Browsing by Author "Wilson, James H."

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    Application of Alternative Technologies to Eliminate Vibrios spp. in Raw Oysters
    Hu, Xiaopei (Virginia Tech, 2004-12-15)
    High pressure processing (HPP) and gamma irradiation were applied to inactivate Vibrio vulnificus (MO624) and Vibrio parahaemolyticus (O3:K6 TX2103) in pure culture and in inoculated live oysters. Vibrio pure culture and inoculated oysters were exposed to pressures of 207 MPa (30 kpsi) to 552 MPa (80 kpsi) for 0 min to maximum of 20 min. More than 5.4 log reductions of V. vulnificus occurred at 345 MPa for 0 min in oysters; 345 MPa for 2 min can achieve 4 log reductions on V. parahaemolyticus. Dosage of 1 kGy gamma-irradiation was proved to be effective in producing Vibrio free oysters with comparable organoleptic quality to raw oysters. Thermal conductivity of shucked oysters was measured to be 0.58 to 0.68 W/m°C, as temperature increased from 0 to 50 °C, using a line heat source probe. The specific heat was measured by differential scanning calorimeter methods. It increased from 3.80 to 4.05 kJ/kg °C, when temperature rose from 10 to 50 °C. The thermal diffusivity was calculated employing the data of thermal conductivity, specific heat and density of shucked oysters. The results showed that, under the tested temperature range, thermal properties did not change significantly with temperature. The dielectric constant and loss factor of oysters were determined by an open-ended coaxial line probe connected to a network analyzer at frequency of 30 MHz to 3000 MHz from 1 to 55 °C. The penetration depth of dielectric heating was calculated to be 1.1 cm with the dielectric constant of 55 and loss factor of 14. A two-dimensional mathematical model was established to simulate the heat transfer of microwave heating using a fish gel. Finite difference method was utilized to solve partial differential heat transfer equations. The model was able to predict the temperature distribution in heated fish gel with an accuracy of ± 8°C. Applying the developed mathematical model, the lethality of Vibrio spp., artificially inoculated in live oysters, was estimated collectively by integrating the individual localized lethality of designated heating units. The predicted lethality was compared with microwave enumeration data on Vibrios in oysters. The observed maximum log reductions by microbial enumeration were 4.4 and 3.4 for V. vulnificus and V. parahaemolyticus, respectively. The lethality calculated by integrating temperature profiles was acceptable. The discrepancy between the estimated lethality and microbial test was attributed to the simplified model construction. The quality of processed oysters, including color, aroma and texture properties, was evaluated instrumentally by a digital image system, an electronic nose and universal testing machine. The performance of two electronic nose systems on their abilities to detect oyster aroma and classify the aroma data into distinct groups was evaluated using a trained sensory panel and microbial tests. Cyranose 320 system has demonstrated potential as a quality assessment tool due to its sound correlation with microbial quality data and sensory evaluation scores. According to the quality measurement results, high pressure processing conditions were recommended to be at 345 MPa for less than 3 min and 379 MPa for less than 1.5 min. Deterioration of the quality was distinct for oyster meats exposed to 60 °C or above by thermal processing. The critical thermal processing condition was identified to be 55 °C for 2 min. With careful control, microwave processing could be considered as a candidate for seafood processing to reduce potential bacterial hazard but still retain the quality of the product.
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    The effect of hydrogen on the fatigue life of high strength steel
    Wilson, James H. (Virginia Tech, 1978-08-05)
    Torsional fatigue tests were conducted on 4370 steel oil quenched and tempered at 1000° F in (l) the uncharged state, (2) the hydrogen charged state, and (3) in a hydrogen environment. The tests were conducted on both smooth (Kt = l.l) and V-notch (Kt = 3.8) test specimens. A statistical analysis conducted at the 99% confidence limit for the smooth test specimens indicated that precharging with hydrogen increased the fatigue life of the material and also the fracture surface of the test specimens changed from a circumferential crack to a 45° diagonal crack. At a 90% confidence limit, charging with hydrogen did not affect the fatigue life of the V-notched specimens. At a 99% confidence limit for both the smooth and V-notched test specimens, testing in a hydrogen environment increased the fatigue life of the material. Bending fatigue tests were also conducted on the same material and the results indicated that charging with hydrogen decreased fatigue life of smooth test specimens (Kt = l.l) but increased the fatigue life for V-notched specimens (Kt = 2.4 and 3.8).
