Effects of Chemical Treatment and Pasteurization on the Shelf Life of Kunun Zaki (Sorghum and Maize Gruel)

Abstract

This study was aimed to investigate the effects of chemical treatment as well as pasteurization on the shelf life of “kunun zaki” (a non-alcoholic beverage commonly consumed by the people of northern Nigeria), to increase the shelf life and preserve the quality of the beverage. Kunun zaki was produced by dry -cleaning, washing, steeping (sorghum for 24 hours and maize for 48 hours), malting for 72 hours at room temperature, wet milling, mixing, cooking and filtering to obtain the liquor. The product was treated with 0.1% sodiumbenzoate or sodium metabisulphite or their combinations. These were packed and pasteurized in bottles at 60°C for one hour. Another batch of samples were chemically treated but not pasteurized. Pasteurized samples which were not chemically treated served as control. Samples were stored at ambient temperature and monitored for changes in pH, titratable acidity, total solid, total sugars, acceptability and colour for four weeks. The pH and sugar decreased and the decrease was more pronounced in non pasteurized samples irrespective of chemical treatment. Titratable acidity increased in all samples with storage time. Pasteurized kunun zaki which received no chemical treatment deteriorated after one week of storage. Samples treated with 0.1% sodium benzoate or sodium metabisulphite or their combination without pasteurization deteriorated after two weeks of storage. Samples which were similarly treated and pasteurized were stable for more than three weeks. Pasteurization enhanced effectiveness of chemical preservation and acceptability of kunun zaki.