Microbial characterization of dried foods from Ghana

Bernice Dzifa Kudjawu, Purdue University

Abstract

Traditionally, the most common methods to preserve vegetables and fish in Ghana are sun-drying and smoking, respectively. Convenience foods also are fairly common, which are foods that are mechanically dehydrated and milled into powders. In this research, the dominant microflora of common Ghanaian dried foods such as vegetables; powders; smoked, salted or sun-dried fish; seasonings; spices and oilseeds were investigated by enumerating the total count, yeasts and molds, lactic acid bacteria, coliforms, Bacillus species and Staphylococcus aureus. Dominant microbial species on the dried vegetables were further characterized by colony, cell morphology, and biochemical tests. Molds and Bacillus spp. dominated the flora of all the dried foods examined although coliforms and lactic acid bacteria also were isolated in most of these products. Total counts of the dried vegetables were 103 to 107 CFU/g; powdered products had 104 to 107 CFU/g; smoked, salted or sun-dried fish had 103 to 105 CFU/g; and spices and oil seeds had 102 to 107 CFU/g. Staphylococcus aureus was present at levels of 102 to 103 CFU/g in the fish, seasonings and oilseeds. Aspergillus spp, Rhizopus spp, Eurotium spp, Penicillium spp and Aureobasidium spp. were the major genera of the molds present in the dried vegetables. The dominant Bacillus species in all the samples were Bacillus subtilis and the major lactic acid bacteria were Lactobacillus plantarum. Escherichia coli was not detected in any of the dried vegetables, however, Enterobacter aerogenes was detected in most of these dried vegetables. The pH of the dried vegetables ranged from 2.41 to 7.50; powdered convenience foods had pH values ranging from 4.10 to 6.97. All the dried fish had pH values ranging from 6.10 to 8.00 and seasonings and oil seeds had pH from 4.80 to 8.00. The water activities of all the dried foods were between 0.374 and 0.683 except for roasted corn flour and dawadawa, which were 0.214 and 0.813, respectively; therefore, there is little chance of microbial growth in most of these foods until they are rehydrated. Since there were high microbial levels in the dried foods used in this research, it is recommended that processing and handling procedures be improved to ensure the safety and the quality of the staple foods in Ghana.

Degree

M.S.

Advisors

Cousin, Purdue University.

Subject Area

Agronomy

COinS