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    The Effects of Dietary Lipids on Bone Chemical, Mechanical and Histological Properties in Japanese Quail (Coturnix C. Japonica)
    Liu, Dongmin (Virginia Tech, 2000-06-26)
    Japanese quail were used as animal models in four experiments to evaluate the effects of supplementing diets with different lipids on bone chemical, mechanical, and histological properties. In Exp. 1, laying hens were fed a basal diet containing either 5% soybean oil (SBO), hydrogenated soybean oil (HSBO), chicken fat (CF), or menhaden fish oil (FO). The addition of SBO in the maternal diet increased the levels of total n-6 fatty acids and arachidonic acid (AA, 20:4n-6) in yolk and tibial bones of newly hatched progeny (P<0.01), whereas the maternal FO diet elevated the concentrations of total n-3 fatty acids, eicosapentaenoic acid (EPA, 22:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and total saturated acid, but greatly decreased the amount of AA in both egg and progeny tibiae (P<0.01). The maternal HSBO diet resulted in the accumulation of trans-18:1 fatty acid in egg yolks and tibiae at hatch. The addition of FO or HSBO to the maternal diet significantly lowered the ex vivo PGE2 production of tibiae in newly hatched quail compared to those from hens given the SBO or CF diets (P<0.01). In Exp. 2, the addition of different lipids in the maternal diets did not affect growth, tibial length, diameter or collagen content of the progeny. However, supplementing the maternal diet with 5 % FO or HSBO increased the percent bone ash , increased bone pyridinium crosslinks of collagen, enlarged the cartilaginous proliferative and hypertrophied zones, increased diaphyseal cortical thickness of the tibiae in embryos (P<0.05), and subsequently increased tibial shear force, stiffness (P<0.05) and improved cortical thickness, density and trabecular density in early growth and development of progeny compared to those from hens consuming the SBO or CF diets (P<0.05). In Exp. 3, male quail at one month of age were fed a basal diet containing either 5% SBO, HSBO, CF or FO for seven months. Long-term supplementation in the diets of different lipids did not affect body weight, food intake, tibial length or diameter, but the FO group had the highest tibial percent ash, and both FO and HSBO increased tibial mineral content in aged quail compared to those fed the SBO or CF diets (P<0.05). At 8 months of age, quail fed FO had the highest concentrations of (n-3) fatty acids (20:5n-3, 22:5n-3, 22:6n-3) but the lowest amounts of 20:4n-6 in lipids from tibial cortical bone, whereas the SBO and CF diets greatly elevated (n-6) fatty acids and 20:4n-6 levels. The HSBO diet which contains t18:1 fatty acid resulted in t18:1 accumulation in bone. Long-term supplementation with FO or HSBO increased tibial shear force, stiffness and shear stress, as well as improved cortical thickness and density compared with the SBO or CF diets ( P<.05). In Exp. 4, the addition of SBO or CF to the diet for seven months decreased tibial mineral content compared to the FO diet (P<0.05). Quail fed SBO increased collagen concentration in the tibiae (P<0.05), but the level of collagen crosslinks was higher in quail fed FO or HSBO compared to those given the SBO or CF diets (P<0.05). The PGE2 production in bone organ culture and marrow was greatly increased in quail maintained on the SBO or CF diets (P<0.05). PGE2 production in the bone microenvironment was negatively correlated with the tibial percent ash and collagen crosslinks but had a positive correlation with tibial collagen concentration. The results of these studies demonstrate that either supplementing the maternal diets with or long-term exposure to different lipids alters the chemical composition and metabolism of skeletal tissue in both embryos and aged quail. Maternal dietary SBO or CF had an adverse effect on bone growth and development in embryos. Likewise, long-term exposure to SBO or CF diet impaired bone metabolism and remodeling. In contrast, the FO or HSBO diet had beneficial effects on bone modeling in embryos and remodeling in adult quail.
