UNIVERSITAT POLITÈCNICA DE VALÈNCIA Desarrollo ... - RiuNet

IV. Resultados y discusión. Capítulo II 203
2.2 Preparation of fermented products
2.2.1 Inoculum preparation
Lactobacillus rhamnosus ATCC 53103 (from now on GG) (LGC
Standards S.L.U., Barcelona, Spain) and Streptococcus thermophilus CECT
986 (from now on T) (CECT, Paterna (Valencia), Spain) were activated
from their frozen forms (stored in 40 g/100 mL glycerol at – 80 ºC), by
transferring each one to its selective broth until optimal bacterial growth is
ensured. The selective broths were MRS (Scharlab; Barcelona, Spain) for
GG and M17 (DifcoTM; New Jersey; USA) for T. The incubation
conditions were 37 ºC/24h/anaerobically for GG and 42 ºC/24h/aerobically
for T.
As regards the starter inoculum, strains were independently incubated
in their broths for 24 h and then centrifuged at 10,000 rpm - 10 min at 4 ºC;
the supernatant was subsequently discarded. Immediately afterwards, the
bacteria were resuspended in PBS-1x buffer (10 mmol/L phosphate, 137
mmol/L NaCl, 2.7 mmol/L KCl, pH 7.4) until they reached concentrations
of 10 8 colony forming units (cfu)/mL.
2.2.2 Experimental design for the fermentation process.
Amounts of glucose, inulin and starter inoculum added to the milk were
selected as growth factors (3 independent variables) to obtain fermented
hazelnut milks. Central Composite Design (CCD) with randomised
Response Surface methodology (RSM) was used to analyse the effect of the
different growth factor combinations on the fermentation processing time