Value-added breakfast cereals are receiving increased interest due to changes in lifestyles
and modern trends of health awareness among consumers. Among various cereal grains,
puffed pounded-unripe rice (PPUR) was chosen because of its excellent health beneficial
properties. Feasibility of supplementing the probiotic bacteria Lactobacillus acidophilus
(LA5) into PPUR was investigated using a fluidized-bed coating method. Suitable
fermentation conditions were tested based on a pH criterion of 4.5. Three types of cell
host solutions as sucrose, skim milk and maltodextrin were examined as suitable carriers,
and optimal coating condition was determined. Product qualities were evaluated for
stability. Results showed that milk fermented for 24 hrs gave the highest viable cell count
of approximately 109
to 1010 CFU/mL when optimally mixed with distilled water at milk:
water ratio of 45:105. Skim milk was determined as the most suitable host giving the
highest retention of LA5 cell count. Coating condition at a feed rate of 10 mL/min,
coating time of 5 mins and constant temperature at 50°C gave the highest survival rates of
LA5. Moisture contents and water activity (aw) values of all coated products ranged from
3.38-3.72% wb and 0.201-0.232, respectively. Regarding textural properties, coated PPUR
showed increased hardness and crispiness compared with uncoated samples, while the
variation of coating conditions had no significant effects. Dynamic changes in viable LA5
cell count, textural properties, aw, peroxide value and thiobarbituric acid values fitted well
with various kinetic orders. Findings indicated the feasibility of adding probiotics to dry
products associated with suitable coating solution and offered guidance for product
development and process design.
Fluidized Bed Coating Method
