Sensory Evaluation of Fruits and Selected Food Items by Descriptive Analysis, Electronic Nose, and Electronic Tongue

Abstract

Sensory analysis has long depended on descriptive panels for systematic characterization and quality evaluation of food items. Currently, sensory instruments like e-nose (electronic nose) and e-tongue (electronic tongue) are also being implemented to aid in both descriptive and naïve panel evaluations. The present study employed all three techniques for evaluating the sensory attributes of selected food and fruit items. In the first part, the sensory profiles of different stevia blends with varying ratios of Reb A (Rebaudioside A), Reb D (Rebaudioside A), and Reb M (Rebaudioside A) were evaluated by a descriptive panel (n = 6) and e-tongue. The descriptive panel evaluation of bitter aftertaste (‘bitter taste at 90 seconds’) of stevia blends was well-correlated (R2 = 0.9116) to the e-tongue analysis, suggesting its potential to discriminate and screen stevia blends. In addition, the consumer evaluation of stevia-sweetened ice cream (n = 41) was found to be acceptable although that of carbonated beverages (n = 39) was not satisfactory. PLSR (Partial Least Square Regression) revealed a significant correlation (P < 0.05) between stevia-blend descriptive analysis and consumer liking scores for ice cream and carbonated beverage. The second part explored the correlation between electronic senses (electronic nose and electronic tongue) and descriptive analysis of strawberries and blueberries. A significant correlation (R2 ≥ 0.9095) was observed between the descriptive panel ratings and e-nose and e-tongue analyses, demonstrating their high potential for the prediction of sensory qualities of these berries. The e-nose and e-tongue were found to be more sensitive than the human sensory panel because the discrimination indices of e-nose (DI ≥ 82) and e-tongue (DI ≥ 90) were very high even though the sensory panel did not find any significant differences in some sensory attributes of these berries. The major volatile compounds of both strawberries and blueberries consisted of esters, alcohols, aldehydes, furans, ketones, lactones, terpenes, and terpenoids with a total of 107 and 122 volatiles detected in strawberries and blueberries, respectively. The furaneol concentration (mg/mL) in strawberries had a significant positive correlation (P < 0.05) to overripe aroma (r = 0.806) and was negatively associated with green (r = -0.864), pungent (r = -0.704;), and floral (r = -0.651) aroma notes. The effect of elevated growth temperature appeared to affect the blueberry aroma resulting in the formation of more sulfurous volatile compounds with undesirable aroma notes as detected by the e-nose. However, e-nose headspace analysis could not identify any carboxylic acid or ester in blueberries grown at elevated temperature, which may be the reason of their significantly lower sourness scores as rated by the descriptive sensory panel than the ones grown at ambient temperature.