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Minas cheese is a food product of significant economic importance to the Brazilian dairy industry. With the intent of providing product identity for legal, economic and manufacturing purposes, several studies have been conducted t...
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Minas cheese is a food product of significant economic importance to the Brazilian dairy industry. With the intent of providing product identity for legal, economic and manufacturing purposes, several studies have been conducted to define the proximate composition, starter and ripening microflora and manufacturing protocol for Minas cheese. However, studies have yet to characterize the flavor character of Minas cheese, namely the volatile profile. For this purpose, volatiles were investigated using dynamic headspace sampling and GC-MS analysis. Quantitation was based on the recovery of authentic compounds where available. A total of 54 compounds were positively identified and 51 quantified, including fatty acids (11), alcohols (14), aldehydes (5), ketones (6), esters (7), terpenes (8) and lactones (2). The impact of individual volatile compounds on the flavor profile of Minas cheese is discussed. Some of major metabolic pathways for their biosynthesis are reviewed to indicate the possible origin of the compounds identified.
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Studies were conducted to investigate the effect of initial container pressure on heat penetration parameters using flexible aluminum containers. A pilot scale liquid nitrogen dispenser, regulated to discharge a fine stream of liq...
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Studies were conducted to investigate the effect of initial container pressure on heat penetration parameters using flexible aluminum containers. A pilot scale liquid nitrogen dispenser, regulated to discharge a fine stream of liquid nitrogen (LN_2), provided approximately 10 to 15 psi pressure within the container prior to end-over-end processing in a computer-controlled retort using water immersion with 32 psi over-pressure. Thermal process parameters including the heating rate index (f_h), lag factor (j_h), the cumulative lethality (F_o), cook-value (C_o) and the overall heat transfer coefficient (U_o) were examined in relation to retort temperature (241-261F), rpm (0-15 rpm) and product initial temperature (54-121F) using 5% w/w bentonite suspension with or without liquid nitrogen. Generally, containers with added liquid nitrogen had no impact on evaluated data compared to their counterparts without LN_2 under similar experimental conditions. Estimated overall heat transfer coefficient (U_o) compared favorably with published data, while the C_o/F_o ratio decreased with increasing temperatures as expected. Product cold spot location migrated in either upward or downward direction depending on the mode of heat transfer. Although added LN_2 generally had no limiting effect on both heat transfer and heat penetration data, processing aluminum containers with high initial pressure at high retort temperatures could create excessively high internal pressure that could compromise container seam integrity.
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The need for creating container initial pressure, overpressure requirements and maintenance during thermal processing of thin-walled aluminum containers is briefly discussed. The initial pressure within containers was achieved by ...
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The need for creating container initial pressure, overpressure requirements and maintenance during thermal processing of thin-walled aluminum containers is briefly discussed. The initial pressure within containers was achieved by injecting liquid nitrogen (LN_2) into the container headspace (0.5, 0.75 and 1 in.) prior to seaming. Experiments were conducted using a computer-controlled retort with water-immersion as heating medium, and temperatures ranging from 241 to 261F. Product initial temperature varied from approximately 45 to 135F. Container internal time-pressure history during processing was monitored using a remote pressure sensor mounted within the container. Using water as model food, a dimensionless correlation that related the maximum container pressure to product headspace, initial temperature and pressure was developed. Increasing retort temperature increased the maximum container internal pressure, while increasing product initial temperature decreased the maximum internal pressure developed within the container processing. The effect of product initial temperature on the maximum internal pressure was attributed to the amount/level of entrapped gasses present. Developed correlation using water predicted the internal pressure for 5 % bentonite suspension with marginal errors (2 to 7%). However, the model failed to predict the maximum pressure for oil-filled containers.
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Melamine has been used for the adulteration of cereal flours in order to increase their apparent protein content. Crude melamine may contain several by-products, i.e. ammeline, ammelide, and cyanuric acid. The simultaneous analysi...
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Melamine has been used for the adulteration of cereal flours in order to increase their apparent protein content. Crude melamine may contain several by-products, i.e. ammeline, ammelide, and cyanuric acid. The simultaneous analysis of all four chemicals is difficult because of the formation of an insoluble salt between melamine and cyanuric acid. A simple and convenient high-performance liquid chromatography (HPLC) method for the detection of the adulteration of cereal flours with all four chemicals is proposed herein. The precipitate formation between melamine and cyanuric acid was prevented by using alkaline conditions (pH 11-12) for both standards preparation and sample extraction. The method uses matrix-matching, which involves the construction of a calibration curve on a blank (negative control) matrix, which is then used for the quantitation of melamine and by-products in adulterated (positive) samples. Matrix-matching compensates for analyte losses during sample preparation, and for matrix effects. The method was successfully applied to wheat, corn, and rice flours, and is expected to be applicable (with some modifications) to soy flour as well. The method allows for the detection of melamine, ammeline, and ammelide at approximately 5 μgg~(-1), and cyanuric acid at approximately 90 μgg~(-1) in wheat flour.
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An alternative, rapid, and reproducible method of analysis for perchlorate in selected food products (fruit and vegetable juice, milk, and bottled water) was developed and validated. Improvements over previous methods were achieve...
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An alternative, rapid, and reproducible method of analysis for perchlorate in selected food products (fruit and vegetable juice, milk, and bottled water) was developed and validated. Improvements over previous methods were achieved by the use of a rugged and inexpensive C_(18) column, a multi-mode OASIS HLB solid-phase extraction cartridge for sample clean-up, and acetic acid for pH adjustment and protein precipitation. The hydrophobicity of the perchlorate anion gives it good retention and separation characteristics on C_(18) chromatographic columns. The C_(18) column allowed for the use of 90% of acetonitrile at a low flow rate (0.3 ml min~(-1)), without splitting, and could also be regenerated with organic solvents, unlike an ion-exchange column. Perchlorate levels in selected commercial food samples were: < 1.0-2.1 ngg~(-1) (fruit and vegetable juices, reported here for the first time), < 1.0-5.0 ng g~(-1) (milk), and < 1.0ng g~(-1) (bottled water).
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The production of thermally concentrated fruit juices uses temperatures high enough to achieve at least a 5-log reduction of pathogenic bacteria that can occur in raw juice. However, the transportation and storage of concentrates ...
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The production of thermally concentrated fruit juices uses temperatures high enough to achieve at least a 5-log reduction of pathogenic bacteria that can occur in raw juice. However, the transportation and storage of concentrates at low temperatures prior to final packaging is a common practice in the juice industry and introduces a potential risk for postconcentration contamination with pathogenic bacteria. The present study was undertaken to evaluate the likelihood of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella surviving in cranberry, lemon, and lime juice concentrates at or above temperatures commonly used for transportation or storage of these concentrates. This study demonstrates that cranberry, lemon, and lime juice concentrates possess intrinsic antimicrobial properties that will eliminate these bacterial pathogens in the event of postconcentration recontamination. Bacterial inactivation was demonstrated under all conditions; at least 5-log Salmonella inactivation was consistently demonstrated at -23 degrees C (-10 degrees F), at least 5-log E. coli O157:H7 inactivation was consistently demonstrated at -11 degrees C (12 degrees F), and at least 5-log L. monocytogenes inactivation was consistently demonstrated at 0 degrees C (32 degrees F).
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Experiments were conducted using Bacillus stearothermophilus spores in 0.5% w/w carboxymethylcellulose suspension to evaluate come-up contributions from the tubular heat exchanger. A lab-scale UHT/HTST simulator that allowed sampl...
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Experiments were conducted using Bacillus stearothermophilus spores in 0.5% w/w carboxymethylcellulose suspension to evaluate come-up contributions from the tubular heat exchanger. A lab-scale UHT/HTST simulator that allowed samples to be collected at the exit of the heat exchanger and holding tube was used with operating temperatures up to 270F. The bulk mean residence time in the heat exchanger ranged from 30 to 89 sec, while that in the holding tube ranged from 4 to 14 sec. It was observed that between 40% and 51% of the cumulative lethality (F_(250)~(11)) at the exit of the holding tube, was contributed by come-up in the tubular heat exchanger. This come-up contribution was determined on the basis of having an F_(250)~(11) of 8.5 min in the holding tube alone. It was evident that come-up lethality will depend on product initial temperature, residence time and temperature history in the heat exchanger, with higher temperatures obviously contributing more lethality. Therefore, the entire aseptic system becomes even more complex since several critical parameters need to be monitored, controlled and documented. Experimental data compared favorably with computer-simulated data using the Asepti-CAL~(TM) software, with the software package giving more conservative results. Ultimately, come-up credit (CUC) should be tested on a pilot scale or industrial setup by way of reduced residence time (i.e. increased fluid flow rate), reduced holding tube length or temperature in order to determine if CUC can be applied towards the lethality required for the product. Monitoring and control devices become critical to ensure consistency and reproducibility in product residence time and time-temperature history, in the tubular heat exchanger.
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Validation is defined as the element of verification focused on collecting and evaluating scientific and technical information to determine whether the HACCP plan, when properly implemented, will effectively control the hazards. T...
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Validation is defined as the element of verification focused on collecting and evaluating scientific and technical information to determine whether the HACCP plan, when properly implemented, will effectively control the hazards. The primary focus of validation for industry is to determine that critical limits at critical control points are capable of controlling the identified hazards; however, other elements such as monitoring can also be validated. Validation may involve the use of scientific publications, historical knowledge, regulatory documents, experimental trials, and other approaches. This paper reviews how the industry in the United States has validated elements of HACCP plans.
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Using a 2 kW, 27.12 MHz RF heater, studies were conducted to evaluate the effectiveness of RF heating in inactivating surrogates of both Listeria and Escherichia coli cells in milk under continuous flow conditions. Depending on pr...
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Using a 2 kW, 27.12 MHz RF heater, studies were conducted to evaluate the effectiveness of RF heating in inactivating surrogates of both Listeria and Escherichia coli cells in milk under continuous flow conditions. Depending on product residence time and RF power level, RF heating was found to be capable of inactivating both Listeria and E. coli in milk, with E. coli being the more heat sensitive of the two. For a total residence time of 55.5 s (i.e., 29.5 and 26 s in the applicator and holding tube, respectively), up to 5- and 7-log reductions were found for heating Listeria and E. coli, respectively at 1200 W, and an applicator tube exit temperature of approximately 65 degrees C. This study demonstrates that RF heating could be used to effectively pasteurize milk by manipulating incident power levels and flow rate. While these studies have been conducted under mild fluid flow (laminar) conditions, further studies are necessary to justify its industrial application using more realistic flow conditions..
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The purpose of this study was to develop data on the risk of listeriosis to support a science-based strategy for addressing Listeria monocytogenes in foods in the United States. Eight categories of ready-to-eat foods were collecte...
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The purpose of this study was to develop data on the risk of listeriosis to support a science-based strategy for addressing Listeria monocytogenes in foods in the United States. Eight categories of ready-to-eat foods were collected over 14 to 23 months from retail markets at Maryland and northern California FoodNet sites. The product categories included luncheon meats, deli salads, fresh soft "Hispanic-style" cheeses, bagged salads, blue-veined and soft mold-ripened cheeses, smoked seafood, and seafood salads. The presence and levels of L. monocytogenes in the samples were determined by rapid DNA-based assays in combination with culture methods. Of 31,705 samples tested, 577 were positive. The overall prevalence was 1.82%, with prevalences ranging from 0.17 to 4.7% among the product categories. L. monocytogenes levels in the positive samples varied from <0.3 MPN (most probable number) per g to 1.5 X 10~5 CFU/g, with 402 samples having levels of <0.3 MPN/g, 21 samples having levels of >10~2 CFU/g, and the rest of the samples having intermediate levels. No obvious trends with respect to seasonality were observed. Significant differences (P < 0.05) between the sampling sites were found, with higher prevalences for threes categories in northern California and for two categories in Maryland. Significantly (P < 0.001) higher prevalences were found for in-store-packaged samples than for manufacturer-packaged samples of luncheon meats, deli salads, and seafood salads, while 16 of the 21 samples with higher counts were manufacturer packaged. The data collected in this study help to fill gaps in the knowledge about the occurrence of L. monocytogenes in foods, and this new information should be useful in the assessment of the risk posed by L. monocytogenes to consumers.
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