Developement of analytical methodologies for roasted coffee and green coffee oil authentication

Author(s)

Maria Izabel Milani

• Document type: Doctoral Thesis
• Press: Araraquara. 2020-03-06.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2020-02-13
• Advisor: Helena Redigolo Pezza

Abstract

Coffee is a fundamental commodity for Brazilian economy. In 2018, 58 million of coffee bags were exported, which is equivalent to more than a third of global coffee production, generating a revenue of US$5.3 billion. That is why is necessary a rigid quality control of this kind of product. Nowadays, coffee authentication is performed by microscopy technique and, unfortunately, the results obtained are subjective and the technique used is obsolete for the purpose. In this work, we propose the use of spectroscopic methodologies as alternative for microscopy techniques; Nuclear Magnetic Resonance and Infrared absorbance were used together with chemometric tools. NMR technique showed itself quite robust and allowed the identification of coffee fraud by the observation of NMR spectra, mainly when the adulterant utilized was starch-based, with detection limits ranging from 0.32 up to 0.86% (g each 100g of coffee); however, infrared spectroscopy techniques, both near and medium, allow a higher analytical frequency and they do not need any sample preparation steps, as occurs with samples in 1H-NMR method; the results from all three methods were submitted to chemometric analysis and obtained a correct classification rate of 100% in all cases. A coffee by-product that has been gaining attention of commercial markets is the green coffee oil, which is obtained from unroasted coffee beans and has innumerous health benefits associated with its consumption and utilization due to its several compounds associated with beneficial properties; green coffee oil has a high commercial value and, with it, its authentication is necessary because, as occurs with coffee itself or other vegetable oils with high commercial value, green coffee oil may be subject of fraud. In this work, we intent to authenticate green coffee oil commercial samples using vibrational spectroscopy associated with chemometric tools and portable equipment with easy handling. The developed SIMCA model allowed us to differentiate adulterated samples from pure one with 1% adulteration limit. Also, it was evaluated the conversion rate from triacylglycerols in free fatty acids as markers of storage time. The methodologies developed proved to be robust, trustable, precise and require minimum or no sample preparation steps. (AU)

• FAPESP's process: 16/14773-0 - Development of methods to detect adulteration in roasted coffee and oil coffee
• Grantee: Maria Izabel Milani
• Support Opportunities: Scholarships in Brazil - Doctorate