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    Effects of Maternal Dietary Fats and Antioxidants on Growth Rate and Bone Development of Commercial Broilers
    Taylor, Douglas Lumont Jr. (Virginia Tech, 1998-05-26)
    The effect of maternal dietary fats on growth rate and bone development of commercial broilers was examined. Three hundred fifty female chicks were winged banded, weighed and equally divided among six starter pens (1.52 X 3.66m) with litter floors. At 20 wk of age, each pen was fed a basal laying diet supplemented with either 3% chicken fat (CF), soybean oil (SBO) or menhaden oil (MO). Each diet was provided with or without the antioxidant ethoxyquin, producing a total of six dietary treatments. Addition of fats [soybean (SBO), menhaden oil (MO), chicken fat (CF), soybean + antioxidant (SA), menhaden + antioxidant (MA), and chicken + antioxidant (CA)] to the maternal diet altered the tissue and yolk composition of hens to reflect the dietary source. Response variables measured were body weight, tibia weight and length, and breaking strength (stress, force, energy, bone wall, and diameter). Chick tissue from hens fed a MO and MA diet exhibited greater (P<0.01) amounts of DPA (22:5n3), DHA (22:6n3) and total n-3 fatty acids than the remaining dietary treatments. Tissues from chicks fed a SBO and SA diet displayed larger levels of 18:2n6 and total n-6 fatty acids when compared to all other treatments. Male and female chicks from the menhaden type diets (MO and MA) were lighter (P<0.01) during grow out period than from soybean (SBO and SA) and chicken (CF and CA) type diets. Chicks tibiae diameter from CF maternal diet tended to be larger than the MO maternal diet, with significance being noted at d 14 (P<0.01) and 28 (P<0.01). Increases were observed in shear force and stress required to break chick tibia from SBO maternal diet compared to those from the CF and MO maternal diets. The SBO maternal diet stimulates growth rate and bone development and strength of the progeny. (Key words: chickens, bone development, breaking strength, growth rate, fatty acids)
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    Environmental effects on the fatigue behavior of copper nickel alloys
    Sudarshan, T. S. (Virginia Polytechnic Institute and State University, 1984)
    Mode I and Mode III fatigue tests were performed on copper nickel alloys in helium, salt water environments. The hydrogen, oxygen, two alloys used air and in this investigation were 90-10 and 70-30 copper nickel. Both alloys contained iron which was added to improve the erosion corrosion resistance. The extent of cracking varied with the test environment. Tests showed that oxygen and humid air promoted cracking while salt water helium was used as the baseline retarded cracking when environment. Hydrogen promoted cracking when compared to helium but retarded cracking if comparisons were made with oxygen or humid air. The environmental effects (helium as the base case} in the Mode I tests in gaseous environments were manifested in the form of shorter fatigue lives, easier crack initiation, marginally higher crack growth rates and the development of intergranular fracture at the surface. These effects were accompanied by a change in the near surface deformation characteristics. The increases in fatigue life induced by testing in aqueous environments were greatly extended if the copper nickel was galvanically coupled to steel. Mode III tests showed the same ranking of environmental effects as Mode I tests and also showed multiple initiation, brittle fracture and secondary cracking. Two models were proposed to explain the observed results. One was based on the dilation-aided diffusion of oxygen ahead of the crack tip and subsequent oxidation of internal iron particles. The oxidation caused a volume expansion which produced internal tensile strains and facilitated fracture. The other mechanism was based on dilation-aided transport of hydrogen with subsequent accumulation of hydrogen at interfaces, resulting in a lowering of the interfacial strength and promoting intergranular fracture. The observed increases in life in the aqueous environments were rationalized by the reduced oxygen content available in the stagnant solutions. These observations suggest that the presence of iron accelarates fatigue in copper nickel alloys exposed to aggressive environments. Thus, any application involving fatigue loading with simultaneous exposure to aggressive environments should attempt to ensure that the iron content of the copper nickel alloys is minimized.
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    Host plants of the tobacco flea beetle, Epitrix parvula F.
