Juan José Mangas Alonso

Capillary liquid chromatographic determination of neutral phenolic compounds in apple juices

Capillary liquid chromatography (CLC) is evaluated as an alternative to conventional HPLC to analyse complex phenolics. Several neutral phenolic compounds were separated on a packed-reversed phase fused-silica capillary column, and determined with UV detection. A conventional liquid chromatographic equipment was adapted for such purposes. Application of the proposed method to the quantification of neutral phenols in apple juices is reported. Phenolics are extracted and fractionated into neutral and acidic compounds by means of a C18 solid-phase cartridge. Typical recoveries ranging from 90 to 105% are obtained and reproducibility between extractions is <7% in all cases. Mass detection limits are at the sub-nanogram level.

Determination of amino acids in ripening apples by high performance liquid chromatography

High performance liquid chromatography (HPLC) was used to monitor amino acid changes in ripening apples in order to increase knowledge of the biochemistry of this type of fruit with a view to determining the optimum ripening time and evaluating the potential influence of the amino acid content of the different apple varieties studied on the juices and fermented beverages nmade from them.ZusammenfassungDie Hochleistungsflüssigchromatographie wurde angewendet, um Reifungsprozesse zu untersuchen mit dem Ziel, das Wissen über die Biochemie des Reifungsprozesses zu verbessern, einerseits um das Reifungsoptimum zu erkennen und andererseits um die mögliche Bedeutung des Gehalts an Aminosäuren der verschiedenen Apfelsorten für die daraus hergestellten Säfte und Gärungsgetränke festzustellen.SummaryHigh performance liquid chromatography (HPLC) was used to monitor amino acid changes in ripening apples in order to increase knowledge of the biochemistry of this type of fruit with a view to determining the optimum ripening time and evaluating the potential influence of the amino acid content of the different apple varieties studied on the juices and fermented beverages nmade from them.

A novel method for the determination of total 1,3-octanediols in apple juice via 1,3-dioxanes by solid-phase microextraction and high-speed gas chromatography

In this work, a novel, simple and fast method based on solid-phase microextraction (SPME) followed by high-speed gas chromatography (HSGC) was developed for the analysis of total 1,3-octanediols in apple juices by means of derivatization reaction to volatile 1,3-dioxanes. The derivatization reaction, SPME conditions, glycosidically bound fraction and 1,3-nonanediol as a surrogate standard were studied. The formation of 1,3-dioxanes from 1,3-diols was confirmed by GC-MS. The method was validated obtaining a regression coefficient (r(2)) of 0.9996, precisions between 0.3 and 9.8%, extraction recoveries in the range 94.7-112.2% and LOD of 2.9 microg l(-1). Experimental design has been employed in the optimization of extraction factors and robustness assessment. The method was applied to the analysis of 21 Asturian apple varieties finding a double reciprocal relationship between the concentrations of saturated and unsaturated 1,3-octanediol.

Characterization of Spanish ciders by means of chemical and olfactometric profiles and chemometrics

A comparative study of the aroma (volatile composition and olfactometric profiles) of Asturian and Basque still ciders in two maturation stages was conducted. Among the major volatile compounds, amyl alcohols, ethyl lactate and ethyl acetate were quantitatively relevant in all of the ciders studied. The minor fraction mainly consisted of fatty acids, volatile phenols and alcohols. Three PLS-discriminant models with low prediction errors were constructed. When the volatile composition was used, ciders could be differentiated by their maturation stage, 4-ethylcatechol being strongly associated to matured ciders. The olfactometric profiles allowed the classification of ciders according to both their origin and maturation stage. Odorants such as p-cresol and a sweet-character unknown component were correlated to origin of ciders, whereas 1-octen-3-one and one unknown spicy-vegetal odorant were highly correlated to the maturation stage.