Apesar de Escherichia coli O157:H7 ainda ser considerado o principal sorotipo envolvido com surtos de enfermidades veiculadas por alimentos entre as E. coli produtoras de toxina de Shiga (STEC), outros sorogrupos estão ganhando importância, como O26, O45, O103, O111, O121 e O145, que estão sendo denominados de \"Top Six STEC non O157\". As STEC são responsáveis por sintomas que variam de uma simples diarreia até diarreia sanguinolenta, que pode evoluir ainda para síndrome hemolítica urêmica e púrpura trombótica trombocitopênica, podendo ocasionar danos crônicos como falência renal e levar a óbito. Para tanto, apresentam diversos fatores de virulência, entre eles, as toxinas de Shiga (Stx) ou verotoxinas (Vtx). Os veículos destes micro-organismos são diversos alimentos, sendo o principal deles, as carnes moídas. Apesar da importância da carne moída como veículo transmissor de STEC, pouco se conhece sobre a sua presença nesse alimento comercializado na cidade de São Paulo, SP. Sendo assim, o objetivo deste trabalho foi pesquisar a presença de STEC em carne moída comercializada no varejo da cidade de São Paulo e caracterizar tais isolados quanto à presença dos seguintes fatores de virulência: stx1, stx2, eae e ehx. Foram coletadas 248 amostras em diferentes bairros da cidade de São Paulo. Para a detecção de E. coli sorogrupo O157 foi utilizada a metodologia ISO 16654 e para a detecção dos sorogrupos O103, O111, O145 e O26 foi empregada a metodologia descrita pelo Surveillance Group for Diseases and Infections of Animals (NRM 006). Uma amostra de carne moída (0,4%) apresentou o micro-organismo pesquisado. A identificação genotípica e bioquímica caracterizou esse isolado como STEC O157:H7, portador de todos os fatores de virulência pesquisados: stx1, stx2, eae e ehx. Foi constatada, também, a expressão das proteínas stx em células Vero. Esse é o primeiro relato da presença de E. coli O157:H7 produtora de toxina de Shiga em carne moída no Brasil. / Although Escherichia coli O157:H7 is still considered the most important serotype involved in foodborne disease outbreaks among Shiga toxin-producing E. coli (STEC), other serogroups are receiving more attention such as O26, O45, O103, O111, O121 and O145, that are being called the \"Top Six STEC non O157\". STEC are responsible for symptoms ranging from simple diarrhea to bloody diarrhea, which can further evolve to hemolytic uremic syndrome and thrombotic thrombocytopenic purpura, which may cause damage such as chronic renal failure and lead to death. To do so, they have several virulence factors, including the Shiga toxins (Stx) or verotoxins (Vtx). The vehicles of these microorganisms are many foods, most notably, the ground beef. Despite the importance of ground beef as a vehicle for transmitting STEC, little is known about their presence in this kind of food sold in São Paulo, SP. Therefore, the objective of this study was to investigate the presence of STEC in ground beef sold at retail level in Sao Paulo city and characterize the isolates for the presence of the following virulence factors: stx1, stx2, eae and ehx. 248 samples were collected in different districts of Sao Paulo city. For the detection of E. coli O157 serogroup the methodology ISO 16654 was used and for the detection of serogroups O103, O111, O145 and O26 the methodology described by the Surveillance Group for Diseases and Infections of Animals (NRM 006) was used. One sample of ground beef (0.4%) showed the presence of the microorganism studied. The biochemical and genotypical identification characterized this isolate as STEC O157:H7, carrying all of the investigated virulence factors: stx1, stx2, eae and ehx. The expression of stx proteins in Vero cells was also observed. This is the first report on the isolation of E. coli O157:H7 Shiga toxin-producing from ground beef in Brazil.

