Algorithms for automated temperature controls to cure peanuts

The introduction of affordable control networks for peanut dryers has made it possible to easily vary the curing temperature based on ambient air conditions. Previous research has used ambient temperature, relative humidity, and humidity ratio as possible control parameters. Peanuts from the same field were cured using four 0.11 m dryers to a moisture content of approximately 0.11 kg kg. Four different algorithms, one for each dryer, were used to calculate the desired plenum temperature based on ambient conditions. They were: (1) conventional control (CC); (2) drying rate control (DRC1); (3) modified drying rate control (DRC2); and (4) relative humidity control (RHC). Peanuts cured significantly faster (0.42 kg h) using DRC2 compared to peanuts cured using DRC1 (0.23 kg h), RHC (0.29 kg h), and CC (0.35 kg h). Curing with DRC2 was not significantly faster than with CC (0.60% h). No significant differences in milling quality, as indicated by percent splits, percent bald kernels, and shelled stock value, were found due to drying treatments. The percent split kernels averaged 9.8% over all temperature control methods and ranged from 8.7 to 10.2%. Shelled stock value ranged from 959.89 to 978.74 US$ t. Peroxide values and free fatty acids were acceptable for all curing treatments and were not significantly different. Seed germination ranged from 83 to 87%, but was not significantly different. Flavor ratings determined by a flavor panel on a scale from 1 to 8, with 6 being acceptable and 8 being the best, were all greater than 7.1. Historical weather data from Dawson, GA indicated that DRC2 would result in a higher plenum temperature. These tests indicated that maximum recommended drying rates may be too conservative for efficient operation of commercial operations. © 2002 Elsevier Science B.V. All rights reserved.