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Traditionally, microbial contamination in powders has not beenconsidered an important problem due to their low water activity (aw)which limitsmicrobial growth during storage (FDA, 2015). Microorganismsare not inactivated at low levels of aw; instead, however, they becomehighly resistant to standard decontamination procedures such asheat (Laroche, Fine, & Gervais, 2005). For this reason, microbial contaminationis becoming a subject of ever-increasing concern: in particular,contamination caused by pathogenic microorganisms that are presentin the rawpowdermaterial andwhich is used in the elaboration of foodstuffs.This problem is remarkable in flours since several studies havefound counts from 3 to 5 log10 cycles of total viable counts (Bullerman& Bianchini, 2009; Sauer, 1992; Victor et al., 2013). Other studies defineSalmonella spp., Escherichia coli and Bacillus cereus, as pathogenic, andLactobacillus spp., as spoilage, as the microorganisms of major interestin flour and wheat (Berghofer, Hocking, Miskelly, & Jansson, 2003;Eyles,Moss,& Hocking, 1989; Richter,Dorneanu, Eskridge,& Rao, 1993).Wheat used for flour production is traditionally stored at low humidityprior to use. Immediately before the wheat enters the mill,water is added to increase the wheat's moisture and aw. This step increasesthe outer bran layer's plasticity, preventing its fracture duringmilling and facilitating its separation from the flour in the course ofthe milling process (Berghofer et al., 2003). This step can nevertheless
be a source of contamination. Consecutive milling and sifting processes
are performed to obtain refined flour; these processes generate a considerable
amount of heat. Moisture condensation can thereby lead to
the build-up of flour residues inside the equipment, wheremicroorganisms
can accumulate and eventually contaminate the milled products
(Berghofer et al., 2003).
As aw of these products is low, dry heat treatments are ineffective in
ensuring microbial decontamination; moist heat treatments cannot be
used either, since they might alter the product's characteristics. Thus
there is a need to find alternatives to heat for the decontamination of
flours and powders. One of these potential alternatives would be UV-C
light.
UV-C light has been used in the decontamination of air, surfaces and
water.Moreover, the food industry has recently displayed an increasing
interest in UV-C light for the hygienization of liquid and solid foodstuffs,
since UV-C radiation is capable of inactivating pathogenic and spoilage
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