Extraction of Cigar Tobacco Leaf Protein and the Amino Acid Composition and Antioxidant Activity of Its Hydrolysate

Purpose To study the extraction of cigar leaf protein and the amino acid composition and antioxidant activity of hydrolysates, providing theoretical and technical basis for the in-depth development and utilization of tobacco leaf protein resources.

Methods Using alkali-extraction and acid-precipitation method to extract cigar tobacco leaf protein, determine the optimal extraction conditions; pepsin, complex protease, alkaline protease, papain and neutral protease were used to hydrolyze the extracted cigar tobacco leaf protein, determine the degree of hydrolysis of different enzymes on cigar tobacco leaf protein, and the amino acid composition and antioxidant activity of the hydrolysates were analyzed.

Results The optimal extraction conditions for extracting cigar tobacco leaf protein were as follows: the solid-liquid ratio was 1∶25 (g∶mL), the alkali dissolution pH was 8.0, the alkali dissolution time was 80 min, the extraction temperature was 60 ℃, the acid deposition pH was 3.0, and the optimal extraction rate of protein was 79.08%. Cigar tobacco leaf protein had the best effect by pepsin hydrolysis, with a hydrolysis degree of 15.52%. After pepsin hydrolysis of cigar tobacco leaf protein, the content of free amino acids was the highest; the contents of essential amino acids, hydrophobic amino acids, negatively charged amino acids, and positively charged amino acids were higher than other protease hydrolysates; and the ratio of essential amino acids to total amino acids, and the ratio of essential amino acids to nonessential amino acids were higher than those specified in FAO/WHO standards. With the increase of enzymatic hydrolysis time, the scavenging ability of pepsin hydrolysates on superoxide anion radicals, DPPH radicals, and hydroxyl radicals increased, with the highest scavenging rate of superoxide anion radicals (57.54%).

Conclusion Using alkali-extraction and acid-precipitation method can better extract cigar tobacco leaf protein, and hydrolyzing it with pepsin can improve its amino acid composition and proportion, enhance its nutritional value, and enhance the antioxidant capacity of the hydrolysate of cigar tobacco leaf protein.