Figures (2)  Tables (3)

    • Figure 1. 

      FT-IR spectra of different molecular weights of OSA-modified starches.

    • Figure 2. 

      Optimization results of extraction factors (extraction time, extraction method, ratio of solid to liquid, different molecular weights of OSA-modified starches).

    • Extraction methods*Factors in the extraction process**
      StirringUltrasonic-assisted extractionMicrowave-assisted extractionExtraction time (min)Ratio of solid to liquid (mg/mL)Concentration of OSA-modified starch (mg/mL)
      Indicators and their valuesStirring speed:
      500 r/min;

      Extraction time:
      40 min      		Ultrasonic intensity:
      1000 W;

      Extraction time:
      40 min      		Microwave intensity:
      1,000 W;

      Extraction time:
      5 min      		10105
      201510
      302015
      402520
      503025
      * The experiments were designed by the single-factor method and replicated three times; the extraction was carried out with the medium molecular weight OSA-modified starch solution (15 mg/mL) and a solid-liquid ratio of 20 mg/mL. ** The single-factor experiments were used under optimal extraction conditions. Medium molecular weight of OSA-modified starch was used. One of the variables was optimized, and the others were constant.

      Table 1. 

      Optimization factors and indicators of the extraction process.

    • SampleMolecular weight (104 Da)DS (×103)Viscosity (Pa·s)
      Hst-OSAS20.002.491.196
      H-OSAS12.512.510.921
      M-OSAS9.252.530.528
      L-OSAS2.342.570.444
      Lst-OSAS1.612.600.386
      Notation of the molecular weight was as follows: Hst-OSAS, highest molecular weight OSA-modified starch; H-OSAS, high molecular weight OSA-modified starch; M-OSAS, medium molecular weight OSA-modified starch; L-OSAS, low molecular weight OSA-modified starch; Lst-OSAS, lowest molecular weight OSA-modified starch.

      Table 2. 

      Molecular weights, degree of substitution, and viscosity of OSA-modified starches.

    • SampleDPPH radical scavenging activity (%)Equivalent to Trolox (μM)**Equivalent to FeSO4
      (mM)
      Hst-OSAS11.41 ± 0.77a885.72 ± 3.21a1.460 ± 0.048a
      H-OSAS23.70 ± 3.43b888.94 ± 8.32a1.515 ± 0.026b
      M-OSAS33.63 ± 0.45c896.20 ± 9.86b1.615 ± 0.067c
      L-OSAS54.84 ± 4.94d895.06 ± 8.63b1.497 ± 0.034d
      Lst-OSAS55.47 ± 3.85d889.43 ± 7.92a1.382 ± 0.018e
      * Each experiment was repeated three times and expressed as mean ± SD. Different letters in the same column represent a significant difference between the two groups of data (p < 0.05). ** Trolox, a water-soluble analog of vitamin E, is used as a control antioxidant standard.

      Table 3. 

      In vitro antioxidant results of extraction solution.*