Bioaccessibility of Ca, Mg, Mn and Cu from whole grain tea-biscuits: Impact of proteins, phytic acid and polyphenols.

Levels of some essential minerals (Ca, Mg, Cu and Mn) were determined in ten different types of experimentally prepared hard biscuits. In relation to the wheat flour-based reference sample, other investigated samples were enriched with different ratios of integral raw materials of different origin or various dietary fibers in view of improving their functionality and nutritive quality. The goal of the research was to evaluate enriched biscuits as additional sources of calcium, magnesium, copper and manganese in nutrition and to investigate if the modifications of wheat flour based biscuit composition significantly change the amounts of total and bioaccessible minerals in the final product. Since our results indicated significant changes of mineral bioaccessibility among the samples, obtained results were correlated to the content of proteins, phytic acid and polyphenols for the sake of assessing their impact as limiting factors of mineral bioaccessibility in these types of foods.

Optimisation of an extraction procedure and chemical characterisation of Croatian propolis tinctures.

Three spectrophotometric methods for the quantitative determination of different flavonoid groups and total phenolics in Croatian propolis samples were optimised and validated. The assay based on the formation of aluminium chloride complex (with galangin as a standard) was applied to the quantification of flavones and flavonols, while the 2,4-dinitrophenylhydrazine method (with pinocembrine as a reference) was used for the quantification of flavanones. Total phenolic content was measured by the Folin-Ciocalteau method using reference solution of caffeic acid:galangin:pinocembrine (1:1:1). Through analytical validation, the most suitable extraction conditions (with respect to time, temperature and concentration of extraction solvent) were determined, and final conditions for the extraction were established (80% ethanol, 1 h at the room temperature). The appropriate ratio between the mass of raw propolis and the extraction solvent volume was also established. By the application of the optimised method of extraction, 10 propolis tinctures were prepared and subjected to the analysis of general pharmacopoeial parameters, which are fundamental for the creation of quality specification (relative density, dry residue of extract, content of ethanol, methanol and 2-propanol). Additionally, the content of waxes as the main inactive constituents was determined in order to observe the level of their migration from crude propolis to the prepared tinctures.

Nitrate and nitrite in vegetables from areas affected by war-time operations in Croatia.

To evaluate nitrate and nitrite contents in cabbage and potatoes, the most consumed vegetables in Croatia, and to examine if war-time operations in Croatia affected nitrate and nitrite levels in vegetables, potatoes and cabbage cultivated in the war region (East Slavonia) and out of war regions were analyzed. Data showed that nitrate contents were higher in the samples from the war region (32% and 24% in potatoes and cabbage, respectively) but differences were not statistically significant. The nitrate levels found in potato samples (196 mg NaNO3/kg fresh weight (FW) and cabbage samples (911 mg NaNO3/kg FW) were comparable with levels reported for other countries. The nitrite contents in potatoes (321 micrograms NaNO2/kg FW) and cabbage (173 micrograms NaNO2/kg FW) were lower than the contents reported for most other countries. Further examinations of nitrate and nitrite concentrations in vegetables in Croatia as well as examinations of the influence of war-time operations on accumulation of these toxic contaminants are necessary.

Trichloroethene and tetrachloroethene in ground waters of Zagreb, Croatia.

At the end of 1986 the presence of chlorinated hydrocarbons was detected in the ground water of the industrial area of Zagreb, Croatia. Concentrations of trichloroethene and tetrachloroethene were close to or exceeded maximum admissible concentrations prescribed by the Public Health Regulations for drinking water (30 micrograms/l for trichloroethene and 10 micrograms/l for tetrachloroethene). The pumping-site situated within the area had been temporarily closed until a water-treatment plant based upon adsorption on activated carbon was built. Analysis of the results of adsorption of the investigated chlorinated hydrocarbons on activated carbon in granules confirmed a remarkably better adsorption of tetrachloroethene compared to trichloroethene. By constant monitoring and replacing of saturated carbon at the appropriate time, the concentrations of trichloroethene and tetrachloroethene in drinking water consumed by approx. 20% of the city population never exceeded maximum admissible concentrations in the course of 10 years.

Spectrofluorometric method for determination of the total mercury content in natural waters.

A simple and highly selective spectrofluorometric method for the determination of the total mercury (Hg) in natural waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, has been made the basis of this sensitive method. Organic and inorganic Hg compounds in water samples were decomposed with sulphuric acid and potassium permanganate. Precipitated manganese dioxide and excess oxidants (permanganate) were destroyed with hydroxylammonium chloride. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. This method is suitable for the determination of total Hg in drinking and surface waters. The method gives reliable results down to a concentration of 0.5 micrograms Hg per litre of water. The water samples analysed by this method gave a mean recovery and standard error of 97.3 +/- 2.39 for added Hg.

Effect of frozen storage on the degree of vitamin B6 degradation in different foods.

Investigation of the effect of freezing and storage at -18 degrees C for 5 months on the stability of total vitamin B6 in foods of different origin leads to the conclusion that the decrease in vitamin B6 content ranged from 18.92% to 60.26% and that the loss is significantly greater in food of animal origin (an average of 55.0%). Obviously, biostructure, that is chemical composition, is one of the basic factors affecting the degradation degree of vitamin B6 in foods preserved by freezing. However, in relation of their biological value and with reference to the declaration allowing deep-frozen vegetables to be stored for 12-24 months, some foods of vegetable origin preserved by freezing exhibit a relatively high loss of biological value in terms of vitamin B6 as early as after 5 months of storage.

Modified lumiflavin procedure for determination of riboflavin in soybean.

Investigation of the application of different methods for riboflavin determination proved the lumiflavin method recommended by Hausheer et al. to be the most suitable one for determining riboflavin in materials of complex composition, such as soybean. However, due to inadequate preparation of the blank sample, the method is burdened by a positive error. By modifying the blank sample and certain modifications in the procedure, more precise results, greater speed and simplification of the method were achieved. The soybean sample analysed by this modified procedure gave a mean recovery and standard error of 102.9 +/- 2.1 for added riboflavin, which is very satisfactory.

An improved simple procedure for the determination of thiamine in food.

A modified fluorometric method for the determination of thiamine in food is described. The procedure is simple, reproducible, does not demand costly outfit and chemicals and is not susceptible to interference. The recovery of added thiamine is good.