    Glass, Edward H. (Virginia Tech, 1940-05-15)
    A study of the host plants of the tobacco flea beetle was made in Pittsylvania County from April 1 to September 23, 1939. The work was divided into field observations, rearing experiments end population studies. From field observations made throughout the season it was found that this insect fed mostly on the solanaceous plants. especially tobacco. In the spring before the tobacco was transplanted and in the late summer after the harvesting of the crop, the flea beetle fed on a wide variety or plants. Rearing experiments were made using 29 plant species representing 11 families most of which were known as hosts of the adult beetle. These were planted in a small plot of land of a common tobacco soi1. Beetles were caged over these for 4 days and records were kept as to the number of adults that developed from the eggs laid. No beetles emerged from any of the non-solanaceous plants, whereas at least a few developed on all the Solanaceae tested. Many more beetles developed on tobacco, potato and jimson weed than on any of the others. For the population studies tobacco flea beetle and solanaoeous weed counts were made in 14 tobacco fields selected for this purpose. Beetle counts were made at weekly intervals from May 26 until the middle of August and were computed to show the average number of beetles per tobacco plant. Weed counts were made in June and September and were computed to show the average number of weeds per 100 square yards. The data indicated that only tobacco in the beds and potato in the field were of importance in building up the early flee beetle infestation of tobacco.
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    Identifying a non-invasive measure of bone status in dairy cattle
    Keene, Beth E. (Virginia Tech, 2003-08-01)
    The objectives of this research were to evaluate non-invasive measures of bone mineral content (BMC) and bone mineral density (BMD) as rapid, on-farm tools to assess phosphorus (P) status in dairy cows. In addition, the effects of parity and stage of lactation on measures of BMC of the fused 3rd and 4th metacarpal bone and of caudal vertebrae 14 and 15 were assessed. The caudal vertebrae and right front metacarpal (sample pairs) were excised from 107 Holstein cull cows following slaughter. Parity, age, and days in milk (DIM) of the donor animal were obtained for 43 pairs of samples. Samples were grouped by parity (1, 2, 3, and >4) and stage of lactation (Stage 1 = < 90 DIM, Stage 2 = > 90 and < 150 DIM, Stage 3 = >150 and < 250 DIM and Stage 4 = > 250 DIM). Samples were analyzed for BMC and BMD with dual energy X-ray absorptiometry (DXA), BMC with radiographic photometry (RP), breaking strength with mechanical methods, and mineral content with chemical procedures. Estimates of BMC obtained with RP and DXA were poorly related to chemical measures of actual BMC and to measures of breaking strength. In caudal vertebrae 14 and 15, increasing stage of lactation decreased energy to peak load with the lowest values observed in late lactation. Stage of lactation had no effect on BMC measured chemically in the caudal vertebrae or metacarpal. Parity did not affect breaking strength of the metacarpal or caudal vertebrae or total ash or P content of any bone. Results indicated that imaging techniques are not useful measures of BMC in mature dairy cattle.
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    Improving Fried Product and Frying Oil Quality Using Nitrogen Gas in A Pressure Frying System
    Innawong, Bhundit (Virginia Tech, 2001-07-20)
    The commercial pressure frying has been limited to frying huge amount of products due to its dependence on the amount of moisture released from the food for generating the desired pressure. This study investigated the feasibility of using nitrogen gas as a substitute for steam in the pressure frying system. The effects of various process conditions (source of pressure, frying temperature and pressure) on fried product and frying oil qualities were evaluated. Frying experiments were performed on breaded/battered poultry products including chicken nuggets (homogenous) and chicken fillets (marinated, intact muscle). Efforts were also made to develop rapid methods to determine frying oil quality and discriminate among fresh, marginal and discarded oils using a chemosensory (also known as electronic nose) or Fourier transform infrared spectroscopy (FTIR-ATR). Frying temperature and pressure affected fried food quality. An increase in frying pressure resulted in tender, juicier products with less oil uptake due to high moisture retention. An increase in frying oil temperature resulted in an increased moisture loss, oil uptake resulting in less tender and juicier products. Compared with frying using steam released from food, using nitrogen provided similar or better quality fried products in terms of moisture retention, juiciness and texture. The reused oils from the fryer using nitrogen gas was better in quality than the system using steam as evidenced from the physical, chemical and chemosensory measurements.
