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

Abstract

Californian-style black olives require a sterilization treatment that produces a carcinogenic contaminant, acrylamide. Thus, this compound was evaluated in two different olive cultivars using an electronic nose (E-nose). The sterilization intensity had a significant influence on the final phenol concentrations, acrylamide content, and volatile compounds. Increasing the sterilization intensity from 10 to 26 min (F0) reduced the phenol content, but it promoted acrylamide synthesis, leading to a wide range of this toxic substance. The Ester and phenol groups of volatile compounds decreased their content when the sterilization treatment increased; however, aldehyde and other volatile compound groups significantly increased their contents according to the thermal treatments. The compounds 4-ethenyl-pyridine, benzaldehyde, and 2,4-dimethyl-hexane are volatile compounds with unpleasant odours and demonstrated a high amount of influence on the differences found after the application of the thermal treatments. The “Manzanilla Cacereña” variety presented the highest amount of phenolic compounds and the lowest acrylamide content. Finally, it was found that acrylamide content is correlated with volatile compounds, which was determined using multiple linear regression analysis (R2 = 0.9994). Furthermore, the aroma of table olives was analysed using an E-nose, and these results combined with Partial Least Square (PLS) were shown to be an accurate method (range to error ratio (RER) >10 and ratio of performance to deviation (RPD) >2.5) for the indirect quantification of this toxic substance.

Burn Defect and Phenol Prediction for Flavoured Californian-Style Black Olives Using Digital Sensors

“…Phenols are thermolabile, so the high intensity of heat during the sterilization period could have triggered the degradation of these compounds. If we compare the content of phenols with results from other studies carried out by other researchers, it can be seen that the content in this study was slightly higher [ 22 ]. This could have been due to the fact that the flavoured hydrocolloid fillings increased the phenol content of the samples compared to other Californian olives.…”

“…Researchers [ 2 , 22 ] have classified Californian-style black olives subjected to five different thermal sterilisation treatments based on the aromatic profiles of the samples. These researchers reported a strong burn odour from the samples subjected to more aggressive thermal sterilisation treatments.…”

“…Different researchers have studied VOCs in olives. Martín-Tornero et al [ 22 ] subjected olives to thermal treatments and found that aldehydes and other groups of VOCs increased when the thermal treatment was enhanced. The group of alcohols was underrepresented in these olives.…”

“…Regarding the aromas identified in the select quality olives, creosol again stood out (18.4%) with a spicy aroma of cloves and hints of vanilla [ 25 ]. It was followed by the compound benzoaldehyde (12.8%), which has a strong, sharp, sweet and bitter almond aroma [ 37 ], and 4-ethenylpyridine (6.7%), which is noted in the literature for its pungent and unpleasant odour [ 22 ]. Finally, diallyl disulphide was also identified at a proportion of 6.5%, which is notable for its strong garlic odour [ 38 ].…”

Bioavailability of Phenolic Compounds in Californian-Style Table Olives with Tunisian Aqueous Olive Leaf Extracts

“…This elaboration process consists of harvested green olives being submitted to a lye treatment to remove bitterness, while an oxidation process with the air occurs. Finally, the darkened olives are treated with an iron salt and subjected to a thermal sterilization process to microbiologically stabilize the product [ 22 ].…”