Search

The protection of sunflower meal (SFM) proteins by treatments with solutions of malic acid (1 M) or orthophosphoric acid (0.67 M) and heat was studied in a 3 × 3 Latin-square design using three diets and three rumen and duodenum cannulated wethers. Acid solutions were applied to SFM at a rate of 400 ml/kg under continuous mixing. Subsequently, treated meals were dried in an oven at 150°C for 6 h. Diets (ingested at 75 g/kg BW0.75) were isoproteic and included 40% Italian ryegrass hay and 60% concentrate. The ratio of untreated to treated SFM in the concentrate was 100 : 0 in the control diet and around 40 : 60 in diets including acid-treated meals. The use of acid-treated meals did not alter either ruminal fermentation or composition of rumen contents and led to moderate reductions of the rumen outflow rates of untreated SFM particles, whereas it did not affect their comminution and mixing rate. In situ effective estimates of by-pass (BP) and its intestinal effective digestibility (IED) of dry matter (DM), CP and amino acids (AAs) were obtained considering both rates and correcting the particle microbial contamination in the rumen using 15N infusion techniques. Estimates of BP and IED decreased applying microbial correction, but these variations were low in agreement with the small contamination level. Protective treatments increased on average the BP of DM (48.5%) and CP (267%), mainly decreasing both the soluble fraction and the degradation rate but also increasing the undegradable fraction, which was higher using orthophosphoric acid. Protective treatments increased the IED of DM (108%) and CP, but this increase was lower using orthophosphoric acid (11.8%) than malic acid (20.7%). Concentrations of AA were similar among all meals, except for a reduction in lysine concentrations using malic acid (16.3%) or orthophosphoric acid (20.5%). Protective treatments also increased on average the BP of all AA, as well as the IED of most of them. Evidence of higher increases for those AA showing a high resistance to degradation in the untreated meal were also observed. The total supply of metabolisable AA was increased by 3.87 times for sulphur-containing AA, whereas that of lysine was increased by 2.5 times, mainly because of lysine losses with heat treatments. These treatments and especially that with malic acid would be useful to increase the protein value of these meals but their combined use with lysine-rich protein concentrates would improve the metabolisable protein profile.

A new method based on the use of SPME followed by the MDGC-MS analysis was developed to determine pesticides in fruit juice. Different pesticide mixture standards (i.e. Mix 101, 13 and 164) were initially analyzed to optimize the separation conditions. To evaluate the advantages of the two-dimensional system over monodimensional GC, a comparative study on relative standard deviations, detection limits and correlation coefficients was carried out. As a result, selective transfers of some pesticides from the first to the second dimension were at times essential to avoid overlapping. The selected separation conditions from the study with standards were applied to fruit juices spiked with some pesticide standards. The results found in this work prove that the employment of a multidimensional analysis technique permits to avoid false positives obtained frequently on monodimensional techniques as a consequence of interferences of the analytes with matrix components., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A method based on the use of the through oven transfer adsorption-desorption (TOTAD) interface in on-line coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) for the determination of chiral volatile compounds was developed. In particular, the method was applied to the study of the influence of methyl jasmonate (MJ) treatment on the production and enantiomeric composition of selected aroma compounds in strawberry. The compounds studied were ethyl 2-methylbutanoate, linalool and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (i.e. furaneol), which were examined on days 3, 6 and 9 after treatment. The method developed resulted in relative standard deviations (RSDs) of 21.6%, 8.1% and 9.8% and limits of detection (LD) of 0.04, 0.07 and 0.02mg/l for ethyl 2-methylbutanoate, linalool and furaneol, respectively. The application of the RPLC-TOTAD-GC method allowed higher levels of ethyl 2-methylbutanoate, linalool and furaneol to be detected, particularly after 9 days of treatment. Besides, MJ demonstrated to affect the enantiomeric distribution of ethyl 2-methylbutanoate. On the contrary, the enantiomeric composition of linalool and furaneol kept constant in both control and MJ-treated strawberries throughout the study. These results are discussed., (Copyright 2009 Elsevier B.V. All rights reserved.)

