The antimicrobial activity of fatty acids, monolaurin, citric, succinic, fumaric, malic and lactic acid was determined in cultures of two strains of Escherichia coli, three strains of Salmonella sp. and two strains of Clostridium perfringens. Antimicrobial activity was expressed as minimum inhibitory concentration (MIC) that prevented growth and glucose utilization in treated cultures. Caprylic acid was the only acid inhibiting glucose utilization in all cultures. Its MIC varied from 1 to 3 mg/ml. Strains CCM 3954 and CCM 4225 of E. coli were inhibited also by capric acid at 5 mg/ml. Strains CCM 4435<sup>T </sup>and CNCTC 5459 of Cl. perfringens were inhibited by medium-chain fatty acids (C<sub>8</sub> to C<sub>14</sub>), oleic acid and one strain also by linoleic acid. The minimum MICs were those of lauric and myristic acid (between 0.1 and 0.2 mg/ml). Growth of Cl. perfringens, but not other bacteria, was inhibited also by monoglyceride of lauric acid (MIC = 3 mg/ml), and by citric acid (MIC = 4 mg/ml). Inhibitory effects of other acids were not observed at 5 mg/ml. Caprylic and lauric acid did not influence the K<sup>+ </sup>permeability of the cytoplasmic membrane in cells of E. coli CCM 4225 and Cl. perfringens CCM 4435<sup>T</sup>, respectively. In cultures of both strains of E. coli treated with caprylic acid at 5 mg/ml, and in those of Cl. perfringens CCM 4435<sup>T </sup>treated with lauric acid at 1 mg/ml, or with its monoglyceride at 5 mg/ml, the transmission electron microscopy revealed damage of cytoplasmatic structures. In cells of Cl. perfringens the separation of inner and outer membranes was apparent, the integrity of the outer membrane, however, was maintained. It can be concluded that medium-chain fatty acids are more efficient antimicrobials than other, more polar organic acids tested.
Ten weaned rabbits were fed a basal (control) diet containing 0.12 mg Se/kg. In 10 rabbits the basal diet was supplemented with Se-enriched yeast to increase the Se concentration to 0.50 mg/kg. Rabbits were slaughtered at the age of 11 weeks. Samples of meat, liver and hair of 4 rabbits from each group were taken and analyzed. No effect of Se on growth, feed conversion and dressing out percentage was observed. Loin and hindleg meat, liver and hair of control rabbits contained 93, 98, 521 and 267 μg Se/kg, respectively (average values). In treated rabbits the corresponding Se concentrations were 400, 389, 1 414 and 914 μg/kg. Supranutritional Se supply had no effect on the activity of glutathione peroxidase in meat, and oxidative stability of meat expressed as production of thiobarbituric acid-reactive substances in meat stored for 3 and 6 days. Thus, the enrichment of meat with Se is the main benefit of Se supplementation of rabbit diets.
A B S T R A C TDifferent hydrocolloids were examined as possible replacements for traditional phosphate-and citrate-based emulsifying salts in processed cheese production. The following hydrocolloids (at concentrations in the final product of <1.0%, w/w) were chosen: modified starch (with bound sodium octenyl succinate), low methoxyl pectin (alone or combined with lecithin), locust bean gum, K-carrageenan and L-carra-geenan. The products were assessed by sensory analysis, microscopic image analysis and dynamic oscillatory rheometry. Modified starch, locust bean gum and low methoxyl pectin could not be recommended as replacements for traditional emulsifying salts. Model processed cheeses without traditional emulsifying salts of 40% (w/w) dry matter and 55% (w/w) fat-in-dry matter containing 1.0% (w/w) iccarrageenan or i-carrageenan were found to be homogeneous, however the products were hard with fracturable texture.
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