In vivo stability of the complex ochratoxin A – Saccharomyces cerevisiae starter strains

In recent years, several studies have focused on the role of yeasts as adsorbing tools to remove ochratoxin A (OTA) in musts and wines; however, no data are available on the stability of OTA-yeast complex. The present study was designed to assess the ability of five genetically distinct Saccharomyces cerevisiae strains (W13, W28, W46, W47, and Y28), previously studied for their oenological traits and in vitro OTA removal ability, to stably bind the toxin in Uva di Troia grape must (a red variety from Southern Italy). In addition, the effect of temperature, sugar concentration, and addition of ammonium salts on OTA binding was investigated.The highest binding was observed for S. cerevisiae W46 and W28 (42.79–76.44 and 34.51–70.17%, respectively); the other strains (W13, W47 and Y28) removed OTA by 20.34–53.79%. The binding was reversible and the extent of process was strongly affected by the kind of strain. Although the strains W46 and W28 removed OTA efficiently, they did not irreversibly bind OTA (ca. 80–85% release). On the other hand, the complex “S. cerevisiae W13-OTA” exhibited the greatest stability (ca. 55% release).The results obtained may be relevant not only to improve wine safety by integrating the binding ability in the criteria of selection of wine starters, but also for a more general biotechnological purpose, because of the increasing interest in the bioremediation of musts and wines using yeasts.     

Occurrence of aflatoxin B1 in food products derivable from ‘egusi’ melon seeds consumed in southwestern Nigeria

Aflatoxin, the toxic secondary metabolite of Aspergillus flavus and Aspergillus parasiticus has been considered as one of the most serious food safety problems in sub Saharan Africa. Egusi melon seeds is susceptible to these fungal infection during postharvest. Therefore, the content of aflatoxin B1 in three food products derivable from ‘egusi’ melon seeds ogiri’ (fermented melon seed condiment), ‘robo’ (melon ball snacks) and egusi soup destined for human consumption in Nigeria in 2005 and 2006 were determined. Aflatoxin B1 was analysed by thin layer chromatography (TLC) with fluorescent detection. The percentage of samples positive for aflatoxin B1 were for 25% robo, 31.8% for ogiri, and 19.5% for ‘egusi’ soup. Aflatoxin B1 ranged from 2.3 to 15.4 ppb in all samples. The overall mean levels of aflatoxin B1 were for 8.9 ppb for ogiri, 9.7 ppb for ‘robo’ and 7.2 ppb for ‘egusi soup’. All positive melon seeds derived food products analysed in this study contained aflatoxin B1 at concentrations much lower than the 20 ppb permissible limit recommended in Nigerian food and suggests that melon seed derived foods present less risk by human exposure to aflatoxin through their consumption. However, it is important to consider these levels in terms of their contribution to overall daily exposure to aflatoxin levels in food. This is the first report of aflatoxin determination in melon seed food products.