Microbial quality and shelf-life optimization of local millet drink “Zoomkoom’’

Abstract

This research was aimed at improving the shelf-life of millet drink, zoomkoom. This drink is one of the Ghanaian traditional drinks which is gaining popularity since a significant section of the populace either produce or patronize it on a daily base or occasionally. The production and consumption rates are influenced by shelf- life of the millet drink. The objectives of this research were to assess the safety and microbial quality of the drink; determine the nutritional composition of the drink; determine and improve the shelf -life of the drink and determine consumer preference of the improved drink. Field survey and experimental design were adopted as a research design for this study. The population for this study was purposively and conveniently selected and consisted of farmers and sellers of millet grain, producers, retailers and consumers of millet drink. The snowball sampling technique was used to select the sample size of 100 participants for the study. The field survey was done in conveniently selected communities in the northern region of Ghana. The laboratory test was carried out at Microbial Biotechnology and Food and Quality laboratories of Kwame Nkrumah University of Science and Technology. Observation, questionnaire and interview were used to collect data from the field survey. Two samples (market and laboratory controlled) were assayed for the laboratory analysis. Both samples were subjected to nutritional, proximate and mineral analysis using AOAC (2000). Shelf-life of the drink was determined using two different concentrations of 0.025% and 0.05% of potassium sorbate (E202) at different temperatures of 0℃, 5℃, 25℃ and 40℃ for 15 days. Findings from the study indicated very poor microbial quality of the millet drinks sampled from the market with aerobic counts in the range of 7.1×106cfu/ml and9.5×106cfu/ml beyond the safe and acceptable limit of 1.0×104cfu/ml for ready to eat foods as specified by the International Organization for Standardization (ISO) and adopted by the Ghana Standards Authority (GSA) and Food and Drugs Authority (FDA) of Ghana. The nutritional worth of zoomkoom was assessed to determine the dietary benefits of the drink to consumers. The drink was found to be predominantly water based with a moisture content of 84.79±0.71% thus making it a good source of hydration to the consumer. The drink had low fat, protein and fibre contents of 0.29±0.11%, 0.41±0.14% and 0.014±0.002% respectively. The carbohydrate content was found to be 14.41±0.43% and an energy content of 61.87±2.97kcal/g. Though refrigeration extends the shelf-life of the millet drink from less than a day to 3 days, the preservative further extended the shelf-life to 10 days and 15 days at room temperature using 0.025g/100g and 0.05g/100g respectively which indicates ten-fold increase and beyond shelf-life improvement thereby making this intervention suitable for solving the present challenge of short shelf-life and keeping quality of the drink. Finally, the study indicates that consumer acceptability is not significantly influenced by the appearance of the millet drink in the two packaging materials (glass and plastic bottles) as well as a preservative; potassium sorbate (E202).