Tommaso Gomes

Phenolic compounds of virgin olive oil: influence of paste preparation techniques

An experimental investigation was carried out on olive oils of the Ogliarola Salentina and Coratina cultivars to assess the influence of the two different olive grinding techniques and kneading process on the quality of the oils. The experimental data obtained showed that resistance to oxidation, total phenols and phenolic compounds analysed for HPLC were higher in the Coratina oils than in the Ogliarola oils. The use of hammer-crushers plus kneader rather than stone mills plus kneader always produced significant increases in the total phenols. Resistance to oxidation was assessed by the Rancimat method and showed a significant correlation with the amounts of total phenols and of an unidentified substance (peak I) which was conspicuously present amongst the substances evaluated for HPLC.

Oligopolymer, diglyceride and oxidized triglyceride contents as measures of olive oil quality

The objective of this study was to test the qualities of olive oils of different commercial grades by quantifying oligopolymer compounds by high-performance size-exclusion chromatography (HPSEC). The method required no sample manipulation and was accurate and rapid. The mean level of oligopolymers in refined olive oils was 0.70% and was more than twice as high in refined olive pomace oils. Conversely, edible virgin olive oils had no oligopolymer compounds. HPSEC analyses of polar compounds by silica gel column chromatography also allowed determination of oxidized triglycerides and partial glycerides, which help define levels of oxidative degradation and hydrolysis.

Vacuum-packed ripened sausages: evolution of oxidative and hydrolytic degradation of lipid fraction during long-term storage and influence on the sensory properties.

An experimental investigation was carried out with the aim to understand the oxidative and hydrolytic phenomena involving the lipid fraction of vacuum-packed sausages during long-term storage (5 months) and to verify their influence on the sensory characteristics. The data obtained pointed out that the oxidation was more pronounced in the initial stages of storage than in the further period, while the hydrolysis of lipid fraction significantly advanced during the whole storage time, supported by the high moisture level of the product. Both these phenomena resulted to be correlated with the sensory decay of the product. In particular, in the first stage of vacuum storage overall acceptability was found to be negatively correlated (p<0.05) with rancid taste, acid value, and oxidized triacylglycerols. In the further stage the oxidative processes slowed down and affected in a lesser extent the sensory properties, which were more distinctly characterized by the onset of pungent perception attributed to compounds arising from multiple origins such as carbohydrate fermentation. This investigation confirmed the unreliability of thiobarbituric acid reactive substances test and the usefulness of high performance size exclusion chromatography analysis of the polar compounds of the lipid fraction to correctly determine the levels of the oxidative and hydrolytic degradation of the lipid fraction of vacuum-packed ripened sausages during long-term storage.

Non-conventional parameters for quality evaluation of refined oils with special reference to commercial class olive oil

Forty olive oil samples (refined olive oil plus virgin olive oil) were tested to check the possibility of using recent non-conventional analytical parameters to assess quality. The routine analyses prescribed by the EEC Reg. No 2568/91 and subsequent extensions were carried out on all samples. The analytical techniques used included silica gel column chromatography for the separation of polar compounds from oil, and their subsequent high performance size-exclusion chromatography (HPSEC) analysis to quantify the oxidation, polymerisation and hydrolysis product classes. Based on the results obtained, it seems logical to use the percent oligopolymer content to measure the level of oxidation in commercial class olive oil. The diglyceride level can provide information about the extent of hydrolytic degradation.

Traceability of Italian Protected Designation of Origin (PDO) table olives by means of microsatellite molecular markers.

The aim of this work was to develop a DNA microsatellite-based method of analysis to allow traceability of the three Italian Protected Designation of Origin (PDO) table olives in comparison with fruits of another seven highly diffused table olive cultivars. The analyses were carried out by using 16 primer pairs, with a mean of five different alleles detected per primer set, and power of discrimination from 0.56 to 0.90. Allelic error rates in the range of 0-3.8% were observed. By combining data from the most reliable and highly informative microsatellites (DCA3, DCA16, DCA17, DCA18, UDO-043, and GAPU101), it was possible to identify the PDO fruits over the panel of 10 cultivars, with the probability of a chance match between different cultivars as low as 10(-9) and with 0.5% error rate. The amplification profile is independent of environmental and processing conditions and is helpful to verify the authenticity of PDO samples.

