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IV. Resultados y discusión. Capítulo II 199
ABSTRACT
The fermentative process of hazelnut milk with probiotic L. rhamnosus
GG and S. thermophilus was studied in order to develop a new non-dairy
probiotic product. To this end, the effect of different factors (the addition of
glucose, inulin and inoculum), was analysed to ensure sufficient probiotic
survival to exert health benefits in a shorter processing time. The optimised
fermented product was characterised throughout storage time (0, 1, 7, 14, 21
and 28 days) at 4 ºC as to its main physicochemical properties (pH, acidity,
sugar content, proteolytic activity, rheological behaviour, colour and
colloidal stability) and quality parameters (probiotic survival before and
after in vitro digestion and sensory analysis) and determine, thus, its shelf
life. The defined formulation allowed probiotic survival above the
recommended minimum (10 7 cfu/mL) and more than 60% survived the in
vitro digestion. This viability was maintained for 28 storage days. The
metabolic activity of the starters had an expected preference for glucose,
while inulin remained in the product and was able to exert health benefits.
Fermentation modified the rheological behaviour of hazelnut milk giving
rise to the flocculation of macromolecules and dispersed particles forming a
weak gel which generates syneresis on the last storage time controlled.
Nevertheless, sensory evaluation showed well acceptance of the fermented
product until the end of the cold storage (28 days).
Key words: Hazelnut milk, probiotic, prebiotic, response surface
methodology, fermentation optimisation.