Pogodnost sojinih supstrata za mliječno kiselu fermentaciju uz dodatak bakterije Lactobacillus plantarum

Abstract

In this work, growth dynamics of Fresco DVS 1010 culture and human derived isolate Lactobacillus plantarum in milk- water- or lactose-free milk-based soya substrates with sucrose or flavouring compounds (chocolate or caramel) were evaluated. Static anaerobic fermentation was carried out for 8 hours at 37 ± 0.5°C (5% CO2), afterward with storage period for 3 weeks at 6 ± 0.5°C. Although milk is a typical growth medium for lactic acid bacteria, presumable viable counts of Fresco culture reached levels 109 CFU mL-1 after 8 h. Potentially probiotic isolate L. plantarum added after the fermentation process maintained its viability during cold storage above the limit 106 CFU mL-1. Furthermore, the effect of temperature (8-40°C) on the growth dynamics of L. plantarum in a model environment of UHT lactose-free milk (1.5% fat) was investigated. Final densities of studied isolate reached counts 107 CFU mL-1 in stationary phase at all studied temperatures (except for marginal 8°C). During the growth and multiplication of L. plantarum, as a result of metabolic activity, the decrease of pH from initial values about 0.17-1.16 units was recorded. Experimentally, it was found that optimal temperature was close to 34°C, where the fastest growth rate in an exponential phase was recorded (Gr = 0.1684 log CFU mL-1 h-1, td = 1.8 h).U ovom radu ocijenjena je dinamika rasta Fresco DVS 1010 kulture i humanog izolata Lactobacillus plantarum u sojinim supstratima na bazi mlijeka, vode ili bezlaktoznog mlijeka s dodatkom saharoze ili okusa (čokolada ili karamela). Statička anaerobna fermentacija provedena je tijekom 8 sati na 37 ± 0,5°C (5% CO2), nakon čega su proizvodi uskladišteni na 3 tjedna pri 6 ± 0,5°C. Iako je mlijeko tipičan medij za rast bakterija mliječne kiseline, nakon 8 h broj Fresco culture dosegao je brojku od 109 CFU mL-1. Broj potencijalno probiotičkog izolata bakterije L. plantarum dodanog nakon fermentacije ostao je iznad granice od 106 CFU mL-1 tijekom hladnog skladištenja. Nadalje, istražen je učinak temperature (8-40°C) na dinamiku rasta bakterija L. plantarum u modelu okoliša UHT bezlaktoznog mlijeka (1,5% masti). Konačna gustoća promatranog izolata dosegla je brojke 107 CFU mL-1 u stacionarnoj fazi pri svim promatranim temperaturama (osim marginalne 8°C). Tijekom rasta i razmnožavanja bakterija L. plantarum zabilježen je pad pH od početnih vrijednosti oko 0,17-1,16 jedinica kao rezultat metaboličke aktivnosti. Eksperimentalno je utvrđeno kako je optimalna temperatura za rast blizu 34°C, gdje je zabilježena najbrža stopa rasta u eksponencijalnoj fazi (Gr = 0,1684 log CFU mL-1 h-1, td = 1,8 h)