Identification of adulteration in uncooked Jasmine rice by a portable low-cost artificial olfactory system

Development of a portable low-cost artificial olfactory system called as electronic nose (E-nose) for rapid assessment of adulteration percentages in uncooked Jasmine rice (Khao Dawk Mali 105) is reported. White rice was used to adulterate the Jasmine rice at various weight ratios (5, 10, 15, 20, 40, 60 and 80% w/w). Volatile aroma compounds released by rice samples including pure Jasmine, pure White and mixed rice samples were detected by the E-nose (room temperature and 55 °C) and solid-phase microextraction (SPME) in conjunction with gas chromatography-time of flight mass spectrometer (GC-TOFMS). The E-nose exhibited the highest sensor responses to Jasmine rice, mixed rice, and White rice samples, respectively, corresponding to number and total concentration of volatile aroma compounds obtained by SPME/GC-TOFMS analysis. 2-Butanone was found to be the most dominant volatile aroma compound in rice samples. Principal component analysis (PCA) with simple Euclidean plane calculation was used for pattern recognition and evaluation of adulteration percentages. Mean distances of PCA analysis showed a strong correlation and linear relationship (R2 > 0.94) with amount of adulteration percentages at both room temperature and 55 °C. Also, support vector machine (SVM) and back propagation neural network (BPNN) were used to classify and predict adulteration percentages. The results confirmed that the developed E-nose with simple proposed method can be used as alternative tool to quantify the adulterations in rice samples with several advantages including rapid, simple, low-cost, reliable and nondestructive measurement.