Zearalenone or F-2 [2,4-dihydroxy-6-(10-hydroxy-6-oxo-trans-1-undecenyl)-benzoic acid lactone] is an estrogenic mycotoxin synthesized by Fusarium roseum (Link emend.) Sny. & Hans. 'Graminearum.' In addition to its estrogenic activity in animals, it acts as a sex-regulating hormone in F. roseum, and this is the subject of this paper. When amounts of F-2 ranging from 0.1 ng to 10.0 ng were applied to a 1.0-cm diameter disk of Coons' synthetic medium in agar, perithecial formation was enhanced by as much as 100%. Amounts in excess of 10.0 μg inhibited perithecial formation. F-2 has a periodicity of action relative to both enhancement and inhibition of perithecial formation. The ability of F-2 to enhance was greatest up to 4 days of culture age when amounts optimum (0.1 ng and 1.0 ng) for enhancement were used. Optimum inhibition of perithecial formation with inhibitory amounts (10.0 μg and 100.0 μg) occurred when the culture was from 3 to 4 days old. Dichlorvos (2,2-dichlorovinyl dimethyl phosphate), also called VAPONA, inhibited F-2 biosynthesis as well as production of perithecia. Moreover, when F-2 was applied simultaneously with dichlorvos, the inhibition caused by dichlorvos was reduced. A limited study on structure activity relationships was done with the conclusion that the hydroxyl or ketone in the 6′ position of the undecenyl ring is necessary for activity. Further, unsaturation at the 1′,2′ position on the undecenyl ring of F-2 is associated with inhibitory activity at the higher concentrations.

The initial loss rates of available lysine during thermal processing were studied to develop an equation for predicting the specific reaction rate (kT). The reaction order for initial loss was first determined and then the effect of system composition on the specific reaction rate investigated. The ability of the model system in phase three (no further loss with heating) to revert to phase one (initial loss rate) after mixing was also examined. A model system, consisting of protein, glucose and microcrystalline cellulose was utilized. The system composition (pH, water activity and glucose level) and time and temperature of the processing were varied. The reaction resulting in the initial rapid phase (one) of available lysine loss occurs according to first order reaction kinetics. Glucose and temperature have the dominant effect on predicting kT. Both pH and activity also influence the prediction of kT but they act through an interaction with glucose. Once the soy based food system enters phase three, the system does not revert to phase one by the re-slurry method. Sugar exhaustion does not account for the inability to revert to phase one.

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A mathematical model, developed to predict available-lysine losses in a model food system which had undergone an isothermal-nonstirred process, was tested under different process conditions. The model predictions were compared to measured available-lysine losses in both jacketed-mixer processing and extrusion processing. Statistical analysis using a paired t-test analysis indicated a significant correlation between predicted and actual results for the jacket-mixer process. In the extrusion experiment a statistically significant correlation (0.7) occurred when the predicted values were plotted against observed. However, variation due to product backmixing and inaccurate temperature measurement prevented a rigorous test of the model. The reaction order of available lysine loss in casein, single-cell protein and a soy protein isolate were determined at an elevated temperature. The casein and singlecell protein followed fust-order reaction kinetics. The soy isolate initially follows first-order loss but after an approximate loss of 40-50% available lysine, the loss abruptly stops and a no-loss phase occurs.

Sexual reproduction in Gibberella zeae (Fusarium roseum) is regulated by the fungal sex hormone zearalenone, which is known to be synthesized only by species of Fusarium. The presence of cyclic adenosine 3',5'-monophosphate (cAMP) in mycelium of this fungus has been confirmed by analyses with thinlayer and gas-liquid chromatography, fluorescent properties, ultraviolet absorption, competitive protein-binding tests, and degradation by cyclic phosphodiesterase. cAMP but not cyclic guanosine monophosphate increased both the number of perithecia formed and the incorporation of [1-'4C]acetate into zearalenone. It is proposed that cAMP stimulates the synthesis of zearalenone which then exerts its effect directly or indirectly on formation of perithecia.