The basic requirement for probiotic bacteria to be able to perform expected positive effects is to be alive. Therefore, appropriate quantification methods are crucial. Bacterial quantification based on nucleic acid detection is increasingly used. Spray-drying (SD) is one of the possibilities to improve the survival of probiotic bacteria against negative environmental effects. The aim of this study was to investigate the survival of spray-dried Lactobacillus plantarum 564 and Lactobacillus paracasei Z-8, and to investigate the impact on some probiotic properties caused by SD of both tested strains. Besides the plate count technique, the aim was to examine the possibility of using propidium monoazide (PMA) in combination with real-time polymerase chain reaction (PCR) for determining spray-dried tested strains. The number of intact cells, Lb. plantarum 564 and Lb. paracasei Z-8, was determined by real-time PCR with PMA, and it was similar to the number of investigated strains obtained by the plate count method. Spray-dried Lb. plantarum 564 and Lb. paracasei Z-8 demonstrated very good probiotic ability. It may be concluded that the PMA real-time PCR determination of the viability of probiotic bacteria could complement the plate count method and SD may be a cost-effective way to produce large quantities of some probiotic cultures. [Projekat Ministarstva nauke Republike Srbije, br. 046010
The objective of this work was to investigate the survival of autochthonous,
potentially probiotic bacteria Lactobacillus plantarum 564, and the influence
of long-chain polyunsaturated fatty acid omega-3 (omega-3 PUFA) fish oil
fortification on the sensory quality of yoghurt. Three variants of yoghurt
were produced using starter cultures of Lactobacillus delbrueckii ssp.
bulgaricus and Streptococcus thermophilus (Chr. Hansen, Denmark), and the
potentially probiotic Lactobacillus plantarum 564 (Culture Collection of the
Department for Industrial Microbiology, Faculty of Agriculture, University of
Belgrade) as follows: (1) without omega-3 PUFA; (2) with 100 mg/l omega-3
PUFA; and (3) with 200mg/l omega-3 PUFA. The survival of potential probiotic
Lb. plantarum 564, the changes of starter bacteria counts, changes of pH
values, as well as sensory evaluation, were examined during 3 weeks of
yoghurt storage. Cells of Lb. plantarum 564 were maintained at >108 cfug?1.
Starter bacteria counts were >107 cfug?1 for streptococci and >106 cfug?1 for
lactobacilli. The changes of pH were within normal pH of fermented milks.
Sensory evaluation showed that all variants of yoghurt produced with Lb.
plantarum 564 and 2 concentrations of omega-3 polyunsaturated fatty acids had
a high sensory quality (above 90% of maximal quality), and which did not
change significantly throughout the examined storage period. Although the
sensory quality of the control sample was evaluated as better, the
experimental samples fortified with fish oil were also characterized with
very acceptable sensory properties. Results of high viability of potential
probiotic Lb. plantarum 564, as well as very acceptable yoghurt sensory
properties, indicate that this strain can be successfully used in the
production of yoghurt fortified with PUFA omega-3 fish oil as a new
functional dairy product. [Projekat Ministarstva nauke Republike Srbije, br.
III 046010 i br. 046009]
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