Americans consume 28 lbs of ground beef annually. Beef can become contaminated with Salmonella during the initial slaughter process. Whole cuts of meat are ground into other products and the contamination spreads. This increases the risk of food borne illness for many Americans that consume ground beef products. The purpose of this study is to determine if adequate microbial destruction of Salmonella populations in ground beef of different fat levels can be achieved at temperatures that are lower than government guidelines. Ground beef was inoculated with a four-strain mixture of Salmonella. Three fat levels of ground beef were used (10, 17, and 25% fat). Samples of ground beef (10g) were heated in a water bath to target temperatures of 60, 65.5, and 71.1°C. The heated samples were removed from the water bath at predetermined time intervals and cooled in an ice bath. Salmonella was enumerated on plate count agar (PCA). Serotype survival was also analyzed. The heat treatments significantly decreased bacteria populations (p < 0.05) and the 60, 65.6, and 71.1 °C heat treatments were significantly different from each other. The results indicate that fat level had no significant effect on bacterial survival (p > 0.05). Also, S. Senftenburg was found most often during longer exposure to heat treatment. Overall, the results indicate that combinations of heating at 60, 65.6 °C can achieve similar bacterial destruction as heating at 71.1 °C and should be considered by manufactures that use ground beef.

Educational research suggests that middle school is an ideal time to teach food safety since adolescents are in the process of setting life-long behaviors and are, therefore, more likely to synthesize new food safety knowledge into positive behaviors. The objectives of this study were to: 1) Describe the baseline food safety knowledge and attitudes/ behaviors of 7th grade students in East Tennessee 2) determine the relationship with geographic location, socioeconomic status, race, and gender; and 3) compare the current data (Study 2) to a previous study (Study 1) that pre-tested 7th grade students prior to an education intervention. A 40-item survey was administered to 232 students in 12 schools chosen using a weighted, stratified random sample. A hierarchical model was used to obtain least squares means at the school and student levels. To compare Studies 1 and 2, independent sample t-tests and chi-square analysis were applied to determine significant differences in food safety knowledge or attitudes/behaviors between the populations. Study 2 results showed that 63% knew the importance of hand-washing, but only 50% reported ‘always’ washing their hands before eating or preparing food; 50% reported ‘always’ following temperature directions, but 85% did not know how to determine if a hamburger was cooked properly. No statistical difference was found in food safety knowledge for all variables except race, where Asian/Pacific students scored lower (p=0.0005). Males (p=0.0133) and Asian/Pacific students (p=0.0033) reported riskier food handling behaviors. No significant differences (p<0.05) were found between Study 1 and 2 in food safety knowledge or attitudes/behaviors. Hand-washing and use of proper temperatures, as well as differences in behavior within gender and some ethnic groups should be focal points in adolescent food safety education. These results suggest that some differences in knowledge and behaviors are less pronounced in adolescents than those found in similar studies with adults. The results of the comparison between adolescent studies suggest that the food safety curriculum targeted to adolescents of Study 1 would likely be effective at raising student knowledge and improving students’ food handling behaviors in a larger population of 7th grade students.

Chitosan, a deacetylated product of chitin, is a copolymer of 2-amino-2-deoxy-D glucopyranose and 2-acetamido-2-deoxy-D glucopyranose. Chitosan has many functional properties and has various applications in food, agriculture, pharmaceutical, cosmetic industries. However, little is known about the fate of chitosan and its films during prolonged storage. Although it has been reported that chitosan films treated with dry heat or saturated steam became brown, data available on physical characterization of chitosan films is still conflicting. This study was conducted to determine chemical stability and mechanical properties of chitosan films as affected by (1) type of acid used for film preparation (acetic, lactic, citric, and hydrochloric acid), (2) final pH of the films (regular vs. neutralized), (3) storage conditions (temperature of 4, 22, and 80°C, and relative humidity 20 and 70%), and (4) time (up to 5 months). Development of colored compounds was observed with a Hunter colorimeter and UV-Vis spectrometer, while polarized microscope was used to observe micro-structural changes in the film. Accumulation of hydroxymethyl-furfural (HMF) was monitored by high performance liquid chromatography. Neutralized films stored at high temperature and high humidity showed more darkening and higher HMF levels than regular films stored at lower temperature under dry conditions. Polarized microscopy showed presence of birefringent crystals only in the films stored at high temperature. Effects of type of acid and storage conditions on mechanical properties of chitosan films were evaluated on films stored for a period of 1 year. Dynamic mechanical analysis showed that citric acid films were brittle while lactic acid films were flexible even at room temperature. Thermal degradation of the films started at temperatures around 200 °C regardless on type of acid used for film preparation. Glass transition temperature (Tg’) of chitosan films appeared to be between 40 ºC to 50 ºC. Our study has shown accumulation of HMF and development of crystallinity at higher temperature and high humidity in chitosan films, whereas films stored at lower temperatures (4 ºC and 22 ºC) had low levels of HMF and no crystals were observed. Among all the films tested, acetic acid films were found to be the best for food application with least HMF accumulation and better overall mechanical properties compared with lactic, citric, and hydrochloric acid films.

