Effect of cooking methods on the phytosterol content in nine selected vegetables

Phytosterol contents in nine vegetables such as paprika (red, yellow, and orange), kohlrabi, bamboo shoot, cherry tomato, cucumber, Chinese chive, and corn were analyzed by gas chromatography. Individual contents of ${\beta}$-sitosterol, campesterol, and stigmasterol in fresh and cooked vegetables (boiling, grilling, stir-frying, deep-frying, steaming, roasting, and microwaving) were determined and compared. Total phytosterol content of paprika, cucumber, Chinese chive and cherry tomato ranged from 23.19 to 46.51 mg/kg (0.002-0.005%) of fresh weight of raw vegetables. Total phytosterol content variation (%) was obtained as follows: [(the content of phytosterol after cooking) - (the content of phytosterol before cooking)] / (the content of phytosterol before cooking) ${\times}100$. Total phytosterol content was found to be high in raw kohlrabi at 138.99 mg/kg fw (0.01%), in corn at 302.86 mg/kg fw (0.03%), and in bamboo shoot at 443.15 mg/kg fw (0.04 %). Total phytosterol content variation (%) in orange paprika ranged from 27.5 to 267.3 while that in cherry tomato ranged from -11.0 to 337.5. Generally, high content variation of total phytosterol was found in stir-fried and deep-fried vegetables. Therefore, higher phytosterol levels were obtained from cooked vegetables than raw vegetables. We suggest that these data will be useful to investigate cooking methods for increased intake of phytosterols.