3.3.4. Storage viability in soy milk
The free planktonic LGG cells were found to maintain their
viability upon incorporation into soy milk and the subsequent
three-day storage at 4 C (Fig. 8), denoting the non-harsh condition
of the soy milk towards the LGG strain. The same results were
observed for the freeze-dried LGG biofilm microcapsules prepared
without or with Hi-Cap, where the viable CFUs were maintained at
z 7 log (CFU/mg) during the three-day storage. Furthermore, theeffect of the Hi-Cap concentration on the storage viability was
found to be minimal. These results indicated that the LGG biofilm
microcapsules were readily incorporated into soy milk products at
the point of consumption and their subsequent refrigerated
storage.
4. Conclusion
The addition of resistant starch in the form of prebiotic Hi-Maize
did not lead to any improvement in the initial cell density and
freeze-drying tolerance of the LGG biofilm microcapsules. These
results reaffirmed previous findings that co-encapsulation of probiotics
with prebiotics did not necessarily lead to improvement in
the capsule properties. On the other hand, the addition of Hi-Cap - a
non-resistant waxy starch that was specifically designed for food
encapsulation - at a sufficiently high concentration (i.e. 0.6% w/v)
resulted in improved stress tolerance of the LGG biofilm microcapsules
upon freeze drying (z2), two-week storage at 4 C
(z6), and heat treatment at 100 C for 30 min (z25), while the
initial cell density remained unaffected.
The addition of Hi-Cap, however, resulted in significantly lower
acid tolerance of the encapsulated cells in SGJ, which was believed
to be caused by insufficient chitosan coating of the microcapsules
due to the increased surface roughness generated by the addition of
Hi-Cap. The future research direction is therefore to improve the
acid-resistant coating of the LGG biofilm microcapsules via layerby-
layer coating approach. Lastly, the LGG biofilm microcapsules
prepared with or without Hi-Cap exhibited good refrigerated
storage viability in soy milk, hence denoting their potential incorporation
into a real food product.