Evidence for the existence of "survival factors" as an explanation for some peculiarities of yeast growth, especially in grape must of high sugar concentration.

The retardation and arrest of fermentation, observed before the complete sugar consumption of high-sugar grape must, come from an inhibition of the yeast metabolism during its decline phase and are variable with the strain. The addition of nutritional growth factors stimulates the initial growth of the yeast but is ineffective in the decline phase. Some substances, known previously as yeast anaerobic growth factors (sterols, oleanolic acid, oxytocin), in some conditions (initially aerated grape must and aerobically cultivated yeast) act by increasing the viability of the resting cells and prolonging their fermentation activity. These substances have been named "survival factors."