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The paper presents a study on physicochemical and structure changes of waxy corn and tapioca starches after hydrothermal modification. It was found that with an increase of the degree of inhibition (low

The aim of the study was to analyse the influence of the type of osmotic substance (sucrose, glucose, xylitol, trehalose, and sorbitol) on the physicochemical properties of freeze-dried fruit (pear and pineapple). Controlling the functional properties of freeze-dried fruit after osmotic dehydration with aqueous solutions at water activity of aw=0.90 is presented. Decrease in the water adsorption index (WAI) was recorded for all dehydrated samples. The largest decrease (for pears and pineapples by 25 and 65%, respectively) was observed in osmoactive solutions containing trehalose. Considerable increase in the FAI was recorded in samples of dehydrated pineapple. In osmoactive trehalose solutions that increase hardly reached 46%, whereas in sorbitol and xylitol its value elevated to 39% and 13%, respectively. Regardless of the osmoactive sweetener applied prior to freeze-drying, an increase in specific surface area (SBET) of dried materials was observed. For dehydrated pears, SBET ranged from 96 to 697 m² g⁻¹, and for pineapple, from 115 to 938 m² g⁻¹. Osmotic dehydration before lyophilisation of fruit samples weakened rehydration relative to the control. The dehydration carried out with osmoactive sweeteners, that is, sorbitol, xylitol, and trehalose, allows obtaining a product with good functional properties that can be successfully used for supplementation of dietary products, in particular for diabetics.

The objective of the study was to demonstrate the applicability of differential pulse polarography (DPP) technique of the ascorbic acid (AA) assay for the analysis of food samples with various matrices. The following validation parameters were determined: selectivity, linearity, precision, accuracy, limit of detection, and limit of quantification. The limits of detection and quantification were 0.17 and 0.5 mg ascorbic acid per 100 g food, respectively. The average recovery of added ascorbic acid from all matrices was 96.3–103.6%. The values of the coefficient of variation calculated on the basis of AA contents for food matrices were in the range 2–9.26% and Horrat values were 0.37–1.10. Ascorbic acid values of the samples obtained from the polarographic method were compared with those obtained from high-performance liquid chromatography with diode-array detection (HPLC-DAD) used as the reference method. The analytical parameters determined showed that the polarographic method was equivalent to the chromatographic method. Validation of the polarographic method of ascorbic acid assay indicates that it can be applied for the analysis of ascorbic acid concentration in food products that do not contain isoascorbic acid. This means that the method can be recommended for routine determinations.

The paper presents a study on structure changes of waxy corn starches after physicochemical modification. The hydrothermal treatment (physical modifications) allowed to obtain pre-gelatinised starch (Merigel) or untreated starch of cook-up type (Resistamyl). Different degrees of cross-linking (low, medium and high) and medium level of substitution were the results of chemical modification of starch. The changes in the structure of modified starch were analysed with the use of the methods of low temperature nitrogen adsorption/desorption and of water vapour sorption. The BET equation was used to determine monolayer capacity (am) from isotherms of water vapour desorption, while the BJH equation was used to determine the surface area (SBJH), volume (VBJH) and mean diameter of pores (DBJH). Starches of the pre-gelatinisation type were characterised by SBETN2 values in the range of 0.18–0.45 m2/g, and starches of the cook-up type - 0.13–0.66 m2/g. Higher values of SBJH were noted for the cook-up starches (SBJH: 0.23–0.60 m2/g) in reference to the starches of the pre-gelatinisation type (SBJH: 0.12–0.32 m2/g). The medium degree of cross-linking of pre-gelatinisation type starches caused a lowering of the value of their monolayer capacity (am ads, am des), while for the cook-up type starches an increase of that value was observed, determined with adsorption and desorption water vapour isotherms. Porosity of the modified starch was determined with the use of mercury porosimetry. A decrease of porosity was noted for starch of the cook-up type (porosity 38.3–52.3%), compared to native waxy corn starch (59.3%). Starches of the pre-gelatinisation type (Merigel) were characterised by an increase of the value in question with increase in the degree of cross-linking: low ML (53.5%)

The obtained results demonstrated an influence of PEF on increase in accumulation of various ions in S. cerevisiae cells. Optimization of particular PEF parameters and ions concentrations in the medium caused twofold increase in accumulation of magnesium and zinc ions and 3.5-fold higher accumulation of calcium ions in the cells. In the case of ion couple, accumulation of magnesium and zinc was, respectively, 1.5-fold and twofold higher in comparison to the control cultures. Yeast cells biomass enriched with Mg(2+), Zn(2+), Ca(2+) as well as Mg(2+) and Zn(2+) (simultaneously) may be an alternative for pharmacological supplementation applied in deficiency of these cations.