Surface-enhanced Raman spectroscopy (SERS) is an emerging and sensitive technique in food analysis providing advantages of rapid detection, simple sample preparation and on-site detection capability over GC and LC methods. Most SERS applications focus on detecting trace amount of analyte in liquid as an alternative approach to HPLC. Herein, we invented an innovative SERS-active needle which is composed with an injection needle and a gold-nanoparticles coated fiber inside the injection needle. The gold nanoparticles-coated fiber was fabricated by reducing gold (III) on a chemically etched stainless wire. The SERS needle can be used to insert into the headspace and liquid sample for simultaneous multiphase sample detection, or a soft tissue like a tomato fruit to detect the analyte inside of the tissue with minimum invasion. Using this needle, we can detect as low as 5 ppb of fonofos in the headspace of water and apple juice samples, compared with the dip method, which cannot detect lower than 10 ppb in water and 50 ppb in apple juice. The SERS needle was also applied in real time pesticide translocation study to monitor internalized thiabendazole in tomato fruit after root uptake. The SERS needle detected thiabendazole inside tomato fruits 30 days after the pesticide exposure in a hydroponic planting environment. Moreover, realizing the advantage of detecting volatile components in the headspace of food sample, we applied the SERS needle in a ground beef spoilage study to detect the spoilage biomarkers in the headspace of the raw beef. As a result, the SERS needle detected volatile spoilage compounds produced by bacteria Lactobacillus. Overall, this invention opens a new field of SERS strategy for broad analytical applications.

No description available.

Microwaves heat food rapidly and foods are prepared in less time. However, due to non-uniform heating nature of microwave cooking, there exists a serious concern over complete elimination of pathogens in the food. There has been an increase in interest to accurately understand the behavior of different food materials in a microwave field and microbial inactivation during microwave cooking. Recent research showed that fat content in muscle food plays an important role in microbial inactivation by increasing the inactivation level with an increase in the fat level. It was also demonstrated that muscle food heats up differently than a vegetable food product. Cooking food in a microwave oven either by covering the food container or not results in significantly different temperature profiles. The current research attempts to use modeling techniques to analyze impact of these factors on microwave heating. Mathematical modeling is faster, easier and economically better than actual experiments in determining heating behavior of a microwave-cooked food. Though modeling cannot completely replace actual experiments, it can be used as a tool to understand the effects of various factors influencing the microwave cooking. A factor that is highly important during microwave processing is dielectric properties of the material. The interaction of microwave with the food is mainly based on its dielectric properties, which can change with temperature. Therefore, determination of dielectric properties of food with respect to temperature becomes critical. The current research project has two parts. One to determine the dielectric properties of food being tested and another is to employ mathematical modeling techniques to analyze the effect of fat content, food type and the effect of cooking food by covering the bowl using the lid and not covering bowl. Dielectric properties of ground beef patties at 4%, 9%, 20% fat levels and frozen broccoli were determined using an open-ended, 3.6 mm diameter, semi-rigid coaxial line with copper conductors, connected to a network analyzer. The properties were determined at various temperatures. Foods were measured in triplicate. Results showed that dielectric constant and dielectric loss factor of low fat ground beef were higher than that of high fat level ground beef. In addition, the dielectric properties of florets were lower than that of stem parts for frozen broccoli. A 1,200W, household type microwave oven was used in this study to heat the food. Food was placed in a microwave-safe glass bowl and cooked for 120 seconds. One headspace and three internal temperature measurements were recorded for every 0.6 seconds. Five replications were performed. Finite element method was used as modeling technique and temperatures were predicted. Experimental and predicted temperature values were compared. Results showed that the model used in the study was more suitable for modeling the uncovered cooking than covered cooking process. Modeling results also revealed that high fat ground beef patties reached higher temperature than low fat patties. In high fat meat products, fat content also contributed to increase in temperature during microwave heating. In vegetable products and low fat meat food, moisture content is mainly responsible for microwave heating. A more extensive study on critical fat level above which fat content helps in increasing temperature is needed. In addition, inclusion of steam properties in the headspace for modeling the covered cooking is recommended. / Master of Science

