Browsing by Author "Flick, George J. Jr."

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    Anaerobic/aerobic pretreatment of blue crab (Callinectes sapidus) cooker wastewater
    Diz, Harry Richard (Virginia Tech, 1994-10-05)
    Wastewater from the pressure cooking of blue crabs presents a difficult treatment challenge. COD concentrations in the range of 15,000 to 30,000 mg/L are found in this wastewater, with TKN concentrations above 2,000 mg/L. Direct discharge of the wastewater, which is currently allowed, adds nutrients to the Chesapeake Bay, and potentially creates local DO depletion in receiving waters. Anaerobic treatment of this wastewater was studied for the reduction of COD. Nitrification was studied for the conversion of ammonia, present at levels above 1,000 mg/L NH3/NHA4-N, to nitrate for possible denitrification. COD reductions averaging above 11,000 mg/L were found to occur in an upflow anaerobic filter operating with less than a 4 day HRT. Further COD reduction in the aerobic reactor resulted in a final effluent averaging 2,400 to 3,100 mg/L soluble COD with a corresponding BOD₅ of 110 to 340 mg/L. Nitrification proved to be inhibited, perhaps by the high levels of NH₃/NH₄-N in the effluent from the anaerobic stage. Nitrification did occur in a batch study, but only after extended aeration, and depletion of BOD. Non-degradable COD was estimated to be 2,900 mg/L in the anaerobic effluent. Monod model kinetic coefficients for the anaerobic stage were determined on a degradable COD basis to be: k = 0.68 day⁻¹, Ks = 3,500 mg/L (degradable portion), Y = 0.19, and Kd = 0.028 day⁻¹. The effect of the addition of certain trace metals (Fe, Ni, Co, Mo) to the feed was investigated. There was no improvement in COD removal performance, and slight inhibition may have occurred.
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    Analysis of crab meat volatiles as possible spoilage indicators for blue crab (Callinectes sapidus) meat by gas chromatography-mass spectrometry
    Sarnoski, Paul J.; O'Keefe, Sean F.; Jahncke, Michael L.; Mallikarjunan, Parameswarakumar; Flick, George J. Jr. (Elsevier, 2010-10-01)
    Traditionally crab meat spoilage has been evaluated using sensory panels. A method was developed using solid-phase microextraction–gas chromatography–mass spectrometry (SPME–GC–MS) to examine the aroma profile of blue crab (Callinectes sapidus) for chemical indicators of spoilage. The chemicals found to correlate best with spoilage were trimethylamine (TMA), ammonia, and indole over a period of 7 days. In addition, chemicals previously not identified in the aroma profile of blue crab were tentatively detected. Scan mode of the mass spectrometer was used to qualitatively determine compounds extracted from the volatile profile of spoiling blue crab by the SPME fiber. Selected ion monitoring (SIM) mode of the mass spectrometer improved resolution, identified compounds at low concentrations, and allowed spoilage related compounds to be detected in one chromatographic run without sample heating. TMA increased linearly. A significant difference in TMA concentrations were found for day 0 and day 4 samples. Indole concentrations corresponded well with sensory and microbial evaluations, in early, mid, and highly spoiled crab meat samples.
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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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    Aquaculture of Pacu (Piaractus mesopotamicus) and a Comparison of its Quality: Microbiological, Sensory, and Proximate Composition
    Pullela, Sharma V. S. (Virginia Tech, 1998-08-21)
    (Piaractus mesopotamicus) initially weighing 72.0 g were fed three diets - a) 0.5% vegetable (zucchini), b) commercial 32% (P32) and c) commercial 36% (P36) protein diets for 24 weeks and their growth performance compared. Processing yields and proximate composition were determined following dressing of pacu. The microbiological quality of pond cultured pacu was compared to aquacultured hybrid striped bass, tilapia, and rainbow trout grown in pond and recirculating aquaculture systems. Sensorial analyses for differences in flavor, preference, and color were also determined. Protein concentration significantly influenced the weights, lengths, specific growth rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Diet insignificantly influenced the processing yields (p > 0.05). The moisture, protein and total lipid contents were significantly affected (p < 0.05) by the dietary protein. The indicative bacterial quality differed significantly for pacu as well as the water used for culturing pacu (p < 0.05) among dietary treatments. Aquaculture production systems significantly influenced the indicative and pathogenic bacterial quality. Listeria monocytogenes, Salmonella spp., Yersinia enterocolitica, and Escherichia coli O157:H7 were not isolated from any of the sampled fish. The qualitative and quantitative results of Clostridium botulinum were influenced by the production system (p < 0.05). Flavor of pacu was comparable to that of hybrid striped bass, tilapia, and rainbow trout, but superior to catfish. Cooking significantly improved the color of the ground fish fillets.
