Influence of Methods of Corn Starch Modification and Used Sweetener on the Functional Properties of Blackberry Jelly-like Dessert.

A study was conducted on selected physicochemical properties of blackberry jelly-like desserts (kissel) prepared from physically modified starches (with various degrees of inhibition) and chemically modified starches (with various degrees of cross-linking). The desserts were conventionally sweetened with saccharose (S) or, as a dietary alternative, xylitol (X). The characteristics of changes in the viscosity of the kissels as a function of temperature and time were determined. It was noted that regardless of the sweetener used, the viscosity of the kissels increased with the decreasing degree of inhibition (high < medium < low). Regardless of the kind of modification of the starch used for the preparation of the kissels and of the kind of sweetener, thixotropy was observed. Desserts prepared from inhibited starch with xylitol (CL + X) were characterised by the biggest range of their hysteresis loop. Progressing retrogradation was noted with the decrease in the temperature of the experiment (+20 °C and +4 °C). After 7 days of storage, kissels sweetened with saccharose were characterised by a low transparency, which may indicate retarded retrogradation; however, on day 28, the transparency significantly increased, exceeding the values of transmittance for samples sweetened with xylitol. The tendency towards syneresis was tested at +4 °C and −22 °C. The substitution of saccharose with xylitol only caused a slight modification of viscosity. Regardless of the sweetener used and of the level of starch inhibition, lower ranges of the hysteresis loop were noted (apart from CL + X) than in the case of kissels obtained from chemically modified starches. Distinctly lower values of kissel "aging" indices were noted in the case of samples obtained from inhibited starches, and their colour did not significantly differ in relation to the dessert prepared from native starch.

A New Method for the Determination of Total Content of Vitamin C, Ascorbic and Dehydroascorbic Acid, in Food Products with the Voltammetric Technique with the Use of Tris(2-carboxyethyl)phosphine as a Reducing Reagent.

The objective of the study was to develop a new method for the determination of the total content of vitamin C and dehydroascorbic acid in food, based on the technique of differential pulse voltammetry with the use of a boron-doped diamond electrode modified with mercury film. A comparison was made between the results obtained with the developed method and a proposed reference method based on high-performance liquid chromatography with spectrophotometric detection. The reduction of dehydroascorbic acid was performed with the use of tris(2-carboxyethyl)phosphine. The interference caused by the presence of tris(2-carboxyethyl)phosphine during the voltammetric determination of ascorbic acid was effectively eliminated through a reaction with N-ethylmaleimide. The conducted validation of the voltammetric method indicated that correct results of analysis of the total content of vitamin C and ascorbic acid were obtained. Analysis of the content of dehydroascorbic acid was imprecise due to the application of the differential method. The results of the analyses and the determined validation parameters of the developed method are characterised by a high degree of conformance with the results obtained with the chromatographic reference method, which indicates the equivalence of the two methods.

Application of a New Dehydroascorbic Acid Reducing Agent in the Analysis of Vitamin C Content in Food.

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 < 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 < 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 Use of Starch Drying Kinetics Curves for Experimental Determination of Its Specific Surface Area.

The most popular method for the calculation of specific surface area is its determination from water vapour sorption isotherms. The study presented here has been designed for the purpose of optimisation and selection of the conditions of drying so as to allow the determination of specific surface area from plotted curves of the drying process. The results indicate that drying curves can be used as the basis for the determination of specific surface area, the values of which do not differ statistically significantly (α = 0.05) from those determined from isotherms of water vapour sorption (adsorption/desorption).

Effect of rapeseed oil aromatisation with marjoram on the content of volatile fraction and antioxidant properties.

The aim of the paper was to study how the process of aromatisation with marjoram affected the composition of volatile fraction and antioxidant properties of rapeseed oil. Different methods of aromatisation were used: direct addition of marjoram essential oil, classical macerations of marjoram herb, and maceration assisted with ultrasound or microwave. The dominant aromatic component in the volatile fraction was γ-terpinene with concentration in the range from 3.15 µg/mL (microwave assisted maceration) to 8.82 µg/mL (classic maceration with shaking). The content of this compound in the mixture of rapeseed oil with essential oil was 152.09 µg/mL. The sample aromatized by the direct addition of essential oil contained the highest amount of volatile substances but simultaneously it had the lowest antioxidant activity.

Effects of Ultrasound Technique on the Composition of Different Essential Oils.

The objective of the experiment was to investigate the stability of the composition of selected essential oils in the model systems containing methanol and hexane solutions which were treated with ultrasound. Solutions of the oils, with a concentration of 90 mg/ml, were subjected to the effect of ultrasounds with a frequency of 20 kHz and an output power of 200 W for periods of 2 min and 10 min at 50% and 80% power. The experiment has shown no significant effect on the composition of the essential oils resulting from the applied parameters of the process in the tested model systems. The study indicates that the sonication parameters adopted in the experiment can be applied in the case of analogous systems containing essential oils in their composition.

Sensory and chemical evaluation of tea brews prepared with the assistance of ultrasound / Avaliação sensorial e química de infusões de chás preparados com o emprego do ultrassom

ABSTRACT: 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.

Effects of operative conditions on products obtained of starch-oil mixtures by single-screw extrusion.

BACKGROUND: 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. METHODS: 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 115/130/150°C, while those with the participation of rapeseed oil and linseed oil were obtained at 120/135/128°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. RESULTS: 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: 80.3–82.6% and 78–79.6%. The largest decrease in solubility (WSI, 55.4–57.1%) 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 (376–397%) 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 230–256 m2/g) determined from the water vapor adsorption isotherm indicates no statistically significant difference at α = 0.05 for products with rapeseed oil, linseed oil, and controls. A significant increase in the specific surface area (SBET 284–347 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 1.9–2.1 g/100 g of starch and for 6% the starch percentage was 2.96–3.5 g/100 g. CONCLUSIONS: The water solubility of starch extrudates with the addition of oils decreases with an increase   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.

Effect of pulsed electric fields (PEF) on accumulation of selenium and zinc ions in Saccharomyces cerevisiae cells.

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.

Precision of dehydroascorbic acid quantitation with the use of the subtraction method--validation of HPLC-DAD method for determination of total vitamin C in food.

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.

Effect of pulse electric fields (PEF) on accumulation of magnesium and zinc ions in Saccharomyces cerevisiae cells.

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.