Carlos Macku

Analysis of Plant Sterol and Stanol Esters in Cholesterol-Lowering Spreads and Beverages Using High-Performance Liquid Chromatography−Atmospheric Pressure Chemical Ionization−Mass Spectroscopy

Plant sterol and stanol esters were separated on a Luna hexyl-phenyl column using a gradient of acetonitrile (90-100%) in water. The eluted compounds were detected by atmospheric pressure chemical ionization (APCI)-mass spectroscopy (MS) in the positive mode. Sterol and stanol esters produced [M + H - HOOCR](+) ions. Application of the hyphenated technique-LC-MS-allowed differentiation between a number of esters of sitosterol, campesterol, stigmasterol, and (tentatively) avenasterol, as well as sitostanol and campestanol esters. With cholesteryl decanoate used as the internal standard, the method showed good linearity, precision, and reproducibility. The method required minimal sample pretreatment and can be applied to samples with high water content (juices) as well as samples with high oil content (margarine spreads). The method could be useful for the analysis of sterol and stanol esters in fortified food products.

Application of simultaneous purging and solvent extraction technique for flavour monitoring of natural products

Abstract A newly developed simultaneous purging and solvent-extraction apparatus was used to investigate variations of volatiles formed from natural bananas during ripening periods. Five alkylacetates and five alkylbutyrates, which give characteristic flavours to banana, were chosen for flavour monitoring during banana ripening. Their formation increased during the ripening period. After 10 days, ester formation reached a maximum at the onset of the fruits senescence period. Three alkyl alcohols increased steadily in concentration for 5 days and plateaued until the late senescence stages. Fresh celery volatiles were also collected using the same apparatus in order to investigate its possible application for collecting headspace volatiles of fresh vegetables. The compounds isolated and identified in the headspace sample from celery were 14 terpenes and two aromatic compounds.

The effect of glycine in the production of toxic volatile aldehydes from heated corn oil

The fatty aldehydes generated from heated corn oil and from several corn oil/glycine mixtures were collected by a dynamic headspace sampling method and subsequently reacted with cysteamine to yield corresponding thiazolidines. Derivatized aldehydes were analyzed by a capillary gas chromatograph with flame photometric detector. Six fatty aldehydes, including formaldehyde and acetaldehyde, decreased in concentration in relation to increasing amounts of glycine in the oil.

Formation of N-alkylpyrroles in corn oil/amino acid model systems

Abstract Corn oil was heated with alanine, cysteine, glycine, phenylalanine, ammonia, methylamine, or ethylamine at 180°C for 4 h. The volatiles formed in the headspace were collected using a simultaneous purging and solvent extraction apparatus and analyzed by gas chromatography and gas chromatography/mass spectrometry. Fourteen mono- and di-alkylpyrroles were identified in the headspace extracts of the corn oil/amino acid mixtures and the corn oil/amine mixtures. It is proposed that α,β-unsaturated fatty aldehydes reacted with the alkylamine produced from the corresponding pyrolyzed amino acid to form 1-alkylpyrroles.