Antonella De Leonardis

Heat-oxidation stability of palm oil blended with extra virgin olive oil.

Rancimat induction time of palm oil (PO), several extra virgin olive oils (EV) and their binary blends have been determined at three different temperatures (120, 130 and 140°C). Analytical composition and oxidation stability of PO/EV blends were found to be a linear combination of the oil partners. Induction time of pure PO was always higher than those of EV oils and blends, in which induction time increased proportionally with the percentage of PO. However, induction time of 80% PO blend was similar to that of pure PO. Fatty acid composition appeared to be the most important factor affecting heat-oxidation stability and a saturated/unsaturated ratio near 1 was the optimally stable composition. Conversely, total phenols had a zero or negative role on the oxidative stability of the blends. Finally, in heat-oxidised oils significant losses of polyunsaturated fatty acids and formation of short-chain fatty acids were recorded.

Catalytic effect of the Cu(II)- and Fe(III)-cyclo- hexanebutyrates on olive oil oxidation measured by Rancimat

In virgin olive oils, various heavy metals deriving from rawmaterials or processing are present. Iron is certainly theelement present at the highest concentration (70 to3600 ng/g), while the other metals present are copper(few tens of ng/g), nickel (2 to 50 ng/g), chromium (2 to500 ng/g), mercury (2 ng/g), cadmium (<10 ng/g), lead(<40 ng/g) and tin (3 to 15 ng/g) [1, 2]. In refined olive oilthe metal contents are lower than metals found in virginoil due to the refining process.Oxidation is the major cause of lipid alteration and thisprocess can be influenced by internal or external factors,such as fatty acid composition, temperature, light, thepresence of metals and enzymes or other catalysts [3–5].In particular, metals catalyze the rate at which free radi-cals are generated [6]. Studies on the oxidation catalyzed by metals have beencarried out using lipid oxidation models [7, 8] or ediblelipid [9–12]. It is very difficult to quantify the effect caused from the sin-gle metals on the oxidation of virgin olive oil. In fact, virginolive oil contains some micro-components that can simul-taneously accelerate (chlorophylls) or delay (phenols,tocopherols and carotenoids) the oxidative process [13].Refined olive oil can be considered a model system help-ful to study oxidation because it has very low contents ofabove-mentioned micro-components.In this study, the Rancimat technique was used in order totest the catalytic effect induced by Cu(II)- and Fe(III)-ionson olive oil oxidation. The Rancimat technique is basedupon the formation of formic acid as a consequence oflipid oxidation [14, 15]. This component is volatile and istrapped in distilled water and conductometrically mea-sured. The result is expressed in induction time definedas the point of greatest inflection of oxidation curvesmeasured by a personal computer. The induction time ina sense could be considered a parameter to measure theoxidative stability of lipids.One refined olive oil was used as model system and themetals were added to the oil in an organic form for easydissolution. The oil was used as such or enriched with anantioxidant compound.

Technological Potential of Lactobacillus Strains Isolated from Fermented Green Olives: In Vitro Studies with Emphasis on Oleuropein-Degrading Capability

Technological properties of two strains of Lactobacillus plantarum (B3 and B11) and one of Lactobacillus pentosus (B4), previously isolated from natural fermented green olives, have been studied in vitro. Acidifying ability, salt, temperature, and pH tolerances of all strains were found in the range reported for similar strains produced in Italy and optimal growth conditions were found to be 6.0–8.0 pH, 15–30°C temperature, and less than 6% NaCl. Moreover, all strains showed very good tolerance to common olive phenol content (0.3% total phenol) and high oleuropein-degrading capability. It was found that medium composition affected the bacterial oleuropein degradation. B11 strain grown in a nutrient-rich medium showed a lower oleuropein-degrading action than when it was cultivated in nutrient-poor medium. Furthermore, enzymatic activity assays revealed that oleuropein depletion did not correspond to an increase of hydroxytyrosol, evidencing that bacterial strains could efficiently degrade oleuropein via a mechanism different from hydrolysis.

