Influence of ultrasonic pretreatments on microwave hot-air flow rolling drying mechanism, thermal characteristics and rehydration dynamics of Pleurotus eryngii.

BACKGROUND: In order to improve the drying efficiency and reduce the drying energy consumption of Pleurotus eryngii, microwave hot-air flow rolling drying (MHARD) coupled with ultrasonic pretreating time (0, 20, 40, and 60 min) was used to investigate the drying profile, thermal characteristics, water migration, microstructure and rehydration dynamics of P. eryngii using differential scanning calorimetry (DSC), low-field nuclear magnetic resonance (LF-NMR) analysis and scanning electron microscopy (SEM). RESULTS: Results showed that the drying time of P. eryngii was 80, 70, 60 and 50 min, accordingly. Energy consumption was significantly reduced by ultrasonic pretreatment, and moisture effective diffusivity (Deff ) was increased with the increase of ultrasonic pretreating time. DSC curves showed that the drying process was accelerated by ultrasonic pretreatment significantly by enhancing the heat transfer. Meanwhile, SEM images showed that the cell was broken and numbers of irregular holes appeared in the ultrasound-pretreated samples. In terms of rehydration dynamics, Page model could well model the rehydration kinetics of dried P. eryngii with R2 > 0.99. CONCLUSION: The findings indicate that ultrasonic pretreatment is a promising method for MHARD of P. eryngii as it can enhance the drying process, and show potential for industrial application. © 2021 Society of Chemical Industry.

Effect of different drying techniques on drying kinetics, nutritional components, antioxidant capacity, physical properties and microstructure of edamame.

The present study aimed to investigate the effect of hot air drying (HD), microwave rolling-bed drying (MRD), hot air microwave rolling-bed drying (HMRD), pulse-spouted microwave vacuum drying (PSMVD) and freeze-drying (FD) on the drying characteristics, quality properties and microstructure of edamame. Six models were fitted the drying curves, and quality attributes were analyzed. Results indicated that Page model was the most suited model for edamame drying. Compared with HD, MRD and HMRD improved the quality of edamame and decreased the drying time by 45.59% and 36.03% respectively. The FD and PSMVD possessed higher rehydration ability, nutrient retention and antioxidant capacity compared with other methods. Moreover, PSMVD products showed a crunchy texture, the less color change and the shortest drying time (70 min). Microscopy images demonstrated a distinct porous structure in PSMVD, which facilitated the moisture transfer. Overall, PSMVD is a promising dehydration method for obtaining high value-added edamame products.

Value-added application of Platycodon grandiflorus (Jacq.) A.DC. roots (PGR) by ultrasound-assisted extraction (UAE) process to improve physicochemical quality, structural characteristics and functional properties.

Platycodon grandiflorus (Jacq.) A.DC. roots (PGR), a Chinese herb with medicinal and edible value, was powdered by freeze drying (FD) and spray drying (SD) after maceration extraction (ME) or ultrasound-assisted extraction (UAE) to develop a new functional food product. Four PGR powders were obtained namely ME-FD, ME-SD, UAE-FD, and UAE-SD and their powder quality, structural properties, and functionalities were evaluated. UAE-FD powder had the highest powder recovery (85.3 ± 5.79%) and also presented better hydration properties due to the larger particle size compared with other three PGR powders. Four PGR powders exhibited similar thermal decomposition process, molecular structure, amorphous characteristics, amino acids composition, and taste profiles. Furthermore, the UAE-FD PGR powders presented the highest Platycodin D (3.68 ± 0.04 mg/g), total phenolic (2.84 ± 0.11 mg GAE/g), and total flavonoids content (2.11 ± 0.14 mg RE/g), resulting in best antioxidant activity (58.67 ± 2.42 µmol Trolox/g). Therefore UAE-FD is an environment-friendly technique for the production of functional PGR powder with improved nutritional and redispersion properties.

Production of protein-loaded starch microspheres using water-in-water emulsion method.

Protein-loaded starch microspheres were prepared by water-in-water (w/w) emulsion method. The effects of the molecular weight of starch and protein used, concentration of solutes in both dispersed and continuous phases and starch to protein mass ratio on the yield, loading capacity and encapsulation efficiency were measured. These parameters were significantly higher in Bovine serum albumin (BSA)-loaded microspheres than in lysozyme-loaded microspheres. An increase in the molecular weight of starch, solute concentration in dispersed and continuous phases increased the yield. The encapsulation efficiency was significantly improved when the starch to BSA mass ratio was increased. When the starch to BSA mass ratio was 15:1, the encapsulation efficiency reached about 100 % with a loading capacity of 7.3 g/100 g. This method is more effective when both core (protein) and shell (starch) materials with high molecular weight are used. This approach is environmentally friendly and the processing parameters can be easily optimized.

Effect of molecular weight of starch on the properties of cassava starch microspheres prepared in aqueous two-phase system.

Starch microspheres (SMs) were fabricated in an aqueous two-phase system (ATPS). A series of starch samples with different molecular weight were prepared by acid hydrolysis, and the effect of molecular weight of starch on the fabrication of SMs were investigated. Scanning electron microscopy (SEM) showed that the morphologies of SMs varied with starch molecular weight, and spherical SMs with sharp contours were obtained while using starch samples with weight-average molecular weight (M¯w)≤1.057×105g/mol. X-ray diffraction (XRD) results revealed that crystalline structure of SMs were different from that of native cassava starch, and the relative crystallinity of SMs increased with the molecular weight of starch decreasing. Differential scanning calorimetry (DSC) results showed peak gelatinization temperature (Tp) and enthalpy of gelatinization (ΔH) of SMs increased with decreased M¯wof starch. Stability tests indicated that the SMs were stable under acid environment, but not stable under α-amylase hydrolysis.

Crystallization and melting properties of mixtures of milk fat stearin and omega-3 rich oils.

Solid milk fat stearin (S25) can be a promising oxidation retarder due to its capacity to entrap liquid oils, especially for incorporating omega-3 (ω-3) rich oils into dairy products. Thermal properties of S25/ω-3 rich oil mixtures are necessary for such application. The effects of S25 on the crystallization and melting behaviours of ω-3 rich oils, namely fish oil (FO), linseed oil (LO) and krill oil (KO), were investigated by differential scanning calorimetry (DSC). Thermograms showed that with S25 concentration increasing, transitions of FO and LO shifted to lower and largely to higher temperatures, respectively, while crystallization temperature of KO slightly decreased. Negative, positive and low values of interaction enthalpy (ΔHint) suggested the adverse, beneficial and limited effect of S25 on the crystallization of S25/FO, S25/LO and S25/KO mixtures, respectively. LO could have the best oxidative stability upon the addition of S25 since their interactions facilitated earlier and stronger crystallization.

Preparation of starch nanospheres through hydrophobic modification followed by initial water dialysis.

Starch nanospheres smaller than 200 nm were produced from hydrophobically modified starch by using initial water dialysis method. The hydrophobic modification of starch was performed by using octenyl succinic anhydride (OSA). The resultant starch nanospheres were characterized by using Fourier transformation infrared (FTIR) spectroscopy, (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy and fluorescence spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS). Effects of degree of substitution (DS) in OSA-starch, initial water content and OSA-starch concentration on morphology and particle size of starch nanospheres were evaluated. The SEM micrographs showed that starch nanospheres with spherical shape and sharp edge can be produced at DS values ≧0.67. The particle size of starch nanospheres decreased significantly (P<0.05) with increase