Osman Erkmen

Effects of starter cultures and additives on the quality of Turkish style sausage (sucuk)

The effects of starter cultures and additives on the quality of Turkish style sausage (sucuk) were investigated during ripening and storage. Total aerobic plate counts (aerobic bacteria), mould and yeast counts, pH, thiobarbituric acid (TBA) value and biogenic amine formation were followed. Aerobic bacteria increased (P<0.05) during the first 10 days of ripening to 9.26 log CFU/g and they decreased (P<0.05) to 5.70 at the end of the storage. Larger reductions (P<0.05) were observed in sausages made with high levels of potassium sorbate, nitrite and nitrate than in those containing low levels of additives and those without additives at the end of storage. During the first 3 days of ripening, the pH values of all sausages decreased (P<0.05) from 5.98 to about 4.53. Later, the pH values increased slowly, due to decomposition of acids to an approximately constant value of about 5.20. TBA values were higher (P<0.05) in the sausages made without additives than in the others. Sausages prepared using high concentration of additives had lower (P<0.05) concentrations of biogenic amines than the others. Addition of starter culture with high concentration of additives (nitrite, nitrate, α-tocopherol, ascorbic acid, potassium sorbate, potassium pyrophosphate and di-potassium hydrogenphosphate) decreased the formation of biogenic amine.

High pressure inactivation kinetics of Listeria monocytogenes inactivation in broth, milk, and peach and orange juices

High hydrostatic pressure kinetics (D, z and k values) of aerobic bacteria (AB) and Listeria monocytogenes inactivation were determined in brain heart infusion broth (BHIB) and foods. The D and k values of L. monocytogenes ranged from 12.1 to 1.14 min and from 0.1907 to 2.0202 min−1, respectively in BHIB at a pressure range 200–700 MPa. D values were about 3.04 and 2.43 min for AB and L. monocytogenes, respectively, in milk at 600 MPa, 2.13 and 1.52 min, respectively, in peach juice, and 1.24 and 0.87 min, respectively, in orange juice. The k values for L. monocytogenes in orange juice (ranged from 0.8024 to 2.6471 min−1) were greater than BHIB (ranged from 0.1907 to 2.0202 min−1), peach juice (ranged from 0.3733 to 1.5151 min−1) and milk (ranged from 0.2096 to 0.0.9477 min−1) at same pressure. The z values of L. monocytogenes were 578, 480, 506 and 576 for L. monocytogenes in milk, BHIB, peach juice and orange juice, respectively. There were significant (p<0.01) difference among kinetic values of AB and L. monocytogenes inactivation in broth and foods.

Effects of high-pressure carbon dioxide on Escherichia coli in nutrient broth and milk

Bactericidal effects of high-pressure carbon dioxide against Escherichia coli were studied under 100, 75, 50 and 25 bar at 20 degrees C, 30 degrees C and 40 degrees C. E. coli suspended in nutrient broth (NB, pH = 6.75) was inactivated under 100, 75, 50, and 25 bar CO2 treatments for 50, 65, 100, and 140 min at 30 degrees C, respectively. Acidification of nutrient broth by dissolved CO2 alone might account for the bactericidal effect under pressure. E. coli was inactivated in NB with initial pH 5.50 and 4.5 at 100 bar for 80 and 95 min, respectively. Treatment at 100 bar CO2 pressure for 6 h caused a decrease of 6.42 and 7.24 log cycles in whole and skim milk, respectively.

Kinetic studies on the high pressure carbon dioxide inactivation of Salmonella typhimurium

Abstract Inactivation kinetics (D and z values) of Salmonella typhimurium under high pressure carbon dioxide (HPCD) from 1.51 to 7.56 MPa at 35°C was investigated in model solutions of brain heart infusion broth (BHIB) and physiological saline (PS). The come-up time to reach a pressure exerts an important effect on the survival of S. typhimurium. The inactivation rates increased with pressure, suspending medium and exposure time. Inactivation followed first order reaction kinetics, with specific inactivation rates (k) and decimal reduction times (D) that varied from 0.0975 to 1.5561 min −1 and from 23.63 to 1.48 min, respectively. The pressure dependence of the S. typhimurium specific inactivation rates can be described by the zp value depending on the model solutions BHIB and PS.

Antimicrobial effects of Turkish propolis, pollen, and laurel on spoilage and pathogenic food-related microorganisms.

The antimicrobial activities of propolis extract, pollen extract, and essential oil of laurel (Laurus nobilis L.) at concentrations from 0.02% to 2.5% (vol/vol) were investigated on bacteria (Bacillus cereus, Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Yersinia enterocolitica, Enterococcus faecalis, and Listeria monocytogenes), yeasts (Saccharomyces cerevisiae and Candida rugosa), and molds (Aspergillus niger and Rhizopus oryzae). Pollen has no antimicrobial effects on the bacteria and fungi tested in the concentrations used. Propolis showed a bactericidal effect at 0.02% on B. cereus and B. subtilis, at 1.0% on S. aureus and E. faecalis, and at 0.2% on L. monocytogenes. The minimum inhibitory concentration of propolis for fungi was 2.5%. Propolis and laurel were ineffective against E. coli and S. typhimurium at the concentrations tested. The results showed that the antimicrobial activity were concentration dependent. Propolis and essential oil of laurel may be used as biopreservative agents in food processing and preservation.

