221. The effect of serum and blood on the growth of lactic acid bacteria in milk

Abstract

Generally speaking, serum and blood do not have a marked effect on the growth of lactic acid bacteria in milk, although certain types appear to be specifically stimulated or inhibited. Heated serum and, to a greater extent, heated blood, usually stimulate growth.Unheated serum may inhibit certain types, e.g.Str. lactis, when a small inoculum of washed cells is used. Under conditions similar to those in practice, no effect was noticeable. It is unlikely, therefore, that “slow starter” is ever attributable to infiltration of serum or the constituents of serum.Small amounts of dextrose are without effect on growth (apart from fermentation of the added sugar) and do not initiate the fermentation of lactose.