Thermal Destruction of Listeria monocytogenes in Ground Pork Prepared with and without Soy Hulls.

D-values and z-values were determined for Listeria monocytogenes Scott A cells heated in raw ground pork prepared with and without soy hulls and in a soy hull/water mixture. Products inoculated with ca. 10 colony-forming units (CFU) per g were sealed in glass vials, immersed in a water bath, and held at 50, 55, 60, or 62°C for predetermined times.

Microflora of Cheddar Cheese Made with Sodium Chloride, Potassium Chloride, or Mixtures of Sodium and Potassium Chloride.

Cheddar cheese samples from three different split lots of cheese curd were prepared with added NaCl, KCl, or mixtures of NaCl/KCl (2:1, 1:1, 1:2 and 3:4, all on wt/wt basis) to achieve a final salt concentration of 1.5 or 1.75%.

Lactic Acid Bacteria in Cheddar Cheese Made with Sodium Chloride, Potassium Chloride or Mixtures of the Two Salts.

Three different split lots of Cheddar cheese curd were prepared with added sodium chloride (NaCl) potassium chloride (KCl) or mixtures of NaCl/KCl (2:1 1:1 1:2 and 3:4 all on wt/wt basis) to achieve a final salt concentration of 1.5 or 1.75%.

Sensitivity of Listeria monocytogenes to Selected Spices.

Ten spices were added separately to tryptose broth which was then inoculated to contain, per ml, 10 or 10 Listeria monocytogenes strain Scott A or V7, respectively, and held at 4°C for 7 d. Strain Scott A appeared to be more sensitive to effects of spices than was strain V7. The population of strain Scott A was decreased to <10/ml in 1 d by 1% sage, in 4 d by 1% allspice, and in 7 d by 1% cumin, garlic powder, paprika, and red pepper.

Lysozyme and Lipase Alter Unfrozen and Frozen/Thawed Cells of Listeria monocytogenes.

Unfrozen and frozen/thawed cells of Listeria monocytogenes strains Scott A, V7, and California were treated with lipase and/or lysozyme. Cells of strain Scott A were more susceptible to the lytic action of lysozyme than were cells of strains V7 and California. Treatment of unfrozen cells with lipase before exposure to lysozyme enhanced cellular lysis.

Transmission Electron Microscopy of Unfrozen and Frozen/Thawed Cells of Listeria monocytogenes Treated With Lipase and Lysozyme.

Unfrozen cells of Listeria monocytogenes typically contained no preplasma space exterior to the plasma membrane (PM) when viewed by transmission electron microscopy. Cells of L. monocytogenes strains Scott A, V7, and California (CA), after freezing and frozen storage, exhibited one or more of the following when viewed with transmission electron microscopy: (a) retraction of cytoplasm and infolding of the PM to form mesosomes, (b) extra-and intracellular rupture of the cell wall (CW), (c) formation of intracellular "bubbles," and (d) damage to the CW and PM that could have resulted from autolysin activity.

Freezing of Listeria monocytogenes and Other Microorganisms: A Review.

When the temperature of microbes is lowered rapidly, some are injured through thermal shock. Frozen cells can be injured mechanically by intra- and extracellular ice crystals. During freezing, as water is removed, there is a concentration of cell solutes which can lead to dissociation of cellular lipoprotein.

Thermal Inactivation of Listeria monocytogenes in Chicken Gravy.

Heat resistance of Listeria monocytogenes strains V7 and Scott A in chicken gravy and changes in heat resistance during refrigerated storage were studied. After chicken gravy was made, it was cooled to 40°C, inoculated with 10 CFU L. monocytogenes per ml of gravy, and then stored at 7°C for 10 d.

Behavior of Listeria monocytogenes in the Presence of Sodium Propionate Together with Food Acids.

Tryptose broth (TB) containing 0.00, 0.05, 0.

Fate of Listeria monocytogenes During the Manufacture of Mozzarella Cheese.

Mozzarella cheese was made from a mixture of pasteurized whole and skim milk which was inoculated to contain 10-10 CFU Listeria monocytogenes (strain Ohio, California, or V7) per ml. Temperature of milk was maintained at 40°C (104°F) for 30 min when curd became resilient and the pH reached 5.90-5.

Ultrafiltration and Reverse Osmosis in Dairy Technology: A Review.

Ultrafiltration and reverse osmosis processes can be useful in the dairy foods industry. When milk is processed, milk fat and casein are rejected fully (e.g.

Behavior of Listeria monocytogenes in the Presence of Flavobacteria in Skim Milk at 7 or 13°C.

Sterile samples of skim milk were inoculated with Listeria monocytogenes (strain Scott A, California, or V7), Flavobacterium lutescens or Flavobacterium species, or a combination of L. monocytogenes plus flavobacteria and incubated at 7 or 13°C for 8 weeks. McBride Listeria agar was used to determine populations of L.

