Flours
Flours are formed from the milling and tempering of the grains ( rice, maize, wheats etc). Thus, it is important to ensure that the initial microbial counts of the grains are within the acceptable range. In addition, the cleanliness of the processing equipments can also help in reducing the microbial load in the flour. Any residue left behind in the equipments will contaminate the flour.
Flour with moisture level less than 12% will not support any microbial growth. Moisture from the atmosphere, equipment or condensate can result in microbial growth in flour.
The fungi in the finished flour are usually Penicillium, Eurotium species and Asp. Candidus.
Spoilage of flour
If the moisture level of the flour is above 12%, xerophilic fungi will grow and that when reaches 17% result in bacteria grow. The growth of bacteria is faster than the fungi, thus it will become the dominant pathogen in flour when the moisture level has exceeded the limit. In the “exposed” flour, the lactic acid bacteria will cause acid fermentation, followed by the yeast’s alcoholic fermentations and lastly the oxidation to form acetic acid by the Acetobacter. This is uncommon in stored flour. Even without the presence of the lactic acid bacteria, micrococci and Bacillus spp. will also produce lactic acid., alcoholic and other phenolic compounds.
Pathogen and toxin production
Dry flour has a low water activities, thus does not support fungal growth in which prevent the occurrence of mycotoxin production.
Salmonella, is also a hazard in flours especially in flours that does not undergoes any heating treatment. It is because heating can kill or inhibit the Salmonella as they are heat sensitive.
Reference:
ICMSF. 2005. Micro-organisms in Foods 6; 2nd Edition. Klumer Academic/ Plenum Publishers; USA. Accessed on 10 July 2008.
Flours are formed from the milling and tempering of the grains ( rice, maize, wheats etc). Thus, it is important to ensure that the initial microbial counts of the grains are within the acceptable range. In addition, the cleanliness of the processing equipments can also help in reducing the microbial load in the flour. Any residue left behind in the equipments will contaminate the flour.
Flour with moisture level less than 12% will not support any microbial growth. Moisture from the atmosphere, equipment or condensate can result in microbial growth in flour.
The fungi in the finished flour are usually Penicillium, Eurotium species and Asp. Candidus.
Spoilage of flour
If the moisture level of the flour is above 12%, xerophilic fungi will grow and that when reaches 17% result in bacteria grow. The growth of bacteria is faster than the fungi, thus it will become the dominant pathogen in flour when the moisture level has exceeded the limit. In the “exposed” flour, the lactic acid bacteria will cause acid fermentation, followed by the yeast’s alcoholic fermentations and lastly the oxidation to form acetic acid by the Acetobacter. This is uncommon in stored flour. Even without the presence of the lactic acid bacteria, micrococci and Bacillus spp. will also produce lactic acid., alcoholic and other phenolic compounds.
Pathogen and toxin production
Dry flour has a low water activities, thus does not support fungal growth in which prevent the occurrence of mycotoxin production.
Salmonella, is also a hazard in flours especially in flours that does not undergoes any heating treatment. It is because heating can kill or inhibit the Salmonella as they are heat sensitive.
Reference:
ICMSF. 2005. Micro-organisms in Foods 6; 2nd Edition. Klumer Academic/ Plenum Publishers; USA. Accessed on 10 July 2008.
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