Advances and trends in starter cultures for dairy fermentations

Abstract

Dairy starter cultures are actively growing cultures of lactic acid bacteria (LAB) to drive the fermentation process.At first, only artisanal starters were used. Though they are still used in certain cases, their microbiological instability promoted a evolution to more defined mixtures of LAB in order to obtain a more stable acidifying activity and quality of the products. However, artisanal starters are valuable sources of new strains for commercial uses. Today, defined, multi- or mono- strain cultures are extensively used around the world to produce cheeses, fermented milks and cream butter. They are commercialized as frozen and freeze-dried cell concentrates, and Direct Vat Inoculation (DVI) starters, to be used directly in the vats, are the last version of them. The phage sensitivity of lactic cultures is always a critical item when the starters are selected for industrial uses. So, a lot of strategies have been developed to minimize this problem, as the obtention of phage-insensitive mutants or the conjugal transfer of resistance plasmids. A lot of attention is receiving the starter adjuncts, used for purposes other than acid formation. They can be used as ripening or protective cultures, to improve the organoleptic characteristics of cheeses or perform a specific antimicrobial activity, respectively. Some probiotic LAB, as Lact. casei/paracasei and Lact. plantarum have demonstrated a starter activity and, so, they can be recognised as probiotic starters. Fundamental and applied research is still needed to better improve starter cultures in the existing production technology and to obtain quantitative data which may yield precious information about the relationship between the cheese environment and bacterial functionality, thus contributing to optimal strain selection. The recent development of microarray technology and comparative genomics will allow to the researchers a more complete genome analysis for a better selection of strains for specific uses.