SYNERGISTIC ACTIVITY OF CAPELIN PROTEIN HYDROLYSATES WITH SYNTHETIC ANTIOXIDANTS IN A MODEL SYSTEM

Capelin protein hydrolysates (CPHs) were examined in a β-carotene-linoleate model system together with synthetic antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butyl hydroquinone (TBHQ). Addition of CPHs was at 0.25 and 1 mg per 5 mL in the above emulsion. BHA and BHT were added at levels of 2.5 and 5 μg and TBHQ at 5 and 10 μg. Absorbance of model emulsion system at 470 nm was recorded every 30 min for 2 h. CHPs and synthetic antioxidants inhibited oxidation of linoleic acid effectively. In the experiment with BHA, the influence of CPHs was significant (p<0.01) for the samples incubated for 60, 90, and 120 min; and in experiments with BHT and TBHQ during the entire incubation period. The influence of added BHA and BHT on inhibition of bleaching of β-carotene in the emulsion system was significant (p <0.01) during the incubation period and after 60, 90 and 120 min when TBHQ was used. A synergistic effect was observed only for CPHs and TBHQ when incubation time was 60, 90, and 120 min.     

THE EFFECT OF AIR-DRYING, FREEZE-DRYING AND STORAGE ON THE QUALITY AND ANTIOXIDANT ACTIVITY OF SOME SELECTED BERRIES

The aim of this study was to analyze the effects of air-drying and freeze-drying and subsequent storage of dried products on the content of polyphenols, anthocyanins and the antioxidant properties of selected berry fruits. The material was raspberry ( Rubus ideaus L. ), strawberry ( Fragaria ananassa Duch ) and bilberry ( Vaccinum myrtillus ). Despite exposure to atmospheric oxygen, the stored freeze-dried fruit retained the properties of the raw material better than the air-dried product. In the case of the latter, there were considerable differences in the retention of total polyphenolic and anthocyanin content as well as antioxidant properties in the three fruit species examined. In particular, bilberry maintained a high polyphenol and anthocyanin content and high antioxidant potential despite the greatest losses of these compounds.

PRACTICAL APPLICATIONS

Consumer demand for food with health-promoting qualities is increasing. The food industry has intensified its efforts to provide high quality, semi-processed products that fulfil this requirement. The results presented in this work indicate that even after long-term storage and despite exposure to atmospheric oxygen, freeze-dried berries retain the antioxidant properties of the raw material to a very high degree. Therefore, lyophilisates can satisfy this particular need. Air-dried berries are much less stable during long-term storage. The dynamics of the changes occurring during the storage of both kinds of product are presented in detail.     

ANTIOXIDANT ACTIVITY OF PHENOLIC FRACTIONS OF EVERLASTING PEA, FABA BEAN AND BROAD BEAN

Extracts of seeds of everlasting pea, faba bean and broad bean were prepared using 80% acetone. Five fractions were separated from each extract on a Sephadex LH-20 column using methanol as the eluate. The antioxidant activity of fractions was investigated in a β-carotene-linoleate model system. For individual fractions, UV spectra were recorded and the content of total phenolics determined. Fractions were also characterized based on the number of phenolic compounds, and their antioxidant activity determined by TLC analysis. Results of β-carotene-linoleate model systems indicated that antioxidant activities of separated fractions were in the order of everlasting pea > faba bean > broad bean. Individual fractions contained several phenolic compounds as noted by TLC. Absorption maxima from UV spectra showed that flavonoids, and not phenolic acids, were the main phenolic compounds in separated fractions. Spots on the plates sprayed with a solution of β-carotene and linoleic acid indicated that many of these compounds can act as natural antioxidants.     

ANTIOXIDANT ACTIVITY OF EXTRACTS OF PHENOLIC COMPOUNDS FROM RAPESEED OIL CAKES

Oil cakes were prepared from commercial rapeseeds of the double-low Bolko variety using a complete technological line. Samples of the oil cake containing 8.1, 9.9, 11.4, and 14.4% moisture were stored for 1, 2 and 3 months at 15C and a relative humidity of 78%. The content of total phenolics in the extracts so obtained did not depend on the moisture content of the oil cake or the length of storage; values ranged from 77 to 81 mg/g. In the extract obtained from nonpressed rapeseeds, a similar content of total phenolics (80 mg/g) was determined. UV spectra of the extracts studied were characterized by maximum absorbance at 330 nm. This wavelength indicates that sinapine was the main phenolic compound in the extracts. However, the extract obtained from the cake with the lowest moisture content and stored for 3 months exhibited a maximum absorbance at 328 nm. All the extracts showed good antioxidant activity, as assessed using a β-carotenelinoleate model system. Antioxidative properties of extracts obtained from rapeseed cakes were similar to those of extracts from nonpressed seeds.     

ELECTRIC SENSOR FOR PROMPT MEASUREMENT OF MOISTURE CONTENT IN SOLID FOOD PRODUCTS

Originally designed sensor for electrical measurement of moisture content in comminuted food was presented. Equations were formulated to demonstrate the dependence of tested sample electrical resistance on resistivity (specific resistance) of food as well as the dependence of investigated sample electrical capacitance on permittivity of food. Experiments were carried out to determine moisture content in wheat flour, potato starch, and raw pork loin serving as examples. The results of these measurements were compared with the results obtained using conventional gravimetry. The measurement of moisture content lasted for between 3 to 5 s, and the time used for a sample preparation was not longer than 60 s. An advantage of the designed sensor of moisture content is that the density of the investigated food sample does not affect the measurement results.     

THE INFLUENCE of HEAT TREATMENT ON the ACTIVITY of LIPO-AND HYDROPHILIC COMPONENTS of OAT GRAIN

Lipids in oat grains are protected against oxidation by various chemical compounds with antioxidant properties. Biologically active compounds such as tocopherols, L-ascorbic acid, thiol, phenolic amino acids and phenol comnpounds feature such properties. Phenolic compounds inhibit lipase activity, protect lipids against oxidation and, as a consequence, protect plant cells against the destructive activity of free radicals. the disadvantage of natural antioxidants is their low resistance to high temperatures since heating over 80C destroys their antioxidant properties. Operation such as drying, blanching, roasting or extrusion destroy the protective system of plant lipids.
The paper is an attempt to explain to what degree extrusion conditions influence activity of natural antioxidants. Oat flour possessing the largest amnount of lipids and biologicaly active compounds compared to other cereal flour was used in the model system. It has been found that oat phenolic compounds are a mixture of free phenolic acids, esters and phenolic acid glycosides as well as flavonols and polyphenols. It has been established that alcoholic extracts produced from oat groat and flour had strong antioxidant properties, whereas the extracts from extruded substances did not reveal such properties. During extrusion, about 50% degradation of phenolic compounds was observed. Phenolic compounds were the main group of organic compounds enabling enzyme activity and playing an antioxidant role.     

Decentralized,stochastic control for a static LQ problem

An original problem statement for the optimal control laws design is presented. A large scale system composed of M linear static subsystems with an interaction and quadratic performance index is considered. A two-level hierarchical control structure is assumed, in which a coordinator and local controllers have access to different information. The so-called elastic constraint (Gessing 1985) is used for coordination. For the problem the possibility of partial decomposition of calculations and a decentralization of the control, as well as an analytical form of the optimal laws are obtained. The influence of the particular subsystem on the control quality is investigated.