Caseins, in the form of micelles, are the most abundant milk protein. The nature of these micelles is still not fully understood and several models have been proposed. The first chapter discusses this topic, along with the importance of milk proteins to the food industry, and their allergenic properties. In the second chapter the changes in the hydrophobicity of dissociated casein micelles are explored. As new applications for milk proteins are discovered, it becomes more important to understand their physicochemical properties when subjected to different treatments. It has been reported that casein micelles disassociate when heated in the presence of ethanol. The changes to the hydrophobicity of milk proteins during that process were evaluated by utilizing the fluorescent hydrophobic probe 1-anilinonaphthalene-8-sulfonic acid (ANS). The results showed that the fluorescence intensity of ANS decreased when the samples were heated. Using the information obtained from the fluorescence spectroscopy it was possible to infer that the hydrophobicity of the milk proteins also decreased when the casein micelles disassociate in the presence of ethanol. The third chapter deals with the association of native casein micelles and whey proteins. This association was thought to only be consequence of whey protein denaturation and interaction with k-casein through S-S linkages. Size exclusion chromatography (SEC) was used to isolate native casein micelles from raw skim milk samples with a pH value of 6.8, 6.0, and 5.5. In a separate experiment, casein micelles were precipitated by lowering the pH of milk to ~4.6, and the vi whey was removed and substituted with protein free serum (PFS). Then, the casein micelles were re-suspended in PFS at a native pH. SDS-PAGE was conducted on the samples utilizing silver staining of total proteins for higher sensitivity of detection. Whey proteins were found in association with the casein micelles at all pH values. Samples of both native pH and re-suspended casein micelles were tested with gel electrophoresis under native and reducing conditions. The bands for the whey proteins were only visible under the reducing conditions. These findings demonstrate that whey proteins are also part of the native casein micelle structure.

Studies were conducted to test the efficacy of several common household products containing antimicrobial compounds for inactivating spores of Bacillus cereus, as a surrogate for B. anthracis, on fresh fruit or vegetables. Additionally, the effect of storage time on hypochlorite activity of household products was determined. Bacillus cereus ATCC 33018 and ATCC 49064 were used in a cocktail for all tests. Household disinfectant and/or cleaning products with potential for sanitization were purchased in a retail market and were selected based upon efficacy against B. cereus in previous tests in milk. The active components were NaOCl, HCl or H2O2. For produce, cantaloupe melons and spinach were obtained from a local retail market and rinsed with sterile deionized (DI) water. Cantaloupe rinds were removed, trimmed to remove the mesocarp, cut into 25 cm2 sections and placed in sterile Petri dishes. Sections of melon and spinach leaves were spot inoculated with 0.1 ml of B. cereus and allowed to dry for 30 min at 25oC. Sanitizing products were sprayed onto the surface of the produce and the produce was allowed to stand for various times. Produce was then placed in neutralizer buffer to arrest the activity of sanitizing compounds and survivors were enumerated on non-selective media. To determine the effect of product age on activity, three commercial NaOCl-containing products that were past, at and 6 mo from the expiration dates were evaluated. Spinach and cantaloupe were tested as described previously. For the cantaloupe melon rind the control population mean was 7.15 + 0.07 log CFU/cm2. The log reduction was > 5.15 for undiluted NaOCl (Clorox®, 6.00% NaOCl) and inactivation took 120 min though the greatest reduction was observed in the first 10 min. For products containing 1.84%-2.40% NaOCl, log reductions were 2.75 to 3.40 over 180 min. For spinach, the control population mean was 7.37 + 0.01 log CFU/leaf. A > 5.84 log reduction in B. cereus spores was found for both undiluted NaOCl (Clorox®) and HCl (The Works Drain Opener, 20.00% HCl). However, the former reduced the viable spore population to the lowest detection level in 10 to 60 min while the latter took approximately 3 h. A 4.23-4.60 log reduction occurred with the 1.84%-2.40% NaOCl-containing products after 180 min. Hydrogen peroxide had the least effective sporicidal capabilities of the solutions tested reducing the population by less than 1 log. With respect to effect of storage on sporicidal activity of HOCl-containing products, samples stored up to 1 year past expiration were compared with those stored for 6 months prior to expiration and purchased fresh. There was no significant difference in the in vitro inactivation of B. cereus spores among the products. B. cereus spores were inactivated to below detectable levels after 1 min in 50% and 25% commercial strength solutions (>4.0 log CFU/ml). These findings were confirmed utilizing cantaloupe rind and spinach leaves treated with HOCl-containing products of the same storage times. B. cereus spores were inactivated to below the level of detection (>5.84 log CFU/cm2, >5.15 log CFU/cm2) in 10 min and 60 min for spinach and cantaloupe respectively, regardless of compound age.

