Comparative studies on red sorghum extracts and other chemicals as preservatives for West African soft cheese

Chemical changes, microbial load, sensory qualities and shelf-life of West African soft cheese under different storage conditions were monitored. In addition, the effectiveness of chemical treatments (i.e. colouring with extracts of leaves and stalks of red sorghum, 5% NaCl; 0.2 or 0.8% sodium metabisulphite (Na 2S 2O 5); 0.2 or 0.8% sodium benzoate and 0.2 or 0.8% propionic acid) as preservatives for West African soft cheese was investigated. The control and treated cheeses were stored under ambient conditions and assessed over a 10-day storage period. The pH of cheeses (control and treated) decreased until the 6th day of storage after which it started to increase. A concomitant increase in titratable acidity up to the 6th day of storage followed by a decrease was also observed in the cheeses. The moisture content of the cheeses decreased during storage. Sodium benzoate (0.8%) and propionic acid (0.8%) were found to be the most effective at reducing microbial load and total viable fungi and bacterial counts. The different treatments extended the shelf-life of cheese as follows: control, 2 days; boiling alone, 4 days; boiling and coating with colourant, 4 days; boiling and salting, 6 days; 0.2% sodium metabisulphite, 4 days; 0.8% sodium metabisulphite, 6 days; 0.2% sodium benzoate, 6 days; 0.8% sodium benzoate, 8 days; 0.2% propionic acid, 6 days and 0.8% propionic acid, 8 days. The use of extracts of leaves and stalks of red sorghum as colourant appeared to have no preservative effect in West African soft cheese.