Effect of Agronomic and technological factors on the formation of ethyl esters in virgin olive oil in Catalonia

Identifier:  TDX:3214

Handle: https://hdl.handle.net/20.500.11797/TDX3214

Authors:  Boudebouz, Abdelaziz

Abstract:
Fatty acid alkyl esters (FAAEs), especially ethyl esters (FAEEs), were recently proposed as a quality parameter and as marker for the freshness, quality and good handling of the olives during virgin olive oil (VOO) processing. They are the result of the esterification of free fatty acids (mainly C16 and C18) with ethanol producing FAEEs or with methanol producing methyl esters (FAMEs). This thesis aims to study the current prevalence of FAAEs in Catalan VOOs and which are the main factors, either agronomical or technological, that increase the risk of FAAEs formation. Thus, both the synthesis of endogenous alcohol in the main Catalan varieties and the levels of alcohols and FAEEs during postharvest were studied to determine the processing factors that affects theFAEEs levels. The results indicated that: (1) the vast majority of extra virgin olive oils produced in Catalonia comply with the International Regulation; however, about 6% of them show a relatively high content (25-35 mg/kg); (2) significant differences can be found between varieties regarding endogenous alcohol content; (3) the storage of olives in large-capacity hoppers leads to damage that induces ethanol generation and sensory quality losses; (4) although during the crushing-malaxing step there is no generation of ethanol, a synthesis of methanol occurs, and also significant amounts of ethanol can reach the oil at the end of the process (up to 25% of ethanol present in olives); and (5) the paste injection rate and water addition flow into the decanter affect the content of alcohols and FAAEs in the oil. The first tend to increase when working closer to the maximum capacity of the decanter and the second tends to drag ethanol with pomace. Besides, low amounts of FAAEs can be synthesized when the oily fraction remains in the vibro-filter unit located after the decanter outlet.