Presence of quercetin-3-O-glucuronoside in Spanish table wines

Quercetin-3-O-glucuronoside has been identified in several Spanish table wines by thin-layer (t.l.c.) and high-performance liquid (h.p.l.c.) chromatographic methods. This is thought to be the first report of its occurrence in wine.     

The saponin content and sapogenol composition of the seed of 13 varieties of legume

The total saponin content of various legume seeds together with their sapogenol composition have been determined. Extraction of the defatted flours was effected with methanol and subsequent acid hydrolysis yielded the soyasapogenols which were analysed using gas and thin-layer chromatography. The saponin levels ranged from 0–0.65% for defatted seed while the major sapogenol present in these saponins was soyasapogenol B. The figures obtained are compared with those previously reported and reasons are suggested for the discrepancies.     

Determination of nitrite and nitrate levels in meat and vegetable products by high performance liquid chromatography

A range of fresh and processed meat and vegetable products was analysed by h.p.l.c. for nitrite and nitrate contents. Satisfactory results were obtained for vegetable products and most meats, but some meat products were subject to matrix interference. Sucrose, sulphate and phosphate did not affect results. Added sodium chloride decreased retention time of nitrite and increased apparent levels of both nitrite and nitrate. Ascorbic and erythorbic acids decreased apparent nitrite levels and correspondingly increased apparent nitrate levels.     

Simultaneous determination of proline and betaines by high performance liquid chromatography

A method is described for the simultaneous determination by reversed-phase h.p.l.c. of proline, glycinebetaine, trigonelline and stachydrine. The mobile phase was water containing 0.02M dibutylamine phosphate at pH 3.0. The compounds were separated in a Dextropak Radial-PAK Cartridge and were detected by a differential refractometer. Total time of elution was 8 min. The method was applied to the analysis of leaves of two tropical grasses and a tropical legume which had been subjected to water stress.     

High performance liquid chromatographic determination of soluble carbohydrates in commercial drinks

High performance liquid chromatography was carried out to determine the soluble sugar content in canned soft drinks and commercial fruit juices stored in different types of containers. The total amount of sugars ranged from 9.2 to 13.5 g 100 ml^?1 for the soft drinks, 10 to 14 g 100 ml^?1 in fruit nectars and 3 g 100 ml^?1 in tomato juice. The individual sugar content of soft drinks varied between different batches, although the total amount remained fairly constant for each kind of drink or juice. Only in tomato juice where sucrose was not present, did the values for glucose and fructose remain constant.     

Wine phenolics—analysis of low molecular weight components by high performance liquid chromatography

Low molecular weight phenolic compounds were separated by high performance liquid chromatography on hydrocarbon-bonded reverse phase packings, with a water-methanol elution gradient. Phenolic compounds were extracted from wine with ethyl acetate. A first extraction at pH 7 enabled isolation of neutral molecules (catechins, procyanidins, flavonols, aromatic alcohols); a second extraction at pH 2 was performed to extract phenolic acids. Successive injections of these two extracts in the chromatograph gave the distribution of the different phenolic compounds in the wine under analysis. Analytical data are given for low molecular weight phenolic compounds present in young red Bordeaux wines from different vine cultivars.     

High-performance liquid chromatographic determination of oligosaccharides in leguminous seeds

A simple and reliable high-performance liquid chromatographic (h.p.l.c.) method has been developed for the determination of sucrose, raffinose and stachyose in leguminous seeds. A LiChrosorb NH₂ column (Merck) and an acetonitrile+water solvent (65:35, by vol) at a flow rate of 1 ml min^?1 were used for the separation. An interference type refractive index detector (Tecator) was used for the detection. With this detector the smallest amount of oligosaccharide detectable was 10 ng. With a traditional deflection type refractive index detector the smallest amount of oligosaccharide detectable was 240 μg. The oligosaccharides were extracted by placing the whole, dry seeds in boiling water for 30 min, blending the seeds and water, placing the whole suspension in a shaking bath at 60°C for 60 min, and removing the solid material by centrifuging. The extract was deproteinated by adding 65 parts of acetonitrile to 35 parts of extract (by vol), placing the mixture at 5°C for 60 min, and filtering off the resulting proteinaceous precipitate before injection into the chromatograph. The entire procedure has been successfully applied to soya beans, chick peas, garden peas and red kidney beans with recoveries of added raffinose in the range 97–102%.     

