Noelia Tena

Relationship between sensory attributes and volatile compounds qualifying dry-cured hams.

This work studies the relationship between 45 volatile compounds and 17 sensory attributes (13 flavour perceptions) of dry-cured hams. Volatile compounds were quantified by SPME-GC while the sensory assessment was carried out by 13 panellists. GC-sniffing was used to determine the odour impact zones of the chromatogram. The odour thresholds of the volatile compounds and their sensory characterisation were determined by dilution analysis. Six sensory attributes (acorn odour and flavour, rancid odour, rancid taste, fat rancid and fat pungent flavours) were explained by regression equations (adjusted -R(2)⩾0.70) based on ten compounds: benzaldehyde, 2-heptanone, hexanal, hexanol, limonene, 3-methylbutanal, 3-methylbutanol, 2-nonanone, octanol, pentanol. Acorn flavour attribute was successfully emulated by mixing the volatile compounds selected by the equation. Its odour was evaluated by assessors that gave a sensory description that matches with the target. All the procedures performed for the elucidation of volatile-attribute relations showed a basic agreement in their results.

Evaluation of virgin olive oil thermal deterioration by fluorescence spectroscopy.

The evolution of the fluorescent compounds during the thermal deterioration of virgin olive oil is not yet well-known. Samples of heated virgin olive oils collected from a fryer every 2 h up to 94 h were analyzed to study their fluorescence spectra as well as the evolution of the concentrations of alpha-tocopherol and individual phenols by high-performance liquid chromatography (HPLC). The regions of the fluorescence spectra of the heated oils, diluted in hexane at 1%, were explained by the content of these compounds with regression coefficients higher than 0.90 (R2 adjusted). The fluorescence intensity recorded at 350 nm and the wavelength of the spectrum maximum in the range of 390-630 nm also allowed for the explanation of the increase of the percentage of polar compounds during the experiment. On the other hand, the spectra of the undiluted heated oils indicated that the maximum of the spectrum of any undiluted oil at 490 nm or beyond is related to a percentage of the polar compounds higher than 25%, which is the maximum percentage accepted for edible oils used in frying processes.

Quality Characterization of the New Virgin Olive Oil Var. Sikitita by Phenols and Volatile Compounds

New cultivars with greater adaptability to modern irrigated (super-) high-density orchards and producing good sensory quality oils are highly demanded by an olive oil industry in continuous change. This work analyzes olive oil sensory quality, in terms of phenols and volatiles that are responsible for virgin olive oil flavor, for three cultivars: Picual, which is used for >15% of world olive oil production; Arbequina, which is cultivated worldwide; and the new progeny Sikitita, which is derived from the other two. The availability of data at three different levels of ripeness allowed quantifying the genetic and olive maturity effects on the oil composition by means of the analysis of variance (ANOVA) and principal component analysis (PCA). Phenols and volatiles varied greatly both with genotype and, to a lesser extent, with olive maturity. With regard to the phenol profile, the crossbred cultivar Sikitita showed a higher degree of similarity with the Arbequina variety. The volatile composition of var. Sikitita, however, varies significantly from that of Arbequina, in the first stages of the olive ripeness, and becomes more similar to that of Picual as the level of ripeness increases.

Thermal deterioration of virgin olive oil monitored by ATR-FTIR analysis of trans content.

The monitoring of frying oils by an effective and rapid method is one of the demands of food companies and small food retailers. In this work, a method based on ATR-FTIR has been developed for monitoring the oil degradation in frying procedures. The IR bands changing during frying in sunflower, soybean, and virgin olive oils have been examined in their linear relationship with the content of total polar compounds, which is a preferred parameter for frying control. The bands assigned to conjugated and isolated trans double bonds that are commonly used for the determination of trans content provided the best relationships. Then, the area covering 978-960 cm(-1) was chosen to build a model for predicting polar material content for the particular case of virgin olive oil. A virgin olive oil was heated up to 94 h, and samples collected every 2 h constituted the training set. These samples were analyzed to obtain their FTIR spectra and to determine the composition of fatty acids and the content of total polar compounds. The excellent results predicting the polar material content (adjusted R(2) 0.997) was successfully validated with an external set of samples. The analysis of the fatty acid composition confirmed the relationship between the trans content and the content of total polar compounds.

In-Depth Assessment of Analytical Methods for Olive Oil Purity, Safety, and Quality Characterization

This paper evaluates the performance of the current analytical methods (standard and widely used otherwise) that are used in olive oil for determining fatty acids, triacylglycerols, mono- and diacylglycerols, waxes, sterols, alkyl esters, erythrodiol and uvaol, tocopherols, pigments, volatiles, and phenols. Other indices that are commonly used, such as free acidity and peroxide value, are also discussed in relation to their actual utility in assessing quality and safety and their possible alternatives. The methods have been grouped on the basis of their applications: (i) purity and authenticity; (ii) sensory quality control; and (iii) unifying methods for different applications. The speed of the analysis, advantages and disadvantages, and multiple quality parameters are assessed. Sample pretreatment, physicochemical and data analysis, and evaluation of the results have been taken into consideration. Solutions based on new chromatographic methods or spectroscopic analysis and their analytical characteristics are also presented.

