What is GInaFiT

GInaFiT is a freeware add-in for Microsoft© Excel, aiming at bridging the gap between people developing predictive modelling approaches and end-users in the food industry or research groups not disposing of advanced non-linear regression analysis tools.

More precisely, the tool is useful for testing nine different types of microbial survival models on user-specific experimental data relating the evolution of the microbial population with time. The nine model types are: (i) classical log-linear curves, (ii) curves displaying a so-called shoulder before a log-linear decrease is apparent, (iii) curves displaying a so-called tail after a log-linear decrease, (iv) survival curves displaying both shoulder and tailing behavior, (v) concave curves, (vi) convex curves, (vii) convex/concave curves followed by tailing, (viii) biphasic inactivation kinetics, and (ix) biphasic inactivation kinetics preceded by a shoulder. The models were originally published as Bigelow and Esty (1920) [2], Cerf (1977) [3], Geeraerd et al. (2000) [4], Mafart et al. (2002) [6], Albert and Mafart (2005) [1] and Geeraerd et al. (2005) [5]. Next to the obtained parameter values, the following statistical measures are automatically reported: standard errors of the parameter values, the Sum of Squared Errors, the (Root) Mean Sum of Squared Errors, the R² and the adjusted R².

The tool can be used in two ways. On one hand, for end-users having already a qualitative idea of the general shape of their survival curves, the choice for one of the model types is obvious. On the other hand, if the end-user does not have a clear idea yet, the different model types can be tested and compared. Additionally, the tool has some built-in features testing for mis-use, for example, when trying to identify the complete model with tailing on data not having a tail.

An excellent user manual was developed by the University of Newcastle in the context of UK Food Standards Agency FS241040 in order to guide the end users through the selection of the appropriate model. The user manual can be downloaded by this link .

Further illustrations on the use of GInaFiT can be found in Geeraerd et al. (2005) [5].

References

[1] Albert I. and P. Mafart 2005. A modified Weibull model for bacterial inactivation, International Journal of Food Microbiology, 100, 197-211.

[2] Bigelow W.D. and J.R. Esty 1920. The thermal death point in relation to typical thermophylic organisms, Journal of Infectious Diseases, 27, 602-617.

[3] Cerf O. 1977. A review. Tailing of survival curves of bacterial spores, Journal of Applied Microbiology, 42, 1-19.

[4] Geeraerd A.H., C.H. Herremans and J.F. Van Impe 2000. Structural model requirements to describe microbial inactivation during a mild heat treatment, International Journal of Food Microbiology, 59, 185-209.

[5] Geeraerd A.H., V.P. Valdramidis and J.F. Van Impe 2005. GInaFiT, a freeware tool to assess non-log-linear microbial survivor curves, International Journal of Food Microbiology, 102, 95-105.

[6] Mafart P., O. Couvert, S. Gaillard and I. Leguerinel 2002. On calculating sterility in thermal preservation methods: application of the Weibull frequency distribution model, International Journal of Food Microbiology, 72, 107-113.