The shape of starch granules was analysed by a digital scanning
electron microscope model LEO-1430. Starch dispersions were
placed on double-sided tape and coated with gold (sputtering).
The mean particle size was determined using an inverted optical
microscope (Axiovert 25 Zeiss). Twenty fields were randomly selected
and photographed and 10 granules from each field were
measured (for a total of 200 granules).
2.3.2. X-ray diffraction
The X-ray diffraction diffractogram was obtained from starch in
the powder form containing approximately 11% moisture. The
interval of 2h angles ranged from 4 to 60 in the X-ray Diffractometer
(Model D5000, São Paulo, Brazil), at a rate of 1.2 /min
and operating at a power of 40 kV/20 mA. The diffractogram patterns
were evaluated according to Zobel (1964).
2.4. Functional properties of hard and soft jackfruit seed starch
2.4.1. Swelling power and solubility
Swelling power and solubility were determined according to
the method described by Leach, Mc Cowen, and Schoch (1959)
by weighing 0.1 g of starch in previously weighed centrifuge tubes
and adding 10 ml of distilled water. The suspension was stirred
and placed in a water bath for 30 min at temperatures ranging
from 55 Cto95C, increasing 10 from time to time and centrifuging
for 15 min at 3400g. A 5 ml aliquot was removed from the
supernatant, placed in petri dishes and placed on the stove at
105 C for 24 h to determine the weight of the solubilised starch.
After the outer walls of the tubes were dried, the tubes were carefully
weighed, and the swelling power and solubility were determined
as follows:
Swelling power ¼ðweight of tube þ residue after centrifugationÞ
ðweight of tube plus sample on dry basisÞ=weight of sample
Solubility% ¼ðweight of plate with sample after evaporationÞ
ðweight of plateÞ100
2.4.2. Paste transparency
The paste transparency was determined as described by Craig,
Maningat, Seib, and Hoseney (1989). The paste transparency was
determined by placing the starch suspension (3% w.v.
) in deionised
water. Transmittance (% T) was determined at 650 nm using a
spectrophotometer (Coleman 33D Spectrometer). Samples were
stored at 4 C for 8 days, and transmittance readings were conducted
every 24 h to monitor retrogradation.
2.4.3. Viscosity
Viscosity was determined using a rapid viscosity analyser RVA-
4, with the aid of the Thermocline for Windows software version
2.3, Newport Scientific Pty, Ltd, and according to the N 162 methodology
proposed by the ICC using the Standard 1 profile (Lawal &
Adebowale, 2005).
2.4.4. Gelatinisation
The gelatinisation parameters were determined by Differential
Scanning Calorimetry (DSC) using a differential exploratory calorimeter
(Shimadzu, model DSC 50, coupled to computer software)
in a nitrogen atmosphere at a flow rate of 50 ml min
preparation of the samples, 6
lL of distilled water were added to
2 mg of starch, sealed in tubes and weighed again; to provide the
1
1
. For the