Microencapsulation Of Probiotics And Incorporation In Yoghurt
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Date
2010
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Tamil Nadu Veterinary and Animal Sciences University
Abstract
A study was carried out to microencapsulate four different probiotic cultures
viz., Lactobacillus acidophilus, Lactobacillus helveticus, Bifidobacterium longum and
Bifidiobacterium lactis and preparation of plain yoghurt and frozen yoghurt with
these microencapsulated cultures. Microencapsualtion was done in two different
methods (extrusion and emulsion) by using two different wall materials viz.,
alginate+starch, alginate+gelatin+starch. Six different lots of plain yoghurt and
frozen yoghurt for each of the probiotic culture were prepared. Different treatments of
encapsulation in yoghurt were denoted as PPYI (control), PPYII (extrusionalginate+
starch), PPYIII (extrusion- alginate+gelatin+starch) PPYIV (emulsionalginate+
starch) and PPYV (emulsion- alginate+gelatin+starch). Similarly, the frozen
yoghurt were also named as FPYI, FPYII, FPYIII, FPYIV and FPYV. These yoghurt
and frozen yoghurt were subjected to physico chemical analysis, organoleptic
evaluation, rheological studies and survivability of the yoghurt and probiotic cultures
during storage period. Iron fortified yoghurt was also prepared using encapsulated
iron and effect of iron fortification on yoghurt quality and viability of probiotic was
also tested. Insulin syringe gave the beads with minimum diameter. Size of the
emulsion beads were lower when the emulsifier percentage was less (0.5%). Speed of
addition of CaCl2 solution affected bead shape. SEM analysis of beads revealed
characteristic size, shape and outer and inner structure of the beads. When the beads
were stored in CaCl2, the bead size was found to be reduced .
There was a drastic reduction in the count of all probiotic bacteria in the
control yoghurt every week. But in encapsulated yoghurt there was no significant
reduction in count of probiotics, up to 2nd week after which decrease of one log unit
was observed every week. In control yoghurt at 21 days of storage, lactobacillus
survived four log units and bifidobacterium survived six log units. But in the PPYIII,
there is no significant difference was observed in different probiotics. In control
frozen yoghurt, counts of Lactobacillus acidophilus, Lactobacillus helveticus,
Bifidobacterium longum and Bifidobacterium lactis (cfu/ml) showed highly (P<0.01)
significant difference between storage periods, that decreased every week. But in
treatment frozen yoghurt, one log unit was only found to be decreasing after 2 weeks
of frozen storage. In control frozen yoghurt of 42 days storage, lactobacillus count
was highly significant (P<0.01) and differ with bifidobacterium count indicated by
four log units, and lactobacillus survived one log unit. FPYIII shows highest mean
value which indicates alginate+ gelatin+starch, as a wall material and extrusion
method provides best survivability of all probiotics. There is highly significant
difference (P<0.01) in count of probiotic bacteria when observed in different storage
periods irrespective of iron encapsulation treatments, which infer that iron
fortification does not affect the viability of probiotic bacteria. Highly significant
difference (P<0.01) was observed in TBA values of control and encapsulation
treatment in iron fortified yoghurt.
A highly significant difference (P<0.01) was observed in acidity and pH of
different periods of refrigerated storage in control yoghurt. But in treatment yoghurt,
the difference in acidity at different periods was insignificant. Sensory evaluation
revealed higher scores with regard to flavor and overall acceptability for treatment
frozen yoghurt than for control yoghurt. The same results were observed in sensory
evaluation of plain yoghurt also. Higher yoghurt bacterial count was observed in
encapsulated treatment yoghurt on 21st day of storage when compared to the control.
Decrease in count of probiotic bacteria was observed except in
L. acidophilus during every half an hour of incubation in simulated gastric fluid
(SGF). Statistical analysis revealed a highly significant (P<0.01) difference in count
of probiotic viability assessment in different incubation time in SGF of control and in
encapsulated probiotics. B. longum and B. lactis showed high reduction in count when
compared to other bacteria. Statistical analysis revealed a highly significant (P<0.01)
difference between the probiotic bacteria and bifidobacteria showed poor survivability
compared to lactobacillus group. In viability study, every half an hour of incubation in
simulated intestinal fluid(SIF), reduction in probiotic count was noticed. Statistical
analysis revealed a highly significant (P<0.01) difference in count of probiotic
viability in different incubation time in SIF of control and encapsulated probiotics.
Though the statistical difference was observed in different probiotic bacteria, no
difference was noticed in declining rate of probiotics in SIF. Treatment II showed
better survivability for all probiotic organisms when compared to rest of other
treatments. In all probiotic organisms tested, L. acidophilus showed better
performance in two hr incubation of SGF as well as in SIF after one hr incubation of
SGF. Control yoghurt showed less viscosity where as extrusion method yoghurt
showed high viscosity. Higher serum separation percentage was observed in treatment
yoghurt. Statistical analysis revealed highly significant (P<0.01) higher values for
springiness, adhesiveness for the control yoghurt. On the other hand, higher values
were observed in treatment yoghurt with regard to hardness, cohesiveness, gumminess
and chewiness.
The meltdown for control frozen yoghurt was quicker than treatment
yoghurt. Treatment frozen yoghurt showed higher values for hardness. The cost of
production (in rupees) of control yoghurt was 49.3 where as for treatment yoghurt II,
III, IV and V were 68.3, 69.1, 75.4 and 76.2 respectively. The cost of production (in
rupees) for one kg of control frozen yoghurt was 49.7, where as for treatment frozen
yoghurt II,III,IV and V were 68.7, 69.5, 75.8 and 76.6 respectively.