EFFECTS OF SODIUM LACTATE, SODIUM ACETATE AND SODIUM DIACETATE ON MICROBIOLOGICAL QUALITY OF VACUUM-PACKED BEEF DURING REFRIGERATED STORAGE

Beef samples were cut into the pieces and treated with solutions of 1.8 and 2.5% sodium lactate (SL), 0.1% sodium acetate (SA), 0.1 and 0.2% sodium diacetate (SDA) and their combinations, packed under vacuum and stored in a refrigerator at 4C. Microbiological quality of the samples was investigated during their storage for 21 days. Sodium salts and their combinations significantly (P < 0.05) affected the aerobic plate count (APC). Although growth of lactic acid bacteria (LAB), psychrotrophs and coliforms was delayed in treated samples, they were not completely inhibited. The most effective treatment to delay the growth of microorganisms was the combination of 2.5% SL + 0.2% SDA. The count of bacteria of the samples reached and exceeded the spoilage limit (10⁷?10⁸log cfu/g) after 14 days at 4C.     

A survey of the occurrence and properties of methicillin‐resistant Staphylococcus aureus and methicillin‐resistant Staphylococcus intermedius in water buffalo milk and dairy products in Turkey

Antimicrobial resistance, β‐lactamase activity and mecA gene of Staphylococcus aureus and Staphylococcus intermedius isolated from raw water buffalo milk and dairy products in Turkey were determined. All strains showed resistance to at least one antibiotic but none was resistant to vancomycin. Of the 97 S. aureus and 35 S. intermedius strains, 9 (9.2%) and 2 (5.7%) were resistant to oxacillin and harboured mecA gene. β‐lactamase activity of 13.4% and 5.7% of S. aureus and S. intermedius strains was positive, respectively. Overall, 2.5% and 0.55% of the samples were contaminated with methicillin‐resistant S. aureus and S. intermedius, respectively.     

Biopolymers Produced by Cross-linking Soybean 11S Globulin with Whey Proteins using Transglutaminase

Heterogeneity of biopolymers was determined by cross-linking acetylated-11S acidic subunits (Ac-11S) of soy protein with α-lactalbumin and β-lactoglobulin. The extent of polymerization was determined by electrophoresis and HPLC. Differential scanning calorimetry (DSC) was used to determine thermal properties of starting proteins and biopolymers. HPLC data demonstrated the absence of biopolymers from Ac-11S, acetylated α-lactalbumin and acetylated β-lactoglobulin when each was incubated separately with transglutaminase (TG). However, Ac-11S formed biopolymers with α-lactalbumin and β-lactoglobulin when TG was added. TG catalyzed the formation of heterologous and homologous biopolymers from whey protein isolate (WPI) and soybean 11S globulin (11S). Cross-linking WPI and 11S provided biopolymers with improved heat stability which may be useful to provide functionality to food products.     

Properties of Films Produced by Cross-linking Whey Proteins and 11S Globulin Using Transglutaminase

Transglutaminase (TG) was used to produce films from whey protein isolate, soybean 11S globulin and a mixture of the two (1:1, wt/wt). Solubility of TG cross-linked films was lower than that of control films at pH 3, 4, 6 and 8. Solubility of control films in 6.6M urea and in 10% SDS was higher than that of TG cross-linked films. Hydrolysis of control and TG cross-linked films by trypsin and α-chymotrypsin was similar after 24h incubation. Mean thickness of films ranged from 69 to 77 μm and there were no differences among thicknesses. Average tensile strength values of TG cross-linked films were two times greater than those of the homologous controls.     

