Introduction

‘Ugba' also called ‘Ukpaka' a Nigerian indigenous fermented food, rich in protein₁ is obtained by a solid-state fermentation of the seeds of African oil bean tree (Pentaclethra macrophylla). It is a popular food delicacy in Nigeria especially among the Ibo ethnic group where it serves as snack, side dish or as a food condiment. It is an essential food item for various traditional ceremonies where it is mixed with slices of boiled stock fish (ugba na okpoloko), ganished with boiled vegetables and consumed by all socio-economic class.

The unfermented seeds are bitter to taste and contain toxic alkaloids and saponins (₂). The natural fermentation of the seeds which at present is still done at the house-hold level renders the product nutritious, palatable and non-toxic₃. Its production, like many other African fermented foods, depends entirely on mixed fermentation by microorganisms from diverse sources, some of which may still be alive and active when the product is consumed. The method of production varies from one producer to another resulting in a none uniform product with short shelf-life.

The processes of Ugba production, the microorganisms encountered during the production and the physicochemical properties of the product have variously been reported (₄,₅,₆,₇,₈). The food composition of ugba has also been reported. (₉,₁₀,₁₁) Some of the fundamental problems associated with ‘Ugba' like other Nigerian indigenous fermented foods and beverages include its short shelf life arising from uncontrollable fermentation that occurs after the normal production period and the vulnerability of the product to contamination by pathogenic microorganisms during production and keeping (₁₂,₁₃).

Some attempts to improve the packaging and keeping quality of ugba have been reported including packaging with low and high density polyethylene sachets and Aluminium foil wraps (₁₄), treatment with different concentrations of chemical preservatives including 2% sodium chloride (₁₅). However, none of the methods had been reported to extend the shelf-life of the product beyond eight days.

The present study was aimed at using starter culture and entirely different packaging technique involving screwable bottles and cans and locally adaptable pasteurization to produce and enhance the shelf-life of ugba.

Materials and Methods

The seeds of African oil bean tree (Pentaclethra macrophylla) used in this work were purchased from a local market in Awka, Anambra State, while the traditionally prepared ‘ugba' were purchased from a local producer also in Awka.

Production of

Development of Starter Cultures

Traditional Method

Determination of Physicochemical and Organoleptic Properties

Shelf Life Determination

Results and Discussion

The physicochemical properties of Ugba produced by the modified method compared very well with the ones produced through the traditional method (Table 1). The boiled but uninoculated ugba slices (control) did not have features of ugba after the production period (Table 1). The effect of storage on the physicochemical properties and the microbial counts of ugba produced through the traditional and modified methods are summarized in Table 2. The result shows that whereas microbial numbers increased steadily up to the 3rd week in ugba produced through the traditional method during storage, microorganisms were not isolated from ugba produced by the modified method (Table 2). It presupposes that boiling/pasteurization at 98-100°C (boiling temperature of water) for 30 min was able to completely eliminate the organisms (starter culture) used in the fermentations. However, in an earlier trial run, a holding time of 15min at 98-100°C could not completely eliminate all the organisms. Ogbulie et al (₁₅) reported that pasteurizing ugba for 30 min at 60°C could not appreciably reduce the microbial load and so could not extend the shelf life of the product up to three days. But pasteurization at 90°C for 30 mins reduced the microbial load and was able to extend the shelf life to 8 days.

Bacillus spp were used as starter cultures in this work because they have severally been reported as the major microorganisms that are responsible for the physicochemical and organoleptic features of Ugba (₄,₇) and their presence may explain why pasteurization at 60°C could not significantly reduce the microbial load of the ugba as Bacillus spp are known to produce resistant spores.

A reduction in fermentation time was achieved in this work and this was apparently because the starter cultures used were at their exponential growth phase and have been grown in ugba broth and so lag periods were drastically minimized and the size of inocular used may have been was sufficient to initiate and sustain a fast fermentation rate.

Figure 1

Table 1: Physicochemical Properties of Ugba produced by traditional and the modified methods

Figure 2

Table 2: Effect of Storage on the Properties of Ugba

The effect of storage on the organoleptic properties of ugba is presented in Table 3. The result shows that all the organoleptic parameters of ugba considered in the study became bad after the first week for ugba obtained from the local dealer while the parameters remained virtually the same throughout the six weeks storage period for ugba produced in this study (Table 3).

The major problems of ‘ugba' are its poor shelf life often associated with the uncontrolled fermentation and poor packaging which often allows maggots to develop on the product as a result of eggs laid by flies that gained entry into the wrapped product. The production process also renders the product vulnerable to contamination by pathogenic microorganisms. These difficulties were overcome in the present work by using known organisms (starter culture), a packaging system that does not allow the entrance of extraneous organisms into the product and the use of a pasteurization method that can easily be adapted by the local producers.

Colour, aroma, texture and sliminess are important organoleptic indices of a well fermented ugba and thus are inevitable in its shelf-life determination. These attributes of Ugba were achieved and maintained for six weeks in Ugba produced in this work but dark brown colour, loss of sliminess and production of pungent ammoniacal odor which are signs of spoilage were observed in Ugba purchased from the local dealer during the six weeks storage (Tables 2 and 3). The off flavour was also reported by Ogbulie et al (₁₅) and it was said to be due to increase in ammonia nitrogen during storage as a result of increased hydrolytic activities of microbial enzymes. This explanation was also used to explain the steady rise in pH during the storage (Table 2).

The result of this work not only provided advances for mass production of Ugba with a standardized operational method but also provided means for the production of uniform product with reduction in fermentation time and enhanced product shelf-life. The study has also shown that Ugba can be packaged in returnable and sterilizable containers. The packaging is environment friendly as it will not litter the streets as the leaves used in traditional packaging.

Figure 3

Table 3: Effect of storage on the organoleptic properties of ugba

Correspondence to

Mbata T.I. Department of Applied Microbiology and Brewing Nnamdi Azikiwe University P.M.B. 5025, Awka, Nigeria. E-mail: theoiyke@yahoo.com Tel- 2348032618922