Bromelain

The Model 381-20 of cellulose acetate butyrate ester (CAB) was purchased from Eastman Chemical Company(Kingsport, TN, USA). We bought the EVOH Model ET3803 masterbatch from Nippon Synthetic Chemical Industry Co., Ltd.(Osaka, Japan). Glutaraldehyde aqueous solution (GA, 25 wt%), tert-butanol (>98%), acetic acid, polyphosphoric acid (PPA, phosphorus pentoxide content >85 wt%), butane tetracarboxylic acid (BTCA), acetone, phosphate buffer saline (PBS), phosphoric acid (H₃PO₄), NaOH, LiCl, KCl, MgCl₂, NaCl, and NaSO₄ were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Papain, lysozyme, ovalbumin, bromelain, bovine serum albumin, and pepsin were bought from Sangon Biotech Co., Ltd. (Shanghai, China).

Pumpkin seeds (Cucurbita pepo L.) were provided by Haichuansanxin Food Company (Beitun, China). Alcalase (≥200 U/mg) was purchased by Hefei Bomei Biotechnology Co., Ltd. (Hefei, China). Papain (>200 units/mg) and flavourzyme (30,000 units/g) were purchased from Solarbio Life Science (Beijing, China). Bromelain (3,000–7,000 U/mg), pepsin (1,200 U/g), pancreatin (≥4,000U/g), trypsin (≥50,000U/g), and bile salt and o-Phthalaldehyde (OPA) and dithiothreitol (DTT) were purchased from Sangon Biotech (Shanghai, China). In addition, 8-Anilino-1-naphthalenesulfonic acid (ANS) [≥97% (HPLC)] was purchased from Sigma-Aldrich. Sodium dodecyl sulfate (SDS) and L-Serine (≥BR) were purchased from Sinopharm Chemical Reagent Co., Ltd. Zinc sulfate heptahydrate, sodium hydroxide, nitric acid, n-hexane, ethyl alcohol, and other reagents were of analytical grade and purchased from Chemical Reagent Co., Ltd. (Shanghai, China). Dialysis bags (MD34-500) were purchased from Wuxi Hengkang Medical Technology Co., Ltd.