A laboratory countercurrent steep battery for corn wet-milling

A laboratory-scale steep battery was designed to serve as a research tool for studying continuous countercurrent steeping as performed in corn wet-milling plants. The steep battery consisted of 16 tanks (12 active; 4 for loading and unloading) each of approximately 1 gallon capacity designed to hold 1 kg of corn and associated steepwater. Sequencing of water flow through the 12 active tanks was accomplished via computer control and differed from previous laboratory steep batteries in that it had the capability to recycle steepwater within individual tanks. The system was designed to accommodate a wide range of steep times, steep temperatures, evaporator draw rates, and individual tank steepwater recycle rates. Steepwater profiles for total solids, pH, sulfur dioxide, and total acidity were measured and found to be comparable to industrial profiles reported in the scientific literature, if adjusted to compensate for incoming solids with industrial steepwater. Product yields for corn steeped in the laboratory steep battery were statistically similar to batch-steeped corn fractionated using the same milling procedure. The product yields were also comparable to values found by other researchers using laboratory countercurrent steeping. Operation of the steep battery required continuous monitoring due to potential for breakdown (sticking of floats, pump tubing failure, and electrical failure). When preventative maintenance was used, the system could be operated with few disruptions. The laboratory steep battery can potentially be used to study many of the design parameters of conventional steep systems, as well as to explore alternative water routing schemes. It can also be used to study the effect of steeping chemicals, enzyme adjuncts, or corn quality.