Aranzazu García

Improvement of phenolic compound content in virgin olive oils by using enzymes during malaxation

Abstract The effect of enzyme addition to the olive paste on the phenolic composition of virgin olive oil has been studied. The experiments were carried out with both Picual and Arbequina cultivars, using the continuous two-phase extraction system at industrial scale and for three consecutive seasons. Phenolic compounds, in particular orthodiphenols, increased their concentration in oils when enzymes were added to the olive paste before the malaxation stage. Among non-orthodiphenols, the lignans 1-acetoxypinoresinol and pinoresinol slightly increased their concentration. In general, the positive effect of enzymes was more marked for Arbequina than for the Picual cultivar. The peroxide index and “Rancimat” stability of oils were also positively affected when using enzymes. Besides, wash waters from the vertical centrifuge showed a higher concentration of phenolics when the pastes were treated with enzymes. Therefore, the use of enzymatic formulations during the extraction process of olive oil may not only increase the oil yield but also the nutritional quality of the oil.

Bactericidal Activity of Glutaraldehyde-like Compounds from Olive Products

The bactericidal effects of several olive compounds (nonenal, oleuropein, tyrosol, the dialdehydic form of decarboxymethyl elenolic acid either free [EDA] or linked to tyrosol [TyEDA] or to hydroxytyrosol [HyEDA]), other food phenolic compounds (catechin, epicatechin, eugenol, thymol, carvacrol, and carnosic acid), and commercial disinfectants (glutaraldehyde [GTA] and ortho-phthalaldehyde [OPA]), were tested against strains of Pseudomonas fluorescens, Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. It was found that the bactericidal activities of olive GTA-like compounds (EDA, HyEDA, and TyEDA) were greater than those exerted by several food phenolic substances. Surprisingly, these olive antimicrobials were as active as the synthetic biocides GTA and OPA against the four bacteria studied. Thus, it has been proposed that the bactericidal activity of the main olive antimicrobials is primarily due to their dialdehydic structure, which is similar to that of the commercial biocides GTA and OPA. Our results clearly reveal that olive GTA-like compounds possess a strong bactericidal activity even greater than that of other food phenolic compounds or synthetic biocides.

Antimicrobial activity of olive solutions from stored Alpeorujo against plant pathogenic microorganisms.

The aim of this work was to assess the in vitro antimicrobial effects that wastewaters from alpeorujo oil extraction have against phytopathogenic bacteria and fungi. Alpeorujo was stored for 6 months and then processed to extract its oil, pomace, and a new liquid waste (OWSA), which was characterized by its content in phenolic compounds. OWSA at 20% decreased bu >4 log the population of Erwinia spp., Pseudomonas spp., and Clavibacter spp. viable cells in test tubes, whereas OWSA at 50% in agar medium was necessary to inhibit mycelial growth of most fungi. It was found that the bactericidal effect was due to the joint action of low molecular mass phenolic compounds, although neither hydroxytyrosol, its glucosides, hydroxytyrosol glycol, nor a glutaraldehyde-like compound individually explained this bioactivity. Hence, OWSA constitutes a promising natural solution to fight plant phytopathogenic bacteria and fungi.

Debittering of Olives by Polyphenol Oxidation

In this study, green olives preserved in acidified brine were debittered by subjecting them to an overpressure of oxygen or air for 1-3 days. It was demonstrated that fruits lost their bitter taste due to the enzymatic oxidation of the phenolic compounds, in particular, the glucoside oleuropein. Hence, the concentrations of both o-diphenols and, to a lesser extent, monophenols decreased in the olives with oxidation. This process also gave rise to a darkening effect on the superficial and interior color of the olives, which turned from yellow-brown to brown. Likewise, the effect of several variables on the oxidation rate of the olives, such as type of gas (oxygen, air), temperature, overpressure level, and size of the olives, was also studied. Results indicate that a new debittering method which could be a promising alternative to the treatment of fruits with NaOH is available to the industry. In addition, a new product with different color and texture from the traditional table olives is presented.

Inhibitors of lactic acid fermentation in Spanish-style green olive brines of the Manzanilla variety.