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    Biogenic Amine Analysis of Fresh and Stored Bluefish (Pomatomus Saltatrix) and Microbiological Survey of Histamine-Forming Bacte
    Gingerich, Todd Matthew (Virginia Tech, 1998-08-20)
    Changes in histamine, putrescine, and cadaverine concentrations in fresh and stored bluefish (Pomatomus saltatrix) were determined using a new HPLC method. The HPLC method utilized a 5.0% (w/v) trichloroacetic acid (TCA) extraction, pre-column fluorescamine derivitization, and fluorescence detection. The derivatives were stable over 24 h. The 5% TCA extraction produced percent recoveries of 98.6%, 98.7, and 100.0% for histamine, cadaverine, and putrescine respectively. The HPLC process including extraction, derivatization, and HPLC analyses was conducted in less than 45 minutes. Fresh bluefish was found to contain between <1 ppm and 99 ppm histamine, and no cadaverine or putrescine. Fresh bluefish fillets were stored at 5, 10, and 15 degrees C until sensory rejection. Fresh bluefish fillets inoculated with Morganella morganii were also stored at the same conditions. Histamine levels as high as 2200 ppm were observed in the inoculated fish stored at 15 degrees C. Overall, histamine achieved higher levels in the bluefish pieces inoculated with Morganella morganii. Histamine was present in greater amounts than putrescine and cadaverine in the bluefish samples. Histamine levels at each temperature exceeded the 50 ppm advisory level established by the FDA before 100% sensory rejection. Putrescine levels increased at each temperature during storage. Cadaverine was present only in uninoculated bluefish stored at 15 degrees C. Consumer risk from histamine poisoning seems to be the greatest in those fish stored at 5 degrees C where acceptance levels were higher and histamine levels above 100 ppm were observed. The presence of histamine-forming bacteria in fish-processing facilities was studied. Environmental sampling techniques were conducted in the Hampton Roads area of Virginia in fish-processing facilities that regularly handle scombroid fish or other fish which are known to accumulate histamine levels greater than 50 ppm. Surfaces that come into contact with the fish were swabbed and the histamine-forming bacteria from these areas were identified. One isolate each of Klebsiella ozaenae and Vibrio alginolyticus, and two isolates of Aeromonas sp. were found in the processing facilities. The study concluded that histamine-forming bacteria do not make up a large part of the microflora associated with fish-processing facilities. Fishing vessels were also sampled and no histamine-forming bacteria were identified.
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    Characterization and treatment of wastewater from blue crab (Callinectes sapidus) processing facilities
    Harrison, Timothy Dane (Virginia Tech, 1993-11-15)
    The process wastewater from three blue crab processing plants in Virginia was characterized. Most of these effluent streams were highly concentrated. For example, the retort water from the cookers exhibited the following concentrations: BOD₅ = 14,000-29,000 mg/L, TSS = 650-6,200 mg/L, TKN-N = 2,500-4,000 mg/L, NH3-N = 70-160 mg/L and Total Phosphorus= 100-185 mg/L. One process effluent contained chloride concentrations exceeding 100,000 mg/L. Analysis of production and effluent characterization data from two mechanized plants revealed that wastewater volumes and concentrations varied significantly between the two plants. Both plants exhibited highly variable daily and seasonal production. Treatability studies were completed on the process wastewater because discharge limits exist for TSS, Oil and Grease and in some cases BODs and ammonia. Settling and filtration studies were performed on these effluents. The organics and nutrients in the wastes were highly soluble and limited reduction of COD (18-65% reduction), BOD₅ (9-49% reduction), TKN-N (9-62% reduction), and TP (10-66%) was achieved by filtration. Acidification of the concentrated effluents caused some coagulation of the contents. Coagulation by pH adjustment was most effective between pH 3.0-4.0. TSS removals of 76- 93%, and BOD5 removals of 6-30% were achieved by pH adjustment, thereby showing promise as a pretreatment method. Anaerobic biological treatment systems appear promising for the treatment of wastewater from blue crab processing plants (effluent BOD₅s ranged from 150-420 mg/L), especially for cooker effluent. However, there is concern that salt from the Harris Claw operation will decrease anaerobic treatment performance and that effluent NH3 and TSS levels will need to be further reduced to meet permit limits. Pretreatment of process wastewater by means of pH adjustment did not improve anaerobic treatability.