Doctor of Philosophy / Food Science Institute / Melvin C. Hunt / Three experiments were conducted to evaluate factors affecting ground beef color stability with the objectives: 1) To characterize color characteristics of different ground muscles from similarly fed and managed cows and steers; 2) To evaluate the contributions different muscles make to overall ground beef color stability; and 3) To determine if cow biological type (beef-type vs. dairy-type) affects ground beef color dynamics. In general, ground muscles from fed cows appeared darker and redder than ground muscles from steers. Chronological age did not affect ground beef color stability of muscles from fed cows. Use of steroid implants or [Beta]-agonists did not affect ground muscle color stability of fed steers or fed cows. Overall color stability varied more in muscle from steers than from fed cows. Fed cow muscles tended to have a greater proportion of saturated and mono-unsaturated fatty acids to poly-unsaturated fatty acids than fed steer muscles. Ground muscles from fed cows had better color stability properties than ground muscles from steer. When muscles of various color stability were blended to make ground beef and packaged in high-oxygen modified atmosphere (HiO[subscript]2 MAP), high color stability muscles (≥ 75%) in formulations maximizes display color life; however, inclusion of low color stability muscles (≥ 25%) in ground beef formulations had deleterious effects on ground beef color life. Ground semimembranosus (SM) from dairy cows exhibited darker initial color than ground SM from beef cows when packaged in HiO[subscript]2 MAP. However, ground SM from dairy cows was more color stable than ground SM from beef cows when packaged in HiO[subscript]2 MAP. Cow trim used as a fat source in ground beef formulations improved color stability compared to young beef trim when packaged in HiO[subscript]2 MAP. Isolating and managing muscle sources enable meat processors to better manage ground beef based upon intrinsic factors affecting ground beef color stability.

Master of Science / Food Science / John Unruh / A factorial arrangement of treatments was used to evaluate the effects of two subprimal types (chuck roll and knuckle), two quality grades (Premium Choice and Select), and three vacuum storage aging times before processing (7, 21, and 42 d) on ground beef patty display color stability and sensory attributes. At the end of each aging time, four knuckles or two chuck rolls representing their respective quality grade categories were combined and ground to form a sample batch. After a final grind, patties were formed using a patty machine, packaged in overwrapped trays, and displayed in a coffin-type retail case under continuous fluorescent lighting. Ground beef patties from chuck roll and Premium Choice subprimals had brighter red visual color scores, less discoloration, and higher (P<0.05) L*, a*, b*, and chroma values than those from knuckle and Select subprimals, respectfully. With increased display time, patties became (P<0.05) darker red and more discolored and had decreased L*, a*, b*, a/b ratio, and chroma values and increased hue angle values. Ground beef patties from Select knuckle subprimals had greater (P<0.05) oxygen consumption rate (OCR) than those from Premium Choice chuck roll, Select chuck roll and Premium Choice knuckle subprimals. Patties from subprimals aged 42 d had a lower metmyoglobin reducing ability (MRA) than those from subprimals aged 7 and 21 d. Greater aging and display times had higher (P<0.05) aerobic and lactic acid plate counts. In addition, thiobarbituric acid reactive substances values increased (P<0.05) from 7 to 21 d of aging and from 0 to 24 h of display. Ground beef patties from Premium Choice subprimals had a higher MUFA:SFA ratio (P<0.05) than those from Select subprimals. All treatments had acceptable sensory panel results with minimal differences due to treatment. Lower (P<0.05) peak force values for slice shear force and Lee-Kramer were recorded for patties from chuck roll, Premium Choice, and 42 d aged subprimals than those from knuckle, Select, and 7 d aged subprimals, respectfully. Overall, Premium Choice chuck rolls aged for fewer days would result in the most color stability and extended display life.

