Effect of modified atmosphere packaging and water activity on growth of Eurotium amstelodami, E. chevalieri and E. herbariorum on a sponge cake analogue.

The combined effects of water activity (aw), oxygen (O2) and carbon dioxide (CO2) levels on growth variables of three species of Eurotium (two isolates of each) on a sponge cake analogue were studied. The use of a multivariate statistical method (PLS) for the analysis of data showed that in general, the fungi had the same behaviour, according to their growth responses, to changes in the three tested factors. However, the maximal growth of E. herbariorum was somewhat more affected by the O2 level at lower CO2 levels. On the other hand, CO2, aw and the interaction between CO2 and O2 were found to be the most significant factors describing growth variables. In addition, the model found in this study had a good predictive power. There was a positive correlation between the CO2 concentration in the bags and the lag phase, and a negative correlation between the growth rate and maximum mycelial growth. In general, no isolates were able to growth when CO2 concentrations were higher than 60% under anaerobic conditions. At lower values of CO2, aw and O2 influenced growth variables. Low levels of O2 (0.02-0. 5%) did not affect the growth variables studied when levels of CO2 in the bags were high. However, when the CO2 concentration decreased, the different O2 levels had an influence on the growth variables, i. e., a small difference in the concentration of O2 can allow fungi to grow.