Mariagrazia Giarnetti

Effect of Olive Oil Phenolic Compounds and Maltodextrins on the Physical Properties and Oxidative Stability of Olive Oil O/W Emulsions

The aim of this work was to study the physical properties and oxidative stability of model olive oil-in-water (o/w) emulsions stabilised by β-lactoglobulin (BLG), enriched with olive phenolic compounds, namely oleuropein, tyrosol and hydroxytyrosol, and added with maltodextrins (MD 7.5–9.9) in different concentrations to modify the viscosity of the continuous water phase. Emulsions were characterized for their viscosity, droplet size distribution, microstructure and interfacial protein coverage. The oxidative stability was monitored by means of hydroperoxides, hexanal and nonanal contents as indices of primary and secondary oxidation products, respectively. At high concentrations, MD increased significantly the viscosity of the emulsions; conversely, the addition of olive phenolic compounds did not show any significant effect on it. Both MD and phenolic compounds resulted to affect both the droplet size and the bigger to smaller particles ratio, with phenolic compounds generally improving the dispersion degree. A delay in the decomposition of hydroperoxides was observed as a consequence of MD addition, which also resulted to affect the efficiency of the phenolic compounds among the different systems. However, the highest protection towards oxidations was obtained when hydroxytyrosol was added. MD effect was related not only to the higher viscosity of the emulsions but also to complex interactions that occurred among the different components of the system.

Antioxidant Behavior of Olive Phenolics in Oil-in-Water Emulsions

The effect of the surrounding molecular environment (β-lactoglobulin as an emulsion stabilizer and maltodextrin as a viscosity modifier) on the antioxidant activity of three olive oil phenolic compounds (PCs) in olive oil-in-water emulsions was investigated. Oxidation potential, phenolic partitioning, and radical quenching capacity were assessed in solution and in emulsion for oleuropein, hydroxytyrosol, and tyrosol; the influence of β-lactoglobulin and maltodextrin concentration was also evaluated. Finally, the observed properties were related to the oxidative stability of the emulsions containing the PCs to explain their behavior. The order hydroxytyrosol > oleuropein > tyrosol was observed among the antioxidants for both oxidation potential and radical quenching activity. Radical quenching capacity in emulsion and anodic potential were complementary indices of antioxidant effectiveness. As the intrinsic susceptibility of an antioxidant to oxidation expressed by its anodic potential decreased, the environmental conditions (molecular interactions and changes in continuous phase viscosity) played a major role in the antioxidant effectiveness in preventing hydroperoxide decomposition.

Shelf life assessment of industrial durum wheat bread as a function of packaging system

This study compared the effect of different packaging systems on industrial durum wheat bread shelf-life, with regard to thermoformed packaging (TF) and flow-packaging (FP). Two TFs having different thickness and one FP were compared by assessing physico-chemical and sensorial properties and volatile compounds of sliced bread during 90days of storage. Texture, aw and bread moisture varied according to a first-order kinetic model, with FP samples ageing faster than TFs. Sensorial features such as consistency, stale odor, and sour odor, increased their intensity during storage. Furans decreased, whereas hexanal increased. The Principal Component Analysis of the whole dataset pointed out that the TF system at reduced thickness could be adopted up to 60days, without compromising the standard commercial life of industrial bread and allowing to save packaging material. The FP system would allow further saving, but it should be preferred when the expected product turnover is within 30days.

Effect of the Type of Oil on the Evolution of Volatile Compounds of Taralli During Storage

Baking process leads to a huge quantity of newly formed volatile compounds, which play a major role in developing the flavor of the final product. The aim of this work was to investigate on the evolution of the volatile profile of taralli as a function of both the kind of oil used in the dough and the storage time. The volatile compounds from the taralli were extracted by headspace solid-phase microextraction and analyzed by gas-chromatography/mass spectrometry (GC/MS). Forty-four volatile compounds were identified in taralli, most of which produced by thermically induced reactions occurring during baking process, such as volatiles deriving from Maillard reaction and/or sugar degradation and lipid oxidation. The results obtained demonstrated the essential role played by the type of oil on the formation and on the release of volatile compounds. The volatile compounds significantly increased during storage and their individual levels were in most cases significantly lower in taralli made with extra virgin olive oil than in those made with refined oils. Finally, the taralli made with extra virgin olive oil, compared with those prepared with other vegetable oils, showed to be more resistant to oxidation, probably due to the presence of natural antioxidants.

Influence of the Different Oils Used in Dough Formulation on the Lipid Fraction of Taralli

An experimental investigation was carried out to evaluate the quality of taralli as a function of the type of oil used in their dough formulation. To this end, 4 types of oil (extra virgin olive oil, olive oil, olive-pomace oil, and refined palm oil) were utilized to prepare taralli to investigate on the lipid fraction degradation and evaluate the taralli acceptability by consumers. The data obtained pointed out that taralli manufactured with extra virgin olive oil were significantly more appreciated than those made with refined oils due to their visual appearance and odor. Moreover, with respect to the other kinds of oil, the use of extra virgin olive oil led to significantly lower values (P < 0.05) of specific absorption at 232 and 270 nm (K(232) and K(270) , respectively) and of triacylglycerol oligopolymers. It also proved to present a much lower content in oxidized triacylglycerols and diacylglycerols than olive-pomace oil and refined palm oil, respectively. Furthermore, trans fatty acid isomers were absent in taralli made with extra virgin olive oil but were constantly present in those produced with refined oils.

Physico-chemical properties and sensory profile of durum wheat Dittaino PDO (Protected Designation of Origin) bread and quality of re-milled semolina used for its production

To help future quality checks, we characterized the physico-chemical and sensory properties of Dittaino bread, a sourdough-based durum wheat bread recently awarded with Protected Designation of Origin mark, along with the quality features of re-milled semolina used for its production. Semolina was checked for Falling Number (533-644s), protein content (12.0-12.3g/100gd.m.), gluten content (9.7-10.5g/100gd.m.), yellow index (18.0-21.0), water absorption (59.3-62.3g/100g), farinograph dough stability (171-327s), softening index (46-66B.U.), alveograph W (193×10-4-223×10-4J) and P/L (2.2-2.7). Accordingly, bread crumb was yellow, moderately hard (16.4-27.1N) and chewy (88.2-109.2N×mm), with low specific volume (2.28-3.03mL/g). Bread aroma profile showed ethanol and acetic acid, followed by hexanol, 3-methyl-1-butanol, 2-phenylethanol, 3-methylbutanal, hexanal, benzaldehyde, and furfural. The sensory features were dominated by a thick brown crust, with marked toasted odor, coupled to yellow and consistent crumb, with coarse grain and well-perceivable sour taste and odor.