Post-harvest strategies for the prevention of fungal growth and mycotoxin production in corn

The overall objective of the research was to assess preservation techniques for corn including methods based on the addition of bicarbonates and phenolic compounds and the application of modified atmospheres. In light of the emergence of ‘Predictive Mycology’, the study also had the goal of developing validated predictive models to describe the growth of the most important fungal contaminators in corn and to assess their ability to model the trends observed in the preservation studies. The research started by fully characterizing the water relations of the growth substrate — yellow dent corn — via the development and modelling of its sorption isotherms. The study then focused on the development of validated predictive models to describe the growth of Aspergillus and Fusarium isolates of greatest importance to corn. Variability of growth by assessing the lag phase durations and colony growth rates of single spores of A. flavus and F. verticillioides was then evaluated. The relationship between fumonisin production and growth of F. verticillioides and F. proliferatum was then investigated. The research then focused on the evaluation of various preservation techniques. The use of modified atmospheres initially containing high levels of CO2 was found to have a large inhibitory effect on growth and fumonisin B1 production by the Fusarium isolates. Models were developed that adequately described the interaction observed between the CO2 and water activity on the growth of the Fusarium isolates. Although the initial headspace O2 level did not affect the rate of growth of the fungi, it had a large impact on fumonisin B1 production, with a shift in the optimum headspace level to 10% from 21% (air) being noted when the water activity of the corn was lowered. Comparing the application of bicarbonate salts and phenolic compounds, bicarbonate salts (in particular ammonium bicarbonate) proved to have the greatest potential for application. Ammonium bicarbonate was the only chemical tested that could completely inhibit both growth and mycotoxin production (fumonisin B1 and aflatoxin B1) at levels that were still sensorially acceptable. The phenolic compounds only significantly reduced aflatoxin B1 and fumonisin B1 production but did not affect growth

The use of essential oils as natural antifungal preservatives in bread products

This review addresses the recent advances of the application of essential oils (EOs) in in vitro systems and in bread systems for the reduction of fungal spoilage. Given the number of research articles concerning the use of EOs as potential antifungal food preservatives, it is generally accepted that they must be given further attention for use in specific food matrices. However, despite the numerous articles stating the antifungal effect of EOs, very few report the actual application in bread or other bakery products and the impact addition can have on dough and bread production, physico-chemical, microbiological and sensorial quality. Advances have been made in the area of food preservation, but further research is necessary to fully comprehend the mode of action and to establish actual food applications of EOs in the bread and bakery industry