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    Chemical, Physical and Sensorial Compositions of Farmed and Wild Yellow Perch (Perca flavescens), Southern Flounder (Paralichthys lethostigma) and Coho Salmon (Oncorhynchus kisutch)
    Gonzalez Artola, Sonia (Virginia Tech, 2004-11-30)
    This study compared chemical, physical and sensorial properties of wild and farmed fish. Farmed yellow perch fillets showed higher lipid contents (2.78% vs. 1.39%); softer texture (0.41 J/g vs. 0.53 J/g); whiter color (higher L* and lower b* values); different fatty acid profile (higher n-3/n-6 ratio), and mineral composition, when compared to their wild counterparts. Similar amino acid profiles and flavor were found between treatments. Dietary protein by itself influenced color and flavor of yellow perch fillets. Yellow perch fed the highest protein concentrations exhibited higher b* (yellow) values and overall flavor was significantly different (p ≤ 0.05) between fish fed a 45% and 55% crude protein (CP) diet. A 12-week feeding trial determined that southern flounder protein requirement to achieve maximum weight was around 50% CP. Farmed southern flounder were found to be higher in lipid content (3.04 % vs. 1.61%), softer (0.24 J/g vs. 0/33 J/g), different in color (lower a* [green to red]), mineral, fatty acid composition (higher n-3/n-6 ratio) and flavor, than wild. The effect of a crab meal-supplemented diet, on flavor and body composition of flounder was analyzed. The inclusion of crab meal as a flavor enhancer affected the flavor and also influenced color of the fillets (lower L* [lightness] and higher b* values). Wild, farmed and growth-enhanced transgenic coho salmon (market-size) were compared, regarding their body composition and nutritional value. All treatments showed highest lipid levels in the ventral frontal sections and lowest in the tail (p ≤ 0.05). Overall wild fish showed lower lipid levels and firmer values in the tail sections (p ≤ 0.05). The insertion of the growth hormone gene affected lipid deposition, texture and color, since transgenic fish showed firmer texture than farmed and similar lipid contents even when fed a high-energy diet. L*, a* and b* values were similar for wild and transgenic coho in most of the body zones. Fillet mineral and amino acid profiles were similar across all groups. No differences were observed in flavor between farmed and wild coho, while panelists preferred the appearance of farmed, when compared to transgenic coho.
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    Control Method for Invasive Aquatic Species introduced via Ballast Water: Effects of Carbon Dioxide Supersaturation on Survivorship of Digesia tigrina (Planaria: Maculata) and Lirceus brachyurus (Isopoda: Crustacea) and Effect of High Hydrostatic Pressure Processing on Freely Suspended and Shellfish Associated T7 Bacteriophage
    Sheldon, Todd August (Virginia Tech, 2005-01-31)
    Control Method for Invasive Aquatic Species introduced via Ballast Water: Effects of Carbon Dioxide Supersaturation on Survivorship of Digesia tigrina (Planaria: Maculata) and Lirceus brachyurus (Isopoda: Crustacea) Survivorship of an aquatic species of planaria (Digesia tigrina) and isopods (Lirceus barchyurus) to elevated levels of carbon dioxide (CO₂) was determined. Both planaria and isopods were exposed to levels of freshwater supersaturated with carbon dioxide, and percent mortality was calculated for various exposure durations, and at various pressure levels. The data collected were graphically analyzed to determine the time necessary to produce mortality in 50% (LT50) of any given sample of specimens tested at a certain pressure level. At 38.6 kPa, 103.4 kPa and 172.4 kPa, the LT50 for planaria was calculated to be 150.3 ± 10.1, 58.6 ± 11.1, and 27.8 ± 6.2 minutes, respectively. At 38.6 kPa, 103.4 kPa and 172.4 kPa , the LT50 for isopods was calculated to be 181.1 ± 52.5, 79.7 ± 21.9, and 40.5 ± 17.0 minutes, respectively. These results suggest that CO₂ supersaturation may be an easily applied, efficient method that would end the unwanted introduction of nonnative aquatic species to habitats via ballast water released from shipping vessels. Effect of High Hydrostatic Pressure Processing on Freely Suspended and Shellfish Associated T7 Bacteriophage The effectiveness of hydrostatic pressure processing (HPP) for inactivating viruses has only been evaluated in a limited number of studies and most of the work has been performed with freely suspended viruses. In this work, the inactivation of freely suspended, as well as shellfish associated bacteriophage T7, by HPP was studied. T7 was selected in hopes that it could potentially serve as a model for animal virus behavior. Both clams (Mercenaria mercenaria) and oysters (Crassostrea virginica) were homogeneously blended separately and inoculated with bacteriophage T7. The inoculated shellfish meat, as well as freely suspended virus samples, were subjected to HPP under the following conditions: 2, 4 and 6 min durations; 241.3, 275.8 and 344.7 Megapascals (MPa) pressure levels; and temperature ranges of 29.4 – 35, 37.8 – 43.3 and 46.1 – 51.7Ë C. Plaque forming unit (PFU) reductions of 7.8 log10 (100% inactivation) were achieved for freely suspended T7 at 344.7 MPa, 2 min and 37.8 – 43.3Ë C. At 46.1 – 51.7Ë C, T7 associated with either clams or oysters was inactivated at nearly 100% (> 4 log10) at all pressure levels and durations tested. The results indicated that T7 is readily inactivated by HPP under the proper conditions, may be protected or made more susceptible by shellfish meat, and may serve as a viable model for the response of several animal viruses to HPP.
