Guillermo Santa-María

Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography

SummaryAn ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r>0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.

Triglyceride composition of ewe, cow, and goat milk fat

The separation and identification of the components in milk fat, which are mainly triglycerides, is a challenge due to its complex composition. A reverse-phase high-performance liquid chromatography (HPLC) method with gradient elution and light-scattering detection is described in this paper for the triglyceride analysis in ewes’ milk fat. Triglyceride identification was carried out by combining HPLC, gas-liquid chromatography (GLC), and the calculated equivalent carbon numbers of several triglyceride standards. Quantitation of partially resolved peaks in the HPLC chromatogram was accomplished by applying a peak deconvolution program. Forty-four fatty acids were identified by GLC analysis, but only 19 were used for the following prediction of triglyceride molecular species; 181 triglycerides were identified, some of which were grouped at the same peak and needed application of the deconvolution program. Consequently, coefficients of variation were close to or lower than 5%. Moreover, the triglyceride composition of ewe, cow, and goat milk fat were compared by using these methods. These results show that ewe milk fat is richer in short- and medium-chain triglycerides, and cow milk fat is richer in long-chain and unsaturated triglycerides.

Supercritical fluid extraction of vegetable and animal fats with CO2—A mini review

Abstract The application of supercritical fluid extraction techniques in vegetable and animal fats is reviewed. Most of the published work has dealt with applications of supercritical CO 2 to extract vegetable oils. In general, the efficiency of the extraction increases with pressure as well as with temperature, provided the pressure is higher than 345 bar. The use of entrainers to enhance the extraction of lipids was also taken into account. Since the glycerides containing polyunsaturated fatty acids have important pharmacological applications, some procedures have been developed for extraction of these compounds from animal fats. Considerable work has been carried out on the extraction of cholesterol from fat. Fractionation of milk fat yields fractions with short- and medium-chain fatty acids enriched in cholesterol and fractions with medium- and long-chain fatty acids low in cholesterol.

1H‐HRMAS NMR study of smoked Atlantic salmon (Salmo salar)

High‐resolution magic angle spinning (HRMAS) NMR spectroscopic data of smoked Atlantic salmon (Salmo salar) were fully assigned by combination of one‐ and two‐dimensional‐HRMAS experiments. Complete representative spectra, obtained after few minutes of analysis time, revealed a large number of minor and major compounds in the sample. The methodology is limited by the low sensitivity of NMR, and therefore HRMAS only enables the determination of the most relevant components. These were fatty acids (FAs), carbohydrates, nucleoside derivatives, osmolytes, amino acids, dipeptides and organic acids. For the first time, spectra were resolved sufficiently to allow semiquantitative determination in intact muscle of the highly polyunsaturated FA 22:6 ω‐3. Additionally, the feasibility of 1H‐HRMAS NMR metabolite profiling was tested to identify some bioactive compounds during storage. This profiling was carried out by the non‐destructive and direct analysis (i.e. without requiring sample preparation and multiple step procedures) of intact salmon muscle. The proposed procedure can be applied to a large number of samples with high throughput due to the short time of analysis and quick evaluation of the data. Copyright

Determination of the triglyceride composition of grapes by HPLC

SummaryThe triglyceride composition of the Tempranillo grape (Vitis vinifera) has been examined by a combination of HPLC and GLC. To identify the triglycerides, equations were applied relating log k′ with the molecular variables: equivalent carbon number, chain length and number of double bonds in each of the fatty acids in the glycerides. Ten triglycerides were found, the principal ones being trilinolein (35.75%), dilinoleyl-olein (21.03%) and dilinoleyl-palmitin (17.02%).

Application of linear discriminant analysis to different proteolysis parameters for assessing the ripening of Manchego cheese

Abstract Different proteolysis parameters, the nitrogenous fractions and the breakdown of caseins, were determined for Manchego cheeses at different stages of ripening. Linear discriminant analysis was applied to these parameters to ascertain the degree of ripening. Two discriminant functions enabling 100% correct classification of the cheeses into fresh, medium ripe and aged were found.

Correlation between lactulose and furosine in UHT-heated milk

The kinetics of furosine and lactulose formation during heat treatment of milk and correlations between these parameters have been studied as a contribution for setting legal standards for heat-processed milks. Activation energies of 93.15 ± 5.87 kJ/mol and 153.2 ± 6.49 kJ/mol for furosine and lactulose respectively were computed from zero-order rate constants. Polynomial and logarithmic equations were developed to predict the furosine content as a function of lactulose content. The polynomial equation proposed fit the experimental data and previously reported data. The standard error of the prediction was lower than ±7.8mg/liter. The application of this equation to observed values for lactulose and furosine in commercial milk samples would allow the detection of milk powder in UHT milk.

Determination of maltodextrins in enteral formulations by three different chromatographic methods

SummaryMaltodextrins (G1 to G11) present in enteral formulations have been determined by three analytical methods —thin-layer chromatography (TLC), high-performance anion-exchange chromatography with pulsed electrochemical detection (HPAEC-PED), and high-performance liquid chromatography with refractive-index detection (HPLC-RI). The repeatability of the three methods was similar. Although HPAEC-PED was more sensitive than HPLC-RI and TLC, the relatively high maltodextrin content of the enteral formulations resulted in reasonable agreement among results from quantitative determination of G1 to G7 by the three methods studied. Differences between methods were higher for compounds G8 to G11.

Determination of free carbohydrates and Amadori compounds formed at the early stages of non-enzymic browning

α-N-acetyl, ϵ-N-(1-deoxy-d-lactulos-l-yl)-l-lysine (ALL) was prepared as a model of protein-bonded lactose, and characterized by NMR. An HPLC method was designed to determine it. Milk model systems containing lactose, α-N-acetyl-l-lysine and salts were heated at 120°C (in the liquid state) or freeze-dried and stored at 45°C and 0·44 aw. Free carbohydrates formed were determined by GC, and ALL by HPLC. Lactulose was formed at higher levels than ALL when heating, whereas the opposite was true during the storage of lyophilizates. It was shown that enolization is the main pathway of lactose degradation at high temperature, and that addition to amino groups predominates at low temperatures and aw.

Enantiomeric analysis of chiral compounds in irradiated foods using multidimensional gas chromatography

The usefulness of both solid phase microextraction (SPME) and multidimensional gas chromatography (MDGC) coupled to mass spectrometry (MS) to detect chiral compounds in irradiated cheese was evaluated. The enantiomeric resolution of relevant chiral aroma compound was achieved by analyzing the extracts obtained from SPME by means of a permethylated beta-CD stationary phase as the main column of the multidimensional system to separate specific selected cuts containing components unresolved in the first dimension. The proposed procedure allowed to determine, in less than 90 min, that no significant variations had been produced in the stereoisomeric distribution of limonene, 3-hydroxybutanone, and 2,3-butanediol in cheese when applying irradiation doses ranging from 0 to 8 kGy.