Abstract: A comparative study of the microbial and chemical qualities of African breadfruit, Treculia africana Decne raw seed and seed boiled with trona was investigated. There was a significant (p< 0.05) decrease in the viable count of the seed boiled with trona (6.28 cfu g-1) when compared to the raw seed (6.53 cfu g-1). Bacteria isolated from the raw seed include Bacillus sp., Staphylococcus sp. and Micrococcus sp. while in the boiled seed and seed boiled with trona, only Bacillus sp. was isolated. The protein, fibre and ash content of the raw seed sample was significantly (p< 0.05) higher when compared to the boiled seed and seed boiled with trona. The antinutrients viz; phytate, tannin and cyanide of the boiled seed and seed boiled with trona were significantly (p< 0.05) lower when compared to the raw seed. Boiling T. africana seed with trona improve the microbial quality and reduce the antinutrient content, however, the protein, ash and carbohydrate content of the seed boiled trona reduced when compared to the raw seed.
INTRODUCTION
African breadfruit (Treculia africana Decne) is a tropical tree crop belonging to the taxonomic family moraceae, genus, Treculia (Enibe et al., 2003). The family consist of about 50 genera and over 1000 species (Tindal, 1965). It can be cultivated from seed and buds. Seed propagated T. africana fruits within four years at reduced height (Okafor, 1980).
Enibe et al. (2003) stated that post harvest processing of the fruit heads can be done in two ways. The harvested fruit head can be sliced and the seeds extracted manually. The mucilaginous layer on the freshly extracted seeds can then be removed using graded concentrations of trona (1-5%) and wood ash as hydrolysing acids for 5-25 min. It can also be processed by partial fermentation of the fruit for some days after which the mucilaginous layer is removed using sand instead of wood ash. The extracted seeds from either method can be boiled, dried and put to various uses.
The seed is a rich source of vegetable oil (10%), protein (17%), carbohydrate (40%) as well as minerals and vitamins (Enibe et al., 2003). Many delicacies including porridges are commonly produced from the seed. Sunday et al. (2000) suggested that pastries, weaning foods, breakfast cereals and beverages can be developed from the seed. In the Southern part of Nigeria, T. africana seed is normally processed for consumption by boiling with trona. Trona is the second most used salt in Nigeria. It is locally known as “kaun”. It is a hydrated sesquicarbonate of sodium (Makanjuola and Beetlestone, 1975). It is commonly used as tenderising agent of food materials such as pulses, cereals, meat and vegetables (Ankara and Dovlo, 1978). The present study was aimed at assessing the microbial and chemical qualities of raw and trona processed African breadfruit (Treculia africana).
Materials and Methods
Materials
Fresh seeds of T. africana were bought at Oba’s Market, Akure.
The seeds were transferred to the Microbiology and Food Science and Technology
laboratories of the Federal University of Technology, Akure in a sterile polythene
bag. The study was conducted between May to August 2005.
Treatment of Seeds
The seeds were weighed (10 g) each into 3 different portions. The first
part (A) was analysed immediately to determine the microbial and chemical qualities.
The second portion (B) was boiled for 30 min after which it was left for 6 h
for adequate cooling. Trona (0.2 g) was added to the third portion (C), which
was also boiled for 30 min after which it was left for 6 h to cool. The three
different samples (A, B and C) were subjected to microbial and chemical analyses.
Microbial Analysis
Nutrient agar (Oxoid) and Potato dextrose agar (Oxoid) were prepared according
to manufacturer’s instruction and used for the isolation of bacteria and
fungi, respectively.
Standard microbiological methods were used for the characterisation of bacteria and fungi isolates (Buchanan and Gibson, 1974; Barnet and Hunter, 1972).
Chemical Analysis
The proximate composition (ash, fat, crude fibre and moisture content) of
T. africana samples was determined using standard Association of Official
Analytical Chemists (AOAC, 1984) method. Protein content was determined using
the microkjeldah method (Nx6.25). Percentage soluble carbohydrate was determined
by subtracting the sum of percentage ash, crude fibre, crude protein, crude
ash and moisture content from one hundred.
Antinutrients viz., tannin, phytate and cyanide were evaluated by the methods of Makkar et al. (1993), Wheeler and Ferrel (1971) and De Bruijn (1971), respectively.
Analysis of Data
The data gathered were analysed using one-way analysis of variance and Duncan
Multiple Range Test compared means.
