Terry C. Nelsen

AOCS Collaborative Study on Sensory and Volatile Compound Analyses of Vegetable Oils

An AOCS collaborative study was conducted to determine the effectiveness of sensory analysis and gas chromatographic analyses of volatile compounds in measuring vegetable oils for levels of oxidation that ranged from none to high. Sixteen laboratories from industry, government, and academia in Canada and the United States participated in the study to evaluate the flavor quality and oxidative stability of aged soybean, corn, sunflower, and canola (low-erucic acid rapeseed) oils. Analytical methods included sensory analyses with both flavor intensity and flavor quality scales and gas-chromatographic volatiles by direct injection, static headspace, and dynamic headspace (purge and trap) techniques. Sensory and volatile compound data were used to rank each of the oils at four levels of oxidation—none, low, moderate, and high. For soybean, canola, and sunflower oils, 85–90% of laboratories correctly ranked the oils by either analysis. For corn oil, only 60% of the laboratories ranked the samples according to the correct levels of oxidation by either analysis. Variance component estimates for flavor scores showed that the variation between sensory panelists within laboratories was lowest for the unaged oils. As storage time increased, the variance also increased, indicating that differences among panelists were greater for more highly oxidized oils. Between-laboratory variance of sensory panel scores was significantly lower than within-laboratory variance.

Relative Resistance of Transgenic Tomato Tissues Expressing High Levels of Tobacco Anionic Peroxidase to Different Insect Species

Different parts of genetically transformed tomato (Lycopersicon esculentum L.) plants that express the tobacco anionic peroxidase were compared for insect resistance with corresponding wild type plants. Leaf feeding by first instar Helicoverpa zea and Manduca sexta was often significantly reduced on intact transgenic plants and/or leaf disks compared to wild type plants, but the effect could depend on leaf age. Leaves of transgenic plants were generally as susceptible to feeding damage by third instar Helicoverpa zea (Boddie) and Manduca sexta (L.) as wild type plants. Green fruit was equally susceptible to third instar larvae of H. zea in both type plants, but fruit of transgenic plants were more resistant to first instar larvae as indicated by significantly greater mortality. Basal stem sections were more resistant to neonate larvae of H. zea and adults of Carpophilus lugubris Murray compared to wild type plants as indicated by significantly greater mortality and/or reduced feeding damage. Thus, tobacco anionic peroxidase activity can increase plant resistance to insects in tomato, a plant species closely related to the original source plant species, when expressed at sufficiently high levels. However, the degree of resistance is dependent on the size of insect and plant tissue involved.

Dusky Sap Beetle Mediated Dispersal of Bacillus subtilis to Inhibit Aspergillus flavus and Aflatoxin Production in Maize Zea mays L.

Laboratory assays were performed with detached milk stage maize ( Zea mays L.) ears and dusky sap beetles ( Carpophilus lugubris Murray) carrying the Kodiak Concentrate formulation of the bacterium, Bacillus subtilis (Ehrenberg) Cohn. After 1 day of exposure to the B. subtilis- contaminated C. lugubris , the colonization of mechanically damaged kernels by Aspergillus flavus Link ex. Fries was reduced from 82% (if the A. flavus was inoculated first) to 41% (if B. subtilis was added by C. lugubris before the A. flavus ). Field cage studies were performed with an autoinoculative device containing B. subtilis into which C. lugubris beetles were introduced. C. lugubris -dispersed B. subtilis reduced visible A. flavus colonization by 97% when the A. flavus was added to purposely damaged maize ears 4 days after C. lugubris were released from the autoinoculator. In 1993 field studies, none of the purposely damaged ears that allowed access to C. lugubris beetles emerging from autoinoculators containing B. subtilis...

Microorganisms for degrading simmondsin and related cyanogenic toxins in jojoba

SummaryFour microorganisms that metabolize simmondsin (S) and related cyanogenic toxins from jojoba (Simmondsia chinensis) were isolated by enrichment: Pseudallescheria boydii, a fungus which specifically degrades simmondsin ferulate but not S; Fusarium moniliforme; “Flavobacterium aurantiacum”; and Pseudomonas maltophilia. The latter three organisms grow on S as a sole carbon and nitrogen source in culture media, but only F. moniliforme attacks S in the complete jojoba meal. Combinations of the four microorganisms at two temperatures, and with free air or limited air exchange for up to 20 days, were tested on jojoba meal to determine an optimum detoxification method. Degradation of toxins was most rapid and complete when Pseudallescheria boydii and Fusarium moniliforme together were incubated on jojoba meal at 25°C with free air exchange for 20 days. Mice were fed fermented meals at 0, 5, 10 and 20% substitution levels to determine detoxification and nutritional quality. Average daily gains during rapid growth of weanling (1–3 weeks) and mature (4–8 weeks) mice did not differ significantly from controls for mice on all diets containing fermented meal. Diets containing fungally detoxified jojoba meal were more efficient for maintaenance of mature weight than jojoba meal detoxified with enzymes naturally present in the meal. Meal can be detoxified by ensilage for 20 days at 80% water content. Detoxification is attributed to as yet unidentified enzymes inherent in the jojoba seed.