Se ha investigado la evolución de la presencia de coliformes, E. coli y enterococos en yogur conservado durante cuarenta días a 7-° C, en 100 muestras de dos variedades elaboradas en España: natural y sabor a fresa, pertenecientes a una marca de gran difusión comercial. También se ha medido el pH y la acidez. Se ha constatado la presencia de coliformes y de E.coli comprobándose, a los diez días de conservación, que resultaba inhibida a consecuencia del nivel de acidez alcanzado; por ello se coincide con Aleksieva (3) en que la investigación de coliformes en el yogur, incluido el E.,coli, como indicadores de su calidad higiénica, debe de realizarse no más tarde de veinticuatro horas desde que terminó de elaborarse. Se ha evidenciado igualmente una contaminación por enterococos que persistió durante todo el periodo de conservación controlado. Por ello estimamos que la búsqueda de enterococos en el yogur es más adecuada que la de coliformes y E.coli, como indicadores de su calidad higiénica, durante todo el periodo de vida comercial.

We have done a research work on the evolution of the presence of coliforms, E. coli and enterococci in yoghurt which was kept at 72 C for 40 days. We have dealt with 100 samples of two varieties: natural and strawberry flavour yoghourt, both of them from a very well known commercial make. It ..has also been measured the pH and acidity of them. It has been checked the presence of coliforms and of E. coli, and in ten days time, we have noticed their extinction which was due to a higher level of acidity. We agree with Ale sieva (3) in the fact that research on coliforms and E. coli in yoghurt as a proof of its hygienic quality should be done not later than 24 hours after its process of elaboration finished. It has also beer checked contamination by enterococci, which persisted throughout the wole period of controlled conservation. Consequently, we think that search on enterococci in yoghourt as a proof of its hygienic quality t".hroughout its time of commercial life is amore appropriate than search on coliforms and E. coli.