Fiveeasy plus fe28 ph meter

The materials used in the study included: dried L. asiatica fruitbody, purchased from Kunming Mushuihua Wild Mushroom Trading Market; 5 × 10⁴ U/g neutral protease, 3 × 10⁴ U/g papain, purchased from Nanning Pangbo Bioengineering Co., Ltd. (Nanning, China); 5 × 10⁴ U/g flavor protease, purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd. (Cangzhou, China).
The equipment used in the study included: EasyPlus Titrator ET18 automatic potentiometric titrator, Mettler-Toledo Instruments Ltd. (Shanghai, China); FiveEasy Plus FE28 pH meter, Mettler-Toledo Instruments Ltd.(Shanghai, China); HH-6 constant temperature water bath, Shanghai Lichen Technology Co., Ltd. (Shanghai, China); centrifuge, Shanghai Anting Scientific Instrument Factory (Shanghai, China); TYM-30L ultra-micro pulverizer, Jinan Ltd. (Jinan, China); PEN3 electronic nose, AIRSENSE Analytics GmbH (Schwerin, Germany); FlavourSpec^® flavor analyzer, G.A.S, Scientific Instruments Co., Ltd. (Dortmund, Germany).

The cartilage of a blue shark (Prionace glauca) was purchased from M/s. Yueqing Ocean Biological Health Care Product Co., Ltd. (Wenzhou, Zhejiang, China). All cartilages were stored at −80 °C for future use and thawed at 4 °C prior to pretreatment. The pretreatment of blue shark cartilage was based on the method of Phanat et al. [36 ] with modifications. The periosteum was removed from the cartilage. Cartilages were then cut into thin slices of 3–5 mm. The slices of cartilage were crushed using a QSJ-B02R1 meat grinder (Guangdong Bear electric appliance Co., Ltd., Foshan, Guangdong, China) and rinsed under running tap water until the ammonia odor disappeared. The cartilages were then immersed in a 0.1 mol/L NaOH at a cartilage-to-solution ratio of 1:10 (w/v) and stirred for 24 h to remove water-soluble substances, non-collagenous proteins, fat and pigments; the solution was refreshed every 8 h. Thereafter, the cartilages were rinsed with deionized water until the wash-down solution was neutral, using a FiveEasy Plus FE28 pH meter (METTLER TOLEDO, Zurich, Switzerland). The cartilages were then immersed in a 5 mmol/L EDTA solution at pH 7.5–8.0 at a ratio of 1:10 (w/v) and stirred for 40 h to remove the minerals; the solution was refreshed every 8 h. Afterwards, the cartilages were similarly rinsed with deionized water until the wash-down solution reached neutral pH.