Efficacy of weak acid preservatives on spoilage fungi of bakery products.

Organic acids and their salts are usually the first choice in the bread industry to restrict fungal spoilage, but their efficacy is pH-dependent and spoilage by fungi remains as a common threat. Therefore, this study aimed to evaluate the susceptibility of spoilage fungi of bakery products to acetic, sorbic, and propionic acids at different pH. Penicillium roqueforti, Penicilium paneum, Aspergillus pseudoglaucus, Aspergillus montevidensis and Hyphopichia burtonii strains isolated from spoiled products had their minimum inhibitory concentration (MIC) defined by macrodilution. The concentrations tested were: (i) sorbic acid up to 32 mM; (ii) propionic acid up to 1024 mM and (iii) acetic acid up to 800 mM with pH adjusted in 4.5, 5.0, 5.0 and 6.0 after setting the agent concentration. The lowest MICs for all agents were obtained at pH 4.5, usually doubling with every 0.5 pH increase. P. roqueforti strains isolated from spoiled products were the most resistant to all tested preservatives; while strains of the related species P. paneum, showed similar tolerance to acetic and propionic acids but was double more susceptible to sorbic acid. Strains of A. pseudoglaucus and A. montevidensis were indistinctly susceptible to the preservatives and were the most susceptible species to propionic and acetic acids. H. burtonii strains demonstrated the most variable behaviour in comparison to the other strains being the most susceptible to sorbic acid, were like Aspergillus strains regarding propionic acid, but tolerate well acetic acid. Propionic acid concentrations usually allowed in baked goods are lower than the concentrations required to inhibit the most tolerant isolates tested in this study. The same is true for sorbic acid at higher pH levels. Spoilage species of bakery ware presents a distinct susceptibility profile to the preservatives commonly used in this sector, but the high tolerance observed is a cause of concern.

Resilience of Biocontrol for Aflatoxin Minimization Strategies: Climate Change Abiotic Factors May Affect Control in Non-GM and GM-Maize Cultivars.

There has been significant interest in the development of formulations of non-toxigenic strains of Aspergillus flavus for control of toxigenic strains to reduce the aflatoxin B1 (AFB1) contamination of maize. In the future, climate change (CC) abiotic conditions of temperature (+2-4°C), CO2 (existing levels of 400 vs. 800-1,200 ppb), and drought stress will impact on the agronomy and control of pests and diseases. This study has examined (1) the effect of two-way interacting factors of water activity × temperature on colonization and AFB1 contamination of maize cobs of different ripening ages; (2) the effect of non-toxigenic strains of A. flavus (50:50 inoculum ratio) on relative control of toxigenic A. flavus and AFB1 contamination of ripening cobs; (3) post-harvest control of AFB1 by non-toxigenic strains of A. flavus in non-GM and isogenic GM maize cultivars using the same inoculum ratio; and (4) the impact of three-way interacting CC factors on relative control of AFB1 in maize cobs pre-harvest and in stored non-GM/GM cultivars. Pre-harvest colonization and AFB1 production by a toxigenic A. flavus strain was conserved at 37°C when compared with 30°C, at the three ripening stages of cob development examined: milk ripe (R3), dough (R4), and dent (R5). However, pre-harvest biocontrol with a non-toxigenic strain was only effective at the R3 and R4 stages and not at the R5 stage. This was supported by relative expression of the aflR regulatory biosynthetic gene in the different treatments. When exposed to three-way interacting CC factors for control of AFB1 pre-harvest, the non-toxigenic A. flavus strain was effective at R3 and £4 stages but not at the R5 stage. Post-harvest storage of non-GM and GM cultivars showed that control was achievable at 30°C, with slightly better control in GM-cultivars in terms of the overall inhibition of AFB1 production. However, in stored maize, the non-toxigenic strains of A. flavus had conserved biocontrol of AFB1 contamination, especially in the GM-maize cultivars under three-way interacting CC conditions (37°C × 1,000 ppm CO2 and drought stress). This was supported by the relative expression of the aflR gene in these treatments. This study suggests that the choice of the biocontrol strains, for pre- or post-harvest control, needs to take into account their resilience in CC-related abiotic conditions to ensure that control of AFB1 contamination can be conserved.

Phytochemical Analysis and Antifungal Activity of Extracts from Leaves and Fruit Residues of Brazilian Savanna Plants Aiming Its Use as Safe Fungicides.

The increasing demand for safe food without preservatives or pesticides residues has encouraged several studies on natural products with antifungal activity and low toxicity. In this study, ethanolic extracts from leaves and fruit residues (peel and seeds) of three Brazilian savanna species (Acrocomia aculeata, Campomanesia adamantium and Caryocar brasiliense) were evaluated against phytopathogenic fungi. Additionally, the most active extract was chemically characterized by ESI-MS and its oral acute toxicity was evaluated. Extracts from C. brasiliense (pequi) peel and leaves were active against Alternaria alternata, Alternaria solani and Venturia pirina with minimal inhibitory concentrations between 350 and 1000 µg/mL. When incorporated in solid media, these extracts extended the lag phase of A. alternata and A. solani and reduced the growth rate of A. solani. Pequi peel extract showed better antifungal activity and their ESI-MS analysis revealed the presence of substances widely reported as antifungal such as gallic acid, quinic acid, ellagic acid, glucogalin and corilagin. The oral acute toxicity was relatively low, being considered safe for use as a potential natural fungicide.