Sensor responses to fat food aroma: A comprehensive study of dry-cured ham typicality

The physicochemical phenomena that explain the sensing mechanisms of gas sensors have been extensively investigated. Nevertheless, it is arduous to interpret the sensor signals in a practical approach when they response to complex mixtures of compounds responsible for food aroma. Thus, the concomitant interactions between the volatiles and the sensor give up a single response affected by synergic and masking effects between compounds. An experimental procedure is proposed to determine the individual contribution of volatile compounds in the sensor response, illustrated with the examples of aroma of dry-cured hams and metal oxide sensors. The results from mathematical correlations and the analyses of pure standards are previously analyzed to describe the behavior of sensors when interacting with individual compounds. A sensor based olfactory detector (SBOD) entailing the use of a capillary column connected to a sensor array as non-destructive detector in parallel with the flame detector served to provide definitive information about the individual contribution of volatile compounds to sensor responses. The sensor responses in this system, which is referred to as sensorgram, were interpreted by taking into account the volatile composition of the samples determined by GC.

Infrared, Raman, and Fluorescence Spectroscopies: Methodologies and Applications

Spectroscopic techniques have emerged in food analysis as rapid and very useful tools for determining a great variety of chemical parameters. They provide elegant, fast, and easy-to-use solutions to tackle analytical challenges as well as a cost reduction. They offer the possibility to control a high number of parameters and properties simultaneously at the different steps of the food and feed chains and can be applied online. Huge instrumental and computer improvements have contributed to the development of near-infrared (NIR), mid-infrared (MIR), Raman, and fluorescence spectroscopies.

Time Course Analysis of Fractionated Thermoxidized Virgin Olive Oil by FTIR Spectroscopy

FTIR spectroscopy has been used to examine the spectral changes taking place in the polar fraction of thermoxidized virgin olive oil and compared to those changes occurring in the neat oil and the nonpolar fraction. It was demonstrated that examination of the polar fraction provides additional and substantially better information of the chemical changes taking place as oxidation proceeds because this fraction concentrates the oxygenated compounds formed. Of particular interest is the enhancement of the OH component of the spectrum (3600-3200 cm(-1)) as well as tertiary alcohol formation (~1167 cm(-1)), including the region associated with epoxides. Time course spectral changes for neat virgin olive oil and its polar and nonpolar fractions are illustrated, compared, and contrasted, demonstrating that the interpretation of neat oil spectra is greatly enhanced by fractionation and may in fact be a preferred means of studying thermoxidation processes.

Virgin olive oil stability study by mesh cell-FTIR spectroscopy

Mesh cell is a rapid tool designed to monitor chemical changes that occurs as a consequence of oxidation at moderate conditions. In this study this accessory has been proposed for assessing virgin olive oil (VOO) stability by Fourier transform infrared (FTIR) spectroscopy. Monocultivar VOOs have been stored in mesh cells under different temperatures (at 23, 35, 65°C) simulating the real conditions during storage and transport (<60°C). In addition to temperature, the samples have been also stored in mesh cells at different light intensities (400, 1000, 7000lx) to evaluate the resistance of the samples to photooxidation. The oil stability of the samples determined by using this accessory has been compared with the oil stability determined with the common methods used for this purpose (e.g. Rancimat). Despite the moderate conditions applied, mesh cell-FTIR spectra have revealed the formation of hydroperoxides and the subsequent formation of alcohols and aldehydes. Unlike other methods that require high temperature to accelerate the oxidation rate, mesh cell-FTIR has allowed differentiate the oil stability of the samples from a multi-factor perspective that includes several properties (temperature and light) and chemical species (primary and secondary oxidation products). The information obtained with this method can be relevant for optimizing handling (e.g. packaging and storage temperature) of VOO samples during their shelf life.

Origin authentication of distillers’ dried grains and solubles (DDGS)—application and comparison of different analytical strategies

In the context of products from certain regions or countries being banned because of an identified or non-identified hazard, proof of geographical origin is essential with regard to feed and food safety issues. Usually, the product labeling of an affected feed lot shows origin, and the paper documentation shows traceability. Incorrect product labeling is common in embargo situations, however, and alternative analytical strategies for controlling feed authenticity are therefore needed. In this study, distillers’ dried grains and solubles (DDGS) were chosen as the product on which to base a comparison of analytical strategies aimed at identifying the most appropriate one. Various analytical techniques were investigated for their ability to authenticate DDGS, including spectroscopic and spectrometric techniques combined with multivariate data analysis, as well as proven techniques for authenticating food, such as DNA analysis and stable isotope ratio analysis. An external validation procedure (called the system challenge) was used to analyze sample sets blind and to compare analytical techniques. All the techniques were adapted so as to be applicable to the DDGS matrix. They produced positive results in determining the botanical origin of DDGS (corn vs. wheat), and several of them were able to determine the geographical origin of the DDGS in the sample set. The maintenance and extension of the databanks generated in this study through the analysis of new authentic samples from a single location are essential in order to monitor developments and processing that could affect authentication.