Frequently, a delay or lack of lactic acid fermentation occurs during the processing of Spanish-style green olives, in particular of the Manzanilla variety. Many variables can affect the progress of fermentation such as temperature, nutrients, salt concentration, antimicrobials in brines, and others. In this study, it was demonstrated that an inappropriate alkaline treatment (low NaOH strength and insufficient alkali penetration) allowed for the presence of several antimicrobial compounds in brines, which inhibited the growth of Lactobacillus pentosus. These substances were the dialdehydic form of decarboxymethyl elenolic acid either free or linked to hydroxytyrosol and an isomer of oleoside 11-methyl ester. Olive brines, from olives treated with a NaOH solution of low concentration up to 1/2 the distance to the pit, contained these antimicrobials, and no lactic acid fermentation took place in them. By contrast, a more intense alkaline treatment (2/3 lye depth penetration) gave rise to an abundant growth of lactic acid bacteria without any antimicrobial in brines. Therefore, the precise cause of stuck fermentation in Manzanilla olive brines was demonstrated for the first time and this finding will contribute to better understand the table olive fermentation process.

Properties of Lignin, Cellulose, and Hemicelluloses Isolated from Olive Cake and Olive Stones: Binding of Water, Oil, Bile Acids, and Glucose

A process based on a steam explosion pretreatment and alkali solution post-treatment was applied to fractionate olive stones (whole and fragmented, without seeds) and olive cake into their main constitutive polymers of cellulose (C), hemicelluloses (H), and lignin (L) under optimal conditions for each fraction according to earlier works. The chemical characterization (chromatographic method and UV and IR spectroscopy) and the functional properties (water- and oil-holding capacities, bile acid binding, and glucose retardation index) of each fraction were analyzed. The in vitro studies showed a substantial bile acid binding activity in the fraction containing lignin from olive stones (L) and the alkaline extractable fraction from olive cake (Lp). Lignin bound significantly more bile acid than any other fraction and an amount similar to that bound by cholestyramine (a cholesterol-lowering, bile acid-binding drug), especially when cholic acid (CA) was tested. These results highlight the health-promoting potential of lignin from olive stones and olive cake extracted from olive byproducts.

Isolation and Characterization of a Secoiridoid Derivative from Two-Phase Olive Waste (Alperujo).

A secoiridoid derivative was isolated from the ethyl acetate extract of two-phase olive waste (alperujo). The structure of this compound was fully characterized as s-trans-(E)-3-(1-oxobut-2-en-2-yl)glutaric acid. The spectroscopic data, including one- and two-dimensional nuclear magnetic resonance, mass spectrometry, infrared analysis, and ultraviolet spectrum, were showed. The origin of this compound has not been previously studied, although it most likely results from the breakdown of the oleuropein (or ligstroside) secoiridoid skeleton via oxidation and decarboxylation of the dialdehydic form of elenolic acid, with this transformation being enhanced by extraction of phenolics with ethyl acetate. In addition, the bactericidal activity of (E)-3-(1-oxobut-2-en-2-yl)glutaric acid and extracts containing it was evaluated against two phytopatoghenic microorganisms Pseudomonas syringae and Agrobacterium tumefaciens.

Olives and Olive Oil Compounds Active Against Pathogenic Microorganisms

Publisher Summary At present, both olive oil and table olives are important components of the Mediterranean diet and are largely consumed throughout the world. In addition, there are many enterprises that commercialize olive leaf extracts to treat a myriad of diseases, many of them caused by microorganisms. This chapter presents features of the main food-related bacteria pathogens investigated in relation to olive antimicrobials. It has been demonstrated that the main phenolic compound in olive brines is hydroxytyrosol, a component of the oleuropein moiety, which inhibited the growth of Lactobacillus plantarum in a model system, but its presence in the brines of both olives non-treated and treated with NaOH did not lead to an explanation for the lack of lactic acid fermentation in the former olive brines. The bactericidal action of virgin olive oil is higher than that of other foodstuffs such as wine, tea, coffee, beer and others. Olive oil could be a hurdle component in certain processed foods and exert a protective effect against foodborne pathogens when contaminated foods are ingested. The antimicrobial compounds of olive oil possess a strong anti- H. pylori activity that could be useful for the prevention of peptic ulcers and cancers in the future.