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

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.