effect of packaging leaf type on quality and flavour profile of ugba (pentaclethra macrophylla benth) seeds

Description

ABSTRACT

African oil beans, Ugba (Pentaclethra macrophylla Benth) seeds were naturally fermented. The seeds were washed, boiled for 6hrs, peeled, cotyledons cooled and cut into different slices, fermented in two different baskets lined with blanched banana (Musa paradisiaca) leaves and blanched cocoyam (Xanthosoma sagittifolium) leaves at room temperature for 3 days. The quality of the ugba prior to fermentation, and after the three days fermentation were checked by determining proximate compositions of the samples using internationally accepted standards. Volatile (flavour) compounds produced during 0, 12, 24 and 36 hrs within the 3 days processes were identified using GC-MS (QP 2010 plus; Shimadzu Corp, Japan). Sensory analysis of the fermented samples were carried out. Moisture, ash, protein, fat. Fibre and carbohydrates contents in the ugba ranged between 47.59±0.0.07-49.64, 1.86±0.09-2.79±0.13, 12.24±0.86-16.55±0.40, 15.17±1.09-16.99±0.69, 3.47±0.32-6.08±0.347 and 11.67±0.89-17.05±1.31 respectively. The ugba fermented with blanched banana (Musa paradisiaca) leaves produced better flavours (volatile compounds) and had better taste. 26 different flavour compounds were identified in the blanched banana (Musa paradisiaca) leaves fermented ugba with flavour profile of 13 esters, 2 alcohols, 6 hydrocarbons, 3 phenols and 1 ketone while 20 different flavours compounds were identified in the blanched (Xanthosoma sagittifolium) leaves fermented ugba with flavour profiles of 6 esters, 2 alcohols, 7 hydrocarbons, 4 phenols and 1 ketone.

 

 

 

CHAPTER ONE

INTRODUCTION

• Background of the study

The African oil bean tree (Pentaclethra macrophylla Benth) is a large leguminous woody plant that belongs to the subfamily of Mimosarde (Kar, 1978). It is a module forming multipurpose tree species of probable African Origin. It grows wild in rain forest and in farm lands where it is carefully conserved by farmers alongside their crops (Duke, 1981). It is frequently cultivated in forest areas with about eight flat glossy brown edible seeds per pod (Eze et al, 2014). It is popular in Nigeria where it is known by several names such as Apara in Yoruba, Ukana in Efik, and, the most prominent, Ugba/Ukpaka in Igbo (Ahaotu, et al., 2013). Ugba is a popular Igbo condiment and delicacy made from traditional household solid state fermentation of African oil bean seeds. The fermentation is a mixed culture alkaline process involving a variety of microorganisms. Although a variety of microorganisms are involved in the process, only the Bacillus spp. appear to be necessary for the development of typical flavor (Isu and Ofuya, 2000). The methods of production and also the length of fermentation vary from one producer to another and with the final intended use. However, the basic method involves boiling the seeds for up to 12 hours, removing and slicing the cotyledons, soaking/washing the sliced cotyledons in several changes of water, and wrapping the sliced cotyledons for the fermentation to take place (Njokuand and Okemadu, 1989). Beans that have been fermented for 2-3 days are taken as a snack delicacy directly or following seasoning and some further processing. Well fermented beans (up to 5 or more days) are added to soup as flavoring. Prepared in different ways, Ugba is an essential food item for various traditional ceremonies, and in instances it may be used as meat substitute in certain soups/gravies particularly for the rural poor people.

Ugba is a traditional food, consumed by over 20 million people in Nigeria (Ogbonna et al., 2001). It is a rich and available source of protein for people, whose staple foods are deficient in protein. The raw seed is a potential source of edible protein and calories containing the twenty essential amino acids and essential fatty acids which make up more than 80% of fatty acids in the oil (Olasupo et al., 2002). The problem of widespread prevalence of protein energy malnutrition (PEM) has resulted in high morbidity and mortality rates, especially among infants and children in low-income groupings in the third world, including Nigeria. The reliance on starchy roots and tubers as well as protein –deficient cereals as main staples result in consumption of stodgy monotonous, non-nutritious diets (Ahaotu, et al., 2013). Africa oil bean are edible after roasting or boiling for 12 hours, though more as a condiment than food. In Nigeria, which is a tropical region like most West Africa countries, they are eaten wrapped in leaves after roasting or boiling for hours. Fermented foods are consumed by a large number of people in different parts of the world (Steinkraus, 1983). In the developing countries in particular, “Ugba” plays a major role by providing essential nutrients and variety in the diet. The fermentation of the African oil bean seed effects better nutrient availability and digestibility with significant softening of the cotyledons (Sanni et al, 2002). The fermented “Ugba” can then be consumed as a snack or used as a condiment in soup mixes and local porridges.

1.2  Statement of Problem

Flavour is considered the quality index of Ugba and plays an important role in consumer acceptability (Wilkens et al., 1970). Although fermented African oil bean seeds have typical flavor and appealing organoleptic quality, differences in flavour range and intensities exist. These vary perhaps as attributes of producer organisms and are due to the various volatile compounds produced by the fermenting population. A great deal of work has been implemented in the microbiological characterization of the fermentation process. However, unlike Asian and Pacific fermented seasoning, only few works has yet been reported, on the effect of processing on the flavor profile of Ugba and their evolution during the fermentation process. Knowledge of the volatile and flavour characteristics of the fermented oil bean seeds and their evolution will aid in the quality control of the process, modification of the flavor, and eventual synthesis of the Ugba flavour products for possible use in the seasoning of various factory processed and even home foods. This is important in view of declining production of seeds, due to deforestation, and the need to extend use of the appealing aroma of Ugba to other food types.

• Main objective

The main objective of this study is to identify the volatile flavor components of African oil bean seeds during natural and pure culture fermentation and the effect of processing on flavor profile.

1.3.2  Specific objective

The specific objectives of this study are;

• To determine the proximate composition of unfermented Ugba
• To determine the organoleptic qualities of the Ugba

1.4     Justification of Study

This research work will throw more light on the processing methods of fermented African oil bean seeds. This study will also be of immense benefit to all consumers of fermented African oil bean seeds in that it will expose them to understand different chemical composition and nutritional level of African oil beans seed. Researchers have shown a lot of nutritional benefits associated with high intake of Ugba. Regular consumption of staples such as Ugba will reduce the risk of suffering certain disease associated with high glycemic carbohydrate foods such as Type 2 diabetes (diabetes mellitus), coronary heart disease, increase in serum triacylglycerolisis, reduced insulin sensitivity, increased blood cholesterol, increased risk of obesity and many other cardiovascular diseases (Byrnes et al., 1985; Ford and Hiu, 2001; Jenkins et al., 1987). Regular consumption of staples with high dietary fiber will reduce this likelihood. With an improved flavor, Ugba will be eaten more frequently and the knowledge of this study will be economically relevant to industrialists who are into flavoring for condiments.

1.5     Scope of Study

In this study, the seed of Ugba will be obtained from the farm and processed into edible slices. Traditional method will be used to process ugba by fermenting in a blanched plantain leaf. Pure cultures of B. subtilis and B. magneta will be will be isolated from the tradition process and used separately to prepare soft ugba in flask to be covered with cotton wool and aluminum foil. The effect of the processes on the flavor profile will be determined from volatile compounds that will be produced. Standard methods will be used to determine the proximate compositions and mineral components of the unfermented ugba.