Ad libitum (AL) feeding of rats leads to obesity and increased result variability, as well as premature morbidity and mortality. It may also alter metabolism and responses to foreign compounds. Moderate dietary restriction (DR) reduces these untoward effects without compromising the sensitivity of rodent bioassays. The diet board (DB) is a novel method for achieving moderate DR in group housing. Food pellets are firmly attached into grooves in an aspen board, and rats have to gnaw the wood in order to eat. Food is available continuously, but due to the effort involved rats eat less. This study simulated a chronic safety test to assess the long-term effects of DB feeding. A total of 146 male and female outbred Sprague-Dawley rats, nine weeks old at onset, were housed in groups of three and fed either AL or with DBs for two years. Food and water consumption were measured at six time points. The rats were weighed every one to two weeks. Body and tibial lengths and epididymal fat weight were measured at necropsy. Modified body mass index was calculated at five time points after one year of age. DB feeding reduced body weight and fat tissue moderately, more so in males. DB males ate less than AL males, but no differences were seen in the total food consumption in the females. There was no consistent difference in the within-group variations of the measured parameters. DB is a workable DR method, albeit some modification could enhance and standardize its DR effects, especially in female rats.

The evolution of dielectric properties of starch-based food pellets with different moisture contents was measured during microwave expansion to determine the effect of water content on the expansion dynamics.Dynamic dielectric measurements were found to be an excellent procedure to in situ monitor and characterize the different stages in the material transformation of food pellets during microwave expansion.Although the maximum bulk expansion of pellets was achieved at a moisture content of approximately 8% (wet basis), comparative analysis showed that a moisture content 10–11% produced the best results considering the tradeoff between the foaming and expansion temperature. This was due to the high expansion index and an expansion temperature that was sufficiently lower than the onset temperature for pellet scorching, which provides an operating window to maximize expansion and minimize the likelihood of burning.Dielectric measurements during microwave heating in short on/off cycles prior to pellet expansion suggested that the water was not as dielectrically bound for high moisture content pellets.