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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

Temperature profile to reach 98°C in the paprika powder, with an initial water activity of 0.88, treated by (A) infrared heating; step (1) 22.6 kW/m2, step (2) 11 kW/m2, and step (3) 0 kW/m2, respectively (B) microwave heating; step (1) 650 W and step (2) 0 W. The Petri dish was moved to the conventional oven during step 3 and step 2 for the infrared and microwave treatment respectively.
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Figure 2: Temperature profile to reach 98°C in the paprika powder, with an initial water activity of 0.88, treated by (A) infrared heating; step (1) 22.6 kW/m2, step (2) 11 kW/m2, and step (3) 0 kW/m2, respectively (B) microwave heating; step (1) 650 W and step (2) 0 W. The Petri dish was moved to the conventional oven during step 3 and step 2 for the infrared and microwave treatment respectively.

Mentions: The IR heat flux was regulated stepwise in order to avoid overheating of the paprika sample’s surface, and thereby reach the treatment temperature as fast and homogenously as possible for the entire sample. The first step of 22.6 kW/m2 enabled a fast heating up, while the second step of 11 kW/m2 reduced the heating rate at the surface and allowed the interior of the sample to be heated by conduction. After the second step, the difference between the highest and lowest temperature in the sample was 24°C as shown in Figure 2A. Therefore a third step of 0 heat flux was applied to let the temperature equilibrate by conduction, making sure that the temperature in the center of the sample reached the target temperature 98°C. During this step the sample was moved to the conventional oven for holding times of 10 respectively 20 min. The necessary heating up time with IR heating was about 3.7 min to reach minimum 98°C in the entire paprika sample.


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)

Temperature profile to reach 98°C in the paprika powder, with an initial water activity of 0.88, treated by (A) infrared heating; step (1) 22.6 kW/m2, step (2) 11 kW/m2, and step (3) 0 kW/m2, respectively (B) microwave heating; step (1) 650 W and step (2) 0 W. The Petri dish was moved to the conventional oven during step 3 and step 2 for the infrared and microwave treatment respectively.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Temperature profile to reach 98°C in the paprika powder, with an initial water activity of 0.88, treated by (A) infrared heating; step (1) 22.6 kW/m2, step (2) 11 kW/m2, and step (3) 0 kW/m2, respectively (B) microwave heating; step (1) 650 W and step (2) 0 W. The Petri dish was moved to the conventional oven during step 3 and step 2 for the infrared and microwave treatment respectively.
Mentions: The IR heat flux was regulated stepwise in order to avoid overheating of the paprika sample’s surface, and thereby reach the treatment temperature as fast and homogenously as possible for the entire sample. The first step of 22.6 kW/m2 enabled a fast heating up, while the second step of 11 kW/m2 reduced the heating rate at the surface and allowed the interior of the sample to be heated by conduction. After the second step, the difference between the highest and lowest temperature in the sample was 24°C as shown in Figure 2A. Therefore a third step of 0 heat flux was applied to let the temperature equilibrate by conduction, making sure that the temperature in the center of the sample reached the target temperature 98°C. During this step the sample was moved to the conventional oven for holding times of 10 respectively 20 min. The necessary heating up time with IR heating was about 3.7 min to reach minimum 98°C in the entire paprika sample.

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