Transformation Kinetics During Fermented Milk Production Using Lactobacillus Johnsonii (La1) and Streptococcus Thermophillus: A Comparison With Yogurt Inoculum

Abstract

Yogurt is commonly produced by a fermentation process of milk using two lactic acid bacteria: Streptococcus thermophillus and Lactobacillus delbrueckii ssp. bulgaricus. In this work, a different starter culture was used to initiate the fermentation process: the probiotic Lactobacillus johnsonii and S. thermophillus. The impact in the kinetics of aggregation and chemical modification due to the use of different starter culture is discussed. This alternative culture produces, in relation to the usual process, a delay in the lactic acid production and consequently, in the pH profiles modifying: a) the transformation of inorganic phosphorous into an organic one, b) the exopolyssacharides production and c) the aggregation process at a rate between 10 and 100 times depending on temperature and inocula concentrations. For the alternative inoculum, two regimes were observed: the first one, corresponding to the primary metabolism, is where the delay in milk transformation happens to affect, to a large extent, this regime and partly the next one. The second regime seems similar to the standard one but, as mentioned, shifted in time. A comparison between both processes is shown.