The effects of different preservation methods on the quality of nunu, a locally fermented Nigerian dairy product

Abstract

Biochemical and microbial analyses were carried out on fresh and preserved nunu for seven days. Fresh nunu contained protein, carbohydrates, lipids, calcium and other nutrients. Fresh samples had an initial pH of 4.4, microbial load of 4.2 x 103 cfu/ml and free fatty acid level of 2.21 mg/g of sample. Unpreserved sample showed appreciable degree of lipolysis, proteolysis and lactose fermentation. Preservation was by physical and chemical means. Physical methods included pasteurization and refrigeration. Pasteurization proved to be the least effective method of preservation. There was an appreciable level of increase in microbial count and biochemical changes. The chemical preservatives used were sodium benzoate and benzoic acid (1% concentration, w/v of sample). Sodium benzoate proved to be the most effective of all methods of preservation. The microbial count was significantly reduced (p < 0.05) and there were very slight biochemical changes. Benzoic acid was also effective, but less than sodium benzoate. Nunu, if well preserved, can thus be a very refreshing and nourishing beverage that is affordable to many.