A study was conducted to compare the efficiency of detection of Escherichia coli O157:H7 EDL 933 on external beef trim by commercial recovery systems based upon of the Microbial-Vac System (M-Vac) and excision sampling. Escherichia coli O157:H7 EDL 933 was cultured in tryptic soy broth for 24 hr at 37°C and transferred for three consecutive days before diluting and spot inoculating onto a 684 cm2 piece of beef trim (10 CFU/684 cm2). Beef trim was sampled with the M-Vac by passing the sampling head over the entire surface area in a vertical sampling pattern. The sampling head sprayed sterile buffer over the beef surface and instantly vacuumed the contents into a sample collection bottle. For the excision method, samples were cut from the beef trim using a coring knife. Sixty cores (3.8 cm diameter) were used per sample with one core directly inoculated by the E. coli O157:H7. Samples (M-Vac collection fluid and 60 excised cores) were held overnight at 4°C to simulate processing conditions, enriched in mEHEC broth at 42°C for up to 18 h, and confirmed positive using the BioControl Assurance Genetic Detection System (polymerase chain reaction based). Of 75 inoculated beef trim surfaces, 96 (± 3.86) and 76% (± 3.86) of samples tested positive for E. coli O157:H7 by the M-Vac and excision methods, respectively. The ability of the M-Vac to detect E. coli O157:H7 significantly better (P<0.05) than excision, combined with the nondestructive nature of the MVac demonstrates that it is a suitable choice for sampling beef surfaces.

There is an emerging market for functional oligosaccharides for use in foods. Currently, technology for the production of oligosaccharides is limited to extraction from plant sources, acid or enzymatic hydrolysis of polysaccharides or synthesis by transglycosylation reactions. Oligosaccharides also can be produced using a Leuconostoc fermentation and restricting the polymer size by the addition of maltose. Maltose limits the dextransucrase reaction, yielding high concentrations of a-glucooligosaccharides. Branched oligomers produced by this process were found to be readily catabolized by bifidobacteria and lactobacillus but were not readily utilized by either Salmonella sp., or E. coli, pointing toward their use in intestinal microflora modification. Branched a-glucooligosaccharides were non-competitive inhibitors of a-glucosidase (maltase), an enzyme required for starch or maltodextrin utilization.

Approximately 6% of children and approximately 4% of adults in the western countries including the United States (US) have food allergies. Milk allergy is reported to be one of the most common food allergies affecting as high as 7% in the US. Celiac disease affects approximately 1% of the US population. Such individuals are required to maintain diets restricting milk and gluten. Autism is estimated to affect over 673,000 in the US. A milk-free gluten-free diet is recommended for autism. The gluten grains identified are wheat, oats, barley and rye and any by-products or cross-bred grains of these products. Foods containing milk and milk by-products include those with casein, whey, curds, and glycomacropeptide (GMP). Literature search indicates problems including high cost, labeling, difficulty in finding specialty items, and quality contributed to difficulties maintaining a gluten-free diet. A study of several local specialty stores and groceries to establish the availability of gluten-free food products that were also milk-free was performed. Celiac consumers were asked to complete a survey on the gluten-free products found in the store survey. The survey was to identify product problems. The conclusion from these two studies was that gluten-free bread products was the most unsatisfactory and there was a need to develop a desirable bread product. Two gluten-free milk-free French breads were developed comparable to wheat French bread. Several gluten-free flours and combination gluten-free flours were tested using the Rapid Visco Analyzer (RVA). Texture, color, microbiological analyses and gluten testing procedures were performed. General and target sensory population studies were performed. The non-Celiac population results revealed marginal acceptability. The Celiac population sensory study rated the gluten-free milk-free breads as acceptable. Intent to purchase both gluten-free loaves of bread was rated acceptable.

