Describing the fate of autochthonous lactic acid bacteria in artisanal raw goat milk cheeses during storage: an Omnibus Modelling approach

Artisanal fermented products constitute a worthwhile source of autochthonous lactic acid bacteria (LAB). Their potential as biopreservatives is noticeable given their pathogen-antagonistic capabilities, technological and organoleptical efficiency. This study aimed to characterise the fate of autochthonous LAB in artisanal fresh raw goat milk cheeses at different temperatures by using an omnibus (one-step) modelling strategy.

Lab-scale cheese prototypes (10g) were artisanally elaborated from raw goat milk. Samples were stored at 4, 12, 18 and 25˚C and LAB were enumerated (ISO:15214) during cheese shelf-life. LAB modelling was externally validated in commercial artisanal fresh cheeses at 8, 15˚C, and at dynamic conditions. All the data processing and modelling procedures were developed in R software.

LAB concentrations (log cfu/g), at different times and temperatures, were estimated following Huang’s model equation. Maximum growth rates averaged 0.15±0.07 and 1.45±0.11 log cfu/g/d at 4 and 25˚C, respectively, meanwhile population increases averaged 1.47±0.08 and 3.42±0.39 log cfu/g. Omnibus modelling allowed to define a general model describing the autochthonous LAB behaviour in these cheeses. Intercept obtained a value of 0.159±0.129, while the slope was 0.066±0.008. The correlation coefficient between experimental and estimated data was 0.991. The model fitted properly to experimental data for both internal and external validation at fixed temperatures. However, a correction factor of 1.235 was applied to the model equation to improve adjustment. Finally, the estimated maximum population density (8.67 log cfu/g) was successfully applied for validation at dynamic temperatures.

These results contribute to a better understanding of autochthonous LAB in artisanal cheeses for their further use as potential new-generation biopreservatives.