Taggiasca extra virgin olive oil colonization by yeasts during the extraction process.

The opalescent appearance of the newly produced olive oil is due to the presence of solid particles and microdrops of vegetation water in which the microorganisms from the olives' carposphere are trapped. Present research has demonstrated that the microbiota of the fresh extracted olive oil, produced in the mills, is mainly composed of yeasts and to a lesser extent of molds. The close link between the composition of the microbiota of the olives' carposphere undergoing to processing, and that of the microbiota of the newly produced olive oil, concerns only the yeasts and molds, given that the bacterial component is by and large destroyed mainly in the kneaded paste during the malaxation process. Six physiologically homogenous yeast groups were highlighted in the wash water, kneaded paste and newly produced olive oil from the Taggiasca variety which had been collected in mills located in the Liguria region. The more predominant yeasts of each group belonged to a single species called respectively: Kluyveromyces marxianus, Candida oleophila, Candida diddensiae, Candida norvegica, Wickerhamomyces anomalus and Debaryomyces hansenii. Apart from K. marxianus, which was found only in the wash water, all the other species were found in the wash water and in the kneaded paste as well as in the newly produced olive oil, while in the six-month stored olive oil, was found only one physiologically homogeneous group of yeast represented by the W. anomalus specie. These findings in according to our previous studies carried out on other types of mono varietal olive oils, confirms that the habitat of the Taggiascas' extra virgin olive oil, had a strong selective pressure on the yeast biota, allowing only to a few member of yeast species, contaminating the fresh product, to survive and reproduce in it during storage.

Effects of some oil-born yeasts on the sensory characteristics of Italian virgin olive oil during its storage.

The olive oil microbiota, mainly composed of yeasts, is associated with the suspended fraction of freshly produced olive oils. Some olive oil yeasts are considered useful as they are able to hydrolyse the bitter tasting secoiridoid compound of the oil, whereas others are considered harmful as they can damage the quality of the oil. Present research demonstrated the influence of some yeast strains belonging to Candida adriatica, Candida diddensiae and Candida wickerhamii species on the olive oil sensory characteristics during its storage. All the tested yeasts survived in the inoculated extra virgin olive oil and, after four months of storage, the suspended yeast cells recovered from the olive oil varied between 50% and 80% of the initial total yeasts, according to their sedimentation capacity. The mean of five analytical indices (free fatty acids, peroxide value, K232, K270 and ΔK) were quite similar and about 60% of the treated samples analysed after four months of storage, on the basis of these indices, were still classed as extra virgin. Completely different results were obtained from the analyses of volatile and non volatile carbonyl compounds according to the yeast used. In the samples of oil treated with C. adriatica and C. wickerhamii, instead of some strains of C. diddensiae, a lower concentration of C6 volatile carbonyl compounds and polyphenols, responsible for positive oil attributes, were found. The sensory attributes of the treated olive oils varied according to the composition of the volatile and non volatile carbonyl compounds produced with the treatments. "Muddy-sediment", "rancid" or both defects were found in olive oil samples treated with C. adriatica DAPES 1933, C. wickerhamii DAPES 1885 and C. diddensiae DAPES 1912 and 1913 strains, whereas olive oil samples treated with C. diddensiae DAPES 1918 and 1922 after four months of storage were defect-free, and still categorized as extra virgin, according to the requirements of both chemical and sensory quality indices of European Community Regulations.

Distribution of dimorphic yeast species in commercial extra virgin olive oil.

Recent microbiological research has demonstrated the presence of a rich microflora mainly composed of yeasts in the suspended fraction of freshly produced olive oil. Some of the yeasts are considered useful as they improve the organoleptic characteristics of the oil during preservation, whereas others are considered harmful as they can damage the quality of the oil through the hydrolysis of the triglycerides. However, some dimorphic species can also be found among the unwanted yeasts present in the oil, considered to be opportunistic pathogens to man as they have often been isolated from immunocompromised hospital patients. Present research demonstrates the presence of dimorphic yeast forms in 26% of the commercial extra virgin olive oil originating from different geographical areas, where the dimorphic yeasts are represented by 3-99.5% of the total yeasts. The classified isolates belonged to the opportunistic pathogen species Candida parapsilosis and Candida guilliermondii, while among the dimorphic yeasts considered not pathogenic to man, the Candida diddensiae species was highlighted for the first time in olive oil. The majority of the studied yeast strains resulted lipase positive, and can consequently negatively influence the oil quality through the hydrolysis of the triglycerides. Furthermore, all the strains showed a high level of affinity with some organic solvents and a differing production of biofilm in "vitro" corresponded to a greater or lesser hydrophobia of their cells. Laboratory trials indicated that the dimorphic yeasts studied are sensitive towards some components of the oil among which oleic acid, linoleic acid and triolein, whereas a less inhibiting effect was observed with tricaprilin or when the total polyphenols extracted from the oil were used. The observations carried out on a scanning electron microscope (SEM), demonstrated the production of long un-branched pseudohyphae in all the tested dimorphic yeasts when cultivated on nutrient-deficient substrates.

