The batter prepared without addition of starter culture represented
fermentation by the natural background flora (spontaneous fermentation).
As shown in Fig. 1, twelve sausage batters were prepared for
each of the four bacterial conditions and with three biological replicates
it resulted in a total of 144 sausage batters being investigated. The sausage
batters were stuffed into 60-ml sterile syringes with the tip end cut
open, covered with plastic bags, and incubated at 24–25 °C, in accordance
with Heir et al. (2010). The fermentation process lasted for
72 h. During four fermentations, one for each combination of NaNO2
and starter culture addition, the pH decline was continuously monitored
by a pH logger (Lutron, WA-2015).