Commercial Instant Coffee Classification Using an Electronic Nose in Tandem with the ComDim-LDA Approach
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Commercial Instant Coffee Classification Using an Electronic Nose in Tandem with the ComDim-LDA Approach Gustavo Yasuo Figueiredo Makimori 1 & Evandro Bona 1 Received: 28 September 2018 / Accepted: 14 January 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Coffee is an important commodity for Brazil and ensuring product quality is a priority. An electronic nose (E-nose), with seven MOS sensors, was used to analyze 53 samples of six different commercial instant coffees produced by the same industry. Thereafter, chemometric tools such as common dimension analysis (ComDim) and linear discriminant analysis (LDA) were applied to classify the samples. ComDim is an unsupervised multiblock analysis able to reduce large data dimensions from different tables. A block for each E-nose sensor with the first derivative of the transient signal was used as ComDim input. Four common dimensions (CDs) were necessary to represent the E-nose data, which accumulated a total variance of 99.86%. Salience tables indicate a relation in CD1 between sensors S1, S3, S5, S6, and S8. Sensors S7 and S9 have more influence on CD2. The scores from the first four CDs were used as input to construct LDA classifiers. All models reached a sensitivity and specificity of 100% in the leave-one-out crossvalidation. Thus, the proposed approach was able to classify correctly the aromatic pattern of different commercial instant coffees. Keywords Multiblock analysis . Chemometrics . Smellprint . Quality control . Coffee
Introduction Despite intense competition from Asian industry, Brazil is still the world’s leading producers and exporters of instant coffee with an exchange income of US$517 million by 2017. Instant coffee is easily and quickly prepared by the consumer; this characteristic guarantees a 3.2% increase per year in the overall consumption rate (ABICS 2017). Two industrial processes can be applied to obtained instant coffee. Spray drying system consists of evaporating almost all solvents from the coffee extract spraying in hot air flow under high pressure. This system is most common and economically viable. Freeze drying system produces a better-quality product and consists of applying low temperature and pressure (sublimation) thereby preserving some coffee features (Villalón-López et al. 2018). The entire production chain influences the final quality of the product; however, roasting and
* Evandro Bona [email protected] 1
Post-Graduate Program of Food Technology (PPGTA), Federal University of Technology – Paraná (UTFPR), P.O. Box 271, Via Rosalina Maria dos Santos – 1233, Campo Mourão, PR CEP 87301– 899, Brazil
ground steps directly affect volatile organic compounds (VOC) (Farah 2012; Yang et al. 2016). Due to variability and the amount of parameters that interfere with the coffee aroma, it is not surprising that more than a thousand different compounds have already been identified (Bona et al. 2012; Bona and dos Santos Ferreira da Silva 2016). Electronic nose (E-nose) is an instrument that through an array
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