Socio-economic relevance of fermented food in developing countries is evident. However, the production of this category of food is still achieved under primitive conditions. Ogi a fermented product from maize, sorghum or millet is usually transformed into gruel or porridge when heated. About a quarter of Nigeria population is said to consume Ogi on a weekly bases. This coupled with increasing industrialization and urbanisation in the country may however dictate the need for large-scale production of Ogi. The proposal for industrialisation of this process will lead to a deliberate and calculated combination of chemical or mechanical steps to aid the manufacture of this product. However, the growth of small-scale or large industries for this product may be confronted with some limiting factors prevalent in most third world countries. Ogi production have some similarities in unit operations when compared with corn starch production, therefore the same technologies may be adopted with appropriate modification in the production of Ogi and this will provide employment to a number of people. This review is with a view to establish the need to mechanise the process and as well as point out the technological and economical implication.
The antimicrobial effect of Corn Steep Liquor (CSL) was investigated over a five day period. The pH and titrable acidity of the liquor were determined, while the antimicrobial effect on some diarrhoea causing organisms such as Escherichia coli, Salmonella enteriditis, Staphylococcus aureus and Vibrio parahaemolyticus was also determined. Using well diffusion method, 0.1 ml (100 l) of the liquor effectively inhibited the growth of the test organisms with zones of inhibition ranging from 4.00 ± 0.28 to 20.20 ± 0.14 mm. The zones of inhibition increased with increasing number of days of fermentation of the filtrate on which is the CSL. However, there was no significant difference (P>0.05) in the antimicrobial properties of the liquor on day 3 and 4 for S. enteriditis, S. aureus and V. parahaemolyticus. The zone of inhibition on day 5 was significantly different (P<0.05) from all other days except in S. enteriditis whose zone of inhibition was not significantly different from day 4 and 5. The degree of inhibition was highest in E. coli (20.20 ± 0.14 mm), followed by V. paraheamolyticus (18.50 ± 2.12mm); while S. enteriditis showed the minimum degree of inhibition to the CSL (13.20 ± 0.28 mm. The total microbial count and the titrable acidity of the liquor increased with increasing number of days and reached a peak on day 4 (355.60 ± 21.07 cfu/ml and 23.25 ± 2.05%, respectively). The pH however decreased with number of days. The result suggests that corn steep liquor which is considered a waste inhibits the growth of some diarrhoeic microbes especially by day four of fermentation.
Precipitation is widely used in processing of biological products, such as proteins. The coagulating properties of Sodom apple ju ice, vinegar, lemon juice and rennet as coagulants of soy protein precipitate fro m soymilk at different temperature were investigated. Soymilk was produced using the hot grind method. The studied coagulants were used to precipitate soy protein fro m the produced milk at d ifferent temperature respectively. The coagulation time was observed to decrease with increasing temperature, with 100℃ giv ing the best time. The p H of the coagulated proteins was observed to decrease with increasing temperature with the optimal pH observed at 70℃ for all the coagulants. No significant difference was observed on the effect of coagulating temperatures on the yield of coagulated soy protein precipitate. Results fro m this study indicate that optimu m coagulating activ ities can be achieved between 70-80℃. Ho wever, the yields by the studied coagulants are not affected by temperature. Thus, imp lying that temperature modulate the coagulating activit ies, pH and not yields of the coagulants. Therefore, production at 70 -80℃ will g ive the best soy protein quality.
The drying kinetics of ogi produced from six varieties of maize at varying soaking period (12, 24 and 36 hrs) and drying temperature of 40, 50 and 60oC, respectively were studied. Seven common thin layer models were evaluated, and the best models were selected. The moisture content of ogi decreased with increased drying temperature and drying time while the drying rate increased with an increase in drying temperature and decreased with an increase in drying time. Logarithmic and two term models best fitted about 40.77% (22 samples each). However, where two term models were selected best, the R2 values ranged from 0.9858-0.99999999, χ 2 = 0.03715-0.000412, RMSE = 0.02206-0.0000677, unlike Logarithmic model that ranged from 0.8876-0.9964, χ 2 = 0.07045-0.001447, RMSE = 0.1084-0.01098. There was no definite pattern for effective moisture diffusivity (Deff) and Activation energy (Ea). This research work strongly suggests that the drying process was predominantly in the falling rate period (FRP) and was significantly affected by the change in temperature and moisture gradient. The activation energy obtained for ogi at varying soaking period and drying temperature ranged from 2.58-12.00 kJ/mol (A4Y), 7.72-44.95 kJ/mol (A4W), 14.53-35.88 kJ/mol (S7Y), 6.02-20.10 kJ/mol (D2Y), 14.024- 45.31 kJ/mol (DIY) and 19.34-64.22 kJ/mol (T3W). It was obviously indicated in this research that the soaking period had less or no impact on the drying behavior of ogi compared with the influence of drying temperature, drying time and initial moisture content.
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