TABLE 1.

Stimulation of growth and acidification by compounds potentially involved in the interactions between S. thermophilus and L. bulgaricus in milka

ComponentCultureFinal cell countEnd pHAcidification pattern (Δacid/Δt)
SLMax 1MinMax 2
Sodium-pyruvic acidSNA+
LNA+
M+
Sodium-formic acidS+NA+++
LNA++
M+
Folic acidSNA+
LNA
M++
NucleobasesSNA++
LNANN+
M+++
Tween 20SNA+
LNA+
M+
Tween 80SNA
LNA
M+
CasitoneS+NA+-+
LNA+NN+
M++NN+
HistidineSNA
LNA-NN
M+
l-Ornithine monohydrochlorideSNA
LNA
M
PutrescineSNA+
LNA-
M
All componentsSNA++++
LNA++
M++NN+
All: sodium-pyruvic acidS+NA-
LNANN+
MNN
All: sodium-formic acidS+NA----
LNANN+
MNN
All: folic acidSNA--
LNA+NN+
MNN
All: nucleobasesSNA-
LNA+-
MNN
All: Tween 20 and Tween 80S+NA--
LNANN+
MNN
All: CasitoneS-NA---
LNANN+
MNN
All: histidineS+NANN-
LNANN+
M+NN
All: l-ornithine monohydrochlorideS+NA+
LNA+
M+NN
All: putrescineS+NA-
LNANN+
M+NN
NoneSNA
LNANN
M
  • a Cultures with single additions were tested versus cultures without additions. Cultures containing all components excluding one were compared to the cultures containing all components (single omissions). The pH was monitored for 19 h upon which dilutions were plated for cell enumeration. The final populations presented were determined from duplicate plating of quadruplate cultures. The acidification rates and final pH values were calculated from the same cultures. Abbreviations and symbols: S, S. thermophilus; L, L. bulgaricus; M, mixed culture; +, positive effect (higher cell count, lower end pH, higher acidification rate, earlier maximal rate); -, negative effect; N, not present; NA, strain not added in the culture.