*2.10. Carbonyl Analysis*

Protein solutions in the presence and absence of resveratrol during storage at 45 ◦C were mixed at a volume ratio of 1:2 with 10 mM DNPH in 2 M HCl. After 10% (*w*/*v*) trichloroacetic acid was added and centrifuged at 10,000× *g* for 5 min, precipitate was washed with 50% ethyl acetate and then dissolved in 6 M guanidine HCl in 20 mM phosphate buffer at pH 2.3. Absorbance at 370 nm was measured and carbonyl content was calculated using an extinction coefficient of 22,000 M−1cm−<sup>1</sup> and expressed as nmol per mg protein [27].

## *2.11. Amino Acid Analysis*

Amino acids except tryptophan were analyzed through acid hydrolysis of proteins by mixing 4 mL of samples with the same volume of 12 M HCl under blown nitrogen for 3 min, followed by hydrolysis at 120 ◦C for 22 h. Then a certain amount of NaOH was added to neutralize, and water was added to give a total volume of 25 mL. Tryptophan was determined by alkaline hydrolysis of proteins with 10 M NaOH and neutralized with a certain amount of HCl. The supernatant was centrifuged after filtering with filter paper. Amino acids were analyzed on the Agilent 1100 HPLC system equipped with an Agilent Hypersil ODS column (Angelon Co., Ltd., New York, NY, USA). Proline was detected at 262 nm, and the other amino acids were detected at 338 nm [6].
