Lipidomics: An omics discipline with a key role in nutrition.

The importance of lipidomics to unveil crucial aspects in the nutrition field is afforded in this article. With this aim, historical facts such as demonization of fats, enthronization of carbohydrates, and subsequent changes in the food pyramid are first discussed. After considering basic and analytical aspects of lipidomics and the upstream information this omics provides, its key role in personalized nutrition (PN), and the importance of lipids as nutrition biomarkers are critically discussed by appropriate examples. Pendent challenges to clarify the role of lipidomics in nutrition are overcome limiting factors, design of new lipidomics-based biomarkers, unveil mechanisms involved in lipidomics processes, and integrate lipidomics with other omics for a more complete and validated information useful in PN. The conclusions of this study also include the scant role of analytical chemists in the lipidomics-nutrition binomial, basically supported on analytical data.

Prediction of texture and colour of dry-cured ham by visible and near infrared spectroscopy using a fiber optic probe.

The potential of visible and near infrared spectroscopy to predict texture and colour of dry-cured ham samples was investigated. Sensory evaluation was performed on 117 boned and cross-sectioned dry-cured ham samples. Slices of approximate thickness 4cm were cut, vacuum-packaged and kept under frozen storage until spectral analysis. Then, Biceps femoris muscle from the thawed slices was taken and scanned (400-2200nm) using a fiber optic probe. The exploratory analysis using principal component analysis shows that there are two ham groups according to the appearance or not of defects. Then, a K nearest neighbours was used to classify dry-cured hams into defective or no defective classes. The overall accuracy of the classification as a function of pastiness was 88.5%; meanwhile, according to colour was 79.7%. Partial least squares regression was used to formulate prediction equations for pastiness and colour. The correlation coefficients of calibration and cross-validation were 0.97 and 0.86 for optimal equation predicting pastiness, and 0.82 and 0.69 for optimal equation predicting colour. The standard error of cross-validation for predicting pastiness and colour is between 1 and 2 times the standard deviation of the reference method (the error involved in the sensory evaluation by the experts). The magnitude of this error demonstrates the good precision of the methods for predicting pastiness and colour. Furthermore, the samples were classified into defective or no defective classes, with a correct classification of 94.2% according to pasty texture evaluation and 75.7% as regard to colour evaluation.

Relationship between pH before salting and dry-cured ham quality.

The effect of pH before salting on pork quality was studied in two sets of experiments: 904 hams, set A; and 104 hams, set B; the latter was used to verify the results from A. After pH measurements, the hams were subjected to the traditional process for producing Spanish dry-cured ham and then evaluated by an expert panel to correlate the sensory characteristics to the pH measurement before salting. The parameters evaluated were pastiness, softness, anomalous cut colour, crusting and white spots. Moisture, non-protein nitrogen, salt, protein, nitrate and nitrite were determined in samples from both experiments. The results obtained in experiment A showed that pastiness is closely related to the pH before salting (p<0.001), but not softness. From the receiver operating characteristics curve, a cut-off point of pH of 5.55 was selected to classify the raw material in two groups: normal-pH and low-pH hams. The pH before salting can also be correlated with the appearance of anomalous cut colour and crusting in hams. White spots were absent in both pH groups. Regarding compositional parameters, there were significant differences in moisture (p<0.001), salt (p<0.001), protein (p<0.001), non-protein nitrogen (p<0.001) and nitrate (p<0.05) contents between low-pH and normal-pH hams. The results from experiment B, confirmed the relationship between pH before salting and the appearance of defective texture and colour in the final product. Also results from experiment B confirmed the compositional parameters found in experiment A. Thus, the pH before salting is a good predictor for meat quality allowing the classification of the raw material in the first stage of manufacture. After classification, some modifications to the processing can improve the final characteristics of dry-cured hams.

New methods for acceleration of meat sample preparation prior to determination of the metal content by atomic absorption spectrometry.

Focused microwave-assisted digestion and ultrasound leaching have been applied for the extraction of Pb, Cd, Cr, Cu, Fe, Zn, Ca, and Mg from raw meat. Semimembranous muscle (SM) of raw pig ham was used for optimizing both the digestion and extraction steps by multivariate approaches. The detection and quantification limits were 0.5 and 0.9 microg kg(-1) for Pb, 0.06 and 0.1 microg kg(-1) for Cd, 0.2 and 1.2 microg kg(-1) for Cr, 0.4 and 3 microg kg(-1) for Cu, 0.04 and 0.1 mg kg(-1) for Fe, 0.012 and 0.017 mg kg(-1) for Zn, 0.3 and 0.4 mg kg(-1) for Ca, and 0.01 and 0.03 mg kg(-1) for Mg. The precision, expressed as relative standard deviation (RSD), ranged between 2.5 and 9.6% for focused microwave-assisted digestion and between 3.5 and 10.6% for ultrasound leaching. The methods were then compared with a reference method and applied to a certified reference material (bovine muscle 184, from the BCR). The t-test, applied to the results obtained from focused microwave-assisted digestion, revealed that they are in agreement (p>0.01) with the certified and estimated values in the case of Pb, Cd, Cr, Cu, Fe, Ca, Mg, and Zn but not in that of Fe. In the case of ultrasound leaching, only the extraction of Pb, Cu, and Ca was quantitative. The method based on microwave digestion provides more accurate and precise results than ultrasound leaching. These new procedures have many advantages with regards to conventional methods, namely, reduction of the extraction time, simplification of the process, avoidance of chemical emissions to the atmosphere, and no losses of metals by volatilization.

Activity of cathepsin B, D, H and L in Spanish dry-cured ham of normal and defective texture.

Thirty-six specimens of Spanish dry-cured ham from 18 different batches were studied to determine the influence of endogenous enzymes on the textural quality of the end product. It was shown that, the residual enzyme activity of cathepsins B+L is a reliable indicator of textural defects associated with strong proteolysis in Spanish dry-cured ham. In contrast, the activity of cathepsin B, which varied widely among samples, was less influential. Salt levels can have a moderate effect on the residual enzyme activities. Other compositional parameters also influence the properties of the end product; the amount of protein in semimembranosus muscle was found to be less and the moisture greater in texturally defective specimens. Also, the efficiency of the drying-curing process was less in hams yielding poor textures.

Full automated robotic method for the determination of chloride, nitrite and nitrate in cured meat products.

A completely automated method to determine the most common parameters in cured meat products is proposed. The approach to full automation is based on the coupling of a robotic station for development of preliminary operations (namely weighing of the sample, grinding, leaching, filtration and transport to the aspiration zone) and a continuous unsegmented manifold for derivatisation and spectrophotometric monitoring of the reaction coloured products. This assembly works in an unattended fashion thus eliminating the bottleneck produced by the determination of these parameters in routine laboratories. The good agreement between results obtained by the proposed method and those from conventional methods for target analytes confirms its excellent performance and usefulness.