Preparation and Study of Flow Characteristics of
Co-processed Acacia gum and Maize Starch
Ibukun O. Adeleke*, Eghosa R. Ize-Iyamu
Department of Pharmaceutics and Pharmaceutical
Technology, College of Pharmacy,
Igbinedion University Okada, Nigeria.
*Corresponding Author
E-mail: ibukun.adeleke@iuokada.edu.ng
ABSTRACT:
Poor die filling as a result of poor flow
characteristic have been one of the challenges in direct compression tableting.
The aim of the work was to prepare and study of the flow characteristics of
co-processed acacia gum and maize starch. Acacia gum was co-processed with
maize starch at varying ratios 0.25:49.75, 0.5:49.5, 1:49 and 1.25:48:75 using
pre-gelatinization method. The flow characteristics of the natives,
co-processed excipients, and cellactose were evaluated using standard
techniques. Acacia gum co-processed with maize starch at ratio 1:49 (Batch C)
gave the best results with bulk and tapped density of 0.54 and 0.63g/cm3 respectively,
angle of repose of 31.79o, Hausner ratio of 1.17, and Carr’s index
of 15.14%. Cellactose which was used as a standard for comparison reflected a
bulk and tapped density of 0.49 and 0.57g/cm3 respectively, angle of
repose of 28.38o, Hausner ratio of 1.12, and Carr’s index of 13.80%.
The study confirmed that co-processing acacia gum with maize starch improved
the flow properties of its natives and compared well with the standard
co-processed excipient.
KEYWORDS: Acacia gum, Maize starch, Co-processed
excipients, Pre-gelatinization method, Flow characteristics, Standard
techniques.
INTRODUCTION:
Co-processed excipients are combinations of two or
more excipients having performance advantages that cannot be achieved using a
physical admixture of the same combination of excipients1.
Co-processing is one of the most widely explored and commercially utilized
methods for the preparation of directly compressible adjuvant2. The
main aim of co-processing is to obtain a product with added value related to
the ratio of its functionality.
Development of co-processed directly compressible
adjuvant starts with the selection of the excipients to be combined, their
targeted proportion, selection of preparation method to get optimized product
with desired physico-chemical parameters and it ends with minimizing avoidance
with batch-to-batch variations. Co-processing is a novel concept in which the
excipient functionality is altered by retaining the favorable attributes and
supplementing with newer ones. This allows production of high-functionality
excipients which can be of a greater importance to the formulator. The high
functionality can be in terms of improved process ability such as flow
properties, compressibility, content uniformity, dilution potential, and
lubricant sensitivity3,4. The search for new excipients is due to
increase tablet machine speed, which requires excipients that will maintain
good compressibility and low weight variation even at short dwelling times.
Shortcomings of existing excipients such a loss of compaction of microcrystalline
cellulose upon wet granulation, high moisture sensitivity, and poor die filling
as a result of agglomeration, the lack of excipients that address the needs of
specific patients such as those with diabetes, hypertension, and lactose and
sorbitol sensitivity; developing the ability of excipients to modulate the
solubility, permeability, or stability of drug molecules and to increase the
performance of excipients to address issues such as disintegration, dissolution
and bioavailability5. Co-processing is the science of particle
engineering of individual excipients, combining two or more conventional
excipients (usually with one or more primary functionality which compromises
other functionalities) into a single multifunctional substance of high functionality
with superior intrinsic performance such as high compatibility, high intrinsic
flow, good lubricating efficiency, improved blending properties and good
binding properties6. Acacia gum co-processed with maize starch is
expected to possess performance advantages that cannot be achieved using a
physical admixture of the same combination of these two excipients. This study
was aimed to study the flow properties of co-processed acacia gum and maize
starch using pre-gelatinization method.
MATERIALS AND METHODS:
Materials:
Maize starch (Sigma-Aldrich, Malaysia), Acacia gum
(Sigma), Cellactose ® 80 (Meggle Group Wasserburg, Germany).
Methods:
Preparation of co-processed acacia gum and maize
starch
The method reported by Ogunjimi and Alebiowu was
adapted6. A 50 g of acacia gum and maize starch mixtures at
different ratios 0.25:49.75, 0.5:49.5, 1:49 and 1.25:48:75 was co-processed.
Acacia gum was dissolved in 50 mL of distilled water to form a viscous
homogenous solution. 50 mL of water was added to the previously sieved starch
to form a slurry. This slurry of the maize starch and water was added to the
viscous homogenous solution of acacia gum and mixed thoroughly using a glass
stirring rod. The homogenous mixture was kept in a water bath and stirred
continuously until the temperature of 50
was attained. It was then dehydrated twice
using acetone, after which it was passed through a muslin bag. The wet coherent
product was wet screened using 355 µm mesh. The wet granules obtained were air
dried for 24 h, dry screened using the same mesh and then stored in a tightly
closed glass bottle for further use.
Determination of particle size and shape:
Optical microscope (LEICA Galen III
Research Microscope, USA) equipped with an integrated camera (Celestron digital
microscope imager, model 44421 was used to study the particle size and shape of
acacia gum, maize starch, co-processed excipients Batch A to D, and Cellactose.
