Microbial identification of potato taste defect from coffee beans

Area of Science:

• Food Science
• Microbiology
• Agricultural Science

Background:

• Coffee is a vital socioeconomic crop globally, yet quality is threatened by defects.
• Potato Taste Defect (PTD) negatively impacts Rwandan coffee quality, characterized by an off-flavor and smell.
• Bacterial contamination is a suspected cause of PTD, potentially exacerbated by pest infestations.

Purpose of the Study:

• To isolate, biochemically characterize, and identify bacteria responsible for PTD in Rwandan coffee.
• To understand the microbial basis of the potato flavor defect in coffee beans.

Main Methods:

• Bacterial isolation and enumeration from Rwandan coffee samples.
• Culturing bacteria on various media and carbon sources to detect odor production.
• DNA extraction, PCR amplification, and 16S rDNA sequencing for bacterial identification.
• Sequence analysis using FinchTV and BLAST.

Main Results:

• Earthy and potato-like odors were predominantly produced by isolated bacteria.
• Potato odor was most prevalent in damaged coffee beans (floaters and hand-sorted).
• Identified bacteria include Enterobacteriaceae and Pantoea, associated with 2-isopropyl-3-methoxypyrazine (IMP) production.

Conclusions:

• Specific bacteria, notably Enterobacteriaceae and Pantoea, are confirmed to cause PTD in Rwandan coffee.
• These bacteria produce IMP, the compound responsible for the potato flavor defect.
• Understanding these microbial agents is crucial for improving coffee quality and preventing PTD.