Potato starch was modified with γ-rays applying doses of 5, 10, 20 and 30 kGy. The effect of irradiation on starch structure was assessed on the basis of blue value (BV), A680/A545 ratio, apparent amylose content and λmax. The results showed that modification of starch led to the reduction of all parameters connected with the starch-iodine complex. The main effects of γ-irradiation on starch granules revealed by scanning and transmission electron microscopies were cracks on the surface. Low-temperature nitrogen adsorption data showed that modification with γ-rays increased specific surface area and volume of mesopores and decreased their average diameter. DSC data indicated decreased crystallinity of starch and facilitated retrogradation taking place after irradiation in the 20% starch gels. Treatment with γ-rays influenced also functional properties of potato starch increasing water absorption, least gelling concentration, solubility, paste clarity and susceptibility to α-amylolysis, and decreasing fat absorption and viscosity.

The objective of the study was the estimation of the ultrasound-assisted preliminary maceration effect on the efficiency of essential oil distillation and on its qualitative and quantitative composition. The experiment included analyses on three herbal materials, i.e. peppermint leaves (Mentha piperita L.), marjoram herb (Origanum majorana L.), and chamomile flowers (Chamomilla recutita (L.) Rauschert). The study showed that the application of preliminary water maceration of raw material, augmented with ultrasounds, had a statistically significant increasing effect on the amount of oil distilled, in the case of mint leaf from 1.32% to 1.46% v/w, and in the case of marjoram herb from 1.13% to 1.27% v/w. In the case of chamomile flowers no significant effect of ultrasound on the amount of oil obtained was observed. Generally, comparing the composition of essential oils obtained in the experiments with the requirements of the relevant standards no unfavourable effect of the distillation augmenting techniques applied was noted. Therefore, it should be expected that the studied distillates of volatile fractions will have the desired biological activity.

d. The aim of the study was to evaluate the fat binding and physicochemical properties of the products under conditions of potato starch extrusion containing rapeseed or linseed oil and rapeseed oil with glycerol.The study dealt with the extrudates of potato starch produced with the addition of rape seed or linseed oil and rapeseed oil and glycerol at 22% humidity. The extrudates were obtained at two screw speeds: 80 rpm and 100 rpm. Extrudates containing rapeseed oil and glycerol (R6G) were obtained at a temperature distribution of 115/130/150deg;C, while those with the participation of rapeseed oil and linseed oil were obtained at 120/135/128deg;C. Water solubility index (WSI), water absorption index (WAI), specific surface area (SBET) and quantity of fat permanently bound were determined for the products obtained.When oils were added, the solubility of extrudates decreased as compared to the control samples (starch without oil; S). Rapeseed oil added to the starch mixture at the levels of 3 g and 6 g in had no sig- nificant effect on the solubility of the product and amounted to: 80.3ndash;82.6% and 78ndash;79.6%. The largest decrease in solubility (WSI, 55.4ndash;57.1%) was demonstrated for samples with 6% addition of rapeseed oil and 10 g glycerol. For these samples (R6G), a significant increase in the index WAI (376ndash;397%) was recorded. Extrudates obtained with the addition of 3 g of rapeseed oil absorbed slightly more water than those with 6 g of oil added. The specific surface area (SBET 230ndash;256 m2/g) determined from the water vapor adsorption isotherm indicates no statistically significant difference atalpha; = 0.05 for products with rapeseed oil, linseed oil, and controls. A significant increase in the specific surface area (SBET 284ndash;347 m2/g) was observed for samples with 6g rapeseed oil and 10 g glycerol added. For samples with 3 g of rapeseed oil, the amount of bound fat was 1.9ndash;2.1 g/100 g of starch and for 6% the starch percentage was 2.96ndash;3.5 g/100 g.The water solubility of starch extrudates with the addition of oils decreases with an increasenbsp;nbsp; in screw speed. Starch extrudates with linseed oil and rapeseed oil plus added glycerol are characterized by an increase in water-absorption capacity with respect to the control extrudates. The products obtained with the addition of rapeseed oil and glycerol exhibit a significant increase in their specific surface area. The quan- tity of fat permanently bound during extrusion depended on: the oil type, its percentage in the mixture and the screw speed. The linseed oil was the least absorbed in the starch structure, but rapeseed oil binding increased with the increase in its level in the mixture.

