Influence of Particle Size Reduction on Structural and Mechanical Properties of Extruded Rye Bran

Rye bran is a high-fibre ingredient also containing starch and protein. The aim of this work was to investigate the effects of extrusion processing and bran particle size on the structural and mechanical properties of extruded rye bran. Native rye bran particle size of 750–1,250 μm was milled to produce feed material with three different average particle sizes (coarse, 440 μm; medium, 143 μm; fine, 28 μm). A co-rotating twin screw extruder was used for extrusion with various processing parameters. Extrusion processing did not have a significant (P?<?0.05) effect on soluble dietary fibre (SDF) content but the amount of insoluble dietary fibre (IDF) increased by 7.1–9.5 % in medium- and 11.3–12.3 % in fine-particle-sized rye bran extrudates as compared to the raw material prior to extrusion. Decreasing the particle size of rye bran to 28 μm resulted in lower amounts of IDF and total dietary fibre, but a higher amount of SDF after extrusion compared to coarse-particle-sized rye bran. Decreasing the particle size of rye bran to 28 μm gave more expanded (179–223 %), less hard (145–336 N), more crispy (2.7–7.2?×?10^?4) and porous (79.2–83.9 %) extrudates compared to the coarse-particle-sized rye bran extrudates, which were less expanded (151–176 %), harder (210–433 N), less crispy (0.5–2.8?×?10^?4) and less porous (64.4–65.1 %). Reduction of the particle size of rye bran significantly (P?<?0.05) increased the crispiness compared to the extrudates made of coarse-particle-sized rye bran. The results demonstrated that the structural and mechanical properties of rye bran extrudates can be improved without starch addition by reducing the particle size of bran.     

Antibiotic survey of Lactococcus lactis strains to six antibiotics by Etest, and establishment of new susceptibility-resistance cut-off values

In order to establish cut-off values for Lactococcus lactis to six antibiotics to distinguish susceptible and intrinsically resistant strains from those having acquired resistances, the minimum inhibitory concentration (MIC) of tetracycline, erythromycin, clindamycin, streptomycin, chloramphenicol and vancomycin was determined in 93 different Lc. lactis strains using the Etest. These bacterial strains were originally isolated from dairy and animal sources in widely separated geographical locations. Cut-offs were defined on the basis of the distribution of the MICs frequency of the studied antibiotics, which in the absence of acquired determinants should approach to a normal statistical distribution. In general, the new cut-off values proposed in this study are higher than previously defined (European Commission, 2005. The EFSA Journal 223, 1-12). Based on these new values, all the strains tested were susceptible to erythromycin, chloramphenicol and vancomycin, and 79 susceptible to all six antibiotics. However, 11 strains (around 12%) were considered resistant to tetracycline (six of which had been identified after screening of a large collection of lactococci strains for tetracycline resistance) and five (5.4%) resistant to streptomycin. Of these, two fish isolates proved to be resistance to both tetracycline and streptomycin. From the tetracycline resistant strains, tet(M) and mosaic tet(L/S) genes were amplified by PCR, demonstrating they harboured acquired antibiotic resistance determinants.