Evaluation of gel properties of soy protein isolate cold gel by texture analyzer

Tofu is a traditional food that originated in China. According to the coagulant classification, it can be divided into tofu made of acid, salt and enzyme. Glycolate tofu is tofu made from gluconic acid lactone (GDL) as a coagulant. It is an acid. Coagulant-like tofu. The traditional manufacturing process usually involves two-step heating: first heating the soymilk under neutral pH conditions, then adding the lactone to acidification and then heating under acidic conditions. The lactone releases protons to neutralize the negative charge of the soy protein polymer, followed by hydrogen bonding, ionic interaction, etc. to form a three-dimensional network.

Using a high field strength ultrasonic-heating process, soy protein can form a gel at a lower temperature, a "cold gel." Compared with traditional thermal gels, cold gels do not require heating when they finally form a gel. They have the following advantages: first, cold gels can protect heat sensitive substances added to the gel; second, soy protein cold gels The preparation can reduce the use of heating equipment in the production process and reduce energy consumption. However, conventional cold gel gels have poor strength and poor gel holding capacity .

1 Preparation process of soy protein isolate cold gel

2 Determination of gel strength of soy protein isolate cold gel

Equipment: Universal TA Texture Analyzer

Probe: P/0.5 (0.5 inch gel strength dedicated probe)

Test conditions: gel formation in a 25 mL beaker at a test speed of 1 mm/s, test mode: 50% deformation

3 test results

(1) Morphology of soy protein isolate cold gel formation

(2) Gel strength of soy protein isolate cold gel

Compared with the traditional heat pretreatment, the two high-field-intensity ultrasonic-heating combined pretreatments can significantly (P<0.05) enhance the water holding capacity and gel strength of the soy protein isolate cold gel. The gel strength of the cold gel prepared by Process 1 (20 kHz, 400 W after ultrasonic treatment for 0, 2, 4, 10 min and 20 min) was gradually increased with the increase of ultrasonic time (gel strength was (5.83±0.31)). g increased to (46.37±1.15) g, while the gel strength of the cold gel prepared in Process 2 (20 min after ultrasonic heating for 20 min, 2, 4, 10 min) was rapid in a short ultrasonic time (within 4 min) Increase (gel strength increased from (5.83 ± 0.31) g to (37.57 ± 2.57) g.