Utilizing native myrosinase in pennycress Thlaspi arvense seeds to reduce glucosinolates in the defatted meal

Abstract: Pennycress is now being grown as an oilseed cover cash crop over winter between corn and soybean. The oil from pennycress seed can be used as feedstock for biofuels production and the defatted meal can be utilized as feed. However, pennycress seeds contain glucosinolate (up to 140 µmol sinigrin/g) which can degrade into allyl isothiocyanate (AITC) and other sulfur-containing compounds. Sinigrin and its breakdown products make the meal unpalatable and may be goitrogenic and hepatoxic if consumed in large quantities. In this study, a glucosinolate reducing step using native myrosinase in the seed, steam, and/or dry heat treatments were incorporated in the oil extraction process. Wild-type pennycress (WTP) and yellow-seeded covercress (1-kg batches) were prepressed, and the moisture of the cakes were adjusted to 30%, and then incubated for 3 h at 45^oC. The incubated press cakes were extracted with hexane and the solvent in the marc was removed under ambient conditions. The resulting defatted meal had sinigrin content of ≤ 30 µmol/g. A comparable sinigrin reduction was also observed in defatted unincubated WTP press cakes (12% MC) when heated for 3 h at 130^oC and within the first hour when heated at 160^oC. For yellow-seeded covercress (7.5% MC), this was achieved after 1 h of heating at 150^oC. Employing steam and dry heat in desolventizing and toasting of the unincubated meal marc reduced the sinigrin in the meal to 50 µmol/g after 45 min of steaming and 1 h of air drying. This indicated that a combination of enzymatic hydrolysis of sinigrin and steam and dry heat treatment in the desolventizer/toaster can produce defatted meal with sinigrin content much lower than 30 µmol/g