The thermogravimetry (TGA) and derivative thermogravimetry (DTG) methods have been used to measure the free water in low-moisture foods. In this study, the 2nd derivative thermogravimetry (2nd DTG) method distinguished the free and bound water based on the speed of moisture evaporation, which could be used for both low-moisture and high-moisture foods. First, the key factors related to moisture evaporation were optimized. Isothermal temperature of 30 ~ 50°C, dynamic temperature of 0.033 ~ 0.133°C/min, and flow rate of nitrogen of 20 ~ 40 mL/min were the optimal parameters for the 2nd DTG method. Under these conditions, the repeatability and reproducibility of the 2nd DTG method were enhanced, its applicability was expanded to high-moisture foods, and the accuracy was ± 4.0% of the nuclear magnetic resonance results. Hence, the 2nd DTG method is better suited for the measurement of free water in foods.

The effects of different concentration of flaxseed gum (FG) (0.1–0.5%, w/w) on the stability of soybean oil emulsion were studied by particle size, rheological properties, creaming stability and nuclear magnetic resonance (NMR). Results showed that emulsion particle size decreased significantly with the increase in FG concentration. Rheological measurements showed FG exhibited thickening and gelling properties. Viscosity, storage modulus, and loss modulus increased accordingly with the increase in FG concentrations, and emulsions with 0.5% FG looked like a viscoelastic solid. Emulsions with a higher FG concentration exhibited better creaming stability and structure. With the increase of FG concentration, the ¹H and ¹³C NMR spectra line widths in high field also increased, which confirms that the interaction between FG and oil molecules is enhanced. These results show that FG can substitute for other emulsifiers or stabilizers in emulsions, and is beneficial to the stability of emulsions.

To improve product quality and osmotic efficiency, the effects of osmotic dehydration (OD) at 120 min and ultrasound-assisted osmotic dehydration (UOD) at 45 min on the nutrient composition, flavor, texture, microstructure, and water state in button mushrooms were investigated. In terms of nutrient composition, the results showed that UOD produced samples with reducing sugar, ascorbic acid, and soluble protein content at significantly higher rates than OD process. Meanwhile, UOD reduced the losses in titratable acidity, free amino acids, and 5′-nucleotides compared to the OD process, and the UOD samples also showed a better texture and microstructure. In addition, low-field nuclear magnetic resonance data revealed that the relative signal intensity of vacuole protons declined during OD process; meanwhile, the UOD was more efficient than the OD treatment. Overall, UOD process not only retained nutrient composition and flavor material more effectively but also improved the texture and efficiency of mushrooms treated with osmosis.