Image–J software (Model 1.48v, Wayne Rasband, USA) was used to analyze the
photomicrographs. The following descriptors were used to study the size and
shape6,7:
Aspect ratio = b/l
---------------------------------Equation 1
Elongation ratio = l/b
----------------------------Equation 2
Roundness = 4πA/p2
---------------------------- Equation 3
Irregularity = p/l -----------------------------------Equation
4
Equivalent circle
diameter=2√(A/π)------------ Equation 5
Where:
b= Length of minor axis (minimum Feret
diameter)
l= Length of major diameter (maximum Feret
diameter)
A= Projected area of the particle
P=Perimeter of the particle
Determination of angle of repose:
A 30 g of natives,
co-processed excipients Batch
A to D, and Cellactose was
passed through an open-ended measuring cylinder which was placed in a clean
sheet of paper. Then the cylinder was slowly lifted. The height of the heaped
formed was measured as ‘h’ (cm), the diameter of the circumference of the heap
was divided into two to obtain its radius. The experiment was performed in
triplicates and the average calculated. The angle of repose was calculated
using the formula:
Angle of repose = tan-1 (h/r)……………….. Equation 6
Where:
h= height of powder cone (cm)
r= radius of the cone base (cm)
Determination of bulk density:
40 g of excipients (natives, co-processed excipients
and Cellactose) was weighed and transferred into a 100 ml measuring cylinder of
known diameter. The volume was calculated using the formula v=
r2h. The bulk volume was noted.
weight of excipient
–––––––––––––––––-------------Equation 7
bulk volume
The experiment was performed for the four batches of
the above-mentioned ratios in triplicate, and the mean was calculated.
Determination of tapped density:
A 40 g of excipients was weighed above (for the
determination of the bulk density) was subjected to 100 tapings (held with hand
like a fulcrum) at a distance of 4.5 cm away from the surface, on a soft padded
surface. The tapped volume was noted and tapped density calculated.
The volume was calculated using the formula v=r2h
Where:
v= tapped volume
r= radius of the measuring cylinder
h= height of the excipient in the cylinder
at 100 taps
The tapped density was calculated as the weight per
unit volume of the excipient. The tapped density recorded was the mean of three
determinations.
Determination of Carr’s (compressibility)
index:
Carr’s index was calculated using the equation:
(Tapped density – Bulk density)
CI = –––––––––––––––-------------– ×100 % Equation 8
(Tapped density)
CI = Compressibility index (%)
Determination of Hausner ratio:
Hausner ratio was calculated as the ratio of tapped
density to bulk density of the excipient.
Tapped density
Hausner ratio = –––––––––––––––––
---------Equation 9
Bulk density
The particle size and shape of the excipients are
shown in Table 1. The aspect ratio of the excipients was found to be in the
range of 0.40 to 0.75 while the elongation ratios are in the range of 1.32 to
2.46. The particle’s irregularity was found to be in the range of 1.89 to 2.89.
The roundness of the particles was found to be in the range of 0.31 to 1.57.
The equivalent circle diameter was found to be in the range of 1.12 to 2.52 µm.
Flow characteristics of excipients:
The flow properties of the co-processed
excipients containing acacia gum and maize starch are shown in Table 2.
Acacia gum co-processed with maize starch
at ratio 1:49 (Batch C) gave the best results with bulk and tapped density of
0.54 and 0.63 g/cm3 respectively, angle of repose of 31.79o,
Hausner ratio of 1.17, and Carr’s index of 15.14 %. Cellactose which was used
as a standard for comparison reflected a bulk and tapped density of 0.49 and
0.57 g/cm3 respectively, angle of repose of 28.38o,
Hausner ratio of 1.12, and Carr’s index of 13.80%.
DISCUSSION:
Morphological characteristics of excipients:
Equivalent circle diameter gives an indication of the
particle size of the excipients.
The results shown in Table 1
indicates that the particles of the excipients were neither perfect circle nor
elongated due to the fact that the aspect ratio was neither one nor close to
zero. Aspect ratio varied
between 0 and 1. Elongation ratio is the inverse of aspect ratio. Roundness
measures how the projected area of the particle resembles that of a perfect
circle with a perfect circle having a roundness of 1. Irregularity measures the surface area compared to
the size of the particle with a perfect circle having irregularity of 3.1426,7,8.
Flow characteristics of excipients:
The bulk density of a powder describes its packing
behavior during tableting, while the tapped density indicates the rate and
extent of packing that would be experienced9. An increase in the
tapped density is an advantage in tableting because the fill volume of the die
would be reduced. The bulk density of the co-processed excipient containing
acacia gum and maize starch is shown in Table 2. An increase in tapped density
was observed in all the batches of the co-processed excipients. As a result,
the co-processed excipients gave good flowability, and complete filling of the
die, hence, uniformity of weight and content of compressed tablets would be
achieved when employed in tableting. The values of Hausner ratio and Carr’s
index of the batches of co-processed excipient are shown in Table 2. The Hausner ratio has been used to predict the flow
behavior of powdered solids. Hausner ratio values less than 1.25 indicates good
flow, while greater than 1.25 indicates poor flow10,11. All the
batches gave good flow property and would therefore be of advantage in direct
compression tableting. The
angle of repose could be used as a qualitative measure of the cohesiveness or
the tendency of powders or granules to flow, for instance, from hoppers through
the feed frame into tableting machines. Such uniformity of flow will minimize
weight variations in tablets produced12. As a general rule, powders with angle of repose
greater than 50o have unsatisfactory flow properties whereas minimum
angles close to 25o corresponds to very good flow.10 All
the batches (A to D) of co-processed excipients possessed satisfactory flow
properties with angle of repose ranging from 31.60 to 33.42o. This
can be attributed to the fact that co-processing the two polymers, acacia gum
and maize starch yielded granules with bigger particle size, hence improving
the flow property of the powders and their subsequent functionality as a direct
compression filler-binder.
CONCLUSION:
Co-processing acacia gum with maize starch gave
co-processed excipient with good flow properties. As a result, the co-processed
excipient can be used in the formulation of directly compressible tablets.
Thus, there will be a reduction in the cost of production of the tablets and as
a result the market price of such tablets will not be high.
CONFLICT OF INTEREST:
The authors declare no conflict of interest.
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Available online from January 27, 2026
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