Control of flour beetle proliferation by refrigeration
Flour is an essential component of any baking recipe. This ingredient is generally kept in storage at room temperature. However, there are certain incidents wherein certain flour packages may contain living organisms that may affect any baking activity (Lewis, 1997). These organisms are flour beetles, which may be commonly found in poorly processed flour. It is therefore essential to identify any procedure that may prevent the occurrence of flour beetles during storage.
This study hypothesized that the occurrence of flour beetles can be controlled by decreasing the storage temperature of the flour.
Three bags of flour of the same size and brand were procured from different stores. This setting was chosen to rule out the factor that the beetles were not influenced by the conditions of the store. The flour in each bag was searched for any presence of beetles. Each bag was split into two equal volumes, of which each one was kept in either the refrigeration (39oF) or at room temperature (72oF). The bags were stored at the specific temperatures for 2 months. After the appropriate incubation periods, the bags were inspected for flour beetles and the number of beetles in each bag was noted.
Using several different batches of flour from different stores, the beetles were not specific to a single store or a single lot of flour. By dividing the flour into several smaller lots, it was shown that there is no difference in the number of beetles from one part of the bag (like the top) versus another part (like the bottom).
The bags held at room temperature were considered as controls so that if any beetle eggs were present in the flour samples, they should hatch at room temperature. Should no beetles be observed in the room temperature bags then the flour contained no eggs, or 8 weeks is insufficient time for the eggs to hatch and the experiment can be repeated with longer incubation times.
Cold temperatures should inhibit the hatching of flour beetle eggs so I would expect few beetles in the bags that were stored in the refrigerator (39oF). I would expect numerous beetles in the room temperature bags.
Table 1. Number of live beetles observed in each sample.
Average for treatment
Figure 1. Effect of temperature on number of flour beetles observed in King Arthur Flour.
This study shows that flour beetle eggs were present in all of the flour bags employed. This investigation also suggests that storage at room temperature allows flour beetles eggs to hatch. Since there were no beetles in the samples from the refrigerator, 39oF is sufficient to inhibit egg hatching. This study may facilitate proper storage of flour and prevention future contamination in the kitchen.
Donald Lewis, Jeffery Hahn, Phil Pellitteri (1997) Insect pests of stored foods. http://www.extension.umn.edu/distribution/nutrition/DJ1000.html Retrieved 4/12/2006.