1a. Objectives (from AD-416):
Continue investigation of recently discovered volatile profile of germinating aspergilli spores on almond and pistachio, including volatile compounds unique to the germinating spores on these hosts; use volatile profile in conjunction with a portable GC-MS system to develop a near real time portable field volatile sampling device capable of early warning detection of aspergilli infected almond and pistachio; remove aflatoxin-producing aspergilli hot spots from almond and pistachio stockpiles and transit containers thus decreasing human health risks and product loss as a result of Aspergillus contamination.
1b. Approach (from AD-416):
ARS: Using key fungi identified from current research the ARS lab will: commence investigation of volatile limits of detection vs. aspergilli contamination levels; continue inoculation of whole almonds and pistachios, increasing complexity of fungi bouquet – apply results to optimizing GCMS detector; conclude all laboratory-based experiments to fully characterize volatiles from all nut components and whole sources; perform inoculations of almonds and pistachios and execute blind tests for detection of inoculated nuts located in laboratory- and field-based stockpiles; and, perform in-field analyses with portable GCMS detector, analyze results, and in disseminate results. Torion: Using results from the ARS lab, Torion personnel will: design custom air sample collection device for volatiles from almond and pistachio stockpiles and containers; concurrently design and implement experiments for MS performance, response, internal references, and quantitation of detected volatiles; build designed collection device; test new hardware in portable GCMS; redesign, build, and test hardware to fix any problems found in initial design; Assist with in-field analyses with portable GCMS detector, analyze results.
3. Progress Report:
ARS Activities: naturally inoculated samples of almond and pistachios were studied for volatile emissions. The major finding was distinct differences in host material for identifiable volatiles from fungal spores (see germane publications noted below). For almonds, the hull material is the host for naturally occurring fungi; for pistachios, the likely material is the kernel itself. Volatile profiles of fungal contamination are different between the two crops. This result is good news for the typical storage conditions for these two crops. Volatile collections: a new collection system was designed and tested during the reporting period and is being incorporated into current in situ collections of sterilized/inoculated nuts this season. Relevant results occur at the end of the season when nuts are harvested. Preliminary results will aid researchers with detection limits, necessary collection times, and expected volatile variations. This SCA will support the parent project by directly advancing the objectives of the in-house D project by developing a portable GCMS for detection of tree nuts contaminated with mycotoxigenic aspergilli. Torion Activities: Designed custom needle trap air sample collection device for volatiles from almond and pistachio stockpiles. The needle trap serves as the primary method for introducing the sample from air collection into the portable GC-MS system. The sorbent packed needle-trap inserted directly into the GC-MS functions as a 1st stage concentrator that can collect enough sample in 5 minutes to detect sample concentrations at the low part per billion levels. If needed, lower detection levels in the part per trillion ranges are possible with a second stage trapping device. Sample would be collected on off-the-shelf thermal desorption tubes and transferred to the needle-trap for injection into the GC-MS.