FACULTY OF TECHNOLOGY
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Item MAIZE STORAGE IN TERMITE MOUND CLAY, CONCRETE, AND STEEL SILOS IN THE HUMID TROPICS: COMPARISON AND EFFECT ON BACTERIAL AND FUNGAL COUNTS(2015) Omobowale M.O.Considering the inadequacy of grain storage structures in Nigeria, which has been partly attributed to high cost and unavailability of construction materials, this study investigated the suitability of using readily available termite mound clay (TMC) for grain silo construction in comparison to conventional reinforced conczu (RC) and galvanized steel (GS) silos for maize storage in the humid tropics. The extent to which temperature and relative humidity affected the quality of stored grain during 8-month unaerated storage, covering both dry and rainy seasons, was evaluated using bacterial and fungal counts as performance parameters. The initial bacterial count of3500 colony forming units (CFU) per gram (CFU g-1) increased to 120000, 11000, and 8800 CFU g-1 for TMC, RC, and GS silos, respectively. There was no fungal activity at the beginning of storage, but fungal activity increased to 1500, 5500, and 350 CFU g-1 in TMC, RC, and GS silos, respectively. Fungal activity was noticed in the TMC silo in the fourth month of storage, which coincided with the start of the rainy season. Fungal counts exceeded the acceptable threshold of 1000 CFU g-1 in the TMC and RC silos. Relative humidity was of greater significance than temperature in affecting all. maize quality parameters considered. TMC was found suitable for constructing silos for short-term grain storage under unaerated conditions. Modification of the current TMC silo design to address permeability issues is expected to improve its performance for longer-term maize storage.Item Effect of Fill Volume on Microclimate and Microbial Activity in Non-ventilated Clay Silos Storing Maize in the Humid Tropics(Department of Agricultural and Environmental Engineering, Faculty of Technology, University of Ibadan, 2019) Omobowale M.O.Silos have a fixed volume at the time of construction; harvests however vary from season to season. Complaints about severe postharvest losses in grains in the humid tropics of southern Nigeria necessitated a study into the effect of fill volume on quality of stored maize. Three clay silos labelled S1 to S3 of the same dimension and capacity (3.5 metric tonnes) were used. The silo walls were painted externally with gloss paint to reduce water absorption and filled with shelled maize. The first silo (S1) was filled with 3 tonnes, the second silo (S2) with 2 tonnes and the third (S3) filled with a tonne of maize for 6 months. Data was collected on microclimatic conditions within the silo and grain quality with increasing time of storage. Temperature, relative humidity (RH) and equilibrium moisture content (EMC) were recorded three times daily for each silo, focusing on the air between the grains and the headspace above the grains. Temperature fluctuations within S1 were smaller as indicated by the statistical range of 2 oC compared to S2 and S3 at 7 and 8 oC respectively. S3 showed high values of RH toward the end of storage, ranging between 65% to 80% at the top level and 76% at the bottom. EMC at the airspace above the grains in S1 increased from 12.0% at the beginning of storage in the dry season to 15.6% at the end of storage in the rainy season compared with S2 and S3 which increased from 12.0 to 17% and 12.0 to 17.2% respectively. Grains were found to be more prone to deterioration with decreasing level of fill because and increase in microbial activity was observed with a decreasing level of fill. Recommendations were made to farmers and grain aggregators on proper actions to take during grain storage given the peculiarities of the humid tropics.Item Effect of Fill Volume on Microclimate and Microbial Activity in Non-ventilated Clay Silos Storing Maize in the Humid Tropics(Department of Agricultural and Environmental Engineering, Faculty of Technology, University of Ibadan, 2019) Omobowale M.O.Silos have a fixed volume at the time of construction; harvests however vary from season to season. Complaints about severe postharvest losses in grains in the humid tropics of southern Nigeria necessitated a study into the effect of fill volume on quality of stored maize. Three clay silos labelled S1 to S3 of the same dimension and capacity (3.5 metric tonnes) were used. The silo walls were painted externally with gloss paint to reduce water absorption and filled with shelled maize. The first silo (S1) was filled with 3 tonnes, the second silo (S2) with 2 tonnes and the third (S3) filled with a tonne of maize for 6 months. Data was collected on microclimatic conditions within the silo and grain quality with increasing time of storage. Temperature, relative humidity (RH) and equilibrium moisture content (EMC) were recorded three times daily for each silo, focusing on the air between the grains and the headspace above the grains. Temperature fluctuations within S1 were smaller as indicated by the statistical range of 2 oC compared to S2 and S3 at 7 and 8 oC respectively. S3 showed high values of RH toward the end of storage, ranging between 65% to 80% at the top level and 76% at the bottom. EMC at the airspace above the grains in S1 increased from 12.0% at the beginning of storage in the dry season to 15.6% at the end of storage in the rainy season compared with S2 and S3 which increased from 12.0 to 17% and 12.0 to 17.2% respectively. Grains were found to be more prone to deterioration with decreasing level of fill because and increase in microbial activity was observed with a decreasing level of fill. Recommendations were made to farmers and grain aggregators on proper actions to take during grain storage given the peculiarities of the humid tropics.