IMPROVEMENT OF COFFEE BEAN QUALITY BY USING Saccharomyces cerevisiae AND PECTINASE DURING THE DRYING PROCESS

In Viet Nam, Robusta coffees are mainly processed by drying method. In this method, natural fermentation of the fruit’s pulp and mucilage occurs during drying period. The reliance on natural microorganisms may cause negative effect on the coffee bean quality. Therefore, the aim of this work was to evaluate the potential of the use of S. cerevisiae and pectinase for Robusta coffee in dry process. In this study, Robusta coffees were inoculated with S. cerevisiae and pectinase as following: TR1 was treated with 1 g yeast; TR2 was inoculated with 3 g yeast, TR3 was a combination of 1 g yeast and 0.2 g enzyme; TR4 was a combination of 3 g yeast and 0.2 g enzyme. The control was without any selected yeast and enzyme. The fruits were incubated for 4 days before sun drying. During incubation, the temperature inside the mass was recorded and samples were collected for determining total bacterial and yeast population. During drying, samples were collected for evaluation of the moisture contents of coffee bean, physical and cup testing. The results show that, in all tests, the number of yeast and total bacteria was higher than the control. The moisture contents of coffee bean in all treatments decreased quicker than in the control. The physical and cup testing of coffee beans in all treatments seen to be better than in the control. The combination of 3 g yeast and 0,2 g pectinase per 1 kg coffee cherries was the best treatment for Robusta coffee fermentation in dry process because this treatment had high total number of bacteria and yeast (3.59 ˟ 106 cfu/g and 31.41 ˟ 104 cfu/g, respectively), high cup-testing score (71.8) and low percentage of defects (1.47%).