Differential Microbial Composition of Monovarietal and Blended Extra Virgin Olive Oils Determines Oil Quality During Storage.

Biagi Angelo Zullo,Gino Ciafardini

doi:10.3390/microorganisms8030402

Biagi Angelo Zullo, Gino Ciafardini

Open Access

https://doi.org/10.3390/microorganisms8030402

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Journal: Microorganisms	Publication Date: Mar 13, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: University of Molise

Abstract

Extra virgin olive oil (EVOO) contains a biotic fraction, which is characterized by various microorganisms, including yeasts. The colonization of microorganisms in the freshly produced EVOO is determined by the physicochemical characteristics of the product. The production of blended EVOO with balanced taste, which is obtained by blending several monovarietal EVOOs, modifies the original microbiota of each oil due to the differential physico-chemical characteristics of the blended oil. This study aimed to evaluate the effect of microbial composition on the stability of the quality indices of the monovarietal and blended EVOOs derived from Leccino, Peranzana, Coratina, and Ravece olive varieties after six months of storage. The yeasts survived only in the monovarietal EVOOs during six months of storage. Barnettozyma californica, Candida adriatica, Candida diddensiae, and Yamadazyma terventina were the predominant yeast species, whose abundance varied in the four monovarietal EVOOs. However, the number of yeasts markedly decreased during the first three months of storage in all blended EVOOs. Thus, all blended EVOOs were more stable than the monovarietal EVOOs as the abundance and activity of microorganisms were limited during storage.

Highlights

Extra virgin olive oil (EVOO) is produced by directly subjecting the olive fruit to mechanical extraction without any further refining process
The microbiological analysis of the four freshly produced monovarietal EVOOs revealed a high abundance of yeasts and bacteria and a low abundance of mold in the EVOOs derived from the Coratina and Ravece varieties
The water content in the four EVOOs varied from 0.22% (w w−1) (Leccino EVOO) to 0.45% (w w−1) (Coratina EVOO) (Table 1). This indicated that the high abundance of yeasts and bacteria in the Coratina EVOO was due to high suspended solid and water contents, which support the growth of microorganisms

Summary

Introduction

Extra virgin olive oil (EVOO) is produced by directly subjecting the olive fruit to mechanical extraction without any further refining process. Several yeast species in the freshly produced EVOO can remain active during the storage period and can improve or deteriorate olive oil quality, depending on their metabolic activity [9]. The fatty acid and triglyceride contents in EVOO can inhibit the growth of several yeast strains Several yeast species, such as Meyerozyma guilliermondii, C. parapsilosis, and C. diddensiae are reported to exhibit concentration-dependent sensitivity to linoleic acid [15]. The flavor of monovarietal EVOOs is determined by the genetic characteristics of the olive tree and the pedo-climatic factors of the production area [16]. These oils meet the needs of the niche market in countries like Italy, where more than 700 varieties of olives are found. This study aimed to analyze the abundance of yeasts in monovarietal and blended EVOOs and to evaluate their effect on oil quality during storage

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