Orientador: José Moacir Marin / Banca: Angela Cleusa de Fátima Banzatto de Carvalho / Banca: Maria da Penha Longo Mortatti Catanozi / Banca: Rubens Toshio Fukuda / Banca: Alessandra Aparecida Medeiros / Resumo: Escherichia coli Shigatoxigênica (STEC) tem sido implicada como agente causador de severas doenças humanas. Amostras de carne moída, moedor de carne e mãos de manipuladores de 23 estabelecimentos comerciais foram testadas para o isolamento de E. coli usando métodos microbiológicos padronizados. Um total de 287 cepas de E. coli isoladas destes diferentes locais foram submetidas ao PCR para detecção de genes stx 1, stx 2 e eae. As cepas positivas para o gene stx foram analisadas verificando se pertenciam ao sorogrupo 0157. Quatro cepas de STEC foram isoladas, sendo 2 de carne moída e 2 de moedor de carne, todas possuíam o gene stx 2, sendo negativas para a presença do gene eae e o sorogrupo 0157. Todas as E. coli isoladas, incluindo as 4 STEC, foram pesquisadas para sua resistência a 12 antibióticos. Altos níveis de resistência frente aos diferentes agentes antimicrobianos foram detectados; as resistências maiores foram observadas para a tetraciclina (76,6%), amoxicilina (64,1 %) e cefalotina (58,8%). Os altos níveis de resistência antimicrobiana salientam a necessidade para a utilização racional destes agentes em bovinos. Foram observadas índices elevados de sensibilidade frente a associação amoxicilina + ácido clavulânico (96,6%), ceftriaxona (92,7%) e gentamicina (90,3%). / Abstract: Shiga toxigenic Escherichía colí (STEC) has been implicated as the causative agent of several human diseases. Samples from 23 retail meat stores (ground beef, grinding-machine and human hand) were assayed for E. calí isolation using microbiological standard methods. A total of 287 E. colí isolates from these different origins were submitted to polymerase chain reaction for the detection of stx 1, stx 2 and eae genes. The isolates positives for stx gene were serotyped for 0157. Four STEC isolates were recovered, 2 from ground beef and 2 from grinding-machine; ali harbored the stx 2 gene and were negative for the presence of the eae gene and the serogroup 0157. Ali E. colí isolates including the four STEC were screened for antibiotic resistance. High levels of resistance against different antimicrobial agents were detected; those most commonly observed were to tetracycline (76.6%), amoxicillin (64.1 %) and cephalothin (58.8%). Such high levels of antimicrobial agents' resistance highlight the need for a more rational use of these agents in cattle. Susceptibility was high for amoxicillin + clavulanic acid (96,6%), ceftriaxone (92,7%) and gentamicin (90,3%). / Doutor

Fresh beef was modified-atmosphere packaged in carbon monoxide or oxygen to prolong red surface color. After comparison of several packaging method using carbon monoxide, steaks pretreated with 5% carbon monoxide for 24 hours and then vacuum packaged had the best combination of color and microbial stability (5 weeks), with the least potential for carbon monoxide inhalation. In the evaluation of ground beef in high-oxygen, modified-atmosphere-packaging, thiobarbituric-acid numbers increased over time, and the flavor was disliked slightly after 6 or 10 days of storage at 2° Celsius. The antioxidant effect of milk-mineral was tested in raw and cooked ground pork stored refrigerated or frozen. Thiobarbituric-acid numbers were low for all raw treatments. For cooked ground pork, thiobarbituric-acid numbers were lower for samples with milk-mineral or sodium-tripolyphosphate, compared to control or samples with butylated-hydroxytoluene. Sodium-tripolyphosphate, a type 2 antioxidant (iron chelator), was also very effective in preventing heme degradation during refrigerated storage.

