Use of a fluorescence front face technique for measurement of lipid oxidation during refrigerated storage of chicken meat

Lipid oxidation in chicken breast was measured during refrigerated storage in air by front face fluorescence and by thiobarbituric acid techniques. Three chicken genotypes were compared: Standard (fast-growing line), Certified (medium-growing line) and Label (slow-growing line). Lipid oxidation was stable during the first 3 days of storage and then increased in the certified and label animal groups. Standard animals were very stable towards lipid oxidation. This study showed a good correlation between fluorescence intensity and thiobarbituric acid reactive substances measurements. Front face fluorescence technique can be used as a valuable index of lipid oxidation in chicken meat.     

Antimicrobial Peptides from the Aurein Family Form Ion‐Selective Pores in Bacillus subtilis

The mechanism of action of aurein 2.2 and aurein 2.3, antimicrobial peptides from the frog Litoria aurea, was investigated. Proteomic profiling of the Bacillus subtilis stress response indicates that the cell envelope is the main target for both aureins. Upon treatment, the cytoplasmic membrane depolarizes and cellular ATP levels decrease. Global element analysis shows that intracellular concentrations of certain metal ions (potassium, magnesium, iron, and manganese) strongly decrease. Selective translocation of some ions over others was demonstrated in vitro. The same set of ions also leaks from B. subtilis cells treated with sublethal concentrations of gramicidin S, MP196, and nisin. Aureins do not permeabilize the cell membrane for propidium iodide thus excluding formation of large, unspecific pores. Our data suggest that the aureins acts by forming small pores thereby causing membrane depolarization, and by triggering the release of certain metal ions thus disturbing cellular ion homeostasis.     

Fecal shedding of enterohemorrhagic Escherichia coli in weaned calves following treatment with probiotic Escherichia coli

The fecal shedding and pathogenicity of enterohemorrhagic E. coli (EHEC) O26:H11, EHEC O111:NM, and EHEC O157:H7 in weaned calves (8 to 10 weeks of age) were compared with and without treatment with a three-strain mixture of probiotic bacteria (competitive-exclusion E. coli). Three groups of 12 calves were each perorally given a five-strain mixture of one of the EHEC serotypes (10(10) CFU of total bacteria per calf). Seventy-two hours later, six calves from each group were each administered 10(10) CFU of probiotic bacteria. None of the EHEC serotypes caused significant clinical disease, although a few calves developed mild transient diarrhea or pyrexia. Gross or microscopic lesions attributable to EHEC were not detected in control or probiotic-treated calves at necropsy. For probiotic-treated calves given E. coli O157:H7 and for probiotic-treated calves given E. coli O111:NM, fecal shedding was reduced compared with that for untreated calves. For the probiotic-treated calves given E. coli O157:H7, the reductions in fecal shedding on days 8, 12, 14, 16, 20, 22, 28, and 30 after peroral administration were statistically significant (P<0.05). For probiotic-treated calves given E. coli O111:NM, there were statistically significant reductions (P<0.05) in fecal shedding on days 6, 8, 10, and 12. In contrast, there was no reduction in fecal shedding for calves administered E. coli O26:H11 and treated with the probiotic bacteria. In fact, calves in both the treated and the nontreated groups continued to shed large populations of E. coli O26:H11 throughout the 32-day trial. At necropsy, E. coli O157:H7 was isolated from five of six untreated calves and from only two of six probiotic-treated calves. E. coli O111:NM was isolated from four of six untreated calves at necropsy and from two of six probiotic-treated calves. However, E. coli O26:H11 was isolated from five of six untreated calves and from all six probiotic-treated calves. The results obtained in this study indicate that probiotic E. coli substantially reduced or eliminated fecal shedding of E. coli O157:H7 and E. coli O111:NM 8 to 30 days and 6 to 12 days after the administration of the probiotic culture, respectively, and reduced the persistence of E. coli O157:H7 in the gastrointestinal tract at necropsy (31 to 33 days after the administration of the probiotic culture). The probiotic E. coli did not reduce fecal shedding or gastrointestinal persistence of E. coli O26:H11.     

The effect of kefir addition on microstructure parameters and physical properties of porous white bread

The effect of kefir concentration on the quality of porous white bread has been investigated. Quality evaluation was done using flatbed scanning (FBS) for measuring crumb porosity, instrumental texture profile analysis (TPA), crust and crumb color (L ^* a ^* b ^*), moisture, specific volume, and density determination techniques. The correlations between porosity, brightness, and firmness were also investigated. Long fermentation time of the sourdough changed significantly (p<0.05) the cell mean area (mm²), cell mean perimeter (mm), firmness (N), chewiness (N), light reflectance, and specific volume (ml/g). A strong correlation was found between microstructure of porous white bread, brightness (L), and firmness from TPA test. Kefir prolonged the shelf life of bread.