Abstract
<p>Fermentation of coffee mucilage is a spontaneous process caused by microorganisms growing in the environment, which is influenced by factors such as the variety, climate and fruit maturity. These external factors play an important role in fermentation evolution because they have effect on the microorganism activity and the substrate transformation time. The objective in this research was to evaluate the effect of different fermentation wet process and evaluated their effect on coffee quality (<em>Coffea arabica</em> L.), as well as on organic acid concentrations and volatile organic compounds content, in the green coffee beans. The study was divided in two phases, one in which the pulping time was delayed and the fermentation methods were modified, and the second phase in which a bioreactor was used to control the pH and temperature of the coffee mass during fermentation. Two control treatments were used: without fermentation (mechanical removal of mucilage) and the traditional fermentation done in the farm. Significant differences in coffee quality were observed. The best quality was obtained from the treatments that used short process times and low temperatures. The concentrations of acetic, lactic and citric acids between the treatments and the control treatments were different. Higher contents of esters and ketones were found in the coffee that obtained the highest quality. The assessed processes lead to the conclusions that it is possible to improve coffee quality throughout introducing changes in the fermentation process, as well as modulating the acidity and fragrance of the final product.</p>
Highlights
Growing specialty coffee market is a response of customers desiring to pay more for unique attributes in the beverage
According to the sensory analysis (Table 1), the final score obtained in all treatments was higher than 80 points; the coffee obtained in this study was classified as Premium according to the SCA scale
This study is the first to show that variations in the coffee fermentation process and variables control, such as pH and temperature, increase the coffee quality under the environmental conditions, variety and methods applied in this research
Summary
Growing specialty coffee market is a response of customers desiring to pay more for unique attributes in the beverage. Coffee quality is an outcome of the intrinsic grain characteristics but for a combination of the environmental characteristics of the place it is grown (altitude, climate, and soils, among others), the ripeness at which it is harvested, and the post-harvest process carried out (JOËT et al., 2010; TOLEDO et al, 2016). The wet method, which is a post-harvest process used to maintain the mildness of the Arabica coffee, involves the mechanical removal of the fruit skin (exocarp or pulp) to expose the jelly layer (mesocarp or mucilage) adhered to the bean’s surface. Pulped coffee is put into tanks to perform mucilage degradation by spontaneous fermentation, to facilitate mucilage removal by washing. In the mucilage degradation process, microorganisms in the environment use mucilage as a substrate for their metabolic processes to generate organic acids among others. The wet process of coffee is associated with a higher acidity, which leads to a Coffee Science, Lavras, v. The wet process of coffee is associated with a higher acidity, which leads to a Coffee Science, Lavras, v. 13, n. 4, p. 465 - 476, oct./dec. 2018
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