Variability of volatile compound profiles during two coffee fermentation times in northern Peru using SPME-GC/MS

Variabilidade dos perfis de compostos voláteis durante dois períodos de fermentação do café no norte do Peru usando SPME-GC/MS

Abstract

The time of the fermentation process of coffee from northern Peru is variable (9 to 48 hours) since coffee farmers do not use standardized processes, causing a variety of coffee qualities. This study aimed to identify volatile compounds in both short (9 hours) and long (32 hours) coffee fermentation processes from coffee farms in northern Peru using Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS) to associate the coffee quality and diversity of volatile compounds. Sensory analyses showed that the short fermentation process (SFP) scored 77.8 ± 0.39 and had chocolate, wood, cardboard, dry, fatty and rough notes, while the long fermentation process (LFP) showed higher punctuations 85.5 ± 3.16 and citrus, fruity, floral, caramel and chocolate sensory attributes. A total of 90 compounds were found in the SFP, whereas 141 compounds were identified in the LFP. Significant differences in the relative abundance of 14 chemical compounds were reported in the SFP and LFP (p < 0.05). From these results, the presence of benzaldehyde, methional, hexanal, 2-heptanone, pentadecane, 1-butanol-3-methyl-acetate, and benzene-acetic acid ethyl ester seems to impact the quality of coffee. The analysis of similarities showed that coffee samples (5 h and 9 h) during the SFP were very variable, whereas coffee samples from LFP showed some tendency to group, which may be related to the difference in altitude and temperature in coffee farms making comparison between them difficult. In addition, this study highlights the complex relationship between coffee fermentation and flavour and the influence of several factors and variables that may affect the composition of flavour and aroma precursors in green coffee beans obtained from wet fermentation.

Keywords:
Coffee; Fermentation time; Peru; Sensory; SPME-GC/MS; Volatile compound; Wet fermentation

Highlights

• A total of 157 volatile compounds was identified in both short (9 h) and long (32 h) coffee fermentation processes from Peru.

• Ninety volatile compounds were found in the short fermentation process, whereas 141 were found in the long process.

• The volatile compounds in coffee samples collected at 5 and 9 hours during the short fermentation process were very different from each other.

• According to sensory attribute, coffee produced using a long fermentation process scored higher than that produced using a short process (85.5 ± 3.16 versus 77.8 ± 0.39 points).

• This study highlighted the complexity of coffee fermentation and the influence of several factors in the attributes and final quality of coffee.