E-Nose Discrimination of Abnormal Fermentations in Spanish-Style Green Olives

Abstract

Current legislation in Spain indicates that table olives must be free of off-odors and off-flavors and without symptoms of ongoing alteration or abnormal fermentations. In this regard, the International Olive Council (IOC) has developed a protocol for the sensory classification of table olives according to the intensity of the predominantly perceived defect (PPD). An electronic nose (e-nose) was used to assess the abnormal fermentation defects of Spanish-style table olives that were previously classified by a tasting panel according to the IOC protocol, namely zapateria, butyric, putrid, and musty or humidity. When olives with different defects were mixed, the putrid defect had the greatest sensory impact on the others, while the butyric defect had the least sensory dominance. A total of 49 volatile compounds were identified by gas chromatography, and each defect was characterized by a specific profile. The e-nose data were analyzed using principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA). The different defects were clearly separated from each other and from the control treatment, independently of PPD intensity. Moreover, the e-nose differentiated control olives from table olives with combined sensory defects despite the dilution effect resulting from the combination. These results demonstrate that e-nose can be used as an olfactory sensor for the organoleptic classification of table olives and can successfully support the tasting panel.

Characterization of Polyphenol and Volatile Fractions of Californian-Style Black Olives and Innovative Application of E-nose for Acrylamide Determination

“…Regarding the volatile compounds, Californian-style black olives have a characteristic odour of a cooked sensory note [ 15 , 23 , 41 ] that is mainly provoked by the thermal treatment that was used to stabilize these types of olives. Following IOC regulations, the results obtained by these researchers can classify table olives that have been submitted to different sterilization treatments into different sensory categories after considering the predominantly perceived defect (PPD) and intensity attributes.…”

“…This type of sensor matrix has been successfully used for the evaluation of trichloroanisole (TCA) in cork stoppers [ 28 ], air quality measurement [ 29 ], or the discrimination of anomalous fermentation defects in table olives [ 15 ]. The odour profile measurements of the olive and brine samples were carried out following the recommendations of the International Olive Council [ 30 ] for the olive tasting panel.…”

“…Acrylamide and volatile compound quantification require long-term extraction and purification methods [ 6 , 15 ]. Moreover, analyses are carried out using expensive equipment, such as with mass spectrometry detectors that are similar to those used for gas [ 4 , 16 ] or liquid chromatography [ 6 , 12 , 17 ].…”

“…In the literature, we were only able to find other devices with voltammetric biosensors for detecting this toxic substance in foods [ 18 , 19 ]. Recently, studies have been carried out using electronic noses to predict the quality of the oil to be processed from the measurements obtained in freshly harvested olives [ 20 ] and to evaluate the odours produced in anomalous fermentations of Spanish-style green olives [ 15 ]. The variation of the volatile organic compounds generated in food after thermal treatments has also been studied to monitor the evaluation of the quality of the oil used for frying [ 21 ], to identify the olfactory profile of rapeseed oil as a function of heating time [ 22 ], or in the sensory evaluation of Californian-style black olive sterilization treatments [ 23 ].…”

Electronic nose application for the discrimination of sterilization treatments applied to Californian‐style black olive varieties

“…These researchers also found that olive cultivar and sterilization treatment has a significant impact on the amount of cooking defect found due to its relationship with a toxic substance (acrylamide) in Californian-style black olives. 26 Other researchers 27 have argued that electronic noses can be used as olfactory sensors to detect abnormal fermentation (such as zapateria, butyric, putrid, and musty) in table olive defects in order to ensure their quality at industrial level. In this way these results indicated the feasibility of these devices as rapid analytical tools for monitoring the elaboration process of table olives.…”