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Objective To optimize the acid hydrolysis-Fehling reagent titration method and the acid hydrolysis-3,5-dinitrosalicylic acid (DNS) colorimetric method to compare the consistency of different methods for measuring starch content in grain crop samples. Methods Experimental conditions, including ethanol washing volume, acid addition volume, acid hydrolysis time, sample solution pH, detection wavelength, chromogenic agent volume, color development time and color development temperature, were optimized to determine the optimal processing conditions for determining the starch content in such products. Results The optimal conditions for the acid hydrolysis-Fehling reagent titration method were as follows: After weighing the sample, fats and soluble sugars were removed using an appropriate amount of petroleum ether and ethanol; 25 mL of hydrochloric acid was added, followed by condensation reflux for 120 minutes; the hydrolyzed sample solution was neutralized with sodium hydroxide, filtered, and the filtrate was titrated with alkaline copper tartrate methyl and ethyl solution at a rate of one drop every 2 seconds. The optimal conditions for the acid hydrolysis-DNS colorimetric method were as follows: After removing fat, sugar and acid hydrolysis, the sample solution pH was adjusted to 8-9; for samples with color and high protein content, 10 mL of lead acetate was added to reduce or eliminate pigment interference; after filtration, 2 mL of DNS was added to the filtrate, followed by color development in a water bath at 90-100 °C for 12 minutes; the absorbance was measured at 540 nm using a spectrophotometer, and the determination was completed within 4 hours. Both methods had a relative standard deviation (RSD) of less than 2% and a relative error (RE) of less than 4%. The measurement results had passed mean consistency test and paired samples t-test. Conclusion The 2 kinds of optimized methods are more efficient and accurate compared to the national standard method, with good accuracy and precision making them suitable for starch content determination in grain crops.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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