STABILITY AND PROPERTIES OF A THERMOSTABLE β-GALACTOSIDASE IMMOBILIZED ON CHTTIN

Thermostable β‐galactosidase from an E. coli transformant containing the enzyme gene from P. woesei was immobilized at pH 4.0 and a glutaraldehyde concentration of 10 mM on chitin isolated from shrimp Crangon crangon shells. These preparations had a specific activity of 43,000 U/g of chitin at 85C using ONPG as substrate. The optimum pH and temperature for immobilized β‐galactosidase activity were 5.2 and 93C. Immobilization shifts the optimum pH for the activity of the enzyme by 0.2 units towards the acid side. The immobilized enzyme is stable at temperatures close to the optimal value, and the residual activity for ONPG hydrolysis of the preparations incubated 5 h in 0.1 M phosphate citrate buffer (pH 5.4) at 90C and 100C was 70% and 40% of the initial value, respectively.     

Real-Time lethality Evaluation During the Flame Sterilization of Canned Foods

A pilot-scale flame sterilizer was interfaced to a microcomputer for real-time thermal process evaluation of individual cans. The computerized system used a photodetector system to synchronize data acquisition at predetermined monitoring sites. Infrared sensors were used to measure can temperatures. Also, a method to measure can surface temperature was developed for infrared sensor calibrations. Foil thermocouples were found to be the most accurate and reliable for surface temperature measurements. However, a thin gauge wire thermocouple attached to the inside of the can end surface was a more practical and economical method for sensor calibration.     

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.     

Performance of the Helical Screw Rheometer for Fluid Food Suspensions

The Helical Screw Rheometer (HSR) consists of a helical screw enclosed in a tight fitting cylinder. When the screw is rotated with the system closed it generates a linearly increasing pressure differential along the axis of the screw. The pressure is proportional to the viscosity of a Newtonian fluid. Viscosity of standard Newtonian fluids measured using the HSR correlated well with measurements on a rotational rheometer with cone and plate fixtures. HSR data on non-Newtonian suspensions analyzed with a power law model (σ= mγ^a) did not agree as well with results from cone and plate fiiures on the rotational rheometer.     

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.     

PROTEOLYTIC ACTIVITY OF CRUDE ENZYME EXTRACTS OF SQUID ILLEX ARGENTINUS LIVER

The extract obtained from the acetone powder of frozen stored squid liver had optimum proteolytic activity against hemoglobin at pH 2.6 to 4.0. About 90% of the activity at pH 3.0 was inhibited by pepstatin and about 15% was inhibited by phenylmethanesulfonyl fluoride or iodoacetamide. The activity was increased by dithiothreitol and cysteine by about 55 and 40%, respectively. At pH 3 the enzyme extract had a temperature optimum of 45 to 50C; at 5C the activity was about 15% of that at 45 to 50C. At pH 7 the optimum activity was at about 45C. Heating of the extract without substrate at pH 3 and 7 caused a rapid decrease in proteolytic activity above 35 and 30C, respectively. A water extract of the liver was used to treat isolated bovine myofibrils at pH 5.5 and 0C. After 20 h a fragment of slightly lower m.w. than that of the myosin heavy chain was detected. After treatment at pH 7 and 0C, little degradation of the myofibrillar proteins was evident. At 20C the myofibrils were hydrolyzed to several products.     

HIERARCHY: A METHOD FOR ANALYSIS AND SYNTHESIS OF HIERARCHIES AND NETWORKS

A set of mathematical and logical objects have been comprised under a new generalized concept of hierarchy. Seven postulates are formulated demarcating the volume of this concept. The compatibility of the existing definitions of hierarchies is attained by comparing them with the more general one by means of nine primary and four secondary invariant characteristics. The latter are derived from Ostwald's 1910 invariants by using Klein's 1872 methods of developing generations of invariants. The generalized concept embodies the former notions of hierarchies. The method for describing a hierarchy is illustrated for the process and the hierarchic system.