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    The Design and Implementation of a Computerized Information System of the Virginia Seafood Processors
    Shoemaker, Charles F.; Flick, George J. Jr. (Sea Grant, Extension Division, Virginia Polytechnic Institute and State University, 1973)
    As the age of the computer is entered into, the storage, retrieval and processing of data or information increases in importance. This importance grows simply from the continuous generation of increasing amounts of information in today's societies. In order not to be overcome by a oncoming deluge of data, the use of the computer is being relied on to handle data storage, retrieval and processing. Although many large organizations now rely solely on their computers for data management, many smaller organizations have yet to make any use of them. The principle reasons delaying the utilization of the computer by such organizations are (1) the availability of a computer, (2) the realization of a need of a computerized information system, and (3) the creation and management of such a system. The first obstacle is being overcome by the introduction of small computers and by the buying of computer time on large computer systems. Today, it is connnon to find companies who operate large computer systems for the purpose of selling computer time to the small user. The second and third reasons are not as clearly defined as the first. However, a particular realization of such a need and the implementation of the computerized information system to service it will be discussed. A simple computerized information system has been designed and placed into operation in the Food Science and Technology Department at the Virginia Polytechnic Institute and State University. This data base consists of information describing the seafood processors in the state of Virginia. The need for such information has been apparent to the extension workers serving the seafood industry as well as to the processors themselves. Data describing the number and location of the processing plants and the products they handle was of obvious importance in advising and planning for a profitable growth of the industry. Having recognized the need for this information, it was decided that the information should be computerized. In this way, the information would be easier to update and process. The acquisition, design and processing of this information or data by the computer programs written for this project will be discussed.
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    Detection, activity and resistance to thermal inactivation of peroxidase in the blue crab (Callinectes sapidus)
    Burnette, Florence Scheulen (Virginia Tech, 1976-12-18)
    Peroxidase is one of the most heat resistant enzymes and may cause undesirable quality changes in thermally processed foods. Peroxidase activity and its resistance to thermal inactivation in fresh and pasteurized lump, claw and flake meat of both male and female blue crabs was determined spectrophotometrically. Activity was greatest in the flake and least in the claw. Male crabs usually exhibited a greater initial activity (λ 0D 460/min) than did females of equal size. The larger the crab for a given sex, the greater the initial activity. Eight isozymes of peroxidase were detected in raw extracts of a 115 g female blue crab following starch gel electrophoresis and nine in a 116 g male. A smaller female crab (96 g) revealed seven bands which were less intense than those of larger females. By extending the time of electrophoresis, twelve bands were detected in the gel containing an extract from the 96 g female crab. The optimum thermal processing times needed to denature peroxidase and to prevent regeneration were studied. Heat inactivation curves indicated two straight line decreasing segments which varied by rate of descent. The first segment which decreased at a faster rate was considered due to heat-labile isozymes and the second segment which decreased at a slower rate due to heat stable isozymes. D values obtained for the enzyme based on the second straight line segment were D80=47 min, D110=18.2 min and D150=11.2 min. A "z" value of 92 F was also obtained for the enzyme.