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    The influence of lactose hydrolysis on the strength and sensory characteristics of vanilla ice cream
    Matak, Kristen E.; Wilson, James H.; Duncan, Susan E.; Wilson, Edward J.; Hackney, Cameron Raj; Sumner, Susan S. (American Society of Agricultural and Biological Engineers, 2003)
    Lactose hydrolysis was investigated as a method of producing a more extrudable ice cream product. Ice cream mixes were treated with lactase from the microbial sources Kluyveromyces lactis and Aspergillus oryzae to produce 0% to 100% lactose hydrolysis. Compression measurements and yield stress tests of frozen ice cream were both affected by the temperature of the samples. As the temperature decreased, the work required to compress the ice cream 10 mm (firmness) and the torsional shear stress both increased. There was a linear relationship between the firmness of lactose-hydrolyzed ice cream (0%, 80%, and 100%) and temperature (r(2) = 0.98, 0.99, and 0.97, respectively). The treated samples were significantly softer that? the control, but not different from each other There was a significant difference (p < 0.05) in ice cream dippability between the control samples (0% hydrolyzed) and the treatment groups (80% and 100% hydrolyzed). The control group was consistently harder to dip. Hydrolysis of lactase in the ice cream mix produced a softer, more extrudable product.
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    Lactose Hydrolysis by Fungal and Yeast Lactase: Influence on Freezing Point and Dipping Characteristics of Ice Cream
    Matak, Kristen E. (Virginia Tech, 1999-01-11)
    Two studies were conducted to examine the effects of lactose hydrolysis on freezing point and dipping characteristics of ice cream. The overall research objective was to determine changes in freezing point, texture and ease of dipping ice cream as a result of lactose hydrolysis. It was also the goal of this research to relate observations from the sensory dippability study with hardness and yield stress data to determine if the latter methods could be used as an alternative to human testing of dippability. In the first experiment, ice cream mixes were treated with lactase (EC 3.2.1.23) to cause 0 to 83% lactose hydrolysis. Lactose hydrolysis decreased the freezing point from -1.63oC in the control (0% hydrolysis) to -1.74oC in the 83% hydrolyzed sample (p < 0.05). Firmness decreased from 0.35 J in the control sample to 0.08 J in the 83% hydrolyzed sample. Lactose hydrolyzed samples melted at a faster rate than the control. There was a difference (p < 0.05) in ease of dipping between samples treated with lactase and the control. There were no perceived differences in sweetness and coldness. In the second study, ice cream mixes were treated with lactase (EC 3.2.1.23) from the microbial sources Kluyveromyces lactis and Aspergillus oryzae to cause 0 to 100% lactose hydrolysis. Compression measurements and yield stress as measured by the vane method were both affected by the temperature of the samples. R2 values for compression measurements as related to lactose hydrolysis were higher then those obtained for yield stress measurements. Human evaluation determined a difference (p < 0.05) between the control samples (0% hydrolyzed) and the treatment groups (80% and 100% hydrolyzed). This research demonstrated a relationship between lactose hydrolysis and ease of dipping ice cream. The results implied that the effect of lactose hydrolysis on the dipping characteristics could be evaluated successfully by three different methods: the vane method, compression measurements, and human evaluation. Changes in freezing point due to lactose hydrolysis were minimal, implying that monitoring freezing point is not enough to determine textural characteristics.
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    Nondestructive Detection of Hollow Heart in Potatoes Using Ultrasonics
    Jivanuwong, Solos (Virginia Tech, 1998-05-04)
    Ultrasonic techniques were used to detect hollow heart in potatoes nondestructively. Fifty Russet Burbank potatoes were evaluated physically and sonically. A pair of dry-coupling 50-kHz ultrasonic transducers were used to generate an ultrasonic pulse with a power level of 0.22 W for the test of acoustic transmission through whole potato tuber in a transverse direction at different locations along the longitudinal axis with a certain interval distance. It was found that the waveform analyses in time domain for a series of transmitted signals along the longitudinal axis of potato tuber, yielded the potential in detecting hollow heart in potatoes noninvasively. The transmission losses for potatoes having hollow heart were found to be greater than 0.28 dB/mm. This value was used as a criterion to indicate potatoes with hollow heart at an accuracy of 98 percent. The ability to detect hollow heart in potatoes was limited to a minimum cavity size of 0.5 cm3 because the interval distance between locations of measurement was relatively large compared to the size of the projected area of hollow heart. The accuracy of the detection would be improved if a smaller contact area for the transmitting transducer were used, and if the intervals between ultrasonic measurement locations were smaller. Physical properties of the tested potatoes were also recorded for consideration of their relationships with ultrasonic parameters. Physical properties of tested potatoes such as modulus of elasticity, tuber length, diameter, and weight, were found to have poor correlation with ultrasonic parameters such as ultrasonic velocity, attenuation coefficient, and root mean square voltage of transmitted signal. This study showed that if all potatoes with weights of 300 g or less were eliminated from a mass of incoming potatoes, only 80 percent of the total mass would have to be examined for hollow heart.