A method based on the use of absorbents as packing materials in the interface of the direct coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) is proposed. To that end, a comparative study on different adsorbents and absorbents was carried out. Specifically, Tenax TA and Gaschrom were used as adsorbents while polydimethylsiloxane and poly(50% phenyl:50% methylsiloxane) were the absorbents tested. Some experimental variables involved in the solvent elimination were separately optimised for adsorbent and absorbent materials. Relative standard deviations (RSD) lower than 10% were achieved in all cases but the use of absorbents showed interesting advantages with respect to adsorbents, namely a simpler performance of the experimental work, which facilitates the sample preparation step and the subsequent gas chromatographic analysis to be performed.

A method based on the on-line coupling of reversed phase liquid chromatography with gas chromatography/mass spectrometry (RPLC-GC-MS) for the chiral evaluation of characteristic constituents of fruit beverage aroma was investigated. The consideration of a variety of parameters involved in the transfer step allowed to achieve relative standard deviations ranging from 0.4 to 10% in most cases and detection limits from 0.2 to 2.5 mg/l. By applying the developed method to fruit beverages, racemic mixtures of ethyl 2-methylbutanoate and gamma-nonalactone were found. This fact suggests the eventual addition of artificial aromas. The method proposed in the present work can be useful to assess reliably the authenticity of aqueous samples, such as fruit beverages.

The variability of the enantiomeric distribution of biologically active chiral terpenes in Mentha piperita plants from different geographical origins was evaluated by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The optimisation of some parameters (i.e. exposure temperature, extraction time and type of fibre) affecting SPME-extraction enabled relative standard deviations ranging from 4 to 13% to be achieved. The use of two different chiral stationary phases allowed to separate the identified chiral terpenes into their corresponding enantiomers as well as to verify the enantiomeric excesses of those compounds which were enantiomerically resolved on both phases. For all chiral terpenes, the enantiomeric composition varied within a very narrow range all over the samples. Consequently, it may be stated that the enantiomeric composition of chiral terpenes in Mentha piperita appears to be independent of the geographical origin of the plant and, thus, any alteration in the characteristic value may be related to an adulteration or inadequate sample handling. These results support the usefulness of the enantiomeric composition of bioactive chiral terpenes in Mentha piperita in authenticity studies.

Chiral terpenes in orange juices were examined by solid-phase microextraction-gas chromatography-mass spectrometry to study the dependence of their enantiomeric composition on the thermal treatment applied during the industrial manufacture. The experimental conditions used in the isolation and concentration of the compounds of interest produced relative standard deviations ranging from 2.9 to 15.1% when absolute areas were used and from 1.7 to 18.3% when normalized areas were used. Recovery varied between 8.8 and 56.1%, and detection limits ranged from 0.11 to 0.32 microg/ml. The enantiomeric compositions of the majority of the chiral terpenes varied within a reasonably narrow range. Nevertheless, the enantiomeric ratio of two monoterpene alcohols, alpha-terpineol and linalool, exhibited considerable variation according to the thermal treatment used in the manufacture of the juices. Therefore, the knowledge of the enantiomeric composition of alpha-terpineol and linalool might be useful for thermal treatment control purposes.

Chiral terpenes in nonprocessed orange juices of different geographical origins were examined by two different approaches: steam distillation-solvent extraction-gas chromatography-mass spectrometry (SDE-GC-MS) and solid-phase microextraction-gas chromatography (SPME-GC). The two sample preparation techniques were compared with regard to their effectiveness in determining the enantiomeric distributions of chiral compounds. Most target compounds exhibited constant enantiomeric ratios in all juices when either of the two approaches was used. Exceptions were found for terpinen-4-ol and beta-citronellol, whose of enantiomeric purity ratios varied significantly according to the geographical origin of the sample. These results may aid in guaranteeing the authenticity and thus the quality and safety of orange juice. A comparison between the two extraction procedures revealed SPME to be more reliable for stereochemical studies, since harsh experimental conditions that can bring about racemization are not required in such studies.