Antonio de Castro

Utilization at high pH of starter cultures of lactobacilli for Spanish-style green olive fermentation.

Inoculation at alkaline pH (above 9) of lye-treated green olives with starter cultures of Lactobacillus pentosus CECT 5138 was studied. Despite an initial loss of viability in the order of 1-2 log cycles on average, depending mainly on time of application, cultures grew and initiated an accelerated fermentation process. Inoculation reduced the population of Enterobacteriaceae, and thereby potential spoilage, and produced a quicker acidification of brines and decrease of pH, when compared with control uninoculated batches. Results obtained throughout three consecutive seasons demonstrated that utilization at high pH of starter cultures of lactobacilli is feasible, provided that the inoculum size takes into account the initial low survival.

Antimicrobial activity of olive oil, vinegar, and various beverages against foodborne pathogens.

The survival of foodborne pathogens in aqueous extracts of olive oil, virgin olive oil, vinegar, and several beverages was evaluated. Vinegar and aqueous extracts of virgin olive oil showed the strongest bactericidal activity against all strains tested. Red and white wines also killed most strains after 5 min of contact, black and green tea extracts showed weak antimicrobial activity under these conditions, and no effect was observed for the remaining beverages (fruit juices, Coca-Cola, dairy products, coffee, and beer). The phenolic compound content of the aqueous olive oil and virgin olive oil extracts could explain their antibacterial activity, which was also confirmed in mayonnaises and salads used as food models. Virgin olive oil in mayonnaises and salads reduced the counts of inoculated Salmonella Enteritidis and Listeria monocytogenes by approximately 3 log CFU/g. Therefore, olive oil could be a hurdle component in certain processed foods and exert a protective effect against foodborne pathogens when contaminated foods are ingested.

Transformation of oleuropein and its hydrolysis products during Spanish‐style green olive processing

Products obtained from elenolic acid glucoside hydrolysis during the storage of Spanish-style green olive brines were elenolic acid and glucose. The disappearance of elenolic acid glucoside from brines followed a first-order kinetics rate and was influenced by the storage temperature. Hydrolysis of this glucoside also occurred in brines ultrafiltered at 10000 Da pore size, indicating that no enzymatic action was needed to break the glycoside bond. Inoculation experiments with microorganisms obtained from a Spanish-style green olive brine demonstrated that this microflora was able to use the glucose formed from elenolic acid glucoside hydrolysis, although in our experiments only yeasts could grow in the assayed brines. It needs to be stressed that the glucose liberated by elenolic acid glucoside hydrolysis may represent about 20% of the total initial glucose in brines at the start of the fermentation step in Spanish-style green olive processing.

Lactic acid fermentation and storage of blanched garlic

The controlled fermentation of peeled, blanched garlic, using a starter culture of Lactobacillus plantarum, was studied and compared with that of unblanched garlic. Blanching was carried out in hot water (90 degrees C) for 15 min. The starter grew abundantly in the case of blanched garlic, producing mainly lactic acid and reaching a pH of 3.8 after 7 days, but its growth was inhibited in unblanched garlic. Ethanol and fructose, coming from enzymatic activities of the garlic, and a green pigment were formed during the fermentation of unblanched garlic, but not of blanched garlic. The blanched garlic fermented by L. plantarum, even without a preservation treatment (pasteurization), was microbiologically stable during storage at 30 degrees C in an acidified brine (approximately 3% (w/w) NaCl and pH 3.5 at equilibrium), but fructans were hydrolyzed. The packed fermented product and that obtained by direct packing without fermentation were not significantly different with regard to flavour.

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.

Analysis of zapatera olives by gas and high-performance liquid chromatography

Abstract Gas chromatography and high-performance liquid chromatography were applied to normal and “zapatera” olive brines obtained from typical fermentation brines of green table olives after different treatments. The zapatera samples were obtained by pH adjustment to 5.1 followed by inoculation with a suspension of sediment from a zapatera brine and incubation at 30°C for 40 days. The compounds determined were lactic acid, C 2 -C 6 fatty acids, acetaldehyde, methanol, ethanol, 2-butanol and n -propanol. Normal and zapatera brines were compared to identify components that indicated spoilage. One of these components was found in the gas chromatogram of the volatile fatty acids from the zapatera samples and identified as cyclohexanecarboxylic acid by gas chromatography-mass spectrometry. A comparison of the corresponding aromagrams revealed quantitative differences in aroma composition. Various relationships calculated from the peak areas of selected unknown components in these aromagrams were so distinct as to provide a basis for characterizing zapatera spoilage.

Table Olives: Varieties and Variations

Publisher Summary Table olives are the products prepared from sound fruits of the cultivated olive tree. Table olive production was initially restricted to the producing regions, mainly around the Mediterranean Sea. Today, however, olive preparation has extended to both North and South America, and even Australia. A characteristic common to almost all olive varieties is their extreme bitterness when tasted fresh. The glucoside oleuropein is responsible for this, and the different processing methods are aimed at removing this compound in order to obtain fruits with more-palatable attributes. It could be said that there are as many processing methods as places where olives are consumed. In an attempt to normalize the different products, the International Olive Council has a Trade Standard Applying to Table Olives, in which the types, trade preparations, quality factors, and other properties are described. This chapter aims to describe in detail the different kinds or classifications applicable to table olives, explaining the distinctive traits for each case.

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.

Effect of processing and storage time on the contents of organosulfur compounds in pickled blanched garlic.

The influence of processing, with and without fermentation, on the contents of organosulfur compounds, namely, γ-glutamyl peptides, S-alk(en)yl-L-cysteine sulfoxides (ACSOs), and S-allyl-L-cysteine (SAC), in pickled blanched garlic was evaluated. For each processing type, the effect of the preservation method and storage time was also analyzed. Blanching in hot water (90 °C for 5 min) hardly affected the individual organosulfur compound content. The fermentation and packing steps negatively affected the levels of all compounds except for SAC. The content of this compound increased during storage at room temperature whereas γ-glutamyl peptides and ACSOs were degraded to various extents. The pasteurization treatment itself had no significant effect on the concentrations of organosulfur compounds. Use of the corresponding fermentation brine in the case of the fermented product in conjunction with refrigerated storage was found to be the best method to preserve the levels of organosulfur compounds in pickled garlic stored for up to one year.

Fermentation of washing waters of Spanish-style green olive processing

Abstract Washing waters of Spanish-style green olive processing are heavily contaminated waste streams that represent an important environmental problem that needs to be solved. These liquids are only generated for 2 months a year and a storage period is needed if high-value substances are to be extracted from them. Fermentation of the washing waters under acidic conditions was studied throughout a year. A lactic acid fermentation took place in vessels with either no initial correction of pH, or pH corrected to 4. When the pH was initially lowered to 3, only yeasts grew and a significant concentration of ethanol was generated. The concentration of phenolic compounds decreased slightly during the fermentation process, particularly hydroxytyrosol, which was found in high concentration in these waste waters. If this orthodiphenol is to be recovered from washing waters, time is required to hydrolyse the elenolic acid glucoside. The glucoside was hydrolysed under the acidic conditions of the washing waters, and the reaction was affected by temperature and pH. Thus, fermentation of washing waters under certain conditions may give rise to solutions with no off-odours and a high concentration of lactic acid and hydroxytyrosol, which are economically interesting products.