The objective of the study was to develop a new method for the determination of total vitamin C and dehydroascorbic acid contents in food using the differential pulse polarography technique, and to compare achieved results to those obtained with the proposed reference method applying HPLC with spectrophotometric detection. Dithiothreitol was used to reduce dehydroascorbic acid into l -ascorbic acid. Interference due to the presence of dithiothreitol during polarographic determination of l -ascorbic acid was efficiently eliminated by clarification of the sample solution with Carrez reagent. Validation of the polarographic method indicates its usefulness for the analysis of foods products that do not contain isoascorbic acid. The coefficient of variation for the analysis of l -ascorbic acid and total vitamin C content ranges from 1.86% to 6.98%, Horrat values from 0.41 to 0.89 and average recovery of l -ascorbic acid ranges from 98% to 104%. Results obtained using the developed method are characterised by high compatibility with those obtained with the HPLC reference method, indicating equivalence of both methods, and in conclusion, the method was deemed fit for purpose for measuring total vitamin C and dehydroascorbic acid in foods.

Extrudates of potato starch with selected proteins (concentrate of soybean proteins, whey proteins and acidic casein) were produced at 22% raw material moisture, and at various process temperatures and extruder screw speeds. Increase of screw speed and temperature had a significant effect on changes in the specific surface area and porosity of products which were tested with the use of low-temperature sorption of nitrogen. The nitrogen adsorption isotherms plotted are of types II and III according to IUPAC, both for the raw material and for the product. Equation BJH was used to determine the surface area (S BJH ), volume (V BJH ) and average pore diameter (D BJH ). For diameters from 35 A to 74 A, the calculated pore volumes assumed values within the range of 23·10 −5 cm 3 /g −55·10 −5 cm 3 /g. Curves of pore size distribution based on average pore diameter within the range of 19.7–23.2 A indicate a large cumulative volume of pores. Extrusion caused a decrease in the specific surface area of the product, from 0.19 m 2 /g to 0.32 m 2 /g. A high correlation was noted between increase in porosity and expansion, and the optimum screw speed and temperature profile.

Potato, wheat, corn and rice starch granules were suspended in water or ethanol and sonicated at frequency of 20 KHz and power 170 W for 30 min. The effect of ultrasonic treatment on starch structure was assessed on the basis of blue value (BV), A680/A545 ratio and λmax determinations. The results showed that modification of starches in both solvents led to the reduction of all parameters connected with the starch–iodine complex. However, depolymerization of starch was higher when it was sonicated in water than in ethanol (e.g. BVs for potato starch: native and sonicated in water and ethanol were equal, respectively, 0.306, 0.275, and 0.279). Starch granules were also observed under scanning and transmission electron microscopes. The main effects of ultrasonic action were cracks and depressions on the surface of granules, which were especially well seen in the case of potato and wheat starches. Ultrasonic treatment, especially in water, influenced functional properties of starch causing an increase of fat and water absorption, least gelling concentration (except potato starch), solubility and swelling power, and a decrease of starch paste viscosity. Effect of ultrasounds on clarity of pastes was rather small, except potato starch for which its value increased from 70.3 to 82.5% after sonication in water.

The cultures of Saccharomyces cerevisiae were treated with pulsed electric fields (PEF) in order to obtain a maximum accumulation of selenium and zinc ions (simultaneously) in the biomass. The following concentrations: 100μgSe/ml and 150μgZn/ml medium were assumed to be optimal for the maximum accumulation of these ions, that is 43.07mg/gd.m. for selenium and 14.48mg/gd.m. for zinc, in the cultures treated with PEF. At optimal PEF parameters: electric field strength of 3kV/cm and pulse width of 10μs after the treatment of 20-h culture for 10min, the maximum accumulation of both ions in the yeast cells was observed. Application of PEF caused the increase of ions accumulation by 65% for selenium and 100% for zinc. Optimization of PEF parameters led to the further rise in the both ions accumulation resulting in over 2-fold and 2.5-fold higher concentration of selenium and zinc.

Cultures of Saccharomyces cerevisiae were treated with pulsed electric fields to improve accumulation of zinc in the biomass. Under optimized conditions, that is, on 15 min exposure of the 20 h grown culture to PEFs of 1500 V and 10 microns pulse width, accumulation of zinc in the yeast biomass reached a maximum of 15.57 mg/g d.m. Under optimum zinc concentration (100 microgram/ml nutrient medium), its accumulation in the cells was higher by 63% in comparison with the control (without PEFs). That accumulation significantly correlated against zinc concentration in the medium. Neither multiple exposure of the cultures to PEFs nor intermittent supplementation of the cultures with zinc increased the zinc accumulation. The intermittent supplementation of the cultures with zinc and multiple exposures on PEFs could even reduce the accumulation efficiency, respectively, by 57% and 47%.

Low-temperature nitrogen adsorption and SAXS were used to analyze the granule surface of wheat and rice starches before and after an action of Bacillus subtilis α-amylase. Results obtained by the first method showed that α-amylolysis caused surface changes arising of new pores or enlarging diameters of pores already existing. According to the SAXS results, the action of enzymes caused complete sharpening of a solid skeletal boundary in the case of wheat starch granules. Partial sharpening of this boundary in the case of rice starch granules could be attributed to the relatively high content of proteins in rice starch.

Cultures of Saccharomyces cerevisiae were treated with PEF to improve accumulation of magnesium in the biomass. Under optimized conditions, that is, on 15-min exposure of the 20-h grown culture to PEF of the 2,000 V and 20-μs pulse width, accumulation of magnesium in the yeast biomass reached maximum 3.98 mg/g dm. It constituted 40% of the total magnesium in the medium. That accumulation significantly correlated against magnesium concentration in the medium. Neither multiple exposure of the cultures to PEF nor intermittent supplementation of the cultures with magnesium increased the magnesium accumulation. The intermittent supplementation of the cultures with magnesium could even reduce the accumulation efficiency by 30%.

Low-temperature nitrogen adsorption and mercury porosimetry were applied for analyzing effect of a-amylolysis upon the porosity of granules of native corn, wheat, rice, and potato starches. Specific surface area (SBET), porosity, pore size distribution, total pore area, and mean pore radius were determined for native and digested granules. It was found that native starch granules are macroporous materials with a small participation of mesopores. In the case of native starches, the highest value of SBET was obtained for rice starch (1.27 m 2 /g) and the lowest ‐ for potato starch (0.14 m 2 /g). Pore size distribution curves obtained by nitrogen adsorption showed peaks in the range of diameters 2‐3 nm (for all starches) and 100‐200 nm (for corn and rice starches). After 60 min of enzyme action, surface area of all starches doubled in comparison to native ones. Arising of the new pores was also noted. The results of mercury porosimetry measurements showed that rice starch had the highest total area of pores and porosity but the lowest mean pore radius among all native starches. The pore size distribution curves for all starches exhibited solely one peak corresponding to the dominant group of pores of the radii in the range 0.5‐8 mm, dependent on the starch source. There were also much smaller peaks situated within the range of 3‐30 mm. After a-amylolysis of corn and rice starches, the average radius of the dominant group of pores diminished. No substantial changes in the pore radii could be noted for potato starch.

Scanning electron microscopy (SEM), atomic force microscopy (AFM), as well as iodine and nitrogen sorption measurements were applied to investigate potato and corn starch granules surface after an action of Bacillus subtilis α-amylase. The SEM images revealed holes and pits (corn starch) or scratches (potato starch) on the surface of modified granules. These results were confirmed by AFM investigation which showed the presence of depressions of approximately 121 nm in diameter. Structure of the surface was not uniform. It consisted of small particles, amylopectin blocklets, of approximately 20 nm in diameter. They became more distinctive after α-amylolysis. Values of iodine binding capacity (IBC) obtained for hydrolyzed granules were lower than for native ones which indicated that the amylose and amylopectin chains building their surface were shortened. Specific surface area, volume and average diameter of mesopores increased for both starches after α-amylolysis.

Culture of Saccharomyces cerevisiae with sodium selenite addition in medium was treated by pulsed electric fields (PEFs). Amino acids from yeast hydrolysates were separated by means of ion-exchange chromatography on amino acid analyzer according to previously established procedure. Selenocysteine was determined in a form of complex with ninhydrin, applying photometric technique. PEF treatment of S. cerevisiae cells resulted in about threefold content increase of selenium bonded within selenocysteine. PRACTICAL APPLICATIONS Se yeast is an attractive source of Se because of its low cost and its ability to act as a precursor for selenoprotein synthesis. Se yeast can be consumed as such and as a nutritional supplement. Another possibility is to use selenized yeast instead of conventional yeast for baking bread. Bread is generally low in Se, and hence the use of selenized yeast for this purpose could result in higher Se intakes because bread is a common product consumed by many individuals (Dumont et al. 2006). The presented way to enrich the baking yeast in selenium, namely selenomethionine, may be successfully applied in yeast production, because the studied method is a relatively simple, nontoxic and cheap technique for introducing macrocompounds into the yeast cells. Such enriched selenium yeast may be a valuable and safe source of selenium at diet supplementation.

In food analysis, a method for determination of vitamin C should enable measuring of total content of ascorbic acid (AA) and dehydroascorbic acid (DHAA) because both chemical forms exhibit biological activity. The aim of the work was to confirm applicability of HPLC–DAD method for analysis of total content of vitamin C (TC) and ascorbic acid in various types of food by determination of validation parameters such as: selectivity, precision, accuracy, linearity and limits of detection and quantitation. The results showed that the method applied for determination of TC and AA was selective, linear and precise. Precision of DHAA determination by the subtraction method was also evaluated. It was revealed that the results of DHAA determination obtained by the subtraction method were not precise which resulted directly from the assumption of this method and the principles of uncertainty propagation. The proposed chromatographic method should be recommended for routine determinations of total vitamin C in various food.

Cultures of Saccharomyces cerevisiae were treated with PEF to improve simultaneous accumulation of magnesium and zinc ions in the biomass. The results showed that the ions concentration in the medium and their mutual interactions affect accumulation in cells. Increasing the concentration of one ion in the medium reduced the accumulation of the second one, in the control as well as in the cells treated with PEF. Under optimized conditions, that is, on 15 min exposure of the 20 h grown culture to PEF of 5.0 kV/cm and 20 μs pulse width, accumulation of magnesium and zinc in yeast biomass reached maximum levels of 2.85 and 11.41 mg/gd.m., respectively, To summarize, optimization of ion pair concentration and PEF parameters caused a 1.5 or 2-fold increase of magnesium and zinc accumulation, respectively, in S. cerevisiae.

Pulsed electric field (PEF) of 1Hz, 1.5 kV, and 1 ms increased the activities of catalase and inulinase over the whole range of applied Se concentrations compared with the non-treated cultures. A significant effect of selenium concentration (in the range of 5-14 microg/ml) on both intra- and extracellular enzyme activities was noted. At a Se concentration of 10 microg/ml, the activities of intra- and extracellular inulinases and extracellular catalase in the PEF-treated cultures reached the maximum of 71 U/g d.m., 46 U/g d.m., and approx. 8 U/ml, respectively. The maximum activity of intracellular catalase of approx. 6 U/ ml (with and without PEF) was recorded at 5 microg Se/ml. Further increasing of selenium concentration caused a decrease in the activity of the enzymes.

K. marxianus was cultivated under conditions of PEF (pulse electric field) action and a selenium source. The culture duration after which cells were treated with PEF, the field exposure time and the selenium concentration in the medium were all optimized. Optimization of culture duration caused a 33% increase in selenium accumulation in cells as compared to the control with no PEF treatment. The highest selenium accumulation--about 167 microg/g dry mass (DM)--was recorded after 3-minute PEF treatment of 16-hour culture. A roughly two-fold increase in selenium content was achieved after optimization of culture duration and PEF treatment time. Finding the optimum selenium concentration in the medium brought about a 13-fold increase of selenium accumulation in the cells of K. marxianus.

The small-angle X-ray scattering investigations of the extrudes are presented. The investigations of the different samples of starch by means of the SAXS indicate the new possibilities for using this method for extrudates examination. Results obtained by SAXS method of close dependance between intensity SAXS scattering and characteristic parameters of the extrudates were shown.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The aim of this work is the evaluation of selenium accumulation and catalase activity in pulsed electric field (PEF) treatedSaccharomyces cerevisiae cells. Cultures ofS. cerevisiae in the medium containing selenium as sodium selenite were treated with PEF. Applied range of field parameters (field frequency of 1 Hz, intensity of 1.5 kV/cm and pulse duration of 1 ms) does not influence the changes of catalase activity which depend only on the concentration of selenium accumulated in the yeast cells. It was noted for the non-PEF-treated cultures that the accumulation of selenium in the yeast cells increased to 60 μg/g dry mass (DM) together with the increase of selenium concentration in medium from 1 to 3 μg/mL. Consequently, the activity of extra- and intra-cellular catalase also increased. At higher selenium concentrations in medium (4–6 ug/mL) its accumulation in the cells reached 127 μg/g DM which resulted in the decrease of catalase activity. In the PEF-treated cultures, twofold higher accumulation of selenium in the cells was obtained in the whole rang e of concentrations applied, which caused the significant decrease of catalase activity.