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    A Thermistor Based Method for Measurement of Thermal Conductivity and Thermal Diffusivity of Moist Food Materials at High Temperatures
    van Gelder, Maarten F. (Virginia Tech, 1997-12-18)
    The purpose of this research was to assess the suitability of the thermistor based method for measuring thermal conductivity and diffusivity of moist food materials at high temperatures. Research focused on aspects of calibration, thermal contact in solid food materials, natural convection in liquid media and the performance in moist food materials at high temperatures. Thermistor probes were constructed in house and calibrated in three materials of known thermal conductivity and diffusivity, water, glycerol, and a heat transfer fluid, HTF 500. With few exceptions, the calibrated probe estimated thermal properties with an error of less than 5%, over the range of thermal properties spanned by the those of the calibration media. An alternate calibration using two media was also investigated. It was found to give better accuracy over a more limited range. Thermal contact in potato and lean beef was investigated through a comparative study that used a miniature line heat source probe as a reference method. The food materials were measured at 25, 50 and 100 °C. Good agreement was found between the measurements with the line heat source probe and the bead thermistor probe, indicating adequate thermal contact at the thermistor probe. The effect of fluid viscosity and the magnitude of the temperature step on the occurrence of natural convection was studied for aqueous solutions of a thickening agent. During a sample time of 30 seconds, convection was absent in solutions with a viscosity of 25 cp or greater, when measured with a temperature step of 1.5 and 2.5 °C, and in solutions with a viscosity of 50 cp or greater, when measured with a temperature step of 5.0 °C. A Rayleigh number was defined to study the notion of a critical Rayleigh number at the onset of convection. This study found that when the Rayleigh number was below 43, convection could not be demonstrated. For a Rayleigh number of 84 and higher, convection was observed. The performance at high temperatures in food materials was studied through tests in tomato concentrate and in a liquid food supplement. Tomato puree and tomato paste were sampled at 100, 130 and 150 °C. The thermal conductivity of tomato puree at 100, 130 and 150 °C was measured as 0.638, 0.645 and 0.647 W/m°C respectively. The thermal diffusivity was 1.63, 1.64 and 1.62 10-7 m2/s respectively. For tomato paste at 100, 130 and 150 °C, a thermal conductivity was obtained of 0.590, 0.597 and 0.534 W/m°C respectively. The thermal diffusivity was 1.63, 1.84 and 2.36 10 -7 m2/s respectively. With some notable exceptions the results of this study agreed well with Choi and Okos (1983). A liquid food supplement was also studied at 95 and 150 °C. The thermal conductivity of the food supplement decreased with increasing solids content from 0.62 W/m°C at a solids level of 15% to 0.41 W/m°C at a solids level of 50%. The results of this study indicate that the thermistor based method was suitable for measuring thermal conductivity and diffusivity of moist food materials at high temperatures. However, the type of thermistor used in the research, a glass encapsulated thermistor, was too fragile for routine work. In particular the high temperature use of the glass thermistor was impacted by its susceptibility to fracture.
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    Water quality at five proposed industrial sites on the Roanoke and New Rivers
    Wilson, James H.; Dickson, Kenneth L. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1977)
    Aquatic ecological surveys were conducted at five potential industrial development sites in Virginia, four on the New River and one site on the South Fork of the Roanoke River.Eighteen physical-chemical parameters were analyzed and biological information was collected in order to determine the physical, chemical, and biological water quality. This study was designed to generate baseline information essential in assessing the environmental impacts of future development in the watershed. The results indicate that the New River and the South Fork of the Roanoke River support diverse populations of macrobenthic invertebrates and that physical and chemical water quality is high, except for increased levels of nitrate in the New River. Although both rivers have water quality that is considered good by biological and chemical standards, they both are vulnerable. If the assimilative capacity of these two rivers is to be preserved as a valuable resource, they must be used intelligently. Future industrial development shouId be managed carefuIly in these watersheds to maintain the high quality of the aquatic environment in the New River and the South Fork of the Roanoke River.