Manufacturing efficiencies and microbioal properties of butter and Ayib - Ethiopian cottage cheese

Four butter-making methods (3 traditional: clay pot - CP, 'mesbekia' - M - a wooden agitator with three to five finger like projections at one end, and a combination of the two - CP+M; and one improved internal wooden agitator fitted to the traditional clay pot - IWA) were evaluated for their efficiencies in terms of fat recovery and churning time at 12 smallholder milk producers in the central highlands of Ethiopia. About 21 litres of milk was needed to produce one kg of butter (83% total solids - TS). An average churning time of 222 min was recorded for the three traditional methods with a mean fat recovery of about 90%. Churning time was significantly reduced by 65% for the IWA as compared to the average of the 3 traditional methods. The effect of holding Ayib (Ethiopian cottage cheese) in whey for different time length (1 h, 2 h and overnight) on Ayib yield was compared. The mean Ayib-making time and temperature was respectively 48 min and 57°C. Weight of Ayib recovered significantly increased with increasing length of time Ayib stayed in whey before separation, amounting to 1266, 1475 and 1776 g per 9.2 litres of buttermilk for 1 h, 2 h and overnight, respectively. About 6 litres of buttermilk was needed to produce one kg of Ayib (20.4% TS). Besides, aerobic mesophylic bacterial count (AMC), counts of enterobacteria, and coliform bacterial count (CC) were performed. Average AMC, counts of enterobacteria and CC of butter samples were 8, 5.3 and 3.8 log cfu/g, respectively, while the counts for Ayib samples were 7.9, 5.1 and 4.4 log cfu/g, respectively. Enterobacter, Escherichia, Klebsiella and Klyuvera were the genera identified, while Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae and Klebsiella gr. 47 are the species commonly isolated from both products. The knowledge on traditional butter- and Ayib-making efficiencies and their microbial properties is essential to increase yield and improve quality and preservation of the products. (Résumé d'auteur)