T. Gallina Toschi

Classification of Pecorino cheeses using electronic nose combined with artificial neural network and comparison with GC–MS analysis of volatile compounds

An electronic nose based on an array of 6 metal oxide semiconductor sensors was used, jointly with artificial neural network (ANN) method, to classify Pecorino cheeses according to their ripening time and manufacturing techniques. For this purpose different pre-treatments of electronic nose signals have been tested. In particular, four different features extraction algorithms were compared with a principal component analysis (PCA) using to reduce the dimensionality of data set (data consisted of 900 data points per sensor). All the ANN models (with different pre-treatment data) have different capability to predict the Pecorino cheeses categories. In particular, PCA show better results (classification performance: 100%; RMSE: 0.024) in comparison with other pre-treatment systems.

Preliminary investigation into development of HPLC with UV and MS-electrospray detection for the analysis of tea catechins

Abstract There is an increasing interest in the biological and technological role of natural antioxidants present in green tea extracts. This is due to the inhibition of the oxidative process showed by tea catechins, which is higher than those of synthetic antioxidants (such as BHT) and other vegetal extracts (rosemary, oregano, grape seeds). In a first step of the work a rapid reversed phase HPLC method for the determination of catechins in green tea extracts, using a binary gradient system, was developed. Commercial green tea extracts were analyzed and the different catechins quantified. EGCG ((−)-epigallocatechin-3-gallate) and EGC ((−)-epigallocatechin) were proposed as index of the antioxidant quality of tea extracts. Subsequentely, the previous chromatographic method was applied on a HPLC–MS system in order to verify the accuracy of some HPLC-DAD results and compare the two detection modes, on such a polyphenolic mixture. The use of mass spectrometry detection in quantification of catechins ensured an higher specificity of the method and a constant qualitative control of the identity of chromatographic peaks thanks to the concurrent acquisition of more than one mass signal (as M+1 and M+Na pseudomolecular peaks).

Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid.

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients (epsilon), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity (epsilon) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.

Routine high-performance liquid chromatographic determination of free 7-ketocholesterol in some foods by two different analytical methods

Two methods for routine analysis of free 7-ketocholesterol (7-k) in foods by high-performance liquid chromatography (HPLC) were compared. The analyzed samples were egg noodles, biscuits prepared with eggs, sweet snacks, grated Parmesan cheeses, and some ingredients utilized in the food industry (whole-milk and whole-egg powder). The enrichment of cholesterol oxides was carried out by solid-phase separation of the total lipids with florisil and silica cartridges for methods A and B, respectively. The 7-k analyses were run in normal-phase HPLC for method A, and a reverse-phase process was used in method B. Identification of the 7-k peak was confirmed by gas chromatography/mass spectrometry analysis and peak purity checkvia spectral analysis with a diode array detector. The quantitation of 7-k was carried out with an internal standard for method A and with a calibration curve for method B. The limit of quantitation (LQ) was 3 × 10−9 g/injection; the limit of detection was ten times lower than the LQ for both methods. The two methods showed good recovery (99%) and good repeatability (coefficient of variation of 3.9 and 3.7% for methods A and B, respectively). These methods allow a fast, sensitive, and reliable determination of one cholesterol oxidation product, which is present at a high concentration level in the first stages of the oxidation process.

A study on cashew nut oil composition

Eight samples of cashew nut oil were assayed, and the component triacylglycerols, fatty acids and several unsaponifiable compounds were analyzed by gas chromatography (GC) and high-performance liquid chromatography (HPLC). Total lipid amount, unsaponifiable percentage, fatty acids, sterols, triterpene alcohols and tocopherols are reported here. The combination of GC and HPLC enhanced the resolution of compound classes.

A novel electrochemical method for olive oil acidity determination

Olive oil is a very important product due to its nutritional value, sensory and antioxidant properties. National and international regulations define basic quality parameters (such as acidity and peroxide index) to discriminate high quality oils (extra virgin olive oil) from those of lower quality. The procedures to measure acidity and peroxide index are manual titration techniques requiring a laboratory environment and trained personnel. In this paper a novel technique, based on electrical impedance spectroscopy, is presented to be suitable for the realization of a simple, low-cost, mobile instrument allowing such measurements to be carried out everywhere and by anybody, with substantial improvements of the current quality control of oil producers of any dimension. The presented method has been validated on 39 olive oil samples, featuring different levels of acidity, peroxide index and total phenolic content. The results show that the emulsion conductance is the electrical parameter best suited to discriminate the oil acidity. Moreover, since the emulsion conductance is also affected by the oil storage conditions (i.e. peroxide index), the presented technique can also be proposed, in a second time, to evaluate product ageing.

Evaluation of 3,5-stigmastadiene content of edible oils: Comparison between the traditional capillary gas chromatographic method and the on-line high performance liquid chromatography-capillary gas chromatographic analysis

SummaryThe quantitation of 3,5-stigmastadiene and other steroidal hydrocarbons, commonly known as steradienes, is a valid tool for the recognition of refining (in particular bleaching) of edible oils; the evidence of this process is nowadays of a great interest due to growing market for “virgin”, cold-pressed, “natural” oils. Due to the long time required (about 4 hours) and the amount of solvents employed (about 650 mL) to perform the official analysis, other methods have been recently proposed, the most important of which involves high performance liquid chromatography coupled with capillary gas chromatography (HPLC-GC). In this study the results of ten oil samples, analysed by both the official method and HPLC-GC, are reported and the two methods compared and discussed, for routine use, in terms of sample preparation, time of analysis and setting up, difficulty and reproducibility.

Sensory and instrumental study of Taralli , a typical Italian bakery product

Taralli is a bakery snack food, typical of the south of Italy, that has currently become very popular worldwide as a savory snack or bread substitute. However, few studies have focused on its physical and sensory characteristics. The present work aims to select sensory and instrumental information that is able to characterize Taralli with similar formulation and size. For sensory characterization purposes, conventional profiling was applied on samples from different producers. All samples were also subjected to physical analysis of appearance and textural proprieties. Three samples of the set, differing only in storage time, were evaluated to assess changes in sensory characteristics during this period and a discrimination test (triangle test) was also applied for this purpose. The test results confirmed that the sensory analysis allowed a description of the entire range of characteristics resulting from stimulation of senses by physicochemical properties of the food. This methodology was effective in evaluating the quality characteristics and identify differences between Taralli samples during different storage times. Instrumental tests were also applied to assess food quality. The results revealed that a combined approach allowed obtaining more information about the product characteristics and definition of quality standards. This study also suggests the use of physical parameters obtained by simple and rapid instrumental tools can support sensory analysis, especially for evaluations that are fatiguing, when decisions made with the sensory data are critical or to provide objective reference standards that are suitable for training purposes.

EFFECTS OF ARCHAIC OLIVE AND OIL STORAGE METHODS STILL USED IN SOUTHERN TUNISIA ON OLIVE OIL QUALITY

The present paper investigated how virgin olive oil quality is influenced by two different storage conditions that residents of Gabes (Southern Tunisia) usually apply to fruits of the Zarazi cultivar: long conservation as oil in glass bottles or traditional storage of olives as sun-dried fruits before processing for oil production. Even if both storage conditions are associated with strong losses in the qualitative characteristics of olive oil, the changes observed were more accentuated for oil stored for two years after its production compared to the oil obtained from olives stored by traditional methods.