Effects of temperature, pH, and controlled water activity on inactivation of spores of Bacillus cereus in paprika powder by near-IR radiation (original) (raw)
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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.
Effect of infrared heating on quality and microbial decontamination in paprika powder
Journal of Food Engineering, 2008
Infrared radiation (IR) was explored as a technique for decontaminating paprika powder. The effect of water activity (a w) and IR heat flux on paprika temperature and water loss were measured during near-or medium-IR heating. Paprika was evaluated in terms of colour, a w , natural flora, and inoculated Bacillus cereus spores. Surface temperatures were considerably higher than temperatures inside the powder, especially at low a w ; greater differences were observed with medium-than with near-IR. Surface darkening was observed, though the overall colour was not considerably affected. IR effectively removed water from paprika, especially at a w 0.5 and 0.8, resulting in unsatisfactory spore reduction. However, at a w 0.8, the load of the natural flora was reduced (P < 0.05). In a w 0.96 powder, areas with high remaining a w displayed a reduction >6 log 10 CFU/g for B. cereus (P < 0.05). In addition, no microbial counts of the natural background flora were observed in the paprika.
Food Science and Quality Management, 2013
Spores of Bacillus cereus, like other bacterial spores, are heat and radiation resistance causing problem in food processing because of the high temperature or irradiation dose needed to inactivate them. In this work, combination treatments of heat and irradiation were tested for their potential to reduce heat-resistance of B. cereus spores in raw milk, carrot juice and water. D T and Z-values were used to characterize heat resistance of these spores, whereas D 10-values were used to characterize radiation resistance. The results obtained indicated that D 85-values ranged from 24.9 to 35.2 min, D 90-values ranged from 7.6 to 11.6 min and D 95-values ranged from 2.4 to 4.7 min. The Z-values of B. cereus spores in the used media ranged from 9.81 to 11.24 o C. The D 10values ranged from 1.9 to 2.6 kGy. Pre-irradiation treatment at 4 kGy followed by heating reduced D 90-values 2.8 to 3.4 times. The obtained findings indicated the effectiveness of irradiation at 4 kGy followed by heating in a same process to ensure safety of raw milk or carrot juice contaminated with Bacillus cereus.
Frontiers in microbiology, 2015
There is currently a need in developing new decontamination technologies for spices due to limitations of existing technologies, mainly regarding their effects on spices' sensory quality. In the search of new decontamination solutions, it is of interest to compare different technologies, to provide the industry with knowledge for taking decisions concerning appropriate decontamination technologies for spices. The present study compares infrared (IR) and microwave decontamination of naturally contaminated paprika powder after adjustment of water activity to 0.88. IR respectively microwave heating was applied to quickly heat up paprika powder to 98°C, after which the paprika sample was transferred to a conventional oven set at 98°C to keep the temperature constant during a holding time up to 20 min. In the present experimental set-up microwave treatment at 98°C for 20 min resulted in a reduction of 4.8 log units of the total number of mesophilic bacteria, while the IR treatment sh...
Food Control, 2017
Among condiments, paprika is one of the most important ones used both for flavouring and improving other sensorial properties of foods. Because of their agricultural origin, spices are often naturally contaminated with various bacteria due to poor sanitation during growth, harvest, drying, and storage. In this study different decontamination methods were compared regarding microbial decontamination efficacy and maintaining the biochemical, aroma and colour properties. Irradiation and steaming, were found to be highly effective for microbial decontamination of spice paprika powders. Only slight changes were detected due to the decontamination treatment for bioactive component content, however significant changes were observed in the levels of volatile aroma compounds. Alternative decontamination methods, such as microwave heating alone and combined with re-wetting and intensive mixing, or radio-frequency heat treatment alone were also performed to evaluate the effect of these treatments. These methods were found to be less effective in the reduction of the mesophilic aerobic total bacterial counts, while the levels of moulds were significantly reduced, if the samples were held for 10 min at the given incubation temperatures. The treatments did not significantly affect chemical compositional parameters, but sample colour was appeared adversely affected.