Effect of Mo addition on microstructure,ordering, and room-temperature mechanical properties of Fe-50Al

The effects of Mo addition on microstructures, phase relationships, order–disorder phase-transition temperatures and room-temperature mechanical properties of Fe₅₀Al_50-nMo_n alloys (n=1, 3, 5, 7, and 9, mole fraction, %) were investigated after solidification and heat treatment. Structural characterization of the samples was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry. Room-temperature mechanical properties were investigated by conducting compression and microhardness tests. Mo₃Al particles precipitated in all alloys because of the limited solid solubility of Mo in the Fe-Al-based phases. The as-cast Fe₅₀Al_50-nMo_n alloys exhibited brittle behavior with high yield strength and limited fracture strain at room temperature. Compared with the as-cast alloys, all the heat-treated alloys except for the Fe₅₀Al₄₁Mo₉ alloy exhibited enhanced mechanical properties at room temperature. The heat-treated Fe₅₀Al₄₃Mo₇ alloy exhibited the highest fracture strain and compressive strength of 25.4% and 2.3 GPa, respectively.     

Three dimensional fracture analysis of FGM coatings under thermomechanical loading

The main objective of this study is to examine the three dimensional surface crack problems in functionally graded coatings subjected to mode I mechanical or transient thermal loading. The surface cracks are assumed to have a semi-elliptical crack front profile of arbitrary aspect ratio. The cracks are embedded in the functionally graded material (FGM) coating which is perfectly bonded to a homogeneous substrate. A three dimensional finite element method is used to solve the thermal and structural problems. Collapsed 20-node isoparametric elements are utilized to simulate the strain singularity around the crack front. The stress intensity factors are computed by using the displacement correlation technique. Four different coating types are considered in the analyses which have homogeneous, ceramic-rich (CR), metal-rich (MR) and linear variation (LN) material composition profiles. In the mechanical loading problems, the composite medium is assumed to be subjected to fixed-grip tension or three point bending. In the thermal analysis, a transient residual stress problem is considered. The stress intensity factors calculated for FGM plates are in good agreement with the previously published results on three dimensional surface cracks. The new results provided show that maximum stress intensity factors computed during transient thermal loading period for the FGM coatings are lower than those of the homogeneous ceramic ones.     

INVESTIGATION OF INHIBITORY EFFECTS OF SEVERAL COMBINATIONS OF SODIUM SALTS ON THE GROWTH OF LISTERIA MONOCYTOGENES AND SALMONELLA ENTERICA SEROTYPE ENTERITIDIS IN MINCED BEEF

Inhibition effects of several combinations of sodium lactate (SL), sodium acetate, sodium diacetate (SDA) on the growth of Listeria monocytogenes and Salmonella enterica serotype Enteritidis were investigated in minced beef. The samples inoculated with 4.60 log cfu/g of Salmonella enteritidis and 4.70 log cfu/g of L. monocytogenes were treated with sodium salts and their combinations and stored at 4C. Sodium salts decreased the growth rate of S. enterica serotype Enteritidis. Combinations of the salts were bactericidal to S. enterica serotype Enteritidis but the growth of L. monocytogenes was delayed only by using the combination of 2.5% SL and 0.2% SDA.     

Partial characterisation of enterocin KP produced by Enterococcus faecalis KP,a cheese isolate

Enterococcus faecalis KP, a bacteriocin‐producing strain, was identified using 16S rRNA gene sequence homology (99%). Enterocin KP from E. faecalis KP was sensitive to papain and ß‐mercaptoethanol, but resistant to trypsin, pepsin, lipase, catalase, α‐amylase, organic solvents, detergents, EDTA and heat treatment (90°C/30 min). It was active at a wide pH range (2.0–8.0) and produced at maximum level in de Mann Rogosa Sharpe broth at 32°C with an inoculum amount of 0.1–1.0% and an initial pH of 5.5–7.5. It was active against some Gram‐positive bacteria, including Listeria monocytogenes. It showed bactericidal activity against L. monocytogenes and its molecular weight was approximately 5.8 kDa.     

Singular perturbations with origin eigenvalues

The aim of this study is to apply singular perturbation theory to systems with origin eigenvalues. If the reduced system has origin eigenvalues with Jordan block sizes equal to one then this guarantees the stability of the original system. However, if these sizes are greater than one then the reduced system does not give any information about the stability of the original system. So another reduced system is obtained using the second derivative of the ‘fast’ part, and it is shown that under some specified conditions, stability or instability of this system implies the stability or instability of the original system.