*2.7. Loading Efficiency*

Loading efficiency of resveratrol was determined by isoelectric precipitation method [24]. The samples with WPI, SPI and SC were adjusted to pH 4.8–4.6 using 0.1 M NaOH or HCl. Loading efficiency of resveratrol was calculated according to following formulation:

$$\text{Loading efficiency} \left(\% \right) = \left(1 - \frac{\text{C}\_{\text{s}}}{\text{C}\_{0}} \right) \times 100 \tag{3}$$

where, C0 and Cs were resveratrol in samples and in the supernatant, centrifuged at 5000× *g* for 20 min, respectively.

#### *2.8. Antioxidant Activity*

ABTS assay was analyzed according to previous methods [25]. In brief, 7.4 mM ABTS and 2.6 mM K2S2O8 were mixed in the dark for 12 h to produce ABTS· <sup>+</sup> solution, which was diluted and mixed with samples or buffer at a volume ratio of 19:1 and kept in the dark for 6 min. The absorbance was measured at 729 nm using a UV-1800 UV–Vis spectrophotometer (Shimadzu Co., Tokyo, Japan). The radical-scavenging activity was calculated as follows:

$$\text{Scavenging capacity} \left( \% \right) = \frac{\text{A}\_{\text{\textdegree}} - \text{A}\_{\text{\textdegree}}}{\text{A}\_{\text{\textdegree}}} \times 100 \tag{4}$$

where Ac and As are the absorbance of radical plus buffer and sample, respectively.

#### *2.9. Sulfhydryl Analysis*

Samples were mixed at a volume ratio of 1:2 with 0.1 M phosphate buffer at pH 8.0 without and with 8 M urea for free and total sulfhydryl determination, respectively. Then absorbance at 412 nm was measured, after 10 mM DTNB was added under vigorous stirring and incubated in the dark for 1 h. Both reagent and sample blanks were subtracted. Content of free and total sulfhydryl was calculated by using a molar extinction coefficient of 13,600 M<sup>−</sup>1cm−<sup>1</sup> and expressed as nmol per mg protein [26].
