Effectiveness of Modified 1-Hour Air-Oven Moisture Methods for Determining Popcorn Moisture

Two of the most commonly used approved grain moisture air-oven reference methods for corn are the air oven method ASAE S352.2, which requires long heating time (72 h) at 103 +/- 1 degrees C for unground samples, and the AACC 44-15.02 air-oven method, which dries a ground sample for 1 h at 130 +/- 1 degrees C, but there is specific moisture measurement method for popcorn. The AACC 44-15.02 recommends a two-stage drying method for grain over 13%. But this involves more handling and drying time. The objective of this study was to develop an air-oven procedure for popcorn that requires short heating time (1h or less) based on existing reference method for ground corn (AACC 44-15.02). In the process of procedure development, two laboratory mills (Wiley Mini-Mill and Perten 3303 Mill) were optimized for mesh screen size and mill gap settings. The approved AACC method recommends using a 20-mesh screen fitted to the Wiley Mill, which failed, with wires breaking during the grinding process, possibly due to the hard nature of popcorn and/or clogging. It was replaced with the 10-mesh screen which produced larger particle size distribution with similar to 73% greater than 840 mu m. The Perten Mill 3303 was set to gap No. 3 which produced similar to 68% particles that were greater than 840 mu m. Additionally, this study evaluated the effectiveness of single-stage moisture measurement with the 14.5% and 16% moisture popcorn samples. Using the proposed procedure, four varieties of popcorn were tested at three different moisture contents (13%, 14.5%, and 16%). The method using the Wiley grinder and 60 min. heating time yielded oven moisture values which were statistically (p<0.05) similar to the approved ASAE S352.2 and AACC 44-15.02 (72-h, whole grain method). The moisture content of ground samples obtained from the Perten 3303 Mill had elevated moisture measurements and bias across the moisture levels when dried for 60 min. A reduction in heating time to 50 min. resulted in Perten mill samples yielding statistically (p<0.05) similar moisture measurements with the reference 72-h, whole grain method.