12 found 50 acetone extracts exhibited the highest TPC values and 80 acetone
the highest DPPH scavenging capacity and TFC values for yellow soybean. The sample flour-solvent mixtures were vortexed 16 times during 4 h of extraction
according to Ferreira et al. 2011. The tubes were then centrifuged by 5810R Centrifuge Hamburg, Germany at 3000 rpm for 10 min, and the extracts were
stored at 5
o
C in the dark for use.
3.7 Radical DPPH Scavenging Capacity
The DPPH 2,2-diphenyl-1-picrylhydrazyl power of samples were evaluated according to the method of Xu and Chang 2007. The sample extract
0.2 mL was added to 3.8 mL ethanol solution of DPPH radical 0.1 mM. The mixture was vortexed vigorously for 1 min and then kept at room temperature in
the dark for 30 min. The absorbance of samples was measured using a UV-Visible Spectrophotometer U-2900, Hitachi, Tokyo, Japan at 517 nm against ethanol as
a blank. A negative control was mixture of DPPH solution and extraction solvent. The inhibitory percentage of DPPH was calculated according to the following
equation:
Inhibition = [1 – A
sample
A
control
] × 100 The DPPH free radical scavenging capacity was expressed as millimoles
of ascorbic acid equivalent per gram of freeze-dried sample mmol of AAEg. The standard calibration curve range was 10 to 1000
μM R
2
= 0.996.
3.8 Total Phenolic Content TPC
Total soluble phenolics in the extracts were determined using a Folin- Ciocalteu assay as described by Xu and Chang 2007. The sample extract 50
μL, distilled water 3 mL, Folin-
Ciocalteu’s reagents 250 μL, and 7 NaCO3 750
μL were vortexed and allowed to stand for 8 min at room temperature. Thereafter, distilled water 950
μL was added to the mixture and the absorbance was read using the U-2900 Spectrophotometer at 765 nm after 2 h of incubation
against distilled water blank. The TPC was expressed as milligrams of gallic acid equivalents per gram of freeze-dried sample mg of GAEg. The TPC was
expressed as milligrams of gallic acid equivalents per gram of freeze-dried sample mg of GAEg. The standard calibration curve range was 10 to 1000
μM R
2
= 0.998.
3.9 Total Flavonoid Content TFC
The TFC was determined using a colorimetric method described by Xu and Chang 2007. The sample extract 0.25 mL, distilled water 1.25 mL, and
5 NaNO
2
solution 75 μL were mixed in a test tube and kept for 6 min of
incubation. Then, 150 μL of 10 AlCl
3
·6H
2
O solution was added to the mixture. After 5 min, a 0.5 mL of 1 M NaOH and 2.5 mL of distilled water were added and
13 vortexed well. The absorbance was measured at 510 nm using an UV-visible
spectrophotometer U-2900, Hitachi. The TFC was expressed as milligrams of catechin equivalents per gram of freeze-dried sample mg of CAEg. The
standard calibration curve range was 5 to 500 μM R
2
= 0.999.
3.10 Textural Analysis
The texture measurement was accomplished by using TA-XT2i Texture Analyzer Stable Micro Systems Ltd., Godalming, Surrey, UK with cylindrical
probe d: 30 mm, h: 50 mm, by performing texture profile analysis TPA. Tempe were compressed to 50 of their original height by two compressions.
Texture profile was generated by keeping pre-test, test, and post-test speeds of 2, 1, and 2 mms respectively. The waiting time between the two-cycles of the TPA
test was 5 s. Textural parameters such as hardness, springiness, stickiness, cohesiveness, and chewiness were evaluated by using Texture Expert 1.22
software.
Figure 5 Position of sample during TPA.
3.11 Color Analysis
Analysis of visual color was performed by using CR310 Chromameter Konica, Minolta, Tokyo, Japan
. Hunter’s color parameters L, a, and b values for the surface of treated tempe were recorded. The L value indicated lightness 0
to 100, a, the red + or green − coordinate, and b, the yellow + or blue −
coordinate. −. The limits for a and b are + or −80. The hue h and chroma C
were calculated according to the following equations Wrolstad and Smith 2010: h = tan
-1
b a⁄ C = √a
2
+b
2
12
3.12 Kinetic Modeling
In this study the changes of quality attributes during thermal process were described as first-order reaction characterized by logarithmic relationship between
concentration of food quality and time that is expressed mathematically as follows Van Boekel 2008:
Force
Sample
