Determinations Of Calibration And Determination Of Crude Protein

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wheat kernels in 150 μm sieve; Wwheat in 75μm sieve = weight of wheat kernels in 75 189 μm sieve; Wpan =
190 weight of empty pan; and Wmaize meal = weight of maize flour.
191 Determination of Crude Protein
192 The crude protein content of the roasted maize was determined in duplicate by Dumas combustion
193 method as described in AACCI Approved Method 46–30.01 (AACC, 1999) using a Leco, model
194 FP-528 (Leco Africa, Kempton Park, South Africa). Calibration of the instrument was done using
195 an alfalfa standard with a known nitrogen content of 3.38 ± 0.04%. A series of blank determinations
196 were performed in order to get rid of any element in the instrument. Calibration of the instrument
197 was done using an alfalfa standard with a known
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For the pyrolysis of samples in pure oxygen (99.9%), 850°C
200 was used as combustion temperature. Crude protein was obtained by multiplying the nitrogen
201 content with the conversion factor 5.68 (Sriperm et al., 2011). Calculated crude protein content was
202 expressed on a 12% moisture basis (Eq. 11), where APC = adjusted protein content; MPC =
203 measured protein content; FMC = final moisture content (12%); and OMC = original moisture
204 content of sample.
APC % = MPC ∗ tuv
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The column temperature was maintained at 36°C and
212 the detection source was ESI+ (electrospray ionisation). The solvents Eluent A2 (100 mL eluent A
213 concentrate [6-aminoquinolyl-N-hydroxysuccinimidyl carbamate + acetonitrile] and 900 mL
214 distilled water) and Eluent B (acetonitrile) were used. The MS analysis was done using a Waters
215 ACQUITY Tandem Triple Quadrupole Spectrometer (Waters Corporation, Massachusetts, USA)
216 with capillary voltage set at 3.5 kV and 15 V for cone voltage. The source and desolvation
217 temperatures were set at 120 and 350°C, and desolvation and cone gases at 350 and 50 L/h,
218 respectively. Tryptophan, glutamine and asparagine were not determined out of the twenty naturally
219 occurring amino acids.
Page 7 of 28 Journal of Food Processing and Preservation
Extraction of 220 Phenolic Compounds
221 A slightly modified method of Wang et al. (2013) was used for extraction of free and bound
222 phenolics. For free phenolic compounds, 1 ± 0.001 g of the roasted maize flour was weighed into a
223 glass vial, 15 mL of 60% chilled aqueous acetone added and sonicated for 10 min at 20°C in the

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