Bruno Stancher

Studies on the physicochemical properties of inulin and inulin oligomers

Abstract Inulin, Raftiline® ST, Raftilose® P and oligofructose in aqueous solutions were investigated at 2.5, 5, 10, 15, 17.5, 20 and 25 g of solute in 100 g of water by physicochemical measurements in order to obtain molecular weights, reducing activities, apparent specific volumes, isentropic apparent specific compressibilities, and 1 H-NMR pulse relaxation times ( T 1 values). Molecular weights have been found to range from 340 to 4620 g mol −1 . Raftilose® P is the only sample which shows reducing capacity and may be expected to be susceptible to the Maillard reaction. Apparent specific volumes lie within the sweet range 0.60–0.64 cm 3 g −1 and increase with degree of polymerisation (DP); this behaviour describes increasing displacement of water as molecular weight increases. Isentropic apparent specific compressibilities increase as concentration of solute, molecular weight and DP increase, showing reduced solute–water affinity. T 1 values decrease with increasing molecular weight and concentration as a result of increased order of protons and reduced water mobility.

High-performance liquid chromatographic determination of carotene and vitamin A and its geometric isomers in foods : Applications of cheese analysis

Abstract A fractionation of retinol geometric isomers and of carotene was achieved, by straight-phase high-performance liquid chromatography, using a LiChrosorb Si 60 5- μm prepacke column and an isocratic mobile phase of methyl ethyl ketone—hexane (10:90). The wavelengths selected for detection of caroten and retinols were 450 nm and 340 nm respectively, and wre changed during the chromatographic run. Two internal standards were used for quantitative analysis: 2-nitrofluorene for retinols and azobenzene for carotene. The proposed method, which has the advantage that all vitamin A active compounds can be evaluated simultaneously, was applied t the analysis of Italian cheese samples. The percentage recoveries of retinol and carotene were 75.7 and 79.6, respectively, and were not affected by cheese fat content, at least in the explored range.

High-performance liquid chromatography of the unsaponifiable from samples of marine and freshwater fish: fractionation and identification of retinol (vitamin A1) and dehydroretinol (vitamin A2) isomers

Retinol (vitamin A1) and dehydroretinol (vitamin A2) geometric isomers, obtained in photosynthetic mixtures or from natural samples, were simultaneously fractionated by means of isocratic normal phase high-performance liquid chromatography. The use of low percentages of isopropanol (0.4-1.1%) as a modifier in hexane was studied, and the resolution of both pairs of retinols (9-cis/all-trans and 13-cis/11-cis) whose baseline separation had not previously been achieved was obtained. The proposed chromatographic method therefore allows the complete separation of all six of the most commonly occurring retinols in natural samples, including the above four mono cis- retinols plus the two 9,13- and 11,13-di-cis- retinols . Photoisomerization of retinal and of retinol in different solvent systems and during the extraction process was also studied, before analyzing the unsaponifiable from fresh and marine water fish, which constitute rich natural sources of both vitamins A1 and A2. Vitamin A2 was found to be present in different relative percentages depending on the analytical matrix. Four cis isomers (9-cis-, 11-cis-, 13-cis- and 9,13-di-cis-retinol or corresponding dehydroretinols ) were found to occur naturally together with the main all-trans form, confirming the need to separate geometric isomers in every dosage of vitamin A-containing compounds.

Chemical composition and functional characterisation of commercial pumpkin seed oil

BACKGROUND Pumpkin (Cucurbita pepo L.) seed oil is a common product in Slovenia, Hungary and Austria and is considered a preventive agent for various pathologies, particularly prostate diseases. These properties are related to its high content of carotenoids and liposoluble vitamins. In this study the carotenoid (lutein and zeaxanthin), vitamin E (α- and γ-tocopherol) and fatty acid contents of 12 samples of commercial pumpkin seed oil were investigated together with the composition of the volatile fraction resulting from the roasting process. RESULTS The aromatic profile obtained from the commercial samples was directly related to the intensity of the roasting process of the crushed pumpkin seeds. The roasting temperature played a crucial role in the concentrations of volatile substances originating from Strecker degradation, lipid peroxidation and Maillard reaction. CONCLUSION The findings suggest that high-temperature roasting leads to the production of an oil with intense aromatic characteristics, while mild conditions, generally employed to obtain an oil with professed therapeutic characteristics, lead to a product with minor characteristic pumpkin seed oil aroma. The nutraceutical properties of the product are confirmed by the high content of α- and γ-tocopherol and carotenoids.

