Oxidation behavior of IG and NBG nuclear graphites

This work studies the oxidation-induced characteristics of four nuclear graphites (NBG-17, NBG-25, IG-110, and IG-430). The oxidation characteristics of the nuclear graphites were measured at 600 °C. The surface properties of the oxidation graphites were characterized by means of scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle methods. The N₂/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were investigated by means of BET and t-plot methods. The experimental results show an increase in the average pore size of graphites; they also show that oxidation produces the surface functional groups on the graphite surfaces. The surface area of each graphite behaves in a unique manner. For example the surface area of NBG-17 increases slightly whereas the surface area of IG-110 increases significantly. This result confirms that the original surface state of each graphite is unique.     

Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere

The effects of irradiation dose (0, 0.5 and 1.0 kGy), headspace oxygen (0, 10 and 20% O₂, balance nitrogen) and storage temperature (5, 15 and 25°C) on the physical, chemical and sensory changes in fresh pork were studied using factorial design experiments. Irradiation in the absence of oxygen extended the sensory shelf life of pork from 9 to 26 days at 5°C and from & lt; 2 to 2 days at 25°C. Oxygen in the package headspace combined with irradiation adversely affected physical, chemical and sensory characteristics of the end product.     

The influence of temperature on the adhesion of mixed cultures of Staphylococcus aureus and Escherichia coli to polypropylene

The adhesion of Staphylococcus aureus and Escherichia coli, in mixed cultures, to polypropylene surfaces was evaluated at 12°C and 30°C. The micro-organisms were isolated from a chicken carcass and cultured in an aqueous extract, prepared from the same carcass, for the production of biofilms on polypropylene coupons. Adhered cells were counted by epifluorescence microscopy with acridine orange staining. Escherichia coli adhered in greater numbers to the coupons than S. aureus at both temperatures. Staphylococcus aureus adhered better at 12°C than at 30°C, while the reverse was true for E. coli. At 30°C, there was no increase in the number of adherent cells ofS. aureus over 8 h, while E. coli increased from a median of 5·0–19·0 per microscope field. At 12°C, the major increase in adherent cell numbers for both species occurred between 2 and 4 h, so that leaving cleaning until 8 h, as is common, would not result in greatly increased biofilms, 2-hourly cleansing is clearly unrealistic. However, total adherent cell numbers were the same at 12° and 30°C between 4 and 6 h incubation. Hence it seems that reduced temperature has little to offer for restricting biofilm formation on polypropylene work surfaces in a well-run food processing plant.     

Bound Water Associated with 7S and 11S Soy Proteins Determined by Vapor Sorption Isotherms and Pulsed NMR

Bound water associated with freeze-dried 7S and 11S proteins was characterized by applying both sorption isotherm and proton pulsed NMR techniques. Over the a_w range 0.10 to 0.97, the water binding capacity of the 7S protein was superior to that of the US protein. There was no significant difference in sorption capacity between unhealed and heated proteins. The isotherms showed a biphasic linear relation so that two states of bound water, namely polymer and capillary water, were distinguished. NMR data followed isotherm data. The NMR mobility of the polymer water was less than that of the capillary water, as expected. However, high mobility was not related to high moisture content in the capillary water region.     

Fat and Water Composition Affects Residual Catalatic Activity in Chicken Breast Heated to Specific End-point Temperatures

Fat and water contents of meat tissues strongly influence their thermo-physical properties. Seven groups of ground chicken breast meat containing varying amounts of fat and water were prepared for this investigation. Each group was heated to end-point temperatures (EPTs) of 69.0 to 71.0°C at 0.5°C intervals. Severity of heat treatments was evaluated by the total process lethality calculated using the General Method. The fat and water contents affected the heating time to reach specific EPTs and the residual catalatic activity at EPTs of 69.0, 69.5 and 70.0°C, but did not affect total process lethality. The variation of the catalase method for determining EPT was related to the sample composition.