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    Determination of decomposition rates in selected mid-Atlantic fish species stored under iced and super-chilling temperatures
    Barua, Mala A. (Virginia Tech, 1991-08-18)
    Three different species of fish (sea trout, Spanish mackerel and catfish) were studied. Samples undergoing normal spoilage were compared with samples which had undergone a sanitizing treatment with alcohol. Differential temperature storage studies were conducted at 290 °F (-1.7 °C) and 32 °F (0 °C). Fish quality was assessed by means of microbiological, chemical and sensory analyses. Quality assessment via measurement of proteolytic and lipolytic enzymes was attempted, but these enzyme activities were not detected in any of the samples. It was not possible to differentiate between the contributions of microbial and autolytic spoilage. Alcohol treated samples (reduced numbers of microorganisms) had shelf-lives extended by 6-10 days over untreated samples. The shelf-life of samples stored at 290 °F was extended by 6-10 days over the shelf-life of samples stored at 32 °F. Treated samples stored at 290 °F received highest sensory scores and untreated samples stored at 320 °F received the lowest scores. It was seen that the three fish species studied had different shelf-lives: sea trout-6 days, Spanish mackerel - 10 days and catfish - 16 days. Decomposition rates differed significantly between species and this factor must be taken into account when marketing strategies are developed by firms engaged in fresh fish sales.
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    Determination of quality attributes of blue crab (Callinectes sapidus) meat by electronic nose and Draeger-Tube analysis
    Sarnoski, Paul J.; Jahncke, Michael L.; O'Keefe, Sean F.; Mallikarjunan, Parameswarakumar; Flick, George J. Jr. (Haworth Press, 2008-01-01)
    In this study, five groups of sequentially spoiled crabmeat were evaluated by a trained sensory panel, and these results were compared with the findings from a Cyranose 320 Electronic Nose and Draeger gas analyzer. Using the electronic nose with filtered compressed breathing air yielded the best results. Although this approach resulted in 100% separation of the known groups, only 30% of the coded unknown samples were correctly identified. All 5 groups of samples analyzed using Draeger-Tubes were found to be significantly different at α=0.05 using a Tukey-Kramer ANOVA statistical procedure. The coded unknown samples were correctly identified at a rate of 83%. The simplicity and precision of this latter procedure may present opportunities for use of Draeger-Tubes by crab processing industries and other food processing industries as an objective method for quality control.
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    Development of Alternative Crab Claw Processing Systems to Minimize Environmental Impact
    Benning, Jennifer Lyn (Virginia Tech, 1997-03-14)
    In the recent years, environmental regulations enforced by federal,state, and local agencies have increasingly addressed water quality issues through progressively more stringent regulations. These regulations have raised concerns in the blue crab industry because processors are now subject to regulations under which new processors are unable to meet the effluent limitations with current processing techniques. This study focuses on the mechanized processing of crab claws. Currently, processors use a brine bath, referred to as the Harris Claw machine, to separate crab claw meat and shell, nd this process yields a waste water which is significantly high in pollutant strength, and is untreatable by biological methods due to the toxicity associated with the high chloride concentrations found in the waste stream. Several alternative crab claw processing systems were developed and evaluated in terms of the meat product yield, the meat product quality, and the wastewater characterization. Two alternatives involved the use of dense media, a 22.5% Staley 1300 corn syrup solution with 5.0% salt and a 30.0% Staley 1300 corn syrup solution, to separate the crab claw meat and shell. These methods, in full scale tests, produced meat yields comparable to that of the brine solution and improved the overall taste of the meat product. However, the effluents had significantly higher BOD5 concentrations. Another alternative to the Harris Claw machine, involved the design, characterization, and testing of a hydraulic separator system (HSS). The HSS was tested on a small scale, but was found to have a meat yield comparable to the Harris Claw machine. The HSS significantly improved the flavor of a final meat product, although the HSS meat product had a significantly lower shelf life than the Harris Claw machine meat product. The waste water quality was improved, because the HSS eliminates the problems associated with a high chloride ion concentration and potentially reduces overall water consumption.