Influence of the Thermal Stabilization Process on the Volatile Profile of Canned Tomato-Based Food

The literature contains several papers dealing with the volatile constituents contributing to the aroma of fresh and processed tomatoes. Along with the traditional tomato-based products, tomato-based pâtés, characterized by complex ingredient formulations, are commonly consumed as a seasoning for pasta, and as a dressing for meats, salads, and sandwiches. To the best of our knowledge, no investigations have been published on the influence of thermal stabilization treatments on the composition of volatile compounds in tomato-based pâtés. To this aim, thermally stabilized and not stabilized tomato-based pâtés were subjected to the analysis of volatile compounds. The results obtained highlighted the influence of the thermal stabilization process on the evolution of volatile composition tomato-based pâtés. In particular, the terpenic compounds showed significant decreases after the thermal stabilization process treatment, due to their degradation and oxidation favored by high temperatures. The thermal stabilization caused, moreover, an increase in volatile compounds deriving from lipid oxidation and Maillard reaction, characterized by low-sensory thresholds, and from the thermal degradation of carotenoids and fresh tomato-derived compounds.

Diacylglycerol isomers in extra virgin olive oil: Effect of different storage conditions

An experimental investigation was carried out with the aim to investigate on the isomerisation of 1,2-diacylglycerols to 1,3-diacylglycerols as a function of the storage conditions, as well as to identify indices useful to evaluate the freshness of the oils. Two oils derived from two different cultivars (Coratina and Ogliarola barese) were stored for two years as follows: in bottles at dark; in clear glass bottles at light; in green glass bottles at light; in bottles at dark, the latter subjected to repeated opening and samplings to simulate domestic use. The obtained results evinced that during the storage period a significant increase in the 1,3-isomers was observed due to an isomerisation from the 1,2 to the 1,3 isomeric form, consequently the 1,3/1,2 ratio increased in both oils. The covariance analysis of the data showed that the isomerisation of diacylglycerols, taking place during time, was affected by the type of oil, probably due to the different initial hydrolysis level, but was not affected by the storage conditions. Among the parameters considered, the total diacylglycerols/1,3-diacylglycerols ratio could be used as freshness index of extra virgin olive oil, since it is not affected by either oil or storage conditions.

Effects of monoacylglycerols on the oxidative stability of olive oil

BACKGROUND The study of pro- and anti-oxidant compounds is important for their influence on the shelf-life and nutritional value of food. The aim of this research was to evaluate the activity of monoacylglycerols (MAG), obtained by partial saponification of a purified olive oil, added in increasing amounts to the same oil and submitted to the Rancimat test and oven test at 60 °C. Besides routine analyses, high-performance size exclusion chromatography analysis of polar compounds was performed. RESULTS The addition of MAG led in all cases to a significant slowdown of the oxidative processes. These trends were more evident as the oxidation went on. The purified oil added with 30 g kg(-1) of MAG after 9 days of oven test at 60 °C presented a level of oxidative degradation significantly lower than the control after only 4 days. CONCLUSION The data showed a marked antioxidant effect of MAG in purified olive oil, contrary to what has been observed by other authors, who noticed either a pro-oxidant or a non-antioxidant activity of these compounds in soybean oil. A different behaviour of MAG during oxidation could depend on the different fatty acid composition of the oil matter they are added to.

Influence of Drying Conditions on Volatile Compounds of Pasta

The effect of drying temperatures on the profile of volatile compounds of pasta was studied. The solid phase microextraction coupled with gas chromatography/mass spectrometry allowed to identify 72 volatile compounds in the samples of not-dried, low-temperature-dried (LT-dried), high-temperature-dried (HT-dried), and wrongly very-high-temperature-dried (WVHT-dried) pastas. The samples of not-dried pasta contained alcohols, aldehydes, short-chain ketones, esters, furans, and some sulfur compounds. In the LT-dried pasta, the volatile aldehydes derived from lipid oxidation were more abundant than in HT-dried pasta. HT-dried pasta showed higher levels of furan and furan derivatives (especially 2-furanmethanol), derived from the Maillard reaction, than LT-dried pasta (p < 0.05). Pyrazines arose from WVHT treatment. Significant differences were observed also for the color indices when comparing pasta subjected to LT and HT drying (p < 0.001). Several volatile Maillard reaction products were significantly correlated (p < 0.05 and p < 0.01) to a* and 100 − L*. The ratio aldehydes/furans allowed distinguishing in a significant way the treatments, independently from the lot characteristics.

Evolution of the volatile compounds of ripened sausages as a function of both storage time and composition of packaging atmosphere

An experimental investigation was carried out to study the evolution of the volatile compounds of ripened sausages as a function of both storage time (time) and composition of packaging atmosphere (MAP). Ripened sausages, prepared at an industrial plant, were packed applying three different atmosphere compositions and were stored for three months. The obtained data evinced that the evolution of the volatile compounds was significantly related to the variable time more than to the variable MAP. The main volatile compounds were those derived from spices. Among them, Δ3-carene was the most abundant and a significant decrease was observed during storage (p<0.05). The volatile compounds derived from lipid autoxidation showed generally a significant increase during storage, suggesting the raise of lipid oxidation also at low oxygen concentration. Moreover, octanal and nonanal were significantly influenced by the atmosphere composition, with the highest values in samples packed at the lowest CO2 concentration.