The aflatoxin contamination of ground red pepper and pistachio nuts sold in Turkey

Total aflatoxin (AFT) and aflatoxin B1 (AFB1) contamination, pH and water activity, and mold and yeast counts in unpacked and packed ground red pepper (GRP) and pistachio nut have been studied from September 2008 to February 2009. 17.1% (14/82) and 23.1% (19/82) unpacked GRP were over AFT and AFB1 legal limits, respectively, while only one packed sample was over legal limit of AFB1 by 89.99 ppb. Both of AFT and AFB1 were detected in 50.5% (48/95) of unpacked pistachio nuts with the contamination levels ranging from 0.007 to 7.72 ppb. Mold and yeast counts in unpacked GRP and mold counts in unpacked pistachio nut were detected over legal limits with 5.9% (5/85) and 1.1% (1/95), respectively. These cases call attention to the importance of aflatoxin content in these foods and need strict prohibition in the use of batches containing aflatoxins.

Antimicrobial effects of pressurised carbon dioxide on Brochothrix thermosphacta in broth and foods

Antimicrobial effects of high-pressure CO2 on Brochothrix thermosphacta were investigated in a batch system. Inactivation rates increased with increasing pressure, temperature and exposure time. B thermosphacta suspended in physiological saline was completely inactivated under 6.05, 3.02 and 1.51 MPaCO2 treatment at 35 °C after 10, 25 and 50 min respectively. Two phases were observed in the survival curves. The earlier stage was characterised by a slow rate of decrease in the number of B thermosphacta, which increased sharply at the later stage. B thermosphacta suspended in brain heart infusion broth was completely inactivated under 6.05 MPaCO2 treatment after 80, 50 and 30 min at 25, 35 and 45 °C respectively. About 6.90 and 5.93 log cycles of B thermosphacta were reduced under 6.05 MPaCO2 pressure at 45 °C in whole and skimmed milk respectively. The sterilisation effects of 6.05 MPaCO2 pressure at 45 °C on both B thermosphacta and aerobic plate count were observed after 150 and 120 min respectively in skinned meat. © 2000 Society of Chemical Industry

Antimicrobial effect of pressurised carbon dioxide on Enterococcus faecalis in physiological saline and foods

Inactivation of Enterococcus faecalis by high-pressure CO2 was investigated in a batch system. Two phases were observed in the survival curves. The earlier stage was characterised by a slow rate of decrease in the number of E faecalis. This rate increased sharply at the later stage. Enterococcus faecalis suspended in physiological saline was completely inactivated under 6.05 and 3.02 MPa CO2 treatment in 18 and 80 min respectively at 35 degrees C. The high pressure of CO2 at 45 degrees C was effective at sterilising orange, peach and carrot juices but ineffective for whole and skimmed milk. A minimum D-value was obtained under 6.05 MPa CO2 pressure at 45 degrees C. Reduction rates of E faecalis were sensitive to pressure, temperature, exposure time, the initial number of cells and the suspending medium.

Kinetic analysis of Listeria monocytogenes inactivation by high pressure carbon dioxide

Abstract High pressure carbon dioxide (HPCD) inactivation kinetics ( D and z values) of Listeria monocytogenes in model solutions of brain heart infusion broth (BHIB) and physiological saline (PS) were evaluated from 1.51 to 6.05 MPa at 25°C. The come-up time to reach a pressure exerts an important effect on the survival of L. monocytogenes . Inactivation followed first-order reaction kinetics, with specific inactivation rates ( k ) and decimal reduction times ( D ) that varied from 0.0668 to 0.5375 min −1 and from 34.49 to 4.31 min, respectively. The pressure dependence of the L. monocytogenes specific inactivation rates can be described by the z value depending on the model solutions PS and BHIB.

Mathematical Modeling of Escherichia coli Inactivation under High-Pressure Carbon Dioxide

Inactivation curves of Escherichia coli under high carbon dioxide pressures (2.5, 5.1, 7.6 and 10.1 MPa) at different temperatures (20, 30, 40 and 45 degrees C) were analyzed using the modified Gompertz model. The phase disappearance (time for complete inactivation of all cells, lambda) and the inactivation rate (mu) of E. coli were inversely related. Inactivation rates (mu) of E. coli were higher at 45 degrees C under 10.1 MPa CO2 pressure than at 25, 30 and 40 degrees C under 2.5, 5.1 and 7.6 MPa CO2 pressure. Increased pressure and temperature had significant effects on the survival of E. coli. The temperature dependence of the inactivation rate constant was analyzed based on the Arrhenius, linear and square-root models. The temperature sensitivity (high E(mu)) determined based on the Arrhenius model was higher at high temperatures. E(mu) (activation energy) value was -186.56 Kjoule/mol at 10.1 Mpa, and -137.24, -167.25 and -183.80 Kjoule/mol at 2.5, 5.1 and 7.6 MPa, respectively. Results of this study enable the prediction of microbial inactivation exposed to different CO2 pressures and temperatures.