganisms associated with the spoilage of sweet potato was isolated from a spoilt and contaminated potato. The sample was purchase from Afaha Nsit Market and then transported in a stetile polythelyn bag to the microbiology laboratory where the sample was allowed to spoil before microbial analysis was carried out. It was examined using the most valuable techniques and procedures such as serial dilution, culture, morphological reading gram-staining, catalase test, microbial examination (microscope) etc.

The microbial load on each cultural plates were 0.120×103 on the nutrient agar plate and macconkey agar at the confirmatory level 0.212×103 and the sample C has a spore form with the microbial load 0.171 x 103 which indicates that a spoiled potato is contaminated and is not fit for human consumption. It is recommended that foods should be thoroughly washed before cooking with portable (clean) water and also potatoes should be stored properly in the light environment to avoid spoilage and microbial infestations because a spoiled potato can lead to food poisoning, diarrhea, small discomfort etc when consumed.  


Microorganisms Associated With the Spoilage of Sweet Potato




  1.1     Background of Study

One of the most pressing problems facing the developing of nation is food scarcity.  Salami and popoola (2007); kana et al (2012) reported that nearly one billion people are challenged by severe hunger in these nation of which 10% are reported dead from hunger related complication in Nigeria, the root crops that are majorly important include cassava, sweet potato and Irish potatoes. After harvest, these tuber suffer looses that result from physical, physiological or pathological factor s in the combination of three factors (Opara and agugo 2014).

Food scarcity and sustain inability is one of the ways of addressing this problems of the food scarcity and shortage due to activities of micro organisms after harvesting. In a FAO/ WHO report of 2012, food scarcity are define as a situation in which all people at all times have both physical and economic access to adequate and nutritious food for an active and healthy life the manner in which the food is produced preserved and distributed are in consideration of the natural processes of the earth and thus sustainable, reducing spoilage, scarcity, malnutrition and poverty.

Sweet potato (Ipoeamo batatas) is a root tuber crop belonging to the family convoluanceae. It is an energy rich carbohydrate food. It thrives very well in moderately warm climate.  The crops is grown extensively in Nigeria especially in northern part and is one of the major subsistence crops in Nigeria. Sweet potato has an enormous potential to be an effective and economic source of food energy (Oyeyipo 2012).

Micro organisms that are responsible for the spoilage of sweet potato produce extra cellular enzymes such as amylase cellulose polygalatunase, xylanases and pectin methyl esterases and these enzymes degrade the cell wall component of produce that  are susceptible leading in some cases of emission of offensive odor and water (salami and Popoola 2007) Amadioha 2012 Oladoye et al 2013.

There are several rots that affect sweet potato after harvest and these rot are linked to a number of factors that are physiological, physical and microbiological. During harvesting, storage, transportation, mechanical damaged occur and this damage has been known to be predisposing tuber to spoilage and storage rot (Oyeyipo 2012).


1.2       Statement of Problem

Fungal pathogen cause spoilage and post harvest spoilage of sweet potato by producing various types of mycotoxins. Mycotoxins are low molecular weight toxic secondary metabolites from fungal species. These mycotoxins are dangerous in small quantities and present extreme toxicity due to their heat resistivity (Okigbo 2004; Shukla et al 2012).        

In the face of the present food situation in Nigeria, one of the major obstacles of food production is that of storage. During harvesting season tuber crops are very much available at cheap prices but this availability is usually short due to storage problems. Tropical crops suffer tremendously due to inadequate storage practices. Sweet potato as crop suffers most as tuber crops.


1.3       Objective of the Study

The objective of the study is to determine out the micro organisms associated with the spoilage of sweet potato tubers, the degree of damage they caused and ways in which they can be prevent.


Microorganisms Associated With the Spoilage of Sweet Potato

1.4  Significance of the Study

This study will be significant important to farmers as it will guide local farmers in Nigeria in the effort to minimize too much loss of their harvested tubers.

  • To document farmers knowledge on field and post harvest diseases of sweet potatoes.
  • To establish the pathogenicity of fungal organisms associated with tuber rots of white sweet potatoes varieties.
  • To study the effectiveness of some chemical fungicides in reducing sweet potato rot in storage.


1.5       Research Questions

  • What is farmers’ knowledge on field and post harvest diseases of sweet potato?
  • What is the effectiveness of some botanical extracts in controlling sweet potatoes rot fungi?
  • What is the pathogenicity of fungi organism associated with tuber of white sweet potatoes varieties?
  • What is the effectiveness of some chemical fungicides in reducing sweet potatoes rot in storage?

1.6       Scope of the Study 

This work includes identification and enumeration of fungi in sweet potato and it also looks at the microorganisms associated with it mode of infection epidemiology and ways to treat and prevent it.

Microorganisms Associated With the Spoilage of Sweet Potato

1.7       Limitation of Study  

  • Inadequate finance
  • Getting information from the internet was not easy.
  • Time constraint the researcher has to attain lectures and do assignment


1.8       Definition of Terms

  • Sweet potato: sweet potatoes are starch root vegetable that are rich in fiber, vitamin and minerals. They are also high in antioxidants that protect your body from free radical damage and chromic diseases.
  • Micro organisms: micro organisms or microbe is a microscopic organism which may exist in its single celled from or a colony of cells.
  • Fungi: fungi are eukaiyetic organisms that include micro organisms such as yeasts, mould and mush rooms.
  • Bacteria: bacteria are small single celled organisms that are found almost every where on earth.
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