Lipolytic activity of Williopsis californica and Saccharomyces cerevisiae in extra virgin olive oil.

Inoculation trials performed with three strains of yeasts, isolated from extra virgin olive oil, Williopsis californica 1,639, Saccharomyces cerevisiae 1,525 and Candida boidinii 1,638, demonstrated that some yeast can lower the quality of the oil during storage. Laboratory tests highlighted a substantial increase in the total diglycerides and free fatty acids in the samples of oil inoculated with the lipase-producing strains of yeasts, W. californica 1,639 and S. cerevisiae 1,525, while in the samples of oil inoculated with the lipase-negative strain C. boidinii 1,638 no differences were found in respect to the uninoculated control. The acidity of the extra virgin olive oil, inoculated with the lipase-producing strains W. californica 1,639 and S. cerevisiae 1,525, during 2 weeks of incubation at 30 degrees C increased respectively from 0.62% to 1.50 and 1.62%, exceeding the limit of 0.8% established by current regulations for this commercial category of olive oil, while in the oil inoculated with the lipase-negative strain and in the uninoculated control, the acidity remained constant throughout. Furthermore, the two strains of lipase-producing yeasts also increased the concentration of the 1.3-diglyceride isomer in the oil lowering the values of the total 1.2-diglycerides/total 1.3-diglycerides ratio considered to be an important index of quality for an extra virgin olive oil. The lipolytic activity of lipase-producing strains W. californica 1,639 and S. cerevisiae 1,525 showed an optimum pH of 6 and 7.5 and an optimum temperature of 20 degrees C and 30 degrees C respectively. Nevertheless, the lipolytic activity was negatively influenced by glucose and polyphenols when the concentration was higher than 0.25% and 0.4% (wt/vol) respectively.

Retinol binding protein: a short half life determinant of protein non enzymatic glycation in diabetes.

The non enzymatic glycation of circulating and structural proteins is the main biochemical consequence of the chronic hyperglycaemia of diabetes mellitus. Retinol binding protein (RPB) is a 21K plasma globulin with an half life of 12 hr; its non enzymatic glycation may reflect the variation of short term metabolic control (1-4 days). In this study two blood samples were withdrawn at four days interval from 24 non insulin dependent diabetic patients. Glycated RBP was measured by a two-site immunoradiometric assay and its variations correlated with the correspondent changes in the blood glucose level. A significant correlation (r = 0.471; p less than 0.02) was found between the time 4/time 0 ratios of glycated RBP and the time 4/time 0 ratios of blood glucose. These data suggest that measurement of non-enzymatically glycated RBP may be a useful tool to evaluate the short term state of non enzymatic glycation in diabetes.

Inhibition of protein non-enzymic glycation induced by Bendazac.

Enhanced non-enzymic glycation of proteins has been suggested to play a role in the pathogenesis of diabetic microangiopathy. Thus pharmacological inhibition of this reaction could be envisaged to delay the development of late diabetic complications. In the present study we have investigated the effect of a new compound, 1-Benzylindazole-3-oxyacetic acid, Bendazac (BDZ) on the in vitro glycation of soluble proteins (albumin and fibrinogen) and isolated glomerular basement membrane (GBM). The data obtained indicate that BDZ is capable of reducing significantly the glycation of albumin and fibrinogen (p less than 0.001). When present in concentrations usually found in patients undergoing therapy (40-80 micrograms/ml), an inhibitory effect on soluble proteins was also observed. Inhibition of glycation of GBM was found only in the presence of the active metabolite (5 hydroxy BDZ) and at high glucose concentrations. These results suggest that BDZ could interfere with protein non-enzymic glycation and its use in patients with diabetes may be then taken into consideration to evaluate the effect on late diabetic complications.

In vivo determination of cell mediated immune response in diabetic patients using a multiple intradermal antigen dispenser.

The in vivo cell mediated immune response using a multiple intradermal antigen dispenser (Multitest) was evaluated in 99 diabetic patients (24 Type I and 75 Type II) and in 50 age matched normal subjects. Seven different antigens (tetanus, diphteria, streptococcus, tubercoline, candida, trichophyton, proteus and a glycerine control) were applied in the forearm and the induration for the antigens tested was measured 48 hours later. A score was calculated adding the arithmetic means obtained with each single antigen. Overall we did not find major differences between diabetic patients and controls except Type I patients of shorter duration (less than 5 years) having a reduced response (p less than 0.05) and both Type I and Type II patients showing an elevated response to candida antigen (p less than 0.001). No correlation was found between the intradermal response and metabolic control. As the intradermal test is a model for delayed type of hypersensitivity, these data suggest that the in vivo lymphocyte to lymphocyte cooperation in patients with long standing diabetes is not impaired.