This study determined antioxidant and sensory effects of cinnamon, cloves, fennel, pepper, and star anise (Chinese 5-spice ingredients) in cooked ground beef. In experiment 1, thiobarbituric acid (TBA) values of cooked samples were measured during refrigerated storage. In experiment 2, trained panelists evaluated cooked samples for rancid, beef, and spice flavor intensity. Total aerobic plate counts were also measured. Mean TBA values were high (3.4) for control samples. In previous studies, TBA values >1.0 were associated with unacceptably rancid cooked meats. At the lowest spice level of 0.1% of meat weight, all spices except pepper had lower TBA values than controls. Thus, the minimum effective level was 0.1% for all spices except pepper. For all spices except cloves, increasing the use level to 0.5% significantly decreased TBA values (dose-response effect). Cloves did not exhibit a dose-response effect, since all clove levels were very effective, and not different, for maintenance of TBA values In experiment 2 (sensory evaluation), there was a high positive correlation (p < 0.01) between TBA values and panel scores for rancid odor and flavor (0.83 and 0. 78, respectively). Hence, TBA values were in good agreement with sensory panel scores as a measure of oxidation during storage. Spice flavor was inversely correlated (p < 0.01) with rancid odor and flavor (-0.57 and -0.61, respectively), suggesting that spices also decreased the perception of rancid flavor in these samples. The 5-spice blends did not inhibit microbial growth of cooked samples during storage, compared to controls, perhaps due to heat inactivation or loss of antimicrobial components from the spices during cooking. In conclusion, all spices and blends had a dual effect, reducing chemical oxidation as measured by TBA values, and also imparting a distinctive flavor to cooked ground beef.

Made available in DSpace on 2014-06-11T19:32:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-10-03Bitstream added on 2014-06-13T19:22:44Z : No. of bitstreams: 1 rodolpho_d_dr_jabo.pdf: 299270 bytes, checksum: 8a1668550cacade414ec08c3350e51f4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Escherichia coli Shigatoxigênica (STEC) tem sido implicada como agente causador de severas doenças humanas. Amostras de carne moída, moedor de carne e mãos de manipuladores de 23 estabelecimentos comerciais foram testadas para o isolamento de E. coli usando métodos microbiológicos padronizados. Um total de 287 cepas de E. coli isoladas destes diferentes locais foram submetidas ao PCR para detecção de genes stx 1, stx 2 e eae. As cepas positivas para o gene stx foram analisadas verificando se pertenciam ao sorogrupo 0157. Quatro cepas de STEC foram isoladas, sendo 2 de carne moída e 2 de moedor de carne, todas possuíam o gene stx 2, sendo negativas para a presença do gene eae e o sorogrupo 0157. Todas as E. coli isoladas, incluindo as 4 STEC, foram pesquisadas para sua resistência a 12 antibióticos. Altos níveis de resistência frente aos diferentes agentes antimicrobianos foram detectados; as resistências maiores foram observadas para a tetraciclina (76,6%), amoxicilina (64,1 %) e cefalotina (58,8%). Os altos níveis de resistência antimicrobiana salientam a necessidade para a utilização racional destes agentes em bovinos. Foram observadas índices elevados de sensibilidade frente a associação amoxicilina + ácido clavulânico (96,6%), ceftriaxona (92,7%) e gentamicina (90,3%). / Shiga toxigenic Escherichía colí (STEC) has been implicated as the causative agent of several human diseases. Samples from 23 retail meat stores (ground beef, grinding-machine and human hand) were assayed for E. calí isolation using microbiological standard methods. A total of 287 E. colí isolates from these different origins were submitted to polymerase chain reaction for the detection of stx 1, stx 2 and eae genes. The isolates positives for stx gene were serotyped for 0157. Four STEC isolates were recovered, 2 from ground beef and 2 from grinding-machine; ali harbored the stx 2 gene and were negative for the presence of the eae gene and the serogroup 0157. Ali E. colí isolates including the four STEC were screened for antibiotic resistance. High levels of resistance against different antimicrobial agents were detected; those most commonly observed were to tetracycline (76.6%), amoxicillin (64.1 %) and cephalothin (58.8%). Such high levels of antimicrobial agents' resistance highlight the need for a more rational use of these agents in cattle. Susceptibility was high for amoxicillin + clavulanic acid (96,6%), ceftriaxone (92,7%) and gentamicin (90,3%).