A new high temperature short time process for microbial decontamination of seeds and food powders (original) (raw)
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Journal of Food Protection, 2005
The thermal treatment of Saccharomyces cerevisiae cells, which were homogeneously incorporated into dried wheat flour particles, was performed for various particle radii (0.8 to 1.6, 1.6 to 2.8, 2.8 to 3.2, and 5 mm) and for an initial water activity of 0.20. A new high-temperature short-time process developed by our laboratory for powder decontamination was used at 150, 200, and 250°C for 5 to 30 s, and significant destruction of up to a 6.7-log reduction, depending on treatment conditions and granule size, was achieved. This study confirms the strong influence of granulometry on the microbial destruction of homogeneously contaminated powdered products. Moreover, a thermal model was developed that takes into account the thermal properties of each component, the variations during heat treatment, and the energy required for phase change. This model provides a tool for predicting yeast destruction.
Water activity affects heat resistance of microorganisms in food powders
International Journal of Food Microbiology, 2005
To study the factors and mechanisms involved in microorganisms' death or resistance to temperature in low-water-activity environments, a previous work dealt with the viability of dried microorganisms immobilized in thin-layer on glass beads. This work is intended to check the efficiency of a rapid heating -cooling treatment to destroy microorganisms that were dried after mixing with wheat flour or skim milk. The thermoresistance of the yeast Saccharomyces cerevisiae and the bacterium Lactobacillus plantarum were studied. Heat stress was applied at two temperatures (150 or 200 jC) for treatments of one of four durations (5, 10, 20, or 30 s) and at seven levels of initial water activity (a w ) in the range 0.10 to 0.70. This new treatment achieved a microbial destruction of eight log reductions. A specific initial water activity was defined for each strain at which it was most resistant to heat treatments. On wheat flour, this initial a w value was in the range 0.30 -0.50, with maximal viability value at a w = 0.35 for L. plantarum, whatever the temperature studied, and 0.40 for S. cerevisiae. For skim milk, a variation in microbial viability was observed, with optimal resistance in the range 0.30 -0.50 for S. cerevisiae and 0.20 -0.50 for L. plantarum, with minimal destruction at a w = 0.30 whatever the heating temperature is. D
Decontamination of food-packing material using moist heat
Depending on the microbiological quality, it may be necessary to reduce the number of microorganisms on the packing material before use with food products. Treatment with hydrogen peroxide at elevated temperatures is most commonly used. Residues of hydrogen peroxide, however, are undesirable. Systems not using chemicals obviously would be preferable. For products which do not allow the growth of bacteria, such as many acid products and products with a low water activity, often it is sufficient to inactivate moulds and yeasts. Moulds and yeasts can be inactivated by temperatures below 100°C provided the water activity is high enough. At low humidities at the same temperatures hardly any reduction in viable count is obtained. A prototype machine was built to investigate the inactivation of microorganisms on the surface of packing material, using moist heat for a short time, similar to the time needed for decontamination by peroxide. The number of viable dry spores of Penicillium roqueforti can be reduced by a factor of Ͼ1000 within 3 s at 90°C and 100% humidity. Moist heat decontamination is a promising method which could help manufacturers pack food in a microbiologically safe manner, without the use of chemicals. Further work is needed, however, to determine the inactivation of other relevant microorganisms.
Efficiency of Pulsed UV Light for Microbial Decontamination of Food Powders
Journal of Food Protection, 2004
The aim of this study was to evaluate the efficiency of pulsed light on the destruction of dried microorganisms on fluidized glass beads and to determine treatment parameters (energy level, water activity, final product quality) for process optimization. The applied drying method allowed microorganisms to remain viable on glass beads or dried powdered products with viability yields approaching 100%. The pulsed UV light system enabled an efficient fluidization of food powders, even for granular products (up to 5 mm diameter) and avoided shadowed areas. For Saccharomyces cerevisiae decontamination, the dose effect of UV rays was preponderant with glass beads and quartz plate, and in this case, 58 J/cm2 were required to decrease the microbial population by 7 log. For colored food powders (black pepper and wheat flour), the thermal effect of pulsed light dominated the UV effect.