Results
Microbial Quality of T. africana Seed
The microbial load reduced significantly (p<0.05) when the seeds were
boiled. There was a further significant reduction in the microbial load when
the seed was boiled with trona (Table 1).
Bacillus sp., Staphylococcus sp., Micrococcus sp. and Rhizopus stolonifer were isolated from the raw seed while Bacillus sp. was the only bacterium isolated from the cooked seed and the seed boiled with trona. Saccharomyces cereviseae and Byssochlamys fulva were, respectively isolated from boiled seed and seed boiled with trona (Table 2).
| Table 1: | Total viable counts of raw and heat processed Treculia
africana seeds |
| * Values are means±SEM of 3 replicates. Values with different superscript are significantly different (p<0.05). A: Raw seed; B: Seed boiled for 30 min; C: Seed boiled with trona | |
| Table 2: | Microorganisms isolated from raw and heat processed T.
africana seeds |
| +: Present; --: Absent; A: Raw seed; B: Seed boiled for 30 min; C: Seed boiled with trona | |
| Table 3: | Proximate compositrion (% wet weight basis)* of raw and boiled
T. africana seed samples |
| * Values are means±SEM of 3 replicates. Values with different superscript are significantly different (p<0.05). A: Raw seed; B: Seed boiled for 30 min; C: Seed boiled with trona | |
| Table 5: | Antinutrient content (mg/100 g wet weight basis)* of raw
and boiled seeds of T. africana |
| * Values are means±SEM of 3 replicates. Values with different superscript are significantly different (p<0.05). A: Raw seed; B: Seed boiled for 30 min; C: Seed boiled with trona. | |
Chemical Quality of T. africana Seed
The protein, fibre and ash content of the raw seed sample was higher when
compared to the boiled seed and seed boiled with trona (Table
3). However, the fat and moisture contents of the boiled seed samples (fat,
2.85%; moisture content 64.82%) and seed boiled with trona (fat, 5.74%; moisture
content, 60.45%) were higher and significantly different (p<0.05) from the
raw seed. The antinutients level in the boiled seed and seed boiled with trona
were significantly lower (p<0.05) when compared to the raw seed (Table
4).
Discussion
Treculia africana Decne seed is an important food item in many parts of Nigeria. The seed is rich in carbohydrate, fat, protein and fibre (Nwufor and Mba, 1987). It may be eaten after boiling or frying (roasting). Sunday et al. (2001) had earlier reported that boiling proved more effective than roasting in reducing the levels of trypsin inhibitor, phytic acid and polyphenols in T. africana seed.
In the present study, T. africana seed was boiled with trona and it was observed that the microbial load and type after boiling with trona was significantly (p<0.05) lower than in the raw seed (Table 1 and 2). The predominant bacteria in the raw seed are Staphylococcus sp., Micrococcus sp. and Bacillus sp. Micrococci are known to be part of the fermentation flora of some foods (Jay, 1996). Bacillus sp. was the only bacteria isolated from the boiled seed and the seed boiled with trona. Bacilli are known to produce spore (Jay, 1996) and this may be responsible for their ability to survive in the heat treated seeds. The results of the proximate composition reveal some differences in the raw seed when compared to the boiled and boiled with trona seeds. The protein, ash and fibre contents in the raw seed were high and significantly different (p<0.05) when compared to the heat treated samples (Table 3). However, the fat and moisture content of the boiled seed and seed boiled with trona were higher and significantly different (p<0.05) from the raw seed. A report by Sunday et al. (2000) revealed that heat processed samples of T. africana had significantly higher and more stable water and fat absorption capacities. In essence, heat processing has a lowering effect on the protein, ash and carbohydrate content of the seed when compared to the raw seed.
The antinutrients (tannin, phytate and cyanide) contents were significantly lower (p<0.05) in the boiled T. africana seeds when compared to the raw seeds. Fasasi et al. (2003) had earlier reported a significant reduction in oxalates, phytate, tannin and cyanide contents of T. africana seeds fermented, autoclaved and toasted. A further reduction of phytate, tannin and cyanide was observed in the seeds boiled with trona (Table 4). This is an indication that the trona may facilitate the reduction of the levels of these antinutrients in the seed. The mechanism behind this is not yet known.
The results of the present study reveal that boiling T. africana seeds with trona may further increase the microbial quality and thereby make it safe for consumtion. Moreover, boiling the seeds with trona may further reduce the level of antinutrients of the seeds and consequently improve the nutritional potentials T. africana seeds.