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    Directory of Seafood Processors' services in Virginia
    (Sea Grant, Extension Division, Virginia Polytechnic Institute and State University, 1973)
    The purpose of this Directory is to provide a list of Virginia seafood processors, the products they market, and their location in the state. The Directory was compiled from questionnaires distributed to the seafood processors and Extension personnel. The Directory is divided into six sections to provide maximum information concerning the seafood industry. Section 11 gives seafood products and lists the names of the companies or individuals who market the product. A complete description of the company can be found in Section I.
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    Effect of environmental stress on the ability of Listeria monocytogenes Scott A to attach to food contact surfaces
    Smoot, L. Michele (Virginia Tech, 1996)
    The attachment and detachment of Listeria monocytogenes Scott A to Buna-N rubber and stainless steel under varying conditions of temperature and pH were investigated. Numbers of attached cells increased with increasing attachment temperatures (10° to 45°C) and time (up to 120 min) for both Buna-N rubber and stainless steel. Cells attached at higher levels on stainless steel at all temperature and pH levels investigated. Rate of attachment was found to be significantly lower at 10°C than 30° and 45°C on Buna-N rubber. When L. monocytogenes was grown at 10°, 30°, and 42°C before exposure to Buna-N rubber at 30°C, differences in rates of adhesion were not significant. A downward shift in the cell suspension holding temperature immediately prior to attachment to Buna-N rubber at 10°C resulted in reduced adhered cell populations. A similar upward shift did not affect attachment at 45°C. Altering the pH of the attachment environment within the pH range of 4 to 9 did not affect the maximum levels of attached cells to Buna-N rubber. However, the measured rates of adhesion indicated slower attachment occurs under alkaline conditions. Growth pH was also found to significantly affect rates of attachment and maximum adhered cell populations to Buna-N rubber. Compared to Buna-N rubber, the rate of attachment to stainless steel was markedly more rapid for all temperature and pH conditions studied and could not be calculated. The ease of removal for cells adhered to Buna-N rubber was significantly affected by growth temperature, but not growth pH. Significant differences in detachment were also found between Buna-N rubber and stainless steel, inferring a stronger attachment to Buna-N rubber. Cell surface hydrophobicity was affected by both growth temperature and growth pH, but differences in hydrophobicity could not be correlated to differences in rates of attachment. Addition of 0.01% trypsin to the attachment medium during cell suspension exposure to both test surfaces resulted in a 99.9% reduction in the adhered cell population when compared to controls. This suggests that proteins may play a role in the initial attachment process for L. monocytogenes.
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    The Effect of Novel Frying Methods on Quality of Breaded Fried Foods
    Bengtson, Rhonda J. (Virginia Tech, 2006-07-17)
    Fried foods are popular around the world. They are also high in fat and considered unhealthy by many people. Reducing the fat content of fried food may allow for even more growth in their popularity, while allowing for healthier eating. Furthermore, vacuum-frying and frying with nitrogen gas have both been shown to extend the life of frying oil. In this study, the use of novel frying methods as a way to reduce fat content of breaded fried foods was evaluated. A pressure fryer was modified so that fish sticks could be vacuum-fried and fried using external gas (nitrogen and compressed air) as the pressurizing media. These products were compared to those pressure fried and fried atmospherically in terms of crust color, moisture content, oil content, texture, and juiciness. Overall, products fried using nitrogen and air were not found to be significantly different (p < 0.05) from each other. These products were both more tender and lower in oil content than steam-fried fish sticks. The energy to peak load of fish sticks fried with air was 123.10 J/kg, fish sticks fried with nitrogen had an energy to peak load of 134.64 J/kg, and fish sticks fried with traditional pressure frying had a peak load of 158.97 J/kg. The crust oil contents of fish sticks fried with air, nitrogen, and steam were 17.35%, 15.88%, and 23.31% oil by weight, respectively. In other words, using nitrogen or air to fry fish sticks reduced the fat uptake in the crust by 31.8% and 25.6% compared to traditional pressure frying, respectively. The only area where vacuum-frying had a significant effect, when compared to pressure-fried and atmospherically-fried fish sticks, was in juiciness. Vacuum-frying created significantly juicier fish sticks than the other two frying methods. Vacuum-fried fish sticks had juiciness of 43.03% (120oC) and 41.31% (150oC), while pressure-fried fish sticks had juiciness of 30.01% (175oC) and 32.93% (190oC), and atmospherically-fried fish sticks had juiciness of 31.56% (175oC) and 29.38% (190oC). In addition, vacuum-fried fish sticks were more tender than atmospherically-fried fish sticks. The results of this study demonstrated that frying with external pressurizing media can be used to reduce oil content in fish sticks, while also creating products that are more tender than conventionally pressure-fried fish sticks. In addition, vacuum-frying, which has been shown to extend oil life compared to pressure frying because of the lower temperatures involved, can be used to create fish sticks that are comparable to pressure-fried fish sticks, but juicier.
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    The Effect of Thermal Processing Schedules and Unit Operations on the Quality of Blue Crab (Callinectes sapidus) Meat
    Smith, Jennifer Lynn (Virginia Tech, 1998-10-23)
    The effects of initial thermal processing, plant sanitation, and employee habits on the microbiological quality of blue crab (Callinectes sapidus) meat were determined in a commercial crab processing facility. Thermal processing was evaluated at 5, 7, and 8 minutes at 250ï °F for the destruction of microorganisms, including Listeria monocytogenes. F-values calculated indicated a sufficient reduction of L. monocytogenes at each processing time. Fresh picked crab meat was evaluated for microbial levels when exposed to ambient temperatures over a four hour period. It was found that time and temperature did not influence the microbial populations significantly except in the fourth hour. Plant sanitation was evaluated based on levels of adenosine triphosphate (ATP) and microbial counts. Areas found to have high levels of ATP typically had low microbial counts, thus suggesting that crab meat residual was the problem. The presence of Listeria species in the plant was determined using a commercial polyclonal antibody test. Listeria species were found under picking tables, on cooler doors, employees' aprons, and on several employees' hands. In a laboratory setting, an automated hand wash was compared with a manual hand wash for the removal of Listeria innocua, as a model for Listeria monocytogenes. It was found that a manual hand wash of 15 seconds was superior to an equal time automated wash. The microbial quality of crab meat was found to be affected by daily plant procedures, and could be changed by modifying procedures.
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    The Effects of E-Beam Irradiation, Microwave Energy and High Hydrostatic Pressure on Presence and Health Significance of Cryptosporidium parvum in Eastern Oysters (Crassostrea virginica)
    Collins, Marina V. (Virginia Tech, 2005-02-09)
    Foodborne disease outbreaks associated with the protozoan parasite Cryptosporidium spp. are an emerging public health concern. Shellfish, including Eastern oysters (Crassostrea virginica) in Chesapeake Bay and other Atlantic coastal waters, have been identified as a potential source of Cryptosporidium parvum infection for humans. The inactivation of C. parvum and other pathogens in raw molluscan shellfish would provide increased food safety for normal and at-risk consumers. The objectives of this study were to evaluate the efficacy of three alternative food-processing treatments (e-beam irradiation, microwave energy, and high hydrostatic pressure processing) on the viability of C. parvum oocysts in Eastern oysters. Oysters were artificially infected with the Beltsville strain of C. parvum and subjected to the three treatments in separate experiments. The effects of the treatments were evaluated by inoculation of the processed oyster tissues using the neonatal mouse bioassay. E-beam radiation of in-shell and shucked oysters treated with doses of 1.0, 1.5 or 2.0 kGy produced significant reductions (P < 0.05) in C. parvum mouse infectivity. A dose of 2.0 kGy completely terminated the infectivity of C. parvum and did not adversely affect the visual appearance of the oysters. Microwave treatments of shucked oysters at time (temperature) exposures of 1 sec (43.2°C), 2 sec (54.0°C), and 3 sec (62.5°C) produced a reduction in C. parvum mouse infectivity of 26.7%, 33.3%, and 46.7%, respectively. Microwave treatments at 2 sec (54.0°C) and 3 sec (62.5°C) showed extensive changes in oyster meat texture and color. Thus due to lack of efficacy and unacceptable tissue changes, microwave treatment of oysters is not considered a viable food processing method. High pressure processing of shucked oysters at all pressures tested (305 MPa, 370 MPa, 400 MPa, 480 MPa, 550 MPa) significantly (P < 0.05) reduced infectivity of C. parvum oocysts as measured by the neonatal mouse bioassay. A treatment of 550 MPa at 180 sec produced the maximum decrease of C. parvum infectivity (93.3%). The results indicate that HPP (high pressure processing) can produce significant (P < 0.05) reductions in infectivity of C. parvum oocysts. Measurement of tristimulus color values of pressurized raw oysters at extended processing times from 120 sec to 360 sec at 550 MPa showed an increase (P < 0.05) in whiteness. One (e-beam irradiation) of the three food-processing treatments shows promise for commercial applications to reduce public health risks from cryptosporidiosis in Eastern oysters.
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    Effects of high hydrostatic pressure processing on Bacillus cereus spores in fresh blue crab meat (Callinectes sapidus)
    Suklim, Kannapha (Virginia Tech, 2006-03-06)
    The Food and Drug Administration has recently expressed concern for the safety of seafood and seafood products. One of the concerns is the presence of Bacillus cereus in fresh blue crab meat. Bacillus cereus is a spore-forming pathogen whose spores survive the customary thermal treatments applied during cooking and pasteurization; therefore it could potentially present a health concern to consumers as the microorganism could increase to pathogenic levels. The objectives of this study were to evaluate the effects of a post-processing method i.e. high hydrostatic pressure treatment on the quality of fresh crab meat and to evaluate the effectiveness of high pressures on the inactivation of B. cereus spores. Fresh blue crab meat was pressurized at 300 and 550 MPa at 25° C for 5 min and stored at 4° C for 31 days to determine the pressurization effects on the microbiological, physical, and sensory quality of the meat. A pressure of 300 MPa caused a 1 log reduction in total aerobic plate count and a 3 day lag period, whereas 550 MPa inactivated 2 logs in total aerobic plate count with no evident lag phase. Physical and sensory qualities of pressurized crab meat were not statistically different from the untreated crab meat (P>0.05). A pressure of 300 MPa extended the shelf-life from 17 to over 24 days with the prevalence of Carnobacterium piscicola at the time of spoilage. Crab meat treated with 550 MPa was not rejected by sensory panels at day 31 and Enterococcus spp. was identified as the predominant microorganism. High hydrostatic pressure (550 MPa at 40° C for 15 min) inactivated less than 1 log (0.66 log) of B. cereus spores inoculated in fresh crab meat. The meat essentially had a protective effect on pressure inactivation of the spores. During storage (31 days), surviving B. cereus was suppressed and outgrown by the other pressure resistant microflora at a storage temperature of 12° C. At 4° C, B. cereus could compete with the other pressure-resistant microflora and was isolated even at the end of the storage period (day 31); however, diarrheal toxin was not detected in any stored samples.
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    Effects of high pressure processing on infectivity of Toxoplasma gondii oocysts for mice
    Lindsay, David S.; Collins, Marina V.; Jordan, C. N.; Flick, George J. Jr.; Dubey, Jitender P. (American Society of Parasitology, 2005-06)
    High pressure processing (HPP) has been shown to be an effective non-thermal method of eliminating non-spore forming bacteria from a variety of food products. The shelf-life of the products is extended and the sensory features of the food are not or only minimally effected by HPP. The present study examined the effects of HPP using a commercial scale unit on the viability of Toxoplasma gondii oocysts. Oocysts were exposed from 100 to 550 MPa for I min in the HPP unit and then HPP treated oocysts were orally fed to groups of mice. Oocysts treated with 550 MPa or less did not develop structural alterations when viewed with light microscopy. Oocysts treated with 550 MPa, 480 MPa, 400 Mpa, or 340 MPa were tendered noninfectious for mice. Mice fed oocysts treated with no or 100 to 270 MPa became infected and most developed acute toxoplasmosis and were killed or died 7 to 10 days after infection. These results suggest that HPP technology may be useful in the removal of T. gondii oocysts from food products.