Frozen “Tofu” Effect: Engineered Pores of Hydrophilic Nanoporous Materials

Abstract

Frozen tofu is a famous Asian food made by freezing soft bean curds, which are naturally porous to store flavor and nutrients. When the narrow pores of the soft bean curd are saturated with water and then frozen, pore widths expand to generate a completely new porous structure—frozen tofu has visibly wider pores than the initial bean curd. Intriguingly, this principle can be generalized and applied to manipulate micro/nanopores of functional porous materials. In this work, we will manipulate the pore size of nanoporous polymeric photonic crystals based on the phase change between water and ice. Wet-drying and freeze-drying methods were applied to shrink or expand the pore size intentionally. This principle is validated by directly observing the optical reflection peak shift of the material. Owing to the change in pore size, the reflection peak of the polymeric photonic crystal structure can be permanently, and intentionally, tuned. This simple but elegant mechanism is promising for the development of smart materials/devices for applications ranging from oil/water membrane separations, health monitoring, and medical diagnostics to environmental monitoring, anticounterfeiting, and smart windows.

Tofu products: A review of their raw materials, processing conditions, and packaging

“…It can increase the storage time and extend the shelf life of food (Kobayashi, Ishiguro, Ozeki, Kawai, & Suzuki, 2020). Frozen tofu is a delicious and famous Asian food made by freezing soft or firm tofu (Ji et al., 2017). It is produced by food companies and extensively used in daily cooking in China and in Japan.…”

Effect and mechanism of freezing on the quality and structure of soymilk gel induced by different salt ions

“…10,31 At the same time, the texture becomes harder and the structure becomes more stable. 32 Salt-directly induced soymilk protein gel has a faster coagulation speed than SPI gel, and the gel network structure is more uniform and denser. 33 In addition, salt ion concentration (200-400 mmol/L) can alter soybean protein aggregation and improve freeze-thaw stability.…”

Comparative Study of Nanocarbon-Based Flexible Multifunctional Composite Electrodes

“…6 Porous materials prepared by pyrolysis, 7 polymer curing 8 or freeze drying method, and foaming technique 9,10 will produce low porosity and weak adhesion. 11,12 In addition, the preparation process of some porous materials is complicated and their properties may be unstable. In this regard, commercial sponge with uniform pore size and stable structure shows great potential in the rational design and design of porous materials.…”

“…Recently, porous materials have been widely used in superhydrophobic materials, adsorption and catalytic materials, energy, electronics, and other fields due to their porosity, flexibility, and strong adsorption capacity. − Conductive porous materials have unique pore structure, large specific surface area, excellent conductivity, and electrochemical performance, as well as broad application prospects in the fields of supercapacitors, electrochemistry, and flexible sensors. , However, conductive porous materials have their limitations, such as uneven pore size distribution and poor adhesion between filler and pore structure . Porous materials prepared by pyrolysis, polymer curing or freeze drying method, and foaming technique , will produce low porosity and weak adhesion. , In addition, the preparation process of some porous materials is complicated and their properties may be unstable. In this regard, commercial sponge with uniform pore size and stable structure shows great potential in the rational design and design of porous materials …”