A new high temperature short time process for microbial decontamination of seeds and food powders
Powder Technology, 2005
The process for heat treatment of seeds and food powders patented and developed by our laboratory is based on very short heat stresses (from 0.1 up to 30 s) at very high temperatures (in the range of 200 to 600 -C) followed by an instantaneous cooling due to a cold gas (À 80 -C). The decontamination of dried powders is difficult, and the difficulty correlates with the presence of a specific microflora adapted to low water content. Using this new thermal process, experiments with Bacillus subtilis spores and Saccharomyces cerevisiae cells dried on glass beads were carried out. Destruction levels obtained are in the range of 5 to 8 log according to initial water activity level. Our results showed that heat resistance of spores and vegetative cells was strongly improved for initial a w values in the range of 0.3 to 0.5. Our work also evaluated the effects of microbial distribution and powder granulometry on decontamination efficiency. The impact of heat treatment on product organoleptic qualities, notably color, has been also measured. D
Dry heat inactivation of Bacillus cereus in rice
Czech Journal of Food Sciences, 2008
The aim of this work was to validate the method of decontamination of rice at the temperature of 120°C (determined as optimal in previous experiments). Bacillus cereus was selected as the marker micro-organism for the monitoring of decontamination. The spores of Bacillus cereus are moderately heat resistant. In order to show the efficacy of our decontamination process, we artificially contaminated the rice under study with B. cereus. Decontamination was carried out in a homogenising steriliser about 20 h after contamination. The sample was first heated to 90°C and held at this temperature for 70 minutes. Then the temperature was increased to 120°C and held for 3 hours. Five samples were taken for microbiological analyses as follows: before the experiment, on reaching 120°C, and then after 1, 2, and 3 h of decontamination. Decontamination of rice from vegetative forms and spores of B. cereus present at the level of 400 CFU/ml was effected by heating to 120°C and holding for 1 hour.
Food Chemistry, 2021
This study was conducted to evaluate the inactivation of Bacillus cereus spore in mesquite flour with intense pulsed light (IPL) and gamma radiation. The physical, chemical, and toxicity of treated mesquite flour were also investigated. The results showed that up to 3.51 log 10 CFU/g B. cereus spore inactivation was achieved with 8 kGy of gamma radiation, and up to 1.69 log 10 CFU/g reductions could be achieved after 28s of catalytic IPL exposure. Although chemometric analysis showed 9-hydroxy-10,12-octadecadienoic acid was slightly increased after a 28scatalytic IPL treatment, the concentration is within the acceptable range. No significant increase in acetic or propionic acids (typical off-flavor volatile compounds) was observed after either treatment. For cytotoxicity, the Caco-2 cell viability analysis revealed that these two technologies did not induce significant cytotoxicity to the treated mesquite flour. Overall, these two technologies exhibit strong potential for the decontamination of B. cereus in mesquite flour.
Radiosensitization of Bacillus cereus spores in minced meat treated with cinnamaldehyde
Radiation Physics and Chemistry, 2012
Minced meat beef inoculated with Bacillus cereus spores was treated with four essential oil constituents. The active compounds were sprayed separately onto the meat in order to determine the concentration needed to reduce by 1 log the population of B. cereus spores. Cinnamaldehyde was the best antimicrobial compound selected. It was mixed with ascorbic acid and/or sodium pyrophosphate decahydrate and tested for its efficiency to increase the relative radiation sensitivity (RRS) of B. cereus spores in minced meat packed under air. Results demonstrated that the radiation treatment in presence of the cinnamaldehyde and sodium phosphate decahydrate increased the RRS of B. cereus spores by two fold. The study revealed also that the irradiation of raw beef meat pre-treated with cinnamaldehyde produced an inhibition of the growth of B. cereus count during refrigerated storage. This technology seems to be compatible with industrial meat processing.