Pertti Varo

Application of an HPLC assay for the determination of folate derivatives in some vegetables, fruits and berries consumed in Finland

Abstract The folate content of 30 commodities of vegetables, fruits and berries, including a few processed products, was determined by high-performance liquid chromatography (HPLC). HPLC was used with a combination with fluorescence and ultraviolet detectors to analyze folate monoglutamate derivatives and their distribution after extraction at pH 6.0 and deconjugation with hog kidney deconjugase at pH 4.9. 5-Methyltetrahydrofolate was the main derivative in all foods studied, but tetrahydrofolate, 5-formyltetrahydrofolate and 10-formylfolic acid were also detected. The sum of the monitored folate derivatives (as μg folic acid) in vegetables ranged from 9 to 114 μg per 100 g and that of berries and fruits from 3 to 36 μg per 100 g. The variation in folate content, which was studied by analyzing raw potato, carrot and cabbage bought from retail shops three times a year, was small. Some of the studied processed vegetable foods were also reasonably good sources of folate. The results obtained with HPLC are rather similar to the previously reported values for vegetables determined by a microbiological method. Several measures for method improvement and quality control of the analysis allowed reliable determination of the main folate forms, particularly 5-methyltetrahydrofolate, in a wide range of plant-derived foods.

Structural characterization of water soluble β-glucan of oat bran

β-glucan was isolated from oat bran in a highly purified form. The bran was characterized for its contents of dietary fiber, β-glucan, fat and protein. The isolated β-glucan was free of protein and contained only glucose in GC sugar analysis. Two types of β-glucan were obtained with different solubilities. Their molar masses were 1.6 million for the less soluble and 1.1 million for the more readily soluble type. No structural differences were found. The two-dimensional correlation NMR spectrum of the isolated β-glucan showed that the glucose units are joined with 1,3- and 1,4-linkages only. The oligosaccharides produced by the action of a specific enzyme, lichenase, were analyzed by HPLC and capillary zone electrophoresis. The major products are 32-β-d-glucosyl cellobiose (trisaccharide) and 33-β-d-glucosyl cellotriose (tetrasaccharide), which account for 95% of the whole. Also, 34-β-d-glucosyl cellotetraose (pentasaccharide) and other oligosaccharides with degree of polymerization (DP) higher than 5 were detected as minor components.

Tocopherols and tocotrienols in Finnish foods: Oils and fats

The tocopherols and tocotrienols of vegetable oils, cod liver oil, margarines, butter and Voimariini dairy spread were analyzed by HPLC. The total tocopherol content varied from 4 (coconut oil) to 242 mg/100 g (wheat germ oil). α-tocopherol equivalents varied from 2 (coconut oil) to 225 mg/100 g (wheat germ oil). Semisoft and soft margarines had an average total tocopherol of 53 and 61 mg, and an average α-tocopherol equivalent of 17 and 27 mg/100 g, respectively. Hard margarines averaged 29 mg total tocopherol and 9 mg α-tocopherol equivalent/100 g. The average tocopherol content of butter and Voimariini was 2 and 15 mg/100 g, respectively, and the average α-tocopherol equivalent 2 and 6 mg/100 g.

Tocopherols and tocotrienols in finnish foods: Fish and fish products

A high performance liquid chromatographic method with fluorescence detection was used to determine the content of tocopherols in Finnish fish species. Samples were obtained from different sea and lake areas. Autumn- and spring-caught fish were analyzed separately.The vitamin E of all species consisted almost entirely of α-tocopherol. Muscle and roe contained relatively high levels of α-tocopherol. High- and medium-fat fish contained 2 mg and low-fat fish 1 mg/100 g on average. In high-fat fish the tocopherol: fat ratio was lower than in low-fat fish.Between-species differences in tocopherol content were observed, as were between-sample differences within the same species. Fish caught in the spring, the spawning season of most species, had a higher tocopherol content (and a lower fat content) than those caught in the autumn. Marine fish had a higher tocopherol (and fat) content than lake fish of the same species.