Salmonella is a leading cause of foodborne illnesses worldwide. In recent years, an increasing number of Salmonella-related outbreaks in produce has been reported. It is therefore important that the produce industry be equipped with rapid, sensitive, specific detection methods for live Salmonella cells in produce to better ensure the produce safety. In this study, we first designed and optimized a loop-mediated isothermal amplification (LAMP) assay for Salmonella detection by targeting the invasion gene (invA). Then we incorporated a chemical reagent, propidium monoazide (PMA) into the sample preparation step to prevent LAMP amplification of dead Salmonella cells. To our knowledge, this is the first study that combined these two novel technologies for live bacterial detection. The PMA-LAMP was evaluated for false positive exclusivity, sensitivity, and quantitative capability. Finally, the PMA-LAMP assay was applied to detect live Salmonella cells in the presence of dead cells in several produce items (cantaloupe, spinach, and tomato). The invA-based PMA-LAMP could avoid detecting heat-killed dead Salmonella cells up to 7.5 × 105 CFU per reaction and could detect down to 3.4 - 34 live Salmonella cells in the presence of 7.5 × 103 heat-killed dead Salmonella cells per reaction in pure culture with good quantitative capability (r2 = 0.983). When applied to produce testing, the assay could avoid detecting heat-killed dead Salmonella cells up to 3.75 × 108 CFU/g and could successfully detect down to 5.5 × 103 - 5.5 × 104 CFU/g of live Salmonella cells in the presence of 3.75 × 106 CFU/g of heat-killed Salmonella cells with good quantitative capability (r2 = 0.993 - 0.949). The total assay time was 3 hours. When compared with PMA-PCR, the PMA-LAMP assay was 10 to 100-fold more sensitive, 2-hour shorter, and technically simpler. In conclusion, the invA-based PMA-LAMP assay developed in this study was an effective tool to specifically detect live Salmonella cells in produce with high sensitivity and quantitative capability.

The U.S. frozen dessert business, including retail and foodservice markets, is the largest in the world. There is a need for deserts that offer better nutritional attributes, such as antioxidants than traditional deserts. Purple rice bran oil (PRBO) is an excellent source of natural antioxidants including tocopherol, tocotrienol, and oryzanol. Adding nano-emulsions of purple rice bran oil (NPRBO) to many products including frozen yogurts (FY) will improve the nutritional profile of the product by substantially increasing the natural antioxidant content. This fortification may have the potential to broaden the FY market. The objectives of this study were to develop and evaluate a frozen yogurt with NPRBO. A stable emulsion was prepared using PRBO (10%), sodium caseinate (5%) and water (85%). The emulsion was sonicated followed by ultra-shearing to produce the nano-emulsion. The nano-emulsion was mixed with the frozen yogurt ingredients to produce a FY-containing-NPRBO (FYNRO). Plain-frozen-yogurt (PFY) and frozen-yogurt-with-sodium caseinate (5%) (FYSC) were used as controls. The yogurts were analyzed for total aerobes (ACP), lactic acid bacteria (LAB), thiobarbituric-acid-reactive-substances (TBARS), peroxide value (PV), rheological properties, microstructure, and α-tocopherol, γ-tocotrienol, and γ-oryzanol content. Triplicate experiments were conducted and data was analyzed at α = 0.05. All of the frozen yogurts had similar texture, melting rate, overrun, fat instability, pH, color and microbial counts. No coliforms were found, ACP counts were <10 CFU/g, and LAB counts were similar for all FY. PVs (mmol/kg of FY) were 3.55, 2.38 and 2.13 for FYNRO, FYSC, and PFY, respectively, while TBARS (µmoles malonaldehyde /kg of FY) values 5.2, 4.57, and 4.66 for FYNRO, FYSC, and PFY, respectively. FYNRO had 6.51 (µg/g oil) α-tocopherol, 12.89 (µg/g oil) γ-tocotrienol, and 754.44 (µg/g oil) γ-oryzanol. No significant physical, chemical, and or microbial properties changed in FYNRO during six weeks of storage at -22 °C. The study demonstrated that FY could be fortified with NPRBO to create a product with unique marketing potential.