Studies on the influence of temperature, relative humidity and microenvironment on the natural fermentation of African oil bean seeds to 'Ugba'.

Abstract

Studies on the enhancement of the traditional production of 'Ugba' (a protein-rich fermented food) from African oil bean seeds were undertaken by fermenting the bean seeds at different temperatures, relative humidities (RH) and microenvironments. Fermentation was monitored by pH, texture, amino-nitrogen content and the viable cell count of the substrate. The 40 degrees C, 98% RH or the 130 microm high density polyethylene (HDPE) treatment increased the fermentation microflora from ca. 10(6) CFU/g to ca. 10(8) CFU/g with high initial changes in pH (5.8-ca. 7.9) and texture (2.0 kg/cm2 to between 1.4 kg/cm2 and 0.9 kg/cm2) in 24 hours. Products with amino-nitrogen contents of between 12.00 mg N/100 g dry matter and 14.00 mg N/100 g dry matter were obtained in 3 days. The cell count of the 30 degrees C, 80% RH or 70 microm treatment increased from 10(6) CFU/g to ca. 10(7) CFU/g and the pH increased from 5.8 to about 6.7 with a coincident decrease in the texture value from 2.0 kg/cm2 to about 1.7 kg/cm2 in 24 hours. Products with amino-nitrogen contents between 15.00 mg N/100 g dry matter and 19.2 mg N/100 g dry matter were obtained after 3 days. Changes in the fermentation indicators were not significant at p < or = 0.05 (pH and texture) and at p < or = 0.01 (amino-nitrogen) after 3 days for the 25 degrees C, 59.9% RH or 50 microm low density polyethylene (LDPE) treatment. Products of fermentation at the combined optimal conditions (80% RH, 35 degrees C, and 70 microm HDPE) compared very well with the traditionally fermented products in terms of pH, texture and amino-nitrogen content.