The role of microemulsions in lipase-catalyzed hydrolysis reactions

The kinetics of the p‐nitrophenyl butyrate hydrolysis reaction, catalyzed by Candida rugosa lipase in the water‐in‐oil microemulsion cetyltrimethylammonium bromide/water/pentanol/hexane, was investigated. The results described in the present manuscript reveal two peculiar characteristics of the reaction: (i) the initial rate of hydrolysis is very fast and (ii) by decreasing the water content of the microemulsion, the reaction rate approaches the typical behavior of reactions performed in aqueous solution. In particular, for microemulsion systems with a high water content, the end points of the reactions are dictated by the shape stability of the microemulsion. For these systems, our methodological approach shows that the process follows a second‐order kinetics equation, indicative of the dual role played by water, which is involved both as a component of the microemulsion, i.e., relevant for the microemulsion stability and as a reagent of the hydrolysis reaction. In contrast, for microemulsions containing a small amount of water, after the hydrolysis reaction the system seems to fall in the no existence range of the microemulsion. Accordingly, the kinetics results are more complex: in the initial stage, the reaction follows a zero‐order kinetics equation, while for longer reaction times a first‐order kinetics equation fits the experimental data, as would be expected for an enzymatic reaction in a homogeneous system.

Evidence of oleuropein degradation by olive leaf protein extract.

The enzymatic activity of raw protein olive leaf extract has been investigated in vivo, on olive leaf homogenate and, in vitro with pure oleuropein and other phenolic substrates. At least two types of enzymes were found to be involved in the degradation of endogenous oleuropein in olive leaves. As for the in vitro experiments, the presence of active polyphenoloxidase and β-glucosidase was determined by HPLC and UV-Visible spectroscopy. Interestingly, both the enzymatic activities were found to change during the storage of olive leaves. Specifically, the protein extracts obtained from fresh leaves showed the presence of both the enzymatic activities, because oleuropein depletion occurred simultaneously with the formation of the oleuropein aglycon, 3,4-DHPEA-EA. In comparison leaves subjected to the drying process showed a polyphenoloxidase activity leading exclusively to the formation of oxidation products responsible for the typical brown coloration of the reaction solution.

Yeast Autolysis in Sparkling Wine Aging: Use of Killer and Sensitive Saccharomyces cerevisiae Strains in Co-Culture

BACKGROUND Sparkling wines produced by traditional method owe their characteristics to secondary fermentation and maturation that occur during a slow ageing in bottles. Yeast autolysis plays an important role during the sparkling wine aging. Using a combination of killer and sensitive yeasts is possible to accelerate yeast autolysis and reduce maturing time. METHODS killer and sensitive Saccharomyces cerevisiae strains, separately and in co-cultures, were inoculated in base wine and bottled on pilot-plant scale. Commercial Saccaromyces bayanus strain was also investigated. Protein free amino acid and polysaccharides contents and sensory analysis were determined on the wine samples at 3, 6 and 9 months of aging. Yeast autolysis that occurs during the production of sparkling wines, obtained with co-cultures of killer and sensitive strains, has influenced free amino acids, total protein and polysaccharides content after 3 months aging time: sparkling wines, produced without the use of these yeasts, have reached the same results only after 9 months aging time. RESULTS These results demonstrate that killer and sensitive yeasts in co-culture can accelerate the onset of autolysis in enological conditions, and has a positive effect on the quality of the aroma and flavor of sparkling wine. CONCLUSION This paper offers an interesting biotechnological method to reduce production time of sparkling wine with economical benefits for the producers. We revised all patents relating to sparkling wine considering only those of interest for our study.

