Analytical Determination of the Severity of Potato Taste Defect in Roasted East African Arabica Coffee

Abstract

The quality of East African coffee beans has been significantly reduced by a flavor defect known as potato taste defect (PTD) due to the presence of 2-isopropyl-3-methoxypyrazine (IPMP) and 2-isobutyl-3-methoxypyrazine (IBMP). Therefore, the aims of this study were to determine the correlation between these methoxypyrazines and the severity of odor attributed to PTD and discover additional analytes that may be correlated with PTD using Fisher ratio analysis, a supervised discovery-based data analysis method. Specialty ground roasted coffees from East Africa were classified as clean (i.e., no off-odor), mild, medium, or strong PTD. For the samples examined, IPMP was found to discriminate between non-defective and defective samples, while IBMP did not do so. Samples affected by PTD exhibited a wide range of IPMP concentration (1.6–529.9 ng/g). Except for one sample, the IPMP concentration in defective samples was greater than the average IPMP concentration in the non-defective samples (2.0 ng/g). Also, an analysis of variance found that IPMP concentrations were significantly different based on the severity of odor attributed to PTD (p < 0.05). Fisher ratio analysis discovered 21 additional analytes whose concentrations were statistically different based on the severity of PTD odor (p < 0.05). Generally, analytes that were positively correlated with odor severity generally had unpleasant sensory descriptions, while analytes typically associated with desirable aromas were found to be negatively correlated with odor severity. These findings not only show that IPMP concentration can differentiate the severity of PTD but also that changes in the volatile analyte profile of coffee beans induced by PTD can contribute to odor severity.

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

“…The natural olfactory threshold of the de novo pyrazines made in roasted coffee by the Maillard and Strecker reaction usually creates a pleasant bouquet. However, PTD is more likely detected when this threshold is exceeded . The present study found considerably higher IPMP and IBMP concentration averages in roasted compared to green coffee beans, with IPMP increasing from 21 to 115 ng g –1 and IBMP increasing from 86 to 158 ng g –1 , and EDMP and FFT rising from below the detection limits to 1644 and 8043 ng g –1 , respectively (Table ), prompting an assessment of how the combination of off-flavor methoxypyrazines and pleasant-odor EDMP and FFT in roasted coffee beans correlated with PTD occurrence.…”

“…1 This study adds to the compendium of data that seeks to identify metabolite profiles in green and roasted coffee beans that correlate with PTD occurrence in brewed coffee. 1,3,29,33 Instrumental methods to identify an array of PTD-fingerprint molecules significantly correlated to PTD by PCA statistical analysis are a crucial complement of the organoleptic results when assessing coffee quality. The findings also revealed a mismatch between PTD occurrence and the concentrations of the purportedly potent PTD-dependent IPMP and IBMP compounds in both green and roast coffee beans.…”

Does Coffee Have Terroir and How Should It Be Assessed?

“…A number of biochemical markers have been identified in coffee with different sensory profiles [1,130]. Modern analytical instruments such as gas chromatography mass spectrometry (GCMS) [28,[131][132][133][134][135], GCMS-Time of Flight (GCMS-TOF) [136], high-performance liquid chromatography (HPLC) with evaporative light scattering detector (ELSD) [133], near-infrared radiation (NIR) [137], and Raman spectroscopy [138] have been utilized to find relationships between biochemical markers and the sensory notes of coffee.…”

Sensory and Physicochemical Characteristics of Two Common Roast Defects in Robusta Coffee

“…Despite extensive studies on coffee roasting, information regarding roast defects is still limited. Few articles published have reported common roast defects on Arabica coffee [7], [15], [19]- [22]. However, Robusta coffee appears to be less explored, probably due to the higher popularity of Arabica coffee.…”