Coffee protein profiles during fermentation using different yeast inoculation methods

Abstract

The objective of this work was to evaluate the protein profiles of natural and semidry fermented Coffea arabica, either subjected to treatments with different yeast inoculation methods with starter culture or to an uninoculated control. Saccharomyces cerevisiae CCMA 0543 and Candida parapsilosis CCMA 0544 were separately inoculated into coffee by directly spraying the cherries on a terrace or in buckets, for 16 hours before sun drying. Protein quantification showed a significant difference between the protein profiles of the samples collected after natural dry fermentation. The MALDI-TOF MS analysis generated a list of 96 peaks with different mass-to-charge ratios (m/z) in the samples collected at the beginning and the end of fermentation. The highest number of peaks in the natural dry coffee was observed at the end of fermentation in the samples inoculated with S. cerevisiae CCMA 0543, in bucket, and in C. parapsilosis CCMA 0544 sprayed on the terrace. However, in the semidry processed coffee, the highest number of peaks was observed in the initial fermentation, with a decrease in the peptide peaks after fermentation. The fermentation with different microorganisms, processing types, and inoculation methods affects m/z profiles, influencing the types of proteins found in coffee.

The Effect of Type and Duration of Digestive Enzyme Treatment on Coffee Bean Composition

“…Decrease in protein content after roasting could be again related to reactions occurring at high temperatures [1]. Protein compounds contribute to the activation of sucrose degradation processes and the formation of aromatic compounds, which are responsible for many aroma notes, e.g., earthy, nutty or honey-like [4,31]. On the other hand, proteins are considered to be responsible for the creation of compounds associated with bitterness of the final brew [11].…”

“…There are numerous factors that influence chemical composition of green coffee, e.g., species and variety of coffee tree, geographical origin, cultivation processes, ripeness and post-harvest processing of coffee fruits [2,3]. Basic methods used for post-harvest processing are dry/natural method, wet method and semi-dry method [4]. There are also less conventional methods, in which production of kopi luwak needs to be included.…”

“…α-amylase is one of the basic amylolytic enzymes and is active in the mouth and small intestine. Digestive enzyme activity might affect carbohydrates and proteins present in green coffee beans and, therefore, change characteristics of the final product [4].…”