Study on Efficiency of Herb Extracts to Inhibit Enteric Bacteria and Application of Jerusalem artichoke as a Prebiotic for Yogurt Production

Abstract

The aim of this research was to study the activity of herb plant extracts (Garcinia
cowa Roxb., Syzygium cumin L., Psidium guajava L., Solanum torvum Sw. and Ageratum
conyzoides L.) against enteric bacteria growth. Antibacterial activities were determined by
agar-well diffusion method against Escherichia coli, Staphylococcus aureus and
Salmonella Typhimurium. Garcinia cowa Roxb. extract against E. coli showed the highest
efficacy with inhibition zone of 2.31±0.22 cm. diameter, zone against S. aureus and
S. Typhimurium equalled 1.77±0.00 cm and 1.45±0.04 cm diameter, respectively. Psidium
guajava L. and Syzygium cumin L. extracts against only S. aureus. No Inhibition zones were
observed for Solanum torvum Sw. and Ageratum conyzoides L. extracts. An extract of
Garcinia cowa Roxb. was added into yogurt, the Garcinia cowa Roxb. extract increased
growth of Lactobacillus bulgaricus and Streptococcus thermophilus by 18.25 % and
22.56%, respectively when compared to plain yogurt (12.00-13.97%). An 80 μl extract of
yogurt (mixed Garcinia cowa Roxb.) inhibited growth of E. coli and S. aureus. To evaluate
properties of Fructo-oligosaccharide extracted from Jerusalem artichoke (Helianthus
tuberosus L.) by 10% Jerusalem artichoke extract was added into yogurt. No difference
were observed for growth rate of L. bulgaricus and S. thermophilus, no differences were
observed between plain yogurt and Jerusalem artichoke yogurt but Jerusalem artichoke
extract promoted growth of L. bulgaricus and S. thermophilus when it was used instead of
dextrose in MRS broth as a carbon source. The results indicated that Garcinia cowa Roxb.
extract is appropriate to use as a supplement in yogurt to efficiently increase the inhibition
of enteric bacteria growth.