Effects of Selenium Fertilization on the Selenium Content of Selected Finnish Fruits and Vegetables

Abstract In order to raise the selenium (Se) content of Finnish foods all agricultural and horticultural multinutrient fertilizers have been supplemented with sodium selenate since autumn 1984. This intervention has affected practically all agricultural products in Finland. The Se content of 16 fruits and vegetables was determined by electrothermal atomic absorption spectrophotometry. The selenate supplemented fertilization has clearly increased the Se content of most vegetables, with onion and the cruciferous vegetables (cabbages, broccoli and swede) showing the highest increments; fruits are still low in Se. The mean Se values (mg/kg dry matter) were potato 0.07, carrot 0.07, swede 0.18, white cabbage 0.23, chinese cabbage 0.35, broccoli 0.75, lettuce 0.03, spinach 0.11, rhubarb 0.05, onion 0.25, pea 0.23, tomato 0.03, cucumber 0.13, apple 0.01, strawberry 0.02 and black currant 0.04. The Se levels for a single food type varied considerably, perhaps reflecting differences in fertilization practices. The...

Effects of Natural Chelating Agents on the Solubility of Some Physiologically Important Mineral Elements in Oat Bran and Oat Flakes

ABSTRACT The solubility of mineral elements from oat bran and flake samples was studied by a method using equilibrium dialysis after enzymatic digestion of starch and proteins. The effects of six potential chelating agents common in food were tested on the solubility of mineral elements. The minerals studied were calcium, magnesium, iron, manganese, zinc and potassium, and the chelating agents were citric, lactic, malic, and ascorbic acids, glucose and xylitol. The mineral elements were tightly bound to the dietary fiber of the samples. Bran fiber bound even the zinc and calcium contributed through the enzymes used. Adding citric, malic, or lactic acids increased the solubility of the mineral elements studied, except for potassium which was easily dialyzable as such. Iron was insoluble in all situations. Citric acid was the most efficient chelating agent in solubilizing the mineral elements. The effect of malic and lactic acids on the solubility of minerals was small. No effect was found with glucose, asc...

Nationwide Selenium Supplementation in Finland— Effects on Diet, Blood and Tissue Levels, and Health

Finnish rocks and soils are low in selenium:The concentration range is only 0.03–0. lOmg/kg. As a result, the selenium content of Finnish agricultural soils is low (0.2–0.3 mg/kg). Low temperatures and high humidity characteristic of the climate in Finland together with relatively low pH and high iron content of the soil favor deposition of selenium in reduced forms (1) known to be poorly available to plants. Thus, the geochemical and climatic conditions explain the fact that Finland is a low-selenium area both with regard to the soil and the biosphere.

Stability of tocopherols and tocotrienols in food preparation procedures

Abstract The stability of tocopherols and tocotrienols during stewing or roasting of meat and fish, cooking of porridge, baking of bread and cake, and cooking of jam was studied using a high-performance liquid chromatographic method. Generally, the food preparation procedures had only minor effects on tocopherols and tocotrienols. However, losses of flour tocopherols and tocotrienols can be significant during cooking and baking, especially if degradative reactions have already started in flours or if the preparation time for dough is long. Baking destroyed about 25% of the α-tocopherol and a-tocotrienol in wheat bread and about 12% of the β-tocopherol and β-tocotrienol. Traditional baking methods destroyed nearly 50% of the α-tocopherol in rye bread.

Stability of tocopherols and tocotrienols during storage of foods

Abstract The storage stability of tocopherols and tocotrienols in wheat flour, rye meal, biscuits, and rye bread at room temperature; butter, margarine, and blueberry jam at +5°C; and frozen strawberries at −18°C was studied using a high-performance liquid chromatographic method. Generally, tocopherols and tocotrienols were found to be fairly stable. However, in 12 months, the losses of α-tocopherol and a-tocotrienol in flours were about 80% and those of β-tocopherol and β-tocotrienol, about 60%. In other foods, the differences between the initial and final contents of tocopherols and tocotrienols were small, mostly of the order of analytical variation.

Transport of feed selenium to different tissues of bulls.

The effects of different types of Se supplementation on the selenium concentration of beef, bovine internal organs and some other tissues were studied. The animals (thirty-two bulls) were kept in four dietary groups from birth until to the age of 13-14 months, and fed on rations containing either 0.03 mg Se/kg (basic level in local feeds), 0.25 mg inorganic Se supplemented as sodium selenite, or 0.25 or 0.4 mg/kg plant Se in dry matter from feed produced by spraying with sodium selenite. Samples of four muscles and ten other tissues and organs were taken at slaughter. Se was determined by an electrothermal atomic absorption method. Se supplementation significantly increased the Se concentration of all tissue samples. The maximum response was caused by the diet containing 0.40 mg/kg plant Se. In muscles, this diet raised the Se concentration by a factor of 10-12. In other samples, the increment was 1.5-7.5 fold, depending on the type of tissue. In general, plant Se raised the Se level more effectively than inorganic Se. Se supplementation did not affect the vitamin E status of muscle tissue.