High-performance liquid chromatography of fat-soluble vitamins : Separation and identification of vitamins D2 and D3 and their isomers in food samples in the presence of vitamin A, Vitamin E and carotene

Vitamins D2 and D3 and their corresponding previtamins and provitamins were resolved by reversed-phase high-performance liquid chromatography using a ternary solvent system (acetonitrile-methanol-water) pumped according to a gradient elution programme. The D vitamins were also resolved in the presence of other lipid-soluble vitamins (A, E and K1) and carotene. The peaks were monitored with a UV-visible variable-wavelength detector and were detected at their maximum absorbance, resulting in maximum sensitivity. Lipid-soluble vitamins and carotene were resolved in extracts obtained from oils and butter, thus permitting their identification in a single chromatographic run.

High-performance liquid chromatography of fat-soluble vitamins. Simultaneous quantitative analysis of vitamins D2, D3 and E. Study of percentage recoveries of vitamins from cod liver oil.

Vitamins D2, D3 and E were resolved and quantified by applying reversed-phase high-performance liquid chromatography to extracts of cod liver oil. The method, using two reversed-phase C18 columns and a ternary mixture of acetonitrile, methanol and water as the eluent resolved all fat-soluble vitamins well, including the pair D2-D3. The extraction procedure was studied; the recoveries, using two different solvents (hexane and diethyl ether) for extractions were 60.6 +/- 1.0 and 77.1 +/- 1.1, 56.9 +/- 1.2 and 74.8 +/- 0.8, and 14.1 +/- 0.7 and 89.8 +/- 1.4% for vitamins D2, D3 and E, respectively.

High-performance liquid chromatography of retinals, retinols (vitamin A1) and their dehydro homologues (vitamin A2): improvements in resolution and spectroscopic characterization of the stereoisomers

A study of mobile phases for the improved high-performance liquid chromatographic resolution of retinal, 3-dehydroretinal, retinol and 3-dehydroretinol stereoisomers is described. By using 1-octanol as a phase modifier in n-hexane, the simultaneous separation of a complex mixture of vitamin A1 and A2 isomers was satisfactorily achieved, while the separation of the corresponding aldehydes required a ternary mixture of 2-propanol, dioxane and n-hexane. All peaks were spectroscopically characterized by recording their UV spectra, which are reported together with comparative tables of the absorbance maxima of the stereoisomers.

Simultaneous high-performance liquid chromatographic analysis of free carotenoids and carotenoid esters.

High-performance liquid chromatography using a non-aqueous reversed phase with gradient elution on C18 columns is a powerful tool for investigating the carotenoid composition of natural samples, e.g., flower petals, and for the simultaneous detection of carotenoids of the widest possible polarity range (xanthophylls, diones, hydrocarbons and carotenoid esters). The comparison of sample extracts submitted or not to saponification allows the presence of carotenoid esters to be revealed through the appearance of the corresponding free hydroxycarotenoids. The gas chromatographic analysis of the fatty acids after alkaline hydrolysis of esters provides further confirmation. In most cases, peaks of various carotenoids were identified by comparison with standards. The wavelengths of the visible absorbance maxima of the chromatographed carotenoids as obtained on-line by the stop-flow method in the eluent system and off-line in carbon disulphide are reported. The esters appear to constitute the main carotenoid fraction in flower petals.

Extraction and determination of polyoxyethylene alkyl ether non-ionic surfactants in water at trace levels

Polyoxyethylene non-ionic surfactants of the type RO(CH2CH2O)text-decoration:overlinenH (where R is an n-alkyl group and text-decoration:overlinen is the number-average degree of polymerisation) are extracted and concentrated from water at trace levels with 1,2-dichloroethane and then determined by a spectrophotometric procedure. Their characteristic polydispersity is checked by gas chromatography.The proposed method, which has been studied in detail on polyoxyethylene dodecyl ethers, is free from interferences from anionic surfactants and the interference of cationic surfactants is also reduced about 15-fold. The determination of non-ionic surfactants in polluted sea waters is considered as a tentative application to a complex matrix.

Determination of polyoxyethylene alkyl ether non-ionic surfactants in waters at trace levels as potassium picrate active substances

Non-ionic surfactants of the type R(OCH2CH2)nOH, where R represents an n-alkyl group and n is the degree of polymerisation, are widely used in house-hold detergent formulations and are found at trace levels (0.01–1 mg l–1) in waters receiving untreated urban liquid sewage. A method based on the extraction of potassium picrate active substances (PPAS) has been investigated in the determination of non-ionics with R = dodecyl by considering both mono- and polydisperse surfactants.The reactivity of monodisperse surfactants (4 ⩽n⩽ 14) as PPAS is explained qualitatively by considering the equilibria involved in the extraction. Commercial polydisperse surfactants with 3.8 ⩽text-decoration:overlinen⩽ 28 (where text-decoration:overlinen is the number-average degree of polymerisation) are also considered and compared with other polydisperse surfactants in which R =p-tert-nonylphenyl. In both surfactant series the proposed method allows the absolute determination of the polydisperse surfactants in the range of text-decoration:overlinen from 13 to at least 28.