Location: Grain Quality and Structure Research2010 Annual Report
1a. Objectives (from AD-416)
Determine the chemical, physical and sensory attributes in "off" odor sorghum grain for the development of a standard reference sample.
1b. Approach (from AD-416)
GIPSA and ARS are involved in the independent research of measuring grain quality characteristics. The parties agree that meeting the objectives of this project will serve to strengthen and enhance the research programs of both entities by furthering the understanding of improved tools and techniques to determine unacceptable odors in grain sorghum and potentially other grains. It is intention of the parties to this Agreement that the research work shall affirm their mutual interest in cooperative research programs and exchanges and shall be for their mutual benefit and the benefit of the people of the United States. GIPSA request ARS to conduct research on the impact of “off” odor in sorghum on the chemical, physical and sensory quality of sorghum grain. GIPSA agrees to award ARS resources to conduct the above research and provide samples with different degrees of off odors. ARS agrees to study physical and chemical variations between molded and healthy sorghum grain. ARS will provide a sub-award to Kansas State University to complete supplemental work to obtain chemical and sensory traits. The project will be conducted as collaboration between GIPSA-ARS. A major criterion for evaluating sorghum grain quality is odor. Both domestic and international customers are very adept in their ability to detect “off odor” in sorghum grain. If an “off odor” exists a red flag immediately is raised and the quality of the sorghum is suspect. ARS would benefit by collaborating with GIPSA on this project to determine a means to evaluate for “off odor” and the inherent chemical components that comprise the “off odor(s)”. The collaboration may lead to the development of a sensory panel for GIPSA that may be used in assessing sorghum grain quality using sensory and chemical analyses.
3. Progress Report
Some volatile compounds present in musty sorghum can be associated with musty odor notes, and can be differentiated in two groups: "dry" and "wet" mustiness, that combine to give an overall musty that is evaluated by grain inspectors. Musty sorghum with "wet" odor notes seemed to have other off-odorant notes as earthy/damp or moldy. The presence of these odor notes may indicate a higher grade of deterioration in the grain, compared with the "dry" musty grain samples. The presence in these samples of some aromatic compounds (such as pyrazines and methoxybenzenes), which were absent in the "musty, dry" sorghum grain samples, corroborated the sensory analysis results. Some references/standards were elaborated using the instrumental aromatic data and the sensory descriptive analysis as the principle potential reference materials for mustiness in grain. These references can allow the USDA inspectors to unify and increase the consistency of the sensory analysis used to grade the sorghum grain. During the next months of the project, new chemicals will be considered (e.g. pyrazines) and used as references. Shelf life study will be continued, and recommendations about references preparation and use can be made. An aspect that needs to be considered for future work is that clean grain samples should be stored in various ways to determine how those storage conditions affect the appearance or disappearance of chemical aromatic compounds over time, and to study the relationship of these compounds with the degradation of the "clean grain odor". Such study would allow recommendations to be made for grain storage.