Effect of Heat Treatment on Dietary Fiber: Interlaboratory Study

The effects of thermal treatments on the dietary fiber composition of cereal and potato samples were studied at 8 laboratories using different analytical methods. Thermal treatments included extrusion cooking for cereals, and boiling and frying for potatoes. No changes in the amounts of dietary fiber or starch were observed in the extruded samples. Heat-treated potato samples contained significantly more water-insoluble dietary fiber (cellulose) and less starch than did raw potato. However, this may be due, at least in part, to the sample preparation procedure rather than the heat treatment alone. The study indicates that gravimetric and sequential hydrolysis methods give similar results, but the variation in most cases is still wide. Further standardization of methods is evidently needed, especially if legislative measures for setting limits on the fiber content of foods are to be introduced. Standardization of starch analysis should also be of primary importance in future work on carbohydrate methodology. This can be concluded from the variation in results concerning this extremely important food constituent. It should be noted that the sample matrix in the present study was simpler than that of complex meals or diets.

Liquid chromatographic determination of folate monoglutamates in fish, meat, egg, and dairy products consumed in Finland

A liquid chromatographic (LC) method with fluorescence and UV detection was used to determine the folate contents of fish, meat, fish and meat products, chicken, eggs, and milk consumed in Finland. 5-Methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolic acid, and folic acid from 24 commodities obtained from supermarkets, retail stores, and different outlets in the Helsinki area were analyzed. Pooled samples were extracted at pH 6.0 in the presence of antioxidants and deconjugated with hog kidney deconjugase. Very low levels of folates were detected in meat and meat products. Fresh fish, fish sticks, and chicken meat contained reasonable amounts (3-13 micrograms/100 g) of tetrahydrofolate and 5-methyltetrahydrofolate. Egg yolk contained high concentrations of 5-methyltetrahydrofolate (140-150 micrograms/100 g); 10-formylfolic acid was also detected (14-17 micrograms/100 g). Between-species differences in folate monoglutamate distributions were observed. The highest levels of tetrahydrofolate, > 5 micrograms/100 g, were found in chicken meat and fillets of rainbow trout, whitefish, and baltic herring. Tetrahydrofolate was most abundant in fresh fish. LC was well suited for analyzing folate compositions of meat, fish, and other foods of animal origin. Recovery of added folates ranged from 49 to 96%.

Effects of supplementation of fertilizers on human selenium status in Finland

The Se concentration of foods can be increased by supplementing fertilizers with soluble Se compounds. In Finland the availability of soil Se for plants is poor owing to the relatively low Se concentration, low pH and high iron content of the soil. Since 1984 multimineral fertilizers have been supplemented with Se (16 mg kg-1 to fertilizers for grain production and 6 mg kg-1 to those for fodder production) in the form of sodium selenate. Within two years a three-fold increase of mean Se intake was observed. The supplementation affected the Se content of all major food groups with the exception of fish. The concomitant human serum Se concentration increased by 70%. In 1990 the amount of Se that was supplemented was reduced to 6 mg kg-1 for all fertilizers. This reduced the mean Se intake by 30% and the serum Se concentration decreased by 25% from the highest levels observed in 1989. Plants take up part of the supplemented selenate and transform it into organic Se compounds, mainly selenomethionine. This affects human nutrition by increasing the Se content of foods of both animal and vegetable origin. According to data obtained in Finland, supplementation of fertilizers with Se is a safe and effective means of increasing the Se intake of both animals and humans that is feasible in countries with relatively uniform geochemical conditions. This kind of intervention requires careful monitoring of the effects on both animal and human nutrition and the environment.

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.

