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A comparative study of infrared and microwave heating for microbial decontamination of paprika powder.

Eliasson L, Isaksson S, Lövenklev M, Ahrné L - Front Microbiol (2015)

Bottom Line: 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 showed a 1 log unit lower reduction for the corresponding temperature and treatment time.Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency.The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Food and Bioscience, SP Technical Research Institute of Sweden , Gothenburg, Sweden.

ABSTRACT
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 showed a 1 log unit lower reduction for the corresponding temperature and treatment time. Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency. The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms.

No MeSH data available.


Related in: MedlinePlus

Reduction of (A) aerobic mesophilic bacteria and (B) bacterial spores in paprika powder, after 10 and 20 min holding times at 98°C. The paprika powder was conditioned to a water activity of 0.88 prior to the IR and microwave treatments.
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Figure 4: Reduction of (A) aerobic mesophilic bacteria and (B) bacterial spores in paprika powder, after 10 and 20 min holding times at 98°C. The paprika powder was conditioned to a water activity of 0.88 prior to the IR and microwave treatments.

Mentions: The naturally occurring microflora in the paprika batch was 6.80 ± 0.10 log cfu/g for aerobic mesophilic bacteria and 6.87 ± 0.13 log cfu/g for the bacterial spores. The similar level detected on the plates for aerobic mesophilic bacteria and bacterial spores, in combination with visual observations of the colonies, indicated that the natural flora of the paprika batch mainly consisted of bacterial spores. As presented in Figure 4, the best microbial reduction was achieved for the microwave treated paprika powder after a holding time of 20 min, with a 4.8 log units reduction for aerobic mesophilic bacteria and a 3.2 log units reduction for the bacterial spores. The corresponding values for the IR treated samples were 3.8 log units and 2.3 log units. This can be compared to the study by Staack et al. (2008b) where a 4 log units reduction of inoculated B. cereus spores was found in paprika powder (water activity 0.88) after 10 min of IR treatment. The less efficient reduction found in the present study could possibly be explained by that a natural flora is more resistant than inoculated B. cereus spores, or may possibly be due to differences in the IR heating set up between the two studies.


A comparative study of infrared and microwave heating for microbial decontamination of paprika powder.

Eliasson L, Isaksson S, Lövenklev M, Ahrné L - Front Microbiol (2015)

Reduction of (A) aerobic mesophilic bacteria and (B) bacterial spores in paprika powder, after 10 and 20 min holding times at 98°C. The paprika powder was conditioned to a water activity of 0.88 prior to the IR and microwave treatments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588691&req=5

Figure 4: Reduction of (A) aerobic mesophilic bacteria and (B) bacterial spores in paprika powder, after 10 and 20 min holding times at 98°C. The paprika powder was conditioned to a water activity of 0.88 prior to the IR and microwave treatments.
Mentions: The naturally occurring microflora in the paprika batch was 6.80 ± 0.10 log cfu/g for aerobic mesophilic bacteria and 6.87 ± 0.13 log cfu/g for the bacterial spores. The similar level detected on the plates for aerobic mesophilic bacteria and bacterial spores, in combination with visual observations of the colonies, indicated that the natural flora of the paprika batch mainly consisted of bacterial spores. As presented in Figure 4, the best microbial reduction was achieved for the microwave treated paprika powder after a holding time of 20 min, with a 4.8 log units reduction for aerobic mesophilic bacteria and a 3.2 log units reduction for the bacterial spores. The corresponding values for the IR treated samples were 3.8 log units and 2.3 log units. This can be compared to the study by Staack et al. (2008b) where a 4 log units reduction of inoculated B. cereus spores was found in paprika powder (water activity 0.88) after 10 min of IR treatment. The less efficient reduction found in the present study could possibly be explained by that a natural flora is more resistant than inoculated B. cereus spores, or may possibly be due to differences in the IR heating set up between the two studies.

Bottom Line: 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 showed a 1 log unit lower reduction for the corresponding temperature and treatment time.Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency.The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Food and Bioscience, SP Technical Research Institute of Sweden , Gothenburg, Sweden.

ABSTRACT
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 showed a 1 log unit lower reduction for the corresponding temperature and treatment time. Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency. The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms.

No MeSH data available.


Related in: MedlinePlus