Assessing Alkyl Methoxypyrazines as Predictors of the Potato-Taste Defect in Coffee

Organoleptic detection (cupping analysis) is typically used to evaluate coffee quality, which is influenced by various flavor compounds, including the relative abundances of 2-isopropyl-3-methoxypyrazine (IPMP) and 2-isobutyl-3-methoxypyrazine (IBMP). IPMP and IBMP are purportedly significant contributors to the potato-taste defect (PTD) in brewed coffee. This study investigated the relationship between PTD-positive coffee samples and concentrations of IPMP, IBMP, and two favorable flavor-note compounds, 2-ethyl-3,5-dimethylpyrazine (EDMP) and 2-furfurylthiol (FFT), formed during coffee roasting. Cupping analysis of 32 roasted coffee samples showed PTD-positive frequencies ranging between 0.13 and 0.39. Quantitative GC/MS measured the IPMP and IBMP metabolites at 21 +/- 1 and 86 +/- 1 ng g(-1) in green beans and 115 +/- 1 and 158 +/- 3 ng g(-1) in roasted beans, respectively, while EDMP (similar to 2000 ng g(-1)) and FFT (similar to 8 ng g(-1)), also formed during the roasting process, were much higher in roasted beans. Logistic regression analysis identified a disparity between PTD occurrence and the abundances of the potential quality predictors IPMP, IBMP, FFT, and EDMP in green and roasted coffee beans, yet a principal component analysis showed that metabolites isolated from roasted coffee beans associated more strongly with PTD occurence. Visual and algorithmic investigation of the regression data results showed a negative correlation between the [IBMP]:[EDMP] and [IBMP]:[FFT] ratios and PTD-negative samples. Similar correlations were extrapolated for the [IPMP]:[FFT] ratio and [IPMP]. Further investigations are needed to understand why increases in PTD-associated compounds correlated with PTD-negative scores.

Automated summary

This study investigated the relationship between potato-taste defect (PTD) positive coffee samples and the concentrations of certain flavor compounds formed during coffee roasting. The results showed that these compounds played an important role in PTD occurrence. Regression analysis revealed a negative correlation between PTD-negative samples and the ratios of IBMP:EDMP and IBMP:FFT. Further research is needed to understand why increases in PTD-associated compounds are correlated with PTD-negative scores.