Carotenoids and retinoids in Finnish foods: dairy products and eggs

As part of an overall composition study of Finnish foods, the carotenoid and retinoid content of 20 dairy product samples and eggs were determined by HPLC. The total beta-carotene (all-trans beta-carotene plus 15-cis beta-carotene) was quantitated for dairy products. For egg and egg yolk, lutein content was also determined. Only traces of lycopene, cryptoxanthin, and alpha-carotene were present. All-trans retinol and 13-cis retinol were the major retinoids in dairy products. Small amounts of 9-cis, 11-cis, and 9,11-cis retinols were found. High values of both retinol and beta-carotene were found in full fat cheeses and whipping cream: from 179.0 (cheese, Edam-type) to 318.7 micrograms/100 g (whipping cream) and from 86.7 (cheese, Edam-type) to 186.5 micrograms/100 g (whipping cream) for all-trans retinol and total beta-carotene, respectively. The retinol content averaged 16.3, 32.6, and 52.2 and that of beta-carotene 9.6, 16.7, and 3.0 micrograms/100 g in milk (1.9% fat), milk (3.9% fat), and human milk, respectively. The major pigment in eggs and egg yolk was lutein, 619.5 micrograms/100 g in eggs and 1575.8 micrograms/100 g in egg yolk. According to this study, at the present level of consumption in Finland, milk, milk products (excluding butter), and eggs result in a daily intake of about 350 retinol equivalents, and consequently, are a major source of vitamin A.

Selenium intake and serum selenium in Finland: effects of soil fertilization with selenium

Since fall 1984 all agricultural multinutrient fertilizers in Finland have been supplemented with sodium selenate in an attempt to improve the nutritional quality of local foodstuffs known to be exceptionally low in selenium. The intervention has been effective from the growing season 1985 and it has affected practically all domestic agricultural products. From 1984 to 1986 the mean Se concentration of different foods increased. The mean Se intake of the population, calculated on the basis of food consumption statistics and from the data of urinary Se excretion, as well as the average serum Se concentration of both urban and rural people increased also during the same period. Enrichment of fertilizers with sodium selenate seems an efficient and predictable way of increasing the Se concentration of foods and the Se intake of people in low-Se areas.

Dietary fibre and fibre fractions in the diet of Finnish diabetic and non-diabetic adolescents

The intakes of total dietary fibre, water-soluble noncellulosic polysaccharides (WSNCP), water-insoluble noncellulosic polysaccharides (WISNCP), cellulose and lignins of 152 diabetic and 74 non-diabetic adolescents were studied. Food consumption data had been collected by means of two 48 h recall interviews. The diabetics obtained more total dietary fibre (33 g vs 18 g) and all fibre fractions than the controls. The fibre density of the diet was higher for the diabetics than for the controls for all meals and snacks. Positive correlations were found between total dietary fibre intake per 1000 kcal and energy-adjusted intakes of total carbohydrate, starch and most vitamins and minerals both in the diabetics and controls. A high concentration of dietary fibre in the diet thus indicated a higher general nutrient density.

Exposure to cadmium from foods, estimated by analysis and calculation--comparison of the methods

Cadmium intake of 40 middle-aged Finnish men was determined both by calculation based on computer files and by analysis of duplicate portions. A significant difference was observed between intake estimates of the two methods. The average calculated cadmium intake was 15.8 micrograms/day compared to the 8.2 micrograms/day obtained by analysis. Factors causing the difference between the methods and affecting the comparability are: (i) expression of concentrations below the detection limit; (ii) the calculation is based on the analysis of foods being only washed and peeled whereas duplicate portions are normally processed; (iii) when duplicate portions are prepared using non-representative lots or brands of food, their cadmium content differs from average values used in calculation; (iv) the level of cadmium content in duplicate portion samples is very low affecting the accuracy of the results. The analytical level of cadmium during the analysis of duplicate portions was somewhat lower as compared to the analysis on which the food composition file and the calculation is based. It seems that the complicating factors identified in the present study potentially affect the reliability and comparability of studies of trace element intakes. Therefore one has to be careful when comparing intake estimates derived independently or by different methods.

Effect of heat treatment of dietary fiber: interlaboratory study

The effects of thermal treatments on the dietary fiber composition of cereal and potato samples were studied at 8 laboratories using different analytical methods. Thermal treatments included extrusion cooking for cereals, and boiling and frying for potatoes. No changes in the amounts of dietary fiber or starch were observed in the extruded samples. Heat-treated potato samples contained significantly more water-insoluble dietary fiber (cellulose) and less starch than did raw potato. However, this may be due, at least in part, to the sample preparation procedure rather than the heat treatment alone. The study indicates that gravimetric and sequential hydrolysis methods give similar results, but the variation in most cases is still wide. Further standardization of methods is evidently needed, especially if legislative measures for setting limits on the fiber content of foods are to be introduced. Standardization of starch analysis should also be of primary importance in future work on carbohydrate methodology. This can be concluded from the variation in results concerning this extremely important food constituent. It should be noted that the sample matrix in the present study was simpler than that of complex meals or diets.