Organic Acids Enhance the Antilisterial Activity of Potassium Sorbate.

Tryptose broth containing 0.0, 0.05, 0.

Survival of Borrelia burgdorferi in Whole Milk, Low Fat Milk, and Skim Milk at 34°C and in Skim Milk at 5°C.

Autoclaved whole milk, low-fat milk, protein-fortified skim milk and regular skim milk were inoculated to contain ca. 10 to 10 Borrelia burgdorferi strains 35210, 35211, or EBNI/ml and stored at 34°C for 16 d. Similarly inoculated skim milk also was held at 5°C for 46 d.

Growth of Listeria monocytogenes at 4, 32, and 40°C in Skim Milk and in Retentate and Permeate from Ultrafiltered Skim Milk.

Pasteurized skim milk and retentate (concentrated fivefold or twofold by volume) and permeate from ultrafiltered skim milk were inoculated with Listeria monocytogenes strains California or V7 and incubated at 4, 32, or 40°C. Changes in populations of the pathogen were determined, growth curves were derived, and generation times and maximum populations calculated for each combination of strain, product, and temperature. Both strains grew faster and achieved higher (ca.

Behavior of Listeria monocytogenes in the Presence of Lactic Acid Bacteria in an Agitated Medium with Internal pH Control.

An agitated medium with internal pH control (IPCM-2) was inoculated to contain Listeria monocytogenes (strain V7, Scott A or California) at ca. 10 CFU/ml and Streptococcus cremoris (Lactococcus lactis subsp. cremoris) or Streptococcus lactis (Lactococcus lactis subsp.

Reducing the Sodium Content of Foods: A Review.

Salt (sodium chloride), a substance essential for life processes, is the second most-used food additive. It is added to foods as a flavoring or flavor enhancing agent, a preservative, or an ingredient responsible for desired functional properties in certain products. Excessive dietary sodium is believed to contribute to hypertension and development of cardiovascular disease which afflicts ca.

Behavior of Listeria monocytogenes in the Presence of Streptococcus lactis in a Medium with Internal pH Control.

Growth of Listeria monocytogenes strains V7, Scott A, and California (initial inoculum 10/ml) at 21 or 30°C in the presence of Streptococcus Iactis (initial inoculum 0.25 or 1.0%) was determined using a medium with internal pH control (IPCM-1).

Fate of Listeria monocytogenes in Sweetened Condensed and Evaporated Milk During Storage at 7 or 21 °C.

Sweetened condensed and evaporated milks were inoculated to contain ca. 10 to 10 cells of Listeria monocytogenes (strains Scott A, California, or V7)/ml. Both inoculated products were cooled from 25°C to 21°C in ca.

Degradation of Aflatoxin B in Dried Figs by Sodium Bisulfite With or Without Heat, Ultraviolet Energy or Hydrogen Peroxide.

Dried fig fruits were spiked to contain 250 ppb aflatoxin B (AFB) and treated with sodium bisulfite (1% in the aqueous phase of the mixture). This treatment caused 28.2% of added toxin to degrade in 72 h at 25°C.

Thermal Inactivation of Borrelia burgdorferi , the Cause of Lyme Disease.

Borrelia burgdorferi strain EBNI was cultivated in BSK-II medium at 34°C, then cultures at different physiological states were heat-treated at temperatures in the range of 50 to 70°C. Numbers of survivors were estimated by the Most Probable Number technique. Log MPN was plotted against treatment time, and resulting survivor curves were linear.

Behavior of Listeria monocytogenes in the Presence of Cocoa, Carrageenan, and Sugar in a Milk Medium Incubated With and Without Agitation.

Enhanced growth of Listeria monocytogenes strain V7 in chocolate milk rather than skim milk was further investigated by testing various concentrations of cocoa powder (two types of Dutch-process, designated A and B), cane sugar, and sodium carrageenan in skim milk at 13 and 30°C with and without agitated incubation. Increasing sugar concentrations (0, 6.5, and 12.

Inhibition of Listeria monocytogenes by Cocoa in a Broth Medium and Neutralization of this Effect by Casein.

Dutch-processed cocoa (0.75 to 10.0%, w/v), when added to a broth medium, inhibited/inactivated Listeria monocytogenes strain V7.

Caffeine and Theobromine.

Two components of cocoa powder, caffeine (1,3,7-trimethylxanthine) and theobromine (3,7-dimethylxanthine), were evaluated for their effect on growth of L. monocytogenes strain V7. Caffeine (0.

Acid-Injury of Listeria monocytogenes.

Acid injury Listeria monocytogenes in solutions of 0.3 and 0.5% acetic, citric and lactic acid at 13 and 35°C was determined.