The distribution and content of anthocyanins in young port wines as determined by high performance liquid chromatography

The distribution and content of anthocyanins in young port wines made in three successive years (1981–1983) from up to sixteen grape cultivars grown at five different sites in the Douro Valley in Northern Portugal has been assessed by high performance liquid chromatography. Distributions are confined to the seven most readily separated and identified anthocyanins and expressed as percentages of their sum (78–97% of the total integrated area). Anthocyanins based on malvidin (Mv) predominated (57–94%). Of these Mv 3-glucoside was the major pigment (43-76%), followed usually by Mv 3-p-coumarylglucoside (1–38%) and then Mv 3-acetylglucoside (2–18%). Peonidin 3-glucoside (2–39%) was prominent in a few cultivars but delphinidin 3-glucoside (1–13%), petunidin 3-glucoside (2–12%) and cyanidin 3-glucoside (trac-4%) were of low proportions throughout. The ratio Mv 3-acetylglucoside/total Mv glucosides appeared characteristic of cultivar, independent of site and a useful aid to identification. The percentages of Mv 3-p-coumarylglucoside were usually lower in ports than in grape skin extracts of the same cultivars. The contents of total anthocyanins in the ports ranged from 143–1080 mg 1^?1 (expressed as malvidin 3-glucoside chloride) and varied according to site and season.     

Tryptophan determination of food proteins by h.p.l.c. after alkaline hydrolysis

The alkaline hydrolysis of proteins prior to tryptophan analysis has been evaluated, and a method for the measurement of tryptophan by reverse phase h.p.l.c. after alkaline hydrolysis has been proposed and compared with published methods. Hydrolysis with either LiOH or NaOH gave similar results. Tryptophan values and the recovery of added 5-methyltryptophan were similar when hydrolysis was made under tap-water vacuum (1500 Pa) or at high vacuum (2 Pa). Partially-hydrolysed starch reduced the losses of tryptophan during hydrolysis better than thiodiglycol. High levels of indolyl-3-propionic acid or 5-methyltryptophan did not further improve tryptophan recovery. 5-Methyltryptophan is the preferred internal standard; its recovery after hydrolysis more closely resembled that of protein-bound tritiated tryptophan from goat casein than did the recoveries of α-methyltryptophan or free ¹⁴C-tryptophan. Under some conditions, the recovery of protein bound tryptophan was lower than the recovery of free tryptophan. The stability of tryptophan in hydrolysates was improved by using a phosphate buffer pH 7.0 containing 0.02% sodium azide.     

Determination of sugars in tropical root crops using 13C N.m.r. spectroscopy: Comparison with the h.p.l.c. method

The ¹³C nuclear magnetic resonance (n.m.r.) spectrum of sugars normally present in foods, viz. glucose, fructose, sucrose, maltose and raffinose contains resonances that are diagnostic of each sugar. The quantity of each sugar is determined by measurement of the ratios of the peak heights of the sugar resonances compared with peak height of an internal standard, present at constant concentration in all solutions. A linear calibration relationship between the peak height ratio and concentration is established for single resonances of glucose and fructose and for two resonances of each of sucrose, maltose and raffinose. Samples of sweet potato and taro flour dried at 40°C, were blended with 80% ethanol, the sugars were extracted and analysed by ¹³C n.m.r. and h.p.l.c. Both methods gave similar results and have similar degrees of reproducibility. The n.m.r. method is useful for quantitation of sugars and identification of other molecules extracted from the food, but requires more material than does h.p.l.c. Drying at 40°C causes a decrease in sucrose content and increases in glucose, fructose and maltose which partly compensate for the loss in sucrose. There is considerable variability of the sugar content between different sweet potato tubers and between different taro corms of the same cultivar as well as across different cultivars. For sweet potato the total sugar content is 0.6-3.6% fresh weight, with considerably more sucrose present than glucose, fructose and maltose. With taro total sugar content is 0.2-0.8% fresh weight. Raffinose is present in one sample only.     

Analysis of sugars and organic acids in ripening mango fruits (Mangifera indica L. var Keitt) by high performance liquid chromatography

The sugars and organic acids present in the pulp of Keitt mangoes at various stages of ripeness were analysed by h.p.l.c. Ripening was associated with a loss in firmness, peel chlorophyll and pulp acidity, with increasing soluble solids and total sugars. The major sugars were identified as glucose, fructose and sucrose. All three increased during ripening; sucrose was found to be in the greatest concentration throughout, with fructose the predominant reducing sugar. Acidity loss was shown by decreasing titratable acidity and increasing pH values. Citric and malic acids were found to be the major organic acids. A large decrease in citric acid and a small reduction in malic acid were responsible for the loss of acidity. Tartaric, ascorbic, oxalic and α-ketoglutaric acids were also shown to be present at low concentrations.     

Measurement of mimosine and its metabolites in biological materials

Recent results in both plant biochemistry and animal metabolism emphasise that, in any research on the nutritional applications of Leucaena leucocephala, measurement of mimosine should be accompanied by measurement of the degradation product 3-hydroxy-4(1H)-pyridone. This may reveal wide differences in the toxic load coming from the feed and in the animal metabolic response to it. The authors suggest that where mimosine analysis can only be performed by the traditional colorimetric method, it should be combined with paper chromatography to estimate ratios of mimosine and 3,4-DHP. However high performance liquid chromatography provides vastly improved methods for simultaneously and precisely analysing both compounds. Published methods are reviewed and a new ion exchange method is described which has been used for the rapid routine analysis of a large number of samples. The chromatographic properties and separation of 2,3-dihydroxypyridine, a recently discovered metabolite, and of 3-glucuronyl-4(1H)pyridone from the above compounds are also reported.     

