Tempering. Based on the connection between the water activity of whole grain and current tempering moisture levels, it would be feasible to temper to a constant water activity rather than to a moisture level. This water activity level would achieve tempering conditions similar to those currently being used, but with more consistency since water activity is more precise than moisture content and can be easily monitored with instrumentation to determine when tempering is complete.
Finally, grain could be tempered to 75 percent relative humidity using saturated sodium chloride and vapor equilibration techniques. Grain would achieve a uniform water activity of 0.75 without the issues caused by adding liquid water. The equilibration time should be similar to current tempering hold times, so mold growth would not have time to begin. Finally, having a consistent starting water activity for tempered wheat will consistently result in flour or farina water activities less than 0.70 aw, preventing mold growth and reducing the rate of rancidity.
Combining Moisture Content and Water Activity
The flour industry has used moisture content levels to control flour and farina quality for many years. Although this procedure has avoided major disasters, it unknowingly placed the specification close to dangerous limits. The addition of a water activity specification would check this possible problem by clearly identifying where the flour or farina is with respect to the growth limits, all with a test that takes less than five minutes.
Further, use of water activity will improve other processes like tempering, where grain can be brought to appropriate relative humidity values that will not only allow excellent processing qualities, but avoid mold growth and other issues. In practice, wheat producers should temper their grain to a specific water activity, then after it has been milled, re-assess the water activity of the flour to make sure it will be safe. A moisture content measurement should then be taken so growers can sell their flour on a weight basis.
Dr. Carter is senior research scientist at Decagon Devices. Reach him at [email protected].
Funding to Improve Low-Moisture Foods
In 2015, a team from the University of Nebraska-Lincoln (UNL) received a portion of a $5 million USDA food safety grant to enhance low-moisture food safety by improving development and implementation of pasteurization technologies. UNL will receive $943,617 over five years.
According to UNL, low-moisture foods, such as nuts, spices, and peanut butter, have been considered at low risk for foodborne illness because they are consumed in a dry state. While microbial growth isn’t possible, the bacteria can survive and stay on the food product for a long time. Foodborne pathogens, such as Salmonella, can cause illness even at very low levels.
UNL research will focus on improving and developing technologies that can kill the bacteria while not affecting food quality. Research includes looking at radio frequency and extrusion processing of the low-moisture products to inactivate the bacteria. Traditional heating heats the product from outside to inside, whereas technology using electromagnetic waves, such as radio frequency waves, volumetrically heats the product. With these methods, according to UNL, the impact on food quality is minimal because the food can be more evenly heated throughout the product to inactivate bacteria.
Research findings will be disseminated to local food processors in Nebraska and across the country.
In addition to UNL, principal co-investigators on the project are Michigan State University, Washington State University, Illinois Institute of Technology, and North Carolina State University.—FQ&S
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