Coffee Testing

de Gois, Jefferson S., Izylla O. Lucena, Paulo S. de O. Cezario, Arnaldo P. da Silva, Igor CA Lima, and Aderval S. Luna. Analytical Methods 10, no. 14 (2018): 1656-1661.

This study describes the multivariable development of a simple method based on the use of dilute nitric acid and ultrasonic-assisted extraction (UAE), followed by determination using inductively coupled plasma optical emission spectrometry (ICP-OES). The method was applied to the multi-element determination of newly developed coffee varieties.

Extraction time and HNO₃ concentration were optimized, achieving quantitative recovery with an extraction time of 15 minutes and 0.6 mol L^-1 HNO₃. After the extraction procedure, 0.48 mol L^-1 HCl was added to stabilize the analytes in the dilute HNO₃ solution. The accuracy of the method was assessed by comparing it with microwave-assisted digestion (MAD) and recovery tests. According to a t-test at a 95% confidence level, the results from UAE were consistent with those obtained from MAD.

A total of thirty-five coffee bean samples were analyzed using the proposed method. The results indicated that the concentrations of various elements were as follows: Ba ranged from 0.2 to 4.5 μg g^-1, Ca from 1507 to 2576 μg g^-1, Cu from 5 to 30 μg g^-1, Fe from 17 to 44 μg g^-1, K from 30,771 to 55,741 μg g^-1, Mg from 2005 to 3327 μg g^-1, Mn from 12.1 to 148.8 μg g^-1, Sr from 1.0 to 7.6 μg g^-1, P from 1105 to 2766 μg g^-1, and Zn from 4 to 12 μg g^-1.

İNCEBAY, Hilal. Journal of Food Composition and Analysis (2024): 106717.

Caffeic acid possesses anti-inflammatory, antimicrobial, anticancer, and immunomodulatory properties, along with antioxidant characteristics. Therefore, accurately determining the content of this acid is important for analytical and therapeutic purposes, as well as for the safety and quality of food samples.

This study aims to determine the content of caffeic acid in Turkish coffee using square wave voltammetry. The method has been successfully applied for the precise determination of caffeic acid, utilizing a glassy carbon electrode modified with a synergistic combination of functionalized multi-walled carbon nanotubes and boron oxide nanoparticles. The proposed platform and method achieved a limit of quantification of 0.04 nM for caffeic acid within a dynamic range of 1.0 nM to 40 μM, and were successfully used for the determination of caffeic acid in Turkish coffee samples.

Domínguez-Hernández, Cristopher, et al. Food Chemistry 388 (2022): 132997.

The ammonium formate version of the QuEChERS method was applied for the first time to extract a set of nine phthalates and one adipate from three types of coffee prepared from coffee capsules (high concentration, medium concentration, and decaffeinated), using gas chromatography coupled with mass spectrometry for the separation and determination of analytes. Matrix-matched calibration showed that the determination coefficients (R²) for all analytes and the matrix were above 0.9983, indicating good linearity. Overall, the assessment of matrix effects revealed moderate signal suppression, while the average relative recovery values for most analytes ranged from 70% to 120%, with relative standard deviation values of ≤19%. Several samples of each coffee type obtained from capsules made of different materials were also analyzed, revealing concentrations of DBP, DEHA, and DEHP in the range of 29.3 to 734 ng/capsule, which are below the established acceptable daily intake levels for some of these samples.

Zhang, H., Feng, X., Liu, D., Wang, X., Wei, J., & Liu, H. (2022). Microchemical Journal, 181, 107822.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established using a tri-functional modified hydrophilic interaction liquid chromatography (HILIC) column to measure chlorate and perchlorate in instant coffee and ready-to-drink (RTD) coffee.
After sample extraction and purification using an MCX column, separation was performed on a Tour DEA column (100 mm x 2.1 mm) with a gradient program employing 0.4% ammonia - 2 mmol/L ammonium acetate solution and acetonitrile as the mobile phase. To ensure the reliability and sensitivity of the method, isotopic internal standards and a multiple reaction monitoring (MRM) model were utilized during quantification. Satisfactory data were obtained during the validation process, with linear ranges for chlorate and perchlorate being 5.0 to 1000 μg/L and 0.5 to 100 μg/L, respectively. The recovery rates for chlorate in coffee samples ranged from 98.7% to 115%, while the recovery rates for perchlorate ranged from 92.3% to 102%, with relative coefficients being satisfactory (<10%). The limits of quantification for chlorate and perchlorate were 5 μg/L and 0.5 μg/L, respectively.

Cina, Mariel, et al. Journal of Food Composition and Analysis 114 (2022): 104777.

Ochratoxin A (OTA) is a secondary metabolite produced by filamentous fungi and is classified as Group 2B by IARC. OTA is present in various foods and beverages.
This study developed and validated a new method for the detection and quantification of OTA in coffee drinks. The extraction procedure is based on dispersive liquid-liquid microextraction and solidification of floating organic droplets (DLLME-SFO). The extracts were analyzed using UHPLC-(ESI+)-MS/MS. The method demonstrated high sensitivity, with limits of detection (LOD) and quantification (LOQ) of 0.3 and 0.9 ng/mL, respectively, and a linear range of 0.3 to 70 ng/mL, with a correlation coefficient (R²) of 0.9962. The relative standard deviation ranged from 1.1% to 8.7% (n = 3). Additionally, satisfactory extraction recovery rates were obtained, averaging 88.3%, with an enrichment factor of 7.