Molecular identification and safety assessment of microorganisms in okpeye sold in Owerri and Onitsha markets in South-eastern Nigeria
Date
2004-10
Authors
Journal Title
Journal ISSN
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Publisher
Federal University of Technology, Owerri
Abstract
Okpeye an indigenous fermented condiment produced from Prosopis africana seeds was assessed to evaluate the microbilogical quality of the condiment. Eighteen (18) commercial samples of okpeye were purchased from six markets in two cities in South Eastern Nigeria. Fifty-nine (59) bacteria colonies were isolated and identified at the species level by phenotyping and sequencing of the 16S rRNA, gyrB and rpoB genes. Bacillus (47.4%) and Staphylococcus (42.3%) were the predominant bacterial species in okpeye. Overall, B. amyloliquefaciens and S. simulans were the most frequently occurring bacteria and were present in all samples. In addition, B. cereus was isolated in samples obtained from all markets. Other bacterial species included B. velezensis, Oceanobacillus caeni, S. cohnii, Escherichia fergusonni and Vagacoccus lutrae. The B. cereus isolates (10) were screened for the presence of 8 enterotoxin genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK, entFM) and one emetic gene (cesB). The non-haemolytic enterotoxin (nhe ABC) and haemolytic enterotoxin (hbl ABD) complexes were present in 70% and 50% of B. cereus respectively. The positive rate of cytK and entFM genes was 70%, while the cesB gene was 30%. The haemolysis test revealed twenty- three isolates out of the twenty-eight isolates tested showing full haemolytic activity on blood agar. Two isolates (O22 and A22) showed partial haemolysis while three (O11, O15 and A12) showed no haemolysis.Antibiotic susceptibility assessment showed that most of the isolates were susceptible to gentamicin, tetracycline, streptomycin, and erythromycin but resistant to ciprofloxacin and vancomycin. These findings highlight the need for further controls to reduce contamination with potential pathogenic bacteria in indigenous fermented condiments such as okpeye. Two isolates that gave the best safety assessment results were used as starter cultures for the fermentation of Prosopis africana
seeds. The bacterial load of seeds fermented with the starter cultures was slightly higher than the spontaneously fermented seeds with a value range of (7.7- 9.4 log10 Cfu/g). The seeds fermented with mixed cultures of B. licheniformis and B. amyloliquefaciens had the highest pH (9.14), temperature (39.96oC) and titratable acidity (TTA) (1.03%) after 168 hours of fermentation. The protein, fat, ash and carbohydrate content were higher in okpeye fermented with starter cultures (B, C and D) than that of the commercial samples (E). The spontaneously fermented sample (A) had the highest protein content (27.80%) than all the other samples. The phytochemical composition showed that okpeye fermented with mixed cultures of B. licheniformis and B. amyloliquefaciens had the highest oxalates (11.52%), saponins (0.05%), phytates (549.75 mg/100g), alkaloids (13.03%) and flavonoids (14.20%) than the commercial and spontaneously fermented samples. The spontaneously fermented samples had the highest tannin (13.29 mg/100g) and total phenol (330.36 mg/g) than all the other samples. The commercial sample had the least phytochemical nutrients except for phytate (58.53 mg/100g) and cyanide (1.60 mg/g). The sensory analysis showed that soup cooked with okpeye fermented with mixed cultures of B. licheniformis and B. amyloliquefaciens had the best results in aroma (7.27), flavour(7.40), appearance (7.30), after taste (7.17) and overall acceptability (7.31). The sensory results showed that okpeye fermented with mixed cultures of B. licheniformis and B. amyloliquefaciens was well accepted by consumers. Based on this acceptability as well as the nutritional composition and phytochemical composition, mixed cultures of B. licheniformis and B. amyloliquefaciens c be recommended in the fermentation of P. africana seeds to produce safe and good quality okpeye.
Description
Doctoral thesis in food microbiology. It contains pictures, tables and graphs.
Keywords
Okpeye, 16srRNA sequencing, starter culture, antibiotics, enterotoxin genes, haemolysis, bacillus, gyrB, rpoB genes., department of food science and technology
Citation
Agunwah, I .M. (2024). Molecular identification and safety assessment of microorganisms in okpeye sold in Owerri and Onitsha markets in South-eastern Nigeria {Unpublished Doctoral Thesis}, Federal University of Technology, Owerri