J. López-Hernández

High-performance liquid chromatographic determination of α-tocopherol in macroalgae

Abstract A high-performance liquid chromatographic (HPLC) method for the microscale determination of α-tocopherol in macroalgae is reported. The method includes microscale saponification and extraction with n -hexane. The presence of α-tocopherol in macroalgae samples was confirmed by HPLC–MS. α-Tocopherol levels as determined in samples by HPLC with UV and fluorescence detection did not differ significantly; however, fluorescence detection has a higher sensitivity (detection limit 10.4 ng/ml, vs. 104 ng/ml with UV detection), as well as good precision (relative standard deviation 1.81%) and recovery (94.3%). Fluorescence detection is also faster. We used this method to determine the α-tocopherol contents of four commercial macroalgae products from northwest Spain as part of nutritional studies in dehydrated Himanthalia elongata and Laminaria ochroleuca , and also in canned Himanthalia elongata and Saccorhiza polychides.

Protein, amino acid and fatty acid contents in raw and canned sea urchin (Paracentrotus lividus) harvested in Galicia (NW Spain)

Moisture, protein, amino acid and fatty acid contents of raw and canned sea urchin (Paracentrotus lividus) gonads were determined. Sea urchin showed a high moisture content (73%) and a high level of proteins (56% dry matter). The canning process, evaluated at 112 °C for 50 min, did not lead to significant changes in protein, amino acid and fatty acid contents relative to the raw sample. © 2000 Society of Chemical Industry

Monitoring of the vitamin C content of frozen green beans and Padrón peppers by HPLC

Abstract: HPLC (using a C18 column, water at pH 2E2 as mobile phase, and UVdetection) was used to monitor the vitamin C content of deep-frozen ([22iC)green beans and Padro“ n peppers over 12 months. Unblanched beans andpeppers lost P97% of their vitamin C within 1 month of freezing, whether or notthey were contained in bags sealed under vacuum. Blanching reduced the beansIvitamin C content by 28%, but limited further decreases to between 3 (vacuumsealed) and 10% (no vacuum) in 12 months. These results conÐrm the utility ofblanching in the preservation of vegetables by deep-freezing. 1998 SCI.(J Sci Food Agric 76, 477E480 (1998)Key words: deep-freezing; HPLC; ascorbic acid; green beans; peppers INTRODUCTIONHumans are among the few mammals incapable of bio-synthesis of ascorbic acid, or vitamin C. The amount ofthis vitamin in foodstu†s should therefore be carefullymonitored with a view to avoiding deÐciency, which inextreme cases causes scurvy and, moreover, leads toreduced resistance to infection (Anderson et al 1987).Vitamin C is almost exclusively found in fruit andvegetables although the amount present varies amongvarieties (Morrison 1975) according to factors such asthe stage of development and size of the produce(Selman and Rolfe 1982), and the time between harvest-ing and processing (Kozar et al 1988). This variation isreNected in the diversity of vitamin C content reportedin the literature for fresh produce.The seasonality and high perishability of fruit andvegetables provides opportunity to apply preservation

Composition of babaco, feijoa, passionfruit and tamarillo produced in Galicia (North-west Spain)

Basic compositional data are evaluated for the subtropical fruits (babaco, feijoa, passionfruit, and tamarillo) growing in Galicia (North-west Spain)

The effects of various culinary treatments on the pigment content of green beans (Phaseolus vulgaris, L.)

The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on the chlorophyll a and b, all-trans-lutein, phaeophytin a and b and all-trans-β-carotene (provitamin A) contents of green beans (Phaseolus vulgaris, L.) were evaluated. The pigments in the fresh and treated beans were determined by gradient elution reverse-phase HPLC with UV detection. Boiling the beans in a covered pot, pressure cooking or microwaving them caused smaller losses of pigments than steamed cooking. Since pressure cooking also generally leads to smaller losses of nutritious components (e.g. vitamin C), it is recommended over the traditional method of boiling beans in a covered pot.

Chemical composition of Padrón peppers (Capsicum annuum L.) grown in Galicia (N.W. Spain)

The water, neutral-detergent fibre, D-glucose, D-fructose, sucrose, vitamin C, organic acid, starch, pectin and major pigment contents of Capsicum annuum L. var. Longum grown in Galicia (N.W. Spain) are determined. After water, insoluble fibre was the most abundant component of these peppers (NDF 2.2 g/100 g of fresh fruit). Their vitamin C content was rather low (24 mg/100 g).

Evaluation of the performance of a multiresidue gas chromatographic method for the determination of aliphatic hydrocarbons in mussels of Galicia (N.W. Spain)

Abstract The determination of aliphatic hydrocarbons in blue mussel ( Mytilus galloprovincialis ) was performed using a multiple component extraction method and temperature-programmed capillary GC using splitless injection mode and flame ionization detection. Calculated recoveries for the overall procedure to give concentrations of the different aliphatic hydrocarbons in the low level end ( ca 10 μg/ml) of the calibration range (2–200 μg/ml) ranged from 70 to 92% [coefficients of variation (CVs) 9–20%]. Limits of detection for the overall procedure were between 40 and 60 ng/g of sample (extraction concentration factor 25 g/ml) and GC-FID determination precision was good (CVs 1–4%). Aliphatic hydrocarbon levels in mussels in Galicia were similar to those found in areas generally considered unpolluted.

Separation of phospholipid classes in sea urchin, paracentrotus lividus by high-performance liquid chromatography.

A simple high-performance liquid chromatography (HPLC) method for determination of major phospholipid classes in sea urchin Paracentrotus lividus is described. The separation was performed on a Tracer Extrasil SI 5 microm 25 x 0.4 cm column and an isocratic mobile phase of acetonitrile-methanol 85%-phosphoric acid (50:50:1.8, v/v). The HPLC method utilizes UV detection at 205 nm. Five phospholipids were identified and quantified: phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM). Fresh and canned samples were analyzed. Students t-test showed no significant difference (P < or = 0.05) between the mean phospholipid contents of raw and canned sea urchin.

Effect of the refining process on Moringa oleifera seed oil quality

We evaluated the physicochemical properties and oxidative stability of the oil extracted from the seeds of Moringa oleifera during its refining process. Refining is accomplished in three stages: neutralization, degumming, and bleaching. Four samples were analyzed, corresponding to each step of the processed and crude oil. Increases in the density, viscosity, saponification value and oxidation of the oil were detected during the refining, while the peroxide value and carotenoid content diminished. Moreover, the refractive index and iodine content were stable throughout the refining. Nine fatty acids were detected in all four samples, and there were no significant differences in their composition. Oleic acid was found in the largest amount, followed by palmitic acid and behenic acid. The crude, neutralized, and degummed oils showed high primary oxidation stability, while the bleached oil had a low incidence of secondary oxidation.

HPLC analysis of organic acids using a novel stationary phase.

In the present work, a high performance liquid chromatographic method with UV detection for the separation of six organic acids including, tartaric, malic, acetic, lactic, citric and succinic is described. The separation was performed on a novel stationary phase TEKNOKROMA, Tr-010065 Mediterranea sea(18) (15 cm x 0.4 cm, i.d. 3 microm) and using water with a 0.1% (v/v) of formic acid as mobile phase. The advantages of this packing over a conventional octadecylsilane (ODS2) column are reported. The method was validated with respect to linearity, limits of detection and repeatabilities within day and between days and satisfactory results were obtained. The proposed method was applied for the determination of these compounds in commercially available white wines. The samples were injected directly without previous treatment. LC-MS was used as a confirmatory technique.