Electronic nose and chemometrics application for propolis differentiation

Electronic nose (e-nose) technology has emerged as a valuable tool for rapid, objective, and reproducible aroma analysis in food and beverages. Mimicking human olfaction, e-noses use an array of metal-oxide sensors (MOS) to detect specific chemical compounds. This study investigates the use of e-nose technology for differentiating propolis samples of varying freshness, obtained from a local producer in São Paulo. The e-nose system consists of eight MOS sensors, each detecting gases like alcohol, propane, methane, and volatile compounds, with data processed via an Arduino microcontroller. Each 2-gram sample was analyzed in triplicate, with measurements lasting two minutes and air purging between analyses. The signal ratio of the sample to air was calculated, and multivariate analysis was performed using Principal Component Analysis (PCA) to reduce data complexity and identify key patterns. PCA revealed that PC1 (82.02%), PC2 (15.49%), PC3 (1.20%), and PC4 (0.69%) accounted for 99.40% of the total variance, with PC1 alone sufficiently differentiating the samples based on storage time. Classes A and B were positioned on the positive axis of PC1, while classes D and E were on the negative axis, and class C was near the center. A PCA bi-plot further revealed that all eight sensors contributed to sample separation, with the MQ-138 sensor (for volatile compounds) located near class C at center of the axis, suggesting its distinctive role in differentiation. In conclusion, the e-nose technology demonstrated high efficacy not only in detecting but also in differentiating propolis samples according to their storage time, offering a reliable method for tracking the freshness and quality of propolis. The ability to identify subtle variations in aroma profiles based on storage conditions highlights the potential of e-nose technology for real-time monitoring and quality control in the food and beverage industry. Moreover, this technology opens up new avenues for rapid, non-destructive analysis of a wide range of products, ensuring product consistency, freshness, and authenticity in commercial applications.