Influence of free fatty acid content on the oxidative stability of red palm oil

The role of free fatty acids (FFA) on the oxidative stability of four different unrefined red palm oils (RPO) has been investigated. Unrefined red palm oil is a typical African edible oil produced by laborious and traditional methods that heavily affect the final product quality. Physicochemical analysis performed on the RPO samples showed a high FFA content (8.3–14.5%), peroxide values between 2.9 and 10.8 meq O2 per kg and a significant presence of carotenoids (up to 1.6 g kg−1). In order to lower the FFA content, the oil was de-acidified (RPO-D) and the treated product resulted with an improved quality when compared with the untreated oil (RPO-U). The de-acidification route, as well as the reduction of the acidity level, caused a reduction in the UV spectrophotometric indices (K232 and K270) whereas the DOBI index increased and both peroxide and carotenoids amounts were unaffected. Furthermore, the oxidation stability of RPO-U and RPO-D was evaluated using two different experimental approaches: a high-temperature method (Rancimat method) and medium-temperature method (reaction induced by the radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile)). Both methods unequivocally showed a significant improvement in the resistance to oxidation of RPO-D when compared to RPO-U and confirmed the crucial pro-oxidant effect of FFA on red palm oil.

Cleaning of olive mill wastewaters by visible light activated carbon doped titanium dioxide

Carbon doped titanium dioxide (CDT) was tested as catalyst for photodegradation of phenolic compounds of olive mill wastewater (OMW). The activation of the catalyst was triggered by exposure to visible light radiation. The cleaning effectiveness of this catalyst towards the polluted wastewater from olive oil industry was demonstrated by means of HPLC and UV-visible spectroscopy combined with phenol compound determination. The photodegradation activity was tested on systems having different initial concentration of phenols and in the presence of different amounts of CDT. By introducing a suitable parameter, namely the ratio between the amount of catalyst and the amount of total phenols Ti/TPh, it was demonstrated that the proposed degradation method could be scaled up without losing its effectiveness. The OMW decolorization occurring in the presence of CDT particles under visible light radiation is marked enough to be directly appreciated with the naked eye. The decolorization is strongly associated with the removal of phenols. In fact, while bleaching the solutions, CDT successfully removed 70% of the phenols in 24 hours. HPLC analysis demonstrates that CDT was effective in degrading the higher part of the phenols of OMW. An exception is represented by hydroxytyrosol that seemed to have high resistance in the first 24 hours of treatment.

Inactivation of Dekkera bruxellensis yeasts in wine storage in brand new oak barrels using low electric current technology

Dekkera bruxellensis is one of the species of yeast, which is most damaging to wine quality, and the tools available to control its growth are limited. In previous studies, non-Saccharomyces yeasts and Dekkera bruxellensis have been significantly restricted during wine-making processes using an innovative approach based on low electric current treatment (LEC). In the present study, LEC techniques were assessed for their capacity to inhibit wine spoilage by D. bruxellensis and to prevent formation of undesirable flavours during storage in oak barrels. Although the effect of SO2 treatment on D. bruxellensis viability and ATP content was more immediate, from the 30th day onward no significant variations between LEC and SO2 treatments were observed. At the end of the trial, LEC treatment had had a comparable effect to that of SO2 addition. Acetic acid content was significantly lower after LEC and SO2 treatments than in untreated wines and volatile phenols were also found to be significantly lower in the LEC treated wine. Moreover, the results from the panel test clearly indicate that no significant differences were found between the LEC and the SO2 treated wines. These results clearly indicate that LEC technology could represent a viable tool to limit yeast spoilage caused by D. bruxellensis. The present work represents, to our knowledge, the first attempt to control D. bruxellensis during red wine storage in oak barrels using LEC. The potential industrial applications of LEC technology include the real future possibility of producing a new, marketable range of healthier wines to satisfy the requirements of modern wine consumers.

Effective assay for olive vinegar production from olive oil mill wastewaters

In this work, an effective and simple approach for vinegar production from olive oil press-mill wastewaters (OMW) is presented. Effects of sterilization and yeast presence on the acetic acid production were investigated. Sugar addition and inoculum of selected yeast starter have been crucial for a satisfactory acidification. In the obtained olive vinegar, the pH and total acidity were 2.92 and 5.6%, respectively. A considerable high level of ash (2%) and total phenols (3600mg/L as GAE) characterized olive vinegar, in comparison with samples of apple, wine and balsamic commercial vinegars. Moreover, a high presence of hydroxytyrosol (1019mg/L) was obtained. This abundant presence of antioxidants makes olive vinegar a promising nutraceutical and environmentally-friendly product, based upon a waste material such as OMW.