The interaction of iron with polyphenols

Iron deficiency affects over two billion people worldwide (Lotfi et al., 1996). However, fortifying foods with highly bioavailable iron is technically challenging because of off-color and off-flavor development, catalytic degradation of vitamins and oxidation of lipids. The role of highly bioavailable iron in the off-color development of foods and beverages is not well understood. The goals of this research included: (1) determining the role of iron in off-color development with simple phenolics and polyphenols as models for more complex systems, (2) evaluating the effect of environmental factors, such as pH, temperature, oxygen, redox potential, reducing agents, and chelating agents, on off-color development, and (3) validating these models in commercial food products. The results demonstrated that the iron that reacts with the simple phenolic, catechol, to develop off-color must be in the oxidized state, and the iron is reduced in the presence of catechol. Iron sources that are typically used for fortification, as well as other metals, were evaluated for off-color development with catechol versus redox potential. Ferrous iron sources with low redox potentials, and ferric iron sources with high redox potentials, caused off-color development with catechol. In addition, only polyphenols that contain ortho-hydroxyl groups caused off-color development with iron. Off-color development was minimized by factors such as low pH, low oxygen content, high temperature, and presence of reducing and chelating agents. All of these factors affected the redox potential of the system. Therefore, the interaction of iron with polyphenols was an oxidation/reduction reaction, where iron was reduced and the polyphenol was oxidized. The off-color development was controlled by the redox potential of the compounds in the system. The commercial foods tested reacted similarly to the models of polyphenols with iron, and methods identified in the models to prevent off-color development were effective in most of the food products examined, suggesting that the proposed models are valid for testing commercial products

Floristic patterns and disturbance history in karri (Eucalyptus diversicolor : Myrtaceae) forest, south-western Australia: 2. Origin, growth form and fire response

We examined the influence of disturbance history on the floristic composition of a single community type in karri forest, south-western Australia. Cover-abundance of 224 plant species and six disturbance and site-based environmental variables were recorded in 91, 20 m x 20 m quadrats. Numerical taxonomic and correlation approaches were used to relate these and 10 plant species-group variables based on origin, growth form and fire response. Ordination revealed no discernable pattern of sites based on floristic composition. However, all 10 species-group variables were significantly correlated with the ordination axes. Species richness within these groups varied with category and with respect to many of the disturbance and site variables. We encountered low diversity of vascular plants at the community level and limited diversity of growth forms. Thus most species were herbs (62.1%) or shrubs (30.3%), and there were no epiphytes and few species of trees or climbers. Although many introduced species were recorded (18.3% of all taxa), virtually all (83%) were herbs that demonstrated little persistence in the community, and there was limited evidence of transformer species. Time-since-fire (and other disturbance) influenced species richness more than the number of recent past fires because of a high proportion of ephemerals associated with the immediate post-fire period. Long-lived shrubs with soil stored seed dominate numerically, and in understorey biomass in comparison with neighboring vegetation types because of their greater flexibility of response following irregular, but intense disturbance events. However, interactions between nutrient status, regeneration mechanisms and community composition may be worthy of further investigation. (c) 2006 Elsevier Masson SAS. All rights reserved

Short-term logging and burning impacts on species richness, abundance and community structure of birds in open eucalypt forest in Western Australia

In 1985 new silvicultural prescriptions for managing jarrah (Eucalyptus marginata) forest in south-west Western Australia came into operation. The most extreme logging treatment (gap release) involved removal of most of the overstorey from patches no larger than 10 ha, followed by a regeneration fire. In the other logging treatment (shelterwood), less wood was removed from a larger area, also followed by a fire. This study examined the impact of these disturbances on the avifauna by monitoring species richness and abundance of birds one year before logging, one year before burning, and for five years after burning. Although 68 bird species were recorded during the seven years of the study, 29 of these were detected fewer than 15 times. Of the other 39 bird species recorded, only two (Gerygone fusca and Acanthiza apicalis) showed a statistically significant treatment effect over time on their abundance. The abundance of G. fusca initially declined in the disturbed treatments and by Year 7 of the study (5 years post-fire) in the gap-release treatment had not recovered its original abundance. A. apicalis increased its abundance in both shelterwood and gap-release treatments. By Year 7, both species in the logged treatments had abundances similar to those in the unlogged treatments. Total abundance of all species varied little across treatments. Species richness was highest by Year 7 in the shelterwood and lowest in the gap-release treatment. In some years community structure varied more at the external-reference sites (not recently logged or burnt) than at the gap-release sites. In particular, there was little overlap in community structure in the external-reference treatment between the first and final years, whereas the pre-logging and final year in the gap-release treatment showed a high degree of overlap. These differences are suggestive of overriding short-term annual variation in broad-scale factors rather than local factors. Yearly variation in rainfall and temperature was documented; during low rainfall periods, populations of foliage arthropods may have been reduced