The distribution of anthocyanins in grape skin extracts of port wine cultivars as determined by high performance liquid chromatography

The distribution of anthocyanins in methanolic skin extracts of 16 grape cultivars used for port wine production and grown at five sites in the Douro Valley in Northern Portugal has been assessed by high performance liquid chromatography. Results are confined to the seven most readily separated and identified anthocyanins and are expressed as percentages of their total (88–99% of the total integrated area). Anthocyanins based on malvidin (Mv) predominated. Of these, Mv 3-glucoside was the major pigment (33–60%), being exceeded by Mv 3-p-coumarylglucoside (2–51%) in only two cultivars; Mv 3-acetylglucoside (1–15%) was consistently the lowest. Peonidin 3-glucoside (1–27%) was prominent in four cultivars, but delphinidin 3-glucoside (1–11%), petunidin 3-glucoside (2–11%) and cyanidin 3-glucoside (trace-6%) were of low proportions throughout. The ratio Mv 3-acetylglucoside/total Mv glucosides appeared characteristic of cultivar, independent of site, and a useful aid to identification of grape cultivars. The coloured pulp of some cultivars contained peonidin 3-glucoside as a major component, present in greater proportions than in the skin; the percentage of Mv 3-p-coumarylglucoside was lower in pulp than in skin. The identities of six of the seven anthocyanins were confirmed by fast atom bombardment mass spectrometry and the structures of the Mv derivatives were determined by nuclear magnetic resonance. The formation of formyl and acetyl anthocyanin artefacts is described.     

Determination of volatile carboxylic acids (C1–C5i) and lactic acid in aqueous acid extracts of silage by high performance liquid chromatography

A simple isocratic h.p.l.c. technique was developed for the simultaneous quantitative analysis of lactic, formic, acetic, propionic, isobutyric, n-butyric and isovaleric acids in aqueous acid extracts of silage. An Aminex HPX-87H strong cation exchange resin column at 41°C, 0.0025M H₂SO₄ mobile phase and ultraviolet detector at 210 nm were utilised. Estimated recoveries of acids added to silage ranged from 98.2 to 103.5%.     

Saponin content of soya and some commercial soya products by means of high-performance liquid chromatography of the sapogenins

Quantitative high-performance liquid chromatography of the sapogenins was used to estimate the saponin content of soya beans (Glycine max (L.) Merr.) and commercially prepared soya flours, protein concentrate, protein isolate and soya milks. The level of saponin in whole soya beans as estimated (0.47%) was in agreement with other recent estimates. Saponins were also found in the various soya flours (0.43–0.67%), protein isolate (0.76%), soya milks (0.022–0.026%) but not in the protein concentrate.     

Factors affecting n-nitrosodimethylamine development in germinated barley

Study of germinated (malting) barley showed that there was no direct correlation between hordenine levels and the development of N-nitrosodimethylamine (NDMA) during kilning. Results also indicated that the repression of NDMA formation by sulphur dioxide was more likely to be linked to a chemical reaction with the nitrosating species and changes in oxygen activity rather than to a simple pH effect. Tyrosinase reduced hordenine levels in vitro. After nitrosation, the tyrosinase-hordenine digest produced more NDMA than equivalent digests of inactivated tyrosinase and hordenine. This effect of tyrosinase was enhanced by catechol and reduced by sodium metabisulphite. Preliminary studies indicated that both embryo and endosperm food reserves are utilised for hordenine production by the embryo. Further investigations with excised barley embryos suggested that while L-tyrosine treatment increased hordenine production, L-methionine treatment increased the potential of the embryos to form NDMA.     

Directed interesterification of a brazilian palm oil and analysis of the original and interesterified oil and its fractions

A commercial sample of the Brazilian palm oil from the north eastern State of Bahia after neutralisation, washing and drying was interesterified in the presence of sodium-potassium alloy (NaK) at 30°C in a nitrogen atmosphere. The catalyst was destroyed by addition of water in a carbon dioxide atmosphere and the interesterified oil was crystallised from light petroleum, yielding an olein and stearin fraction. The fatty acid and triacylglycerol composition of the neutralised oil was determined by gas chromatography (g.c.) and high-performance liquid chromatography (h.p.l.c.) respectively and was shown to be similar to that of Malaysian and African palm oil. The compositions of the interesterified Brazilian oil and its liquid and solid fractions were also determined. The physicochemical characteristics of the olein obtained by interesterification with NaK, such as iodine value (96.8) and its softening point (below ?8°C) indicated its suitability for the use as salad oil.     

The analysis of amino acids in fruit juices by high-performance liquid chromatography

A method is described for the rapid determination of amino acids in liquid foods by high-performance liquid chromatography (h.p.l.c.). The method has proved itself simple and reliable in use and is intended to provide amino acid profiles within 30–40 min of receipt of sample. Method assessment is discussed and the results obtained on typical processed foods are presented.     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.