Thermal Inactivation of Microorganisms
Critical Reviews in Food Science and Nutrition, 2014
This paper serves as an overview of various aspects of thermal processing. Heat processing of foods has a long history and is still one of the most important preservation methods. To guarantee microbiological safety and stability, large safety margins are often applied in traditional heat processes. Because of the need for more fresh like foods, there is a need for milder preservation methods without compromising on safety and stability. The review deals with heat resistance data and mathematical models that describe heat inactivation. The effects of food composition are not yet fully clear and more knowledge of the cell physiology of the target microorganism could be of help in predicting the effects of food constituents. Finally, special attention has been paid to biological time temperature indicators to enable proper process calculations.
Spore inactivation and quality of paprika powder heated by near-infrared radiation
Dried powders, such as spices, may contain high microbial counts, particularly bacterial spores known for their high heat resistance and good survival capability. Although these spores do not germinate in the powders, when added to high-moisture foods a suitable environment is given for microbial growth. In order to reduce the microbiological contamination and inactivate food altering enzymes many processes expose the powder to a moisture environment during the heat treatment.
2011
In biaxial rotation processing of liquid particulates cans, biological validation is necessary in order to estimate process lethality, F 0 , because of the difficulty in using temperature measuring devices to collect time-temperature history at the particle centers. The objectives of the study were: (1) to fabricate an carrot and meat based alginate particle whose heating behaviour matches the heating behaviour of Nylon spheres previously used in heat transfer studies (2) to predict time temperature profile at the alginate fabricated particle in order to calculate the process times using the numerical integration method (3) using initial and final spores count for carrot and meat fabricated particles inoculated with spores of C. sporogenes and G. stearothermophilus, respectively, to determine the number of log reductions, n, in order to calculate process lethality, and to compare the latter with the model predicted values, which were obtained through simulated time temperature profiles of the alginate fabricated particles. Process times were calculated to achieve an accumulated lethality of 3 and 15 min for carrot and meat alginate fabricated particles, respectively. These ranged from 19.5 to 36.4 min for carrot and from 19.3 to 40.1 min for meat alginate particles. The resulting process lethality, F 0 , values ranged from 2.8 to 3.2 min for carrot alginate fabricated particles inoculated with C. sporogenes spores and from 12.5 to 15.4 min for meat alginate fabricated particles inoculated with G. stearothermophilus spores. The evaluated F 0 values were in general slightly lower than the selected targets (3 min for carrot particles with C. sporogenes and 15 min for meat particles with G. stearothermophilus). However, there were no significant differences (p>0.05) in the computed F 0 values between those obtained from biological validation and numerical simulation under the experimental conditions.
Journal of Food Engineering, 2006
The objective of this work was to create a software application (Bugdeath 1.0) for the simulation of inactivation kinetics of microorganisms on the surface of foods, during dry and wet pasteurisation treatments. The program was developed under the Real Basic Ó 5.2 application, and it is a user-friendly tool. It integrates heat transfer phenomena and microbial inactivation under constant and time-varying temperature conditions. On the basis of the selection of a heating regime of the medium, the program predicts the food surface temperature and the change in microbial load during the process. Input data and simulated values can be visualised in graphics or data tables. Printing, exporting and saving file options are also available. Bugdeath 1.0 includes also a useful database of foods (beef and potato) and related thermal properties, microorganisms (Salmonella and Listeria monocytogenes) and corresponding inactivation kinetic parameters. This software can be coupled to an apparatus developed under the scope of the European Project BUGDEATH (QLRT-2001-01415), which was conceived to provide repeatable surface temperature-time treatments on food samples. The program has also a great potential for research and industrial applications.
Decontamination of food products with superheated steam
Journal of Food Engineering, 2007
Food products can often be contaminated with mycotoxins and spores, many of which are resistant to heat. To ensure the safety of our food supply they must be reduced or eliminated from the final product through processing procedures. The effects of superheated steam (SS) as a processing medium on grains contaminated with the Fusarium mycotoxin deoxynivalenol (DON) and with Geobacillus stearothermophilus spores are presented here. The processing temperature was between 110 and 185°C with three steam velocities of 0.65, 1.3 and 1.5 m/s for DON contaminated wheat and between 105 and 175°C at one steam velocity of 0.35 m/s for mixture of sand and spores. Reductions in DON concentration of up to 52% were achieved at 185°C and 6 min processing time. This was due only to thermal degradation and not to solubilization and extraction. The effect of processing with SS on heat resistant spores was conducted for processing times of 0.5-480 min. The thermal resistance constant for G. stearothermophilus was determined to be 28.4°C for the SS processing temperature of 130-175°C. The first 5 min of SS processing were most effective in the reduction of spores. The use of SS has proven itself to be beneficial by reducing the contamination in foods in addition to any drying that may occur.