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Full-Text Articles in Life Sciences

Growth Of Clostridium Sporogenes Pa3679 In A Vacuum-Packaged Meat-Vegetable Product, Julie M. Racz May 1999

Growth Of Clostridium Sporogenes Pa3679 In A Vacuum-Packaged Meat-Vegetable Product, Julie M. Racz

All Graduate Theses and Dissertations

Clostridium sporogenes PA 3679 spores were inoculated into a meat-vegetable mixture before extrusion, cooking, and vacuum packaging into "stewsticks" to simulate Clostridium botulinum growth. The experiment was a 3 x 5 x 2 x 3 factorial which determined the influence of pH, water activity, initial spore load, and storage period on spore survival. Spore levels decreased throughout storage for all treatments. Spore levels decreased linearly (P = 0.02) as water activity increased, in samples that were heated to kill vegetative cells and activate spores. Other significant interactions of heat-treated samples were observed with inoculum level (P < 0.01) and storage time (P < 0.01). Spore levels in stored products were also significantly affected by water activity* inoculum level (P = 0.03), pH * time, water activity* time (P = 0.01), inoculum level * time (P < 0.01), and water activity * inoculum levels * time (P < 0.01). The interaction between pH * water activity * time tended towards significance (P = 0.06). Most probable number estimates in nonheated samples accounted for naturally occurring viable cells and spores, and added spores and were significantly affected by the main effects of inoculum level (P < 0.01) and time (P < 0.01). The two-way interactions of water activity * inoculum level (P = 0.04), pH * inoculum level (P < 0.01),water activity * time (P < 0.01), and three-way interaction of pH * inoculum level * time (P = 0.03) were significant. Spore levels approached 102, or less (compared ...


Influence Of Carbohydrate Starvation On The Culturability And Amino Acid Utilization Of Lactococcus Lactis, Mark R. Stuart May 1999

Influence Of Carbohydrate Starvation On The Culturability And Amino Acid Utilization Of Lactococcus Lactis, Mark R. Stuart

All Graduate Theses and Dissertations

Lactococci are widely used in the cheese industry as a starter culture. Starter cultures face carbohydrate starvation due to the absence of a fermentable carbohydrate in the cheese curd after pressing. Starvation leads to a decreased ability to synthesize ATP, generate a proton motive force, and accumulate nutrients necessary to maintain viability. The aim of this work was to investigate the culturability of lactococci grown with and without lactose in a chemically defined medium, and to define the metabolic changes that occur during carbohydrate starvation.

Lactose metabolism provided energy for logarithmic phase growth and greater cell density in L. lactis ...


In Vitro Growth Of Muscle Satellite Cells Isolated From Normal And Callipyge Lambs, Beatriz T. Rodriguez May 1999

In Vitro Growth Of Muscle Satellite Cells Isolated From Normal And Callipyge Lambs, Beatriz T. Rodriguez

All Graduate Theses and Dissertations

The muscle hypertrophy of lambs expressing the Callipyge phenotype is possibly linked to characteristics of their muscle satellite cells. Therefore, characteristics (proliferation, fusion %, and protein accretion) of cultured satellite cells isolated from the longissimus muscle of Callipyge (n = 3) and normal (n = 3) lambs were compared in this study. In the first experiment, we tested whether or not the lll proliferation rates differ for satellite cells isolated from Callipyge or normal sheep when cultured in the presence of different serum types (horse, normal lamb, or Callipyge lamb). The average population doubling time (PDT, h) during log phase growth was calculated ...


Methanethiol And Cheddar Cheese Flavor, Benjamin Dias May 1999

Methanethiol And Cheddar Cheese Flavor, Benjamin Dias

All Graduate Theses and Dissertations

The use of slower acid-producing starter bacteria for the production of lower fat Cheddar cheese has lead to milder flavor Cheddar cheeses that lack intense Cheddar notes. The metabolism of methionine leads to the production of methanethiol, which is one of the desirable Cheddar cheese flavor compounds. The influence of NaCl and reduced pH was determined for aminopeptidase, lipase/ esterase, and methanethiol-producing capability in selected lactic acid bacteria and brevibacteria in simulated cheese-like conditions. The activity of each enzyme decreased with NaCl addition and pH reduction to approximate a Cheddar cheese environment (5% NaCl and pH 5.2).

The mechanism ...


The Development Of Pediococcus Species As Starters Fro Mozzarella Cheese, Shelby L. Caldwell May 1999

The Development Of Pediococcus Species As Starters Fro Mozzarella Cheese, Shelby L. Caldwell

All Graduate Theses and Dissertations

Bacteriophage infection of Streptococcus thermophilus is a growing concern in the mozzarella cheese industry. One method to control this problem may be to replace S. thermophilus with a starter coccus from a different genus of lactic acid bacteria. This work evaluated the possibility of using genetically modified Pediococcus spp. for this approach. Electroporation was used to introduce genes for lactose utilization from Lactococcus lactis into strains of P. acidilactici and P. pentosaceus. The resulting lactose-positive transformants, P. acidilactici SAL and P. pentosaceus SPL-2, rapidly reduced the pH of lactose broth, accumulated [14C]lactose at a rate higher than a ...


Studies On The Utilization Of Deboned Trout (Oncorhynchus Mykiss) Frames In Fish Snack, S. Muralidharan May 1999

Studies On The Utilization Of Deboned Trout (Oncorhynchus Mykiss) Frames In Fish Snack, S. Muralidharan

All Graduate Theses and Dissertations

Snack food development studies were conducted to iii utilize trout (Oncorhynchus mykiss) frames, a by-product of the filleting operation, using extrusion and conventional technology. Twin screw extrusion studies were conducted to study the effect of fish mince, non-fat dry milk, process temperature, and moisture content on the physicochemical properties of the extruded snack food. Response surfaces were plotted to understand the effects of the independent variables on dependent variables such as bulk density, expansion ratio, shear strength, and water absorption index. Quadratic models expressed the relationship between the dependent and independent variables.

Based on the extrusion studies, conditions suitable for ...


Influence Of Commercial Starter Media On Biochemical Characteristics Of Lactococcus Lactus, Norman Bart Devries May 1999

Influence Of Commercial Starter Media On Biochemical Characteristics Of Lactococcus Lactus, Norman Bart Devries

All Graduate Theses and Dissertations

Five strains of Lactococcus lactis were inoculated individually into six commercial bulk set growth media, 11% non-fat dry milk (NDM), and Elliker's broth. After growth in each medium the strains were tested for rate of acid production, and activities of proteinase, aminopeptidase, and lipase/esterase. Growth in commercial starter media significantly influenced acid production rate (P = 0.040), aminopeptidase activity (P < 0.0001), and lipase/esterase activity (P < 0.0001) .

For selected strain/media combinations, the duration of induced aminopeptidase and lipase/esterase activity was followed. The chosen strains were grown in selected commercial bulk set media, reinoculated into 11% NDM, and enzyme activity was examined for five ...


Heat-Induced Gelation Of Ultrafiltered Whole Milk Concentrate And Product Applications, Hector Alejandro Solorio May 1999

Heat-Induced Gelation Of Ultrafiltered Whole Milk Concentrate And Product Applications, Hector Alejandro Solorio

All Graduate Theses and Dissertations

The heat-induced gelation properties of ultrafiltered (UF) whole milk concentrate were studied under different physical and chemical conditions. total solids concentration, homogenization pressures, heating temperatures, and heating times were found to have a positive correlation with gel strength. The addition of calcium chloride, sodium chloride, or trisodium citrate produced gels of higher strengths and textural properties than the gels obtained with non-salt-treated concentrate. Calcium chloride produced the strongest gels with a cheese-like texture and poor spreadability. Sodium chloride produced gels of intermediate strength with a firm, elastic texture and poor spreadability. Trisodium citrate produced the softest gels with a smooth ...


Heat-Stable Extracellular Enzymes Of Pseudomonas, Ramarathna Koka May 1999

Heat-Stable Extracellular Enzymes Of Pseudomonas, Ramarathna Koka

All Graduate Theses and Dissertations

Psychotrophic bacteria produce heat-stable lipase, protease, and phospholipase. Pervious studies indicate the production of multiple enzymes in several strains of Pseudomonas fluorescens, but conclusive evidence is lacking.

The influence of culture conditions on the production and thermostability of phospholipase, protease, and lipase was investigated in 17 raw milk and environmental isolates. Production and thermostability of the enzymes were influenced by strain, stage of growth, and the culture medium. Cross-reactivity of antibodies raised to a purified protease and a commercial lipase indicated the immunological diversity of the enzymes.

Protease purification was undertaken to investigate the production of multiple proteases within a ...


A Study Of The Effects Of Proteolytic Adjunct Culture On The Physical And Functional Properties Of Low-Fat Mozzarella Cheese, Roxanne Stone May 1999

A Study Of The Effects Of Proteolytic Adjunct Culture On The Physical And Functional Properties Of Low-Fat Mozzarella Cheese, Roxanne Stone

All Graduate Theses and Dissertations

As fat is removed from Mozzarella cheese, the resulting increase in protein content causes the cheese to become tough, thus decreasing the desired physical characteristics of meltability and stretch. Low-fat (6% fat) Mozzarella cheese was manufactured with the addition of several levels of a Lactococcus lactis adjunct culture that was proteinase positive and lactose deficient in an attempt to improve these physical properties. During cheese manufacture , milk was acidified to pH 6.0, then inoculated with Lactobacillus helveticus and Streptococcus thermophilus. Experimental vats were also inoculated with either 0.25, 0.50, or 1.0% of the adjunct culture. Cheeses ...


A Product Development Study: Rainbow Trout Bologna, Marshall Dean Smith May 1999

A Product Development Study: Rainbow Trout Bologna, Marshall Dean Smith

All Graduate Theses and Dissertations

Mechanically deboned rainbow trout (Oncorhynchus mykiss) was analyzed and then used in texture studies. The meat contained a moderately low amount of fat (10% ± 2%, x ± SD). Pre-deboned meat had more calcium than deboned meat (PIF/=0.37). A combined response model predicted formulations for fish sausage that would closely duplicate the texture of commercially available processed meats. A thermal model was developed that helped verify the thermal properties of rainbow trout. Thermal conductivity was measured (k == 0.48 W/m·K) and specific heat was calculated (Cp= 3200 J/kg·K).


The Modification And Use Of High-Oleic Sunflower Oil In The Production Of A Ripened Swiss Cheese-Like Product With Good Flavor Quality, Liangping Yu Jan 1999

The Modification And Use Of High-Oleic Sunflower Oil In The Production Of A Ripened Swiss Cheese-Like Product With Good Flavor Quality, Liangping Yu

Retrospective Theses and Dissertations

Milk fat is considered hypercholesterolemic because it contains cholesterol and a large proportion of saturated fatty acids. The use of vegetable oil to substitute for milk fat in cheesemaking has been proposed to improve the nutritional value of the cheese. However, the quality of vegetable-oil cheese has not been as good as that of traditional cheese. The objectives of this study were to modify vegetable oils to resemble milk fat for use in cheese production and to produce high quality, nutritious Swiss cheese from modified vegetable oils and skim milk;High-oleic sunflower oil (HOSO) was chemically modified by incorporating shortchain ...


Effect Of Dietary Glycolytic Inhibitors On Pork Quality , Brian Thomas Kremer Jan 1999

Effect Of Dietary Glycolytic Inhibitors On Pork Quality , Brian Thomas Kremer

Retrospective Theses and Dissertations

Four studies were performed to determine the effectiveness of short term feeding of several dietary glycolytic inhibitors on the quality of pork. In the first experiment the oxalate was provided to 110 kg pigs in the form of sodium oxalate at levels of 0, 7.0, and 9.7 g/pig. The ingestion of sodium oxalate decreased the rate of muscle pH decline and lowered the pork water loss (WL). In an additional experiment with sodium oxalate, 30 kg pigs were used as a model for market pigs. The sodium oxalate (0 and 2.6 g/pig) again decreased the ...


Dietary Conjugated Linoleic Acid Effects On Quantitative And Qualitative Characteristics Of Pork , Rebecca Lynn Thiel Jan 1999

Dietary Conjugated Linoleic Acid Effects On Quantitative And Qualitative Characteristics Of Pork , Rebecca Lynn Thiel

Retrospective Theses and Dissertations

Conjugated linoleic acid (CLA) consists of a group of geometric and positional isomers of linoleic acid. CLA has been shown to improve animal performance, and composition, be anticarcinogenic, antiatherogenic, and improve immune function. To test the hypothesis that dietary CLA would improve performance and quality characteristics of pork, forty crossbred pigs (8 replications) were fed diets containing 0, .12, .25, .50 or 1.0% CLA by weight of the diet from 26.3 to 114 kg. Average daily gain (P < .05) and gain/feed (P < .05) were improved. Fat depth at the 10th rib decreased as the amount of CLA in the diet increased (P < .05). Ultrasound showed an increase in muscling, but no differences in loin eye area were observed on carcasses. Belly hardness (firmness) increased linearly with an increase of dietary CLA supplementation both lean side up (P < .01) and lean side down (P < .05). CLA as a percentage of total lipids increased (P < .01) in both subcutaneous fat and lean tissue. Day one postmortem loin chops exhibited no differences between controls and CLA supplemented chops for pH, water holding capacity and Warner-Bratzler shear force, and a significant linear increase (P < .05) occurred in Hunter a* (redness) as the amount of CLA in the diet increased. A trained sensory panel found that day one controls exhibited more initial juiciness (P < .05) than did the. 12% dietary CLA supplemented loin chops. No other sensory panel differences were detected. No differences were determined between 1.0% CLA treatments and controls for Hunter color, sensory panel scores, and cook loss or drip loss of loin chops held for 7, 14, 28 or 56 days of fresh storage. A preliminary study of 70/30 fresh pork patties held for 1, 3, 7, or 14 days of fresh storage as measured by Hunter L*, a*, and b* values suggested that CLA supplementation up to .50% enhanced/maintained patty color. Immune response and blood chemistry parameters were measured at 52, 68, 91, and 114 kg live weight. Immune response was not compromised and blood chemistry parameters indicated no pathological conditions as a result of dietary CLA supplementation.


Physicochemical Properties Of Selected Root And Tuber Starches And Characterization Of Extruded, Chemically Modified Corn Starches , Andrew Edward Mcpherson Jan 1999

Physicochemical Properties Of Selected Root And Tuber Starches And Characterization Of Extruded, Chemically Modified Corn Starches , Andrew Edward Mcpherson

Retrospective Theses and Dissertations

The physicochemical properties of normal potato, waxy potato, yam and sweet potato starches were examined and compared. Normal potato and waxy potato starches displayed the B-type x-ray diffraction pattern, whereas yam and sweet potato displayed the CA- and C-type, respectively. X-ray diffraction patterns of Naegeli dextrins of normal potato and waxy potato remained the B-type, but those of yam and sweet potato changed to the A-type. 31P-NMR showed the phosphorus contents of the starches to be primarily phosphate monoesters with no detectable phospholipid in any of the four starches. Normal potato and waxy potato starches displayed lower proportions (13 and ...


Evaluation Of Forage Yield, Quality And Canopy Development Of Various Species Of Amaranths Harvested At Different Stages Of Development , Byron Barrington Sleugh Jan 1999

Evaluation Of Forage Yield, Quality And Canopy Development Of Various Species Of Amaranths Harvested At Different Stages Of Development , Byron Barrington Sleugh

Retrospective Theses and Dissertations

Complete information on the forage nutritive value of amaranth is not available. The objective of this study was to evaluate forage yield, quality, and canopy development of various species of amaranth at different developmental stages. Seven amaranth accessions were established in 1997 and 1998 near Boone, Iowa. Plots were established in a randomized complete block design and subplots were harvested at two-week intervals, starting at 28 days after planting (DAP). In vitro dry matter digestibility (IVDMD), neutral detergent fiber (NDF), crude protein (CP), nitrate, acid detergent fiber (ADF), and acid detergent lignin (ADL), and protein and fiber digestion were determined ...


Lipid Oxidation And Production Of Off-Odor In Irradiated Meat , Cheorun Jo Jan 1999

Lipid Oxidation And Production Of Off-Odor In Irradiated Meat , Cheorun Jo

Retrospective Theses and Dissertations

Emulsion-type raw and cooked pork sausage with different fat content or fatty acids was prepared to determine the effect of irradiation on lipid and cholesterol oxidation, color changes, and volatile production during storage. Lipid oxidation increased with the increase of fat content or irradiation dose in both raw and cooked pork products. Irradiated batters had higher cholesterol oxide content than non-irradiated, and the major cholesterol oxides formed in raw irradiated pork batters were 7alpha- and 7beta-hydroxycholesterol. Hunter a- and b-values of both raw and cooked pork products in aerobic packaging decreased with irradiation regardless of fat content. In vacuum packaging ...


Effect Of The Presence Of The Mammary Gland On Periparturient Immunosuppression In Dairy Cows , Kayoko Kimura Jan 1999

Effect Of The Presence Of The Mammary Gland On Periparturient Immunosuppression In Dairy Cows , Kayoko Kimura

Retrospective Theses and Dissertations

Impaired neutrophil and lymphocyte function during the periparturient period is a contributing factor to the high incidence of infectious disease observed in the periparturient cow. Using 8 multiparous Jersey cows, we demonstrated that populations of T cells, especially T helper cells and gd T cells declined during the periparturient period coincident with reported losses of immune cell function;We hypothesized that milk production may be an important immunosuppressive factor. To test this hypothesis, we used 10 mastectomized and 8 intact multiparous Jersey cows and examined phenotype of peripheral blood mononuclear cells (PBMC), adhesion molecule expression and myeloperoxidase activity in neutrophils ...


The Effects Of Storage, Irradiation, And Processing On Selected Viruses In Ground Pork , Terry Allen Proescholdt Jan 1999

The Effects Of Storage, Irradiation, And Processing On Selected Viruses In Ground Pork , Terry Allen Proescholdt

Retrospective Theses and Dissertations

Viruses are becoming increasingly recognized as major causes of foodborne diseases. While adequate cooking is a time-tested method of inactivating viral contaminants, the numerous outbreaks of viral foodborne disease indicate that either thorough cooking does not occur or that the foods are contaminated after cooking. These studies investigated other methods of inactivating viral contaminants in ground pork and pork products;Storage conditions can be used to decrease viral numbers in pork, but the time needed makes this impractical. At refrigerator (4°C) temperatures, most viruses tested lasted long after the product would be considered spoiled. At home freezer (-20°C ...


Effect Of The Use Of Lipoxygenase-Free Soybean Line On The Sensory Attributes Of Soymilk And Tofu , Ana Victoria Torres-Penaranda Jan 1999

Effect Of The Use Of Lipoxygenase-Free Soybean Line On The Sensory Attributes Of Soymilk And Tofu , Ana Victoria Torres-Penaranda

Retrospective Theses and Dissertations

Flavor is the most important factor limiting consumption of soy foods in Western markets. Soybean lines lacking one or several of the lipoxygenase isozymes involved in flavor have been developed. Sensory evaluation provides relevant information related to actual perception and also presents some challenges that must be addressed. Perception of flavor by people varies according to people's background. The use of terminology to describe the sensory attributes must be addressed. Also, the dynamism of the perceived intensity of some sensory attributes must be considered for evaluation of soy products;In the first part of this study, three groups of ...


Attitudes To Biotechnology And Genetically Modified Food : A Review, Juliana Rose Cannon Jan 1999

Attitudes To Biotechnology And Genetically Modified Food : A Review, Juliana Rose Cannon

Theses : Honours

Debate surrounds the introduction of new biotechnological applications such as genetically modified food (GMF). With this in mind a critical review of the debate, it's emerging themes, and approaches to measurement was undertaken. The intention of this review was to argue that while existing empirical measures have advanced our understanding of attitudes to GMF, they are limited both conceptually and methodologically. Overall, the validity and reliability of research support was compromised. Conceptually, attitudes to GMF were composed of a number of potential dimensions that have yet to be measured. Adherence to sound scale construction techniques may facilitate more reliable ...