Profiling Endosperm Purity of Commercial Mill Streams Preceded by Debranning Using Quantitative Chemical Imaging

Abstract

A brasive debranning is commonly used with hulled grains, such as rice, to remove the outer hull or husk and produce, for example, "polished" white rice (2). At present, preceding the break system with debranning equipment is not commonplace in wheat milling. The increased energy and capital costs of the hardware are issues that require economic justification based on overall mill efficiency and product purity considerations. However, a significant capacity increase in existing mill equipment, with appropriate changes in the flow sheet, can result in a reduction in energy costs (kWhr/ton of wheat) with use of prebreak debranning. Hard wheat milling is one area in which adaptation of the milling system to debran the wheat grain prior to milling is an option that reportedly results in a practical economic pay back (9). The ideal debranning operation in hard wheat milling would evenly remove the outer layers of the pericarp without removing any endosperm or breaking kernels. Potential benefits include the removal of harmful elements from the kernel surface, flour streams with higher "brightness, " and increased flour extraction and mill capacity (3).Direct endosperm purity assessment of individual mill streams using a chemical imaging technique has been described previously (1,11,12). Previous studies were restricted to individual unit processes, such as an individual purifier, laboratory table-top milling study of the break system, or ranking flour stream purity for an experimental pilot mill. Laboratory sieving of postbreak fractions has also been reported (4,5). In this article, we report on the endosperm purity profiles of 29 flour streams from a commercial flour mill running at a capacity of 204 metric tons/24 hr in which the break system is preceded by abrasive debranners (3). Our investigation team included the head operative miller on-site, who shouldered the responsibility for each operational parameter setting and supervised the stopwatch-timed collection of each of the product streams for weighing and various quality analyses. The specimens were produced on-site in Brazil during a routine commercial production process and were sent by air courier to the Kansas State University Microbeam Molecular Spectroscopy Laboratory, where endosperm purity was determined using quantitative chemical imaging with a research model imaging spectrometer (7).We believe that this is the first reported wheat flour endosperm purity profile for a common wheat commercial milling operation in which a debranning process precedes the break system. The goal was to use the best possible chemical definition of wheat endosperm purity to produce this profile. Traditionally, the miller is concerned with the "brightness" of flour and considers a low ash value as being a good attribute. However, flour brightness involves only the part of the electromagnetic spectrum that the human eye can see. In contrast, chemical endosperm purity profiling is selective for endosperm in the presence of nonendosperm, and thus, a binary chemical mixture is...

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