Sławomir Pietrzyk

Effect of mineral elements on physicochemical properties of oxidised starches and generation of free radicals

The objective of this study was to determine the effect of enrichment of oxidised starches with mineral compounds on their physicochemical properties and capability for free radical generation. Potato and spelt wheat starches were oxidised with sodium hypochlorite and, afterwards, modified with ions of potassium, magnesium and iron. The modified starches were analysed for: content of mineral elements, colour parameters (L*a*b*), water binding capacity solubility in water at temperature of 50 and 80 °C, and susceptibility to enzymatic hydrolysis with α-amylase. In addition, thermodynamic characteristics of gelatinisation was determined by differential scanning calorimetry (DSC), and the number and character of thermally generated free radicals was assayed using electron paramagnetic resonance (EPR). Based on the results achieved, it was concluded that the quantity of incorporated minerals and changes in the assayed physicochemical parameters depended not only on the botanical type of starch but also on the type of the incorporated mineral element.

The effect of amylose content and level of oxidation on the structural changes of acetylated corn starch and generation of free radicals

This study was aimed at determining the effect of starch oxidation on its acetylation, structure of starch granules, and generation of free radicals. Corn and waxy corn starches were oxidised by NaClO applied in doses of 10, 20, and 30g Cl/kg of starch, and then acetylated using acetic acid anhydride. The carboxyl, carbonyl, acetyl groups were determined in modified starches. Structural properties of starch granules were evaluated based on molecular weight distribution, gelatinisation, crystallinity, specific surface, intrinsic viscosity. EPR measurements were carried out to establish starch susceptibility to UV irradiation induced generation of free radicals. It was found that the number of carbon centered radicals was dependent on the kind of starch and its chemical modification. Study results allowed concluding that the applied modifications contributed to significant changes in starch granules that were determined not only by the amylose content of starch but also by the degree of its oxidation.

Effects of Saccharose Substitutes on Physicochemical Properties and Free Radical Generation in Oxidized Potato Starch

This study aimed at investigating the effects of saccharose and its substitutes (sorbitol, acesulphame, aspartame) added to potato starch oxidized with sodium chlorate (I) on the physicochemical properties of starch and generation of free radicals at both 150 and 230°C. Oxidized starch with saccharose and its substitutes were analyzed by thermodynamic characterization of pasting, rheological properties, and susceptibility to degradation of 2% pastes. Moreover, a number of generated thermally free radicals in investigated samples was determined by quantitative electron paramagnetic resonance spectroscopy measurements. Saccharose and sorbitol increased considerably the onset temperature of transition (T0) and the peak temperature of transistion (Tp) as determined by differential scanning calorimetry. Among the sweeteners, only aspartame influenced the characteristic viscosities of the starch-sweetener-water systems, reducing the thermal stability of the obtained pastes. Acesulphame K and aspartame caused the largest increase in the susceptibility to retrogradation of 2% pastes of oxidized potato starch. In the presence of sorbitol, the number of radicals generated thermally in starch decreased. This effect, found by quantitative electron paramagnetic resonance spectroscopy measurements, indicates effective interaction of hydroxyl groups of the sorbitol molecule with starch matrix, leading to the stabilization of the starch structure.

Influence of amylose content and oxidation level of potato starch on acetylation, granule structure and radicals’ formation

This study was aimed at determining the effect of the amylose content of starch and oxidation level of potato starch on the structure of starch granules, and susceptibility to chemical modification (acetylation) and subsequent generation of radicals. Potato starch and waxy potato starch were oxidised with sodium hypochlorite applied in doses corresponding to 10, 20, and 30gCl/kg starch, and then acetylated with acetic acid anhydride. The carboxyl, carbonyl, acetyl groups were determined in modified starches. Structural properties of starch granules were evaluated based on gelatinisation, crystallinity, specific surface, intrinsic viscosity, and microphotographs by SEM microscope. The electron paramagnetic resonance (EPR) measurements were carried out to establish starch susceptibility to radical creation upon chemical modification and UV radiation. The amount of formed radicals was treated as a measure of the starch structure stability. The higher amount of amylose and the highest level of oxidation led to strong starch structure destruction and consequently facilitated radical generation. Study results showed also that amylose content as well as the degree of starch oxidation modified consecutive acetylation process. The different effectiveness of the acetylation processes influenced the morphology and structure of starch granules.

THE INFLUENCE OF STORAGE CONDITIONS OF CANDIED FRUITS ENRICHED WITH VITAMIN C BY DIFFERENT METHODS ON ITS CONTENT

The aim of this work was to study the effect of storage conditions of candied fruits enriched with vitamin C on its concentration in that product. The materials were candied fruits (black chokeberry and black currant) enriched with vitamin C by two methods during their production. The final products were stored within 3 months at 8 and 20 ° C. On the basis of the results it was stated that enrichment method affected the concentration of the vitamin C in fruits measured during storage period at the above conditions. doi:10.5219/55

Sorption properties of modified potato starch

Background. Starch is one of the biopolymers most commonly used in the food industry. In its native form its applications are limited. In contrast, its structure is relatively readily modified using various methods, producing starch derivatives of greatly diverse properties. The primary methods used to change characteristics of starch include acetylation and oxidation. Thus obtained raw materials are used as food additives. Stability of these raw materials and food products to a considerable extent depends on their composition and parameters characterizing storage facilities, i.e. relative humidity and temperature. One of the methods to specify adequate ambient conditions is based on water activity supplemented by sorption isotherms. As a result studies investigating correlations between water activity and moisture content are of importance for the optimization of storage conditions and design of certain food processing procedures. For this reason the aim of this study was to assess the effect of modification (oxidation, acetylation and their combination) on sorption properties (described based on sorption isotherms) of potato starch. Material and methods. Analyses were conducted on potato starch and its derivatives produced by acetylation, oxidation and co-modification (acetylation coupled with oxidation). Starch was oxidized using sodium chlorate (I), while acetylation was run using anhydrous acetic acid. Sorption isotherms were determined by the static desiccator method. Results were described applying selected mathematical methods equipped with physical interpretations (BET and GAB) and empirical models (Halsey, Oswin, Henderson, Pelega, Lewicki, Blahovec-Yanniotis). Calculations were made using non-linear estimation.