Gabriel O. I. Ezeike

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on Plastic Kitchen Cutting Boards by Electrolyzed Oxidizing Water

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (approximately 10(10) CFU) was inoculated on a 100-cm2 area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23 degrees C or 35 degrees C for 10 or 20 min; 45 degrees C for 5 or 10 min; or 55 degrees C for 5 min. After each temperature-time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by > or = 5.0 log CFU/100 cm2 on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm2. Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature-time combinations (23 degrees C for 20 min, 35 degrees C for 10 min, and 45 degrees C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E. coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.

Reduction of Campylobacter jejuni on poultry by low-temperature treatment

Campylobacter jejuni is a leading cause of acute bacterial gastroenteritis in the United States, with epidemiologic studies identifying poultry as a leading vehicle in human infection. Studies were conducted to determine rates of C. jejuni inactivation on poultry exposed to different cooling and freezing temperatures. A mixture of three strains of C. jejuni originally isolated from poultry was inoculated onto chicken wings at ca. 10(7) CFU/g. The results of the study revealed that the storage of wings at -20 and -30 degrees C for 72 h reduced the population of C. jejuni on wings by 1.3 and 1.8 log10 CFU/g, respectively. The results with regard to long-term freezing for 52 weeks revealed C. jejuni reductions of ca. 4 and 0.5 log10 CFU/g on wings held at -20 and -86 degrees C, respectively. Protocols were developed to superchill wings in Whirl-Pak bags with liquid nitrogen at -80, -120, -160, and -196 degrees C such that the internal portion of each wing quickly reached -3.3 degrees C but did not freeze. The results with regard to the superchilling of wings at different temperatures for 20 to 330 s (the time required for the wings to reach an internal temperature of -3.3 degrees C) revealed C. jejuni reductions of 0.5 log10 CFU/g for wings held at -80 degrees C, 0.8 log10 CFU/g for wings held at -120 degrees C, 0.6 log10 CFU/g for wings held at -160 degrees C, and 2.4 log10 CFU/g for wings held at -196 degrees C. The superchilling of wings to quickly cool meat to -3.3 degrees C (internal temperature) can substantially reduce C. jejuni populations at -196 degrees C when the wings are submerged in liquid nitrogen, but not at -80 to -160 degrees C when the wings are treated with vapor-state liquid nitrogen. The results of this study indicate that freezing conditions, including temperature and holding time, greatly influence the rate of inactivation of C. jejuni on poultry. The conditions used in the poultry industry to superchill poultry to a nonfrozen-state internal temperature are not likely to substantially reduce Campylobacter populations on fresh products.

ANALYSIS OF DIELECTRIC PROPERTIES OF RICE VINEGAR AND SAKE

The objectives of this study were to determine the dielectric properties of rice vinegar and sake (rice wine) in the 0.3 to 3 GHz frequency range at temperatures from 5 ³ C to 70 ³ C. Dielectric properties of both liquids were analyzed theoretically with the modified Cole–Cole relation including ionic conductivity effect. The important parameters, such as relaxation wavelength, static component of the dielectric constant, and ionic conductivity, were determined at various conditions using the nonlinear least squares method. Penetration depth was estimated under various conditions. The dielectric constant decreased with increasing frequency, concentration, and temperature for both liquid foods. At low frequencies, the loss factor decreased with increasing frequency, but at high frequencies, it increased with frequency. The effect of ionic loss was substantial at higher temperatures and lower frequencies for each material. Dielectric properties of rice vinegar and sake could be adequately analyzed with the modified Cole–Cole relation including ionic conductivity effect.

Refrigeration of Fresh Produce from Field to Home: Refrigeration Systems and Logistics

Lowering the respiration rate of fresh vegetables is essential to preserving market quality. The most important technology for lowering respiration rates remains proper cooling of produce within hours of harvest. In general, harvesting should be done in the early morning hours to minimize field heat. Harvested produce should avoid direct exposure to sun, or field-cool before transport to packing or transportation facilities. Produce will then be cooled to safe storage temperatures. Produce should be shipped to market as soon as possible. Refrigerated loading and unloading areas should be used. Trucks should be cooled before loading, and load pallets should be loaded toward the center of the truck. Insulating plastic strips should be used in the truck and in the loading dock. Produce should be moved rapidly to the storage area, at the appropriate temperature, and displayed at the appropriate temperature range. Room cooling means produce is simply placed in a cold storage room and cools slowly and nonuniformly, mainly through conduction and natural convective contact with refrigerated air. However, a cold room is normally used to store previously cooled produce, and does not have the capacity to remove heat from the uncooled produce. Most cold rooms will increase in temperature after each fresh batch of warmer produce is added. A compromise is to form a cooling area, by partitioning part of the storage using a tarpaulin suspended from the ceiling. This helps reduce temperature fluctuations, but should only be considered as a temporary measure.

Chapter 19 – Refrigeration of Fresh Produce from Field to Home: Refrigeration Systems and Logistics

Lowering the respiration rate of fresh vegetables is essential to preserving market quality. The most important technology for lowering respiration rates remains proper cooling of produce within hours of harvest. In general, harvesting should be done in the early morning hours to minimize field heat. Harvested produce should avoid direct exposure to sun, or field-cool before transport to packing or transportation facilities. Produce will then be cooled to safe storage temperatures. Produce should be shipped to market as soon as possible. Refrigerated loading and unloading areas should be used. Trucks should be cooled before loading, and load pallets should be loaded toward the center of the truck. Insulating plastic strips should be used in the truck and in the loading dock. Produce should be moved rapidly to the storage area, at the appropriate temperature, and displayed at the appropriate temperature range. Room cooling means produce is simply placed in a cold storage room and cools slowly and nonuniformly, mainly through conduction and natural convective contact with refrigerated air. However, a cold room is normally used to store previously cooled produce, and does not have the capacity to remove heat from the uncooled produce. Most cold rooms will increase in temperature after each fresh batch of warmer produce is added. A compromise is to form a cooling area, by partitioning part of the storage using a tarpaulin suspended from the ceiling. This helps reduce temperature fluctuations, but should only be considered as a temporary measure.

Refrigeration of Fresh Produce from Field to Home

Lowering the respiration rate of fresh vegetables is essential to preserving market quality. The most important technology for lowering respiration rates remains proper cooling of produce within hours of harvest. In general, harvesting should be done in the early morning hours to minimize field heat. Harvested produce should avoid direct exposure to sun, or field-cool before transport to packing or transportation facilities. Produce will then be cooled to safe storage temperatures. Produce should be shipped to market as soon as possible. Refrigerated loading and unloading areas should be used. Trucks should be cooled before loading, and load pallets should be loaded toward the center of the truck. Insulating plastic strips should be used in the truck and in the loading dock. Produce should be moved rapidly to the storage area, at the appropriate temperature, and displayed at the appropriate temperature range. Room cooling means produce is simply placed in a cold storage room and cools slowly and nonuniformly, mainly through conduction and natural convective contact with refrigerated air. However, a cold room is normally used to store previously cooled produce, and does not have the capacity to remove heat from the uncooled produce. Most cold rooms will increase in temperature after each fresh batch of warmer produce is added. A compromise is to form a cooling area, by partitioning part of the storage using a tarpaulin suspended from the ceiling. This helps reduce temperature fluctuations, but should only be considered as a temporary measure.

Laser Based Positioning And Drilling System For Placing Temperature Sensor Inside Beef Patty

A compact device for positioning a temperature sensor into the geometric center of a beef patty consisting of a vertical digital stage fitted with a sample holder, a horizontal stage, a laser displacement sensor with a digital voltmeter, and a reversible (rotation) variable speed drill, was developed. With axial adjustment, the horizontal stage was used to contact patty on a drill bit (1/16 inch) and drilling continued to patty center. A wooden block was used to calibrate the system. Thirty fresh and frozen quarter-pound patties each respectively, were drilled to center and stored in a walk-in freezer at -18 o C. Positioning accuracy of sensor tip was determined using an x-ray and imaging system. Mean axial positioning accuracy was 92 and 90% respectively for fresh and frozen patties with no statistical difference, while radial accuracy was consistently 96 to 99.81%. Number of patties with accuracy of 85% or higher was 25 each for fresh (4 patties being perfect) and frozen (8 patties being perfect) patties. Digital imagery over the accuracy spectrum revealed that accuracy was most affected by patty thickness and shape profile. Accuracy could be improved by pre-selecting frozen patties having reasonable shape (flat). The device developed from this study provides a research tool for reliable insertion of temperature sensor into beef part thus enhancing capacity to monitor cooking process and to evaluate product safety.