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The analysis of total vitamin C content in food is most frequently performed by reducing dehydroascorbic acid to ascorbic acid, which is then assayed with the technique of high-performance liquid chromatography combined with spectrophotometric detection. Tris(2-carboxyethyl)phosphine is currently the only agent in use that efficiently reduces dehydroascorbic acid at pH &lt, 2. Therefore, there is a continued need to search for new reducing agents that will display a high reactivity and stability in acidic solutions. The objective of the study was to verify the applicability of unithiol and tris(hydroxypropyl)phosphine for a reducing dehydroascorbic acid in an extraction medium with pH &lt, 2. The conducted validation of the newly developed method of determining the total content of vitamin C using tris(hydroxypropyl)phosphine indicates its applicability for food analysis. The method allows obtaining equivalent results compared to the method based on the use of tris(2-carboxyethyl)phosphine. The low efficiency of dehydroascorbic acid reduction with the use of unithiol does not allow its application as a new reducing agent in vitamin C analysis.

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 objective of the study was to identify suitable additives stabilizing standard solutions of ascorbic acid (AA) that would not cause interference in the analytical process with the use of voltammetry in the determination of the AA content in food products. In addition, the effect of various conditions of storage of selected fruit juices and drinks on the concentration of vitamin C was studied. The study demonstrated that AA degradation was inhibited the most effectively by tartaric acid and its optimum concentration was set to 200 mg L-1. Analysis of selected fruit juices stored in various temperature conditions confirmed that an elevation of temperature and extension of the time of storage caused a decrease in the content of vitamin C in the analyzed samples, while closing the packages caused a limitation of the changes in concentration of this vitamin. On the basis of literature data and of the results obtained in the present study it can be concluded that fruit juices should be stored at a temperature lower than room temperature to retain their nutritive value.

Currently, natural antioxidants and substances with a protective effect on fatty acids are used more and more often instead of synthetic compounds that may have a negative impact on human health. This is related to the prevailing trend of promoting healthy and organic food. Essential oils are interesting in this respect because studies confirm their antioxidant properties. The aim of this study was to analyse the effect of the addition of marjoram oil on the inhibition of changes in the fatty acid profile of rapeseed oil, stored under different temperature conditions. In the experiment, marjoram oil and BHA were added to the batches of rapeseed oil. The samples of rapeseed oil with the addition of marjoram oil and BHA were stored at room temperature and at 40 °C. The negative effect of storage on quantitative changes in fatty acid profile of rapeseed oil was observed. It was found that the ability of selected substances to inhibit unfavourable transformations in fats depends on their concentration and the temperature of storage. Marjoram oil can potentially be used as an additive stabilizing the fatty acid profile in vegetable oils.

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 aim of this study was to estimate the effect of aromatisation of rapeseed oil with rosemary on the content of volatile substances and to analyze the antioxidant properties of the aromatised oils obtained. Rapeseed oil is flavoured by direct addition of rosemary essential oil (F) and by classical macerations of rosemary herb (A, B) as well as by ultrasound assisted maceration (C, D) and microwave assisted maceration (E). The dominant aromatic component was 1,8-cineole whose concentration varied within the range from 25.17 μg/ml in macerate C (sonication, 60 min, 25 °C) to 38.61 μg/ml in macerate D (sonication, 300 min, 25 °C), while in variant F (mixture of oil with essential oil) the content of 1,8-cineole was 1093.21 μg/ml. In spite of the highest concentration of volatile compounds in the sample aromatised through direct addition of essential oil, that variant was characterised by the lowest antioxidant activity. In terms of the capacity for quenching DPPH radicals the most effective were the macerates obtained with the use of sonication.

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 aim of the study was to evaluate sensory and phytochemical (polyphenols, flavonoids and caffeine) estimation of black and green tea brews obtained in an alternative way through brewing with the assistance of ultrasound. Brews produced with the application of sonication for 2 minutes and 1 minute were the most preferred by the sensory evaluation team. Evaluation of the brews in terms of component descriptors, i.e. fragrance, flavour and colour, was varied and depended on the kinds of tea and on the applied experimental factors. It was demonstrated that ultrasound have a significant effect on the extraction of active substances, i.e. polyphenols, flavonoids and caffeine, from black and green tea. The application of sonication caused a significant increase in the concentration of flavonoids (by ca. 29% and 73%), polyphenols (by ca. 34% and 41%) and caffeine (by ca. 51% and 60%) in the tea brews. RESUMO: O objetivo do estudo foi verificar a atividade sensorial e fitoquímica (polifenóis, flavonóides e cafeína) de infusões de chá preto e verde empregando o ultrassom. As infusões produzidas com a aplicação de sonicação por 2 e 1 minutos foram as mais preferidas pela equipe de avaliação sensorial. A avaliação das infusões em termos de descritores de componentes, isto é, fragrância, sabor e cor, foi variada e dependeu dos tipos de chás e dos fatores experimentais aplicados. Foi demonstrado que o ultrassom tem um efeito significativo na extração de substâncias ativas, ou seja, polifenóis, flavonóides e cafeína, do chá preto e verde. A aplicação de sonicação causou um aumento significativo na concentração de flavonóides (em cerca de 29% e 73%), polifenóis (em cerca de 34% e 41%) e cafeína (em cerca de 51% e 60%) das infusões de chá.

Rice grits with different moisture contents (10, 15, 20, and 30%, db) were processed by extrusion cooking in a single-screw extruder. Porosity of the extruded products was analyzed respectively using three different methods: water vapour desorption (WVD), nitrogen adsorption (NA) and mercury intrusion porosimetry (MIP). Pore size distribution was determined in the range of pore radius 1–50 nm (WVD), 1–100 nm (NA) and 3.6–7500 nm (MIP). Extrusion cooking resulted in samples of various porosities. The lowest cumulative pore volume (CPV) determined by NA and MIP and the lowest specific surface area calculated on basis of NA and WVD data were noted for the sample produced at 30% feed moisture content. Pore size distribution curves plotted on the base of MIP showed that the end-products of extrusion were characterized by more diverse porosity in the range of smaller radius (5–50 nm) than rice grits.

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.

Vitamin C performs many important functions in the human organism. Besides, it is used in the therapy and prevention of many diseases, which is why the methods applied to determine it should ensure the correct results. The present paper compares the results of vitamin C determination by means of the spectrophotometric method in agreement with the binding standard PN-A-04019:1998 and the proposed method of the reversed-phase high-performance liquid chromatography with spectrophotometric detection. The comparison was made using the method of calculating the proportion of mean results and the uncertainty of its determination. The analysis of a sample of the certified reference material BCR-43 was conducted. It was shown that because the content of dehydroascorbic acid was not considered, the result obtained by the standardized spectrophotometric method differs in a s ta tis ti cally significant way from the certified value, as opposed to the result obtained by the chromatographic method. Results of determining vitamin C content in blackcurrant, apple and grapefruit juices by means of the two methods indicate statistically significant differences. Compatible results were obtained only for orange juice. This is caused by insufficient selectivity of the spectrophotometric method of vitamin C determination. The suggested chromatographic method is more selective than the spectrophotometric method and it enables to consider the content of dehydroascorbic acid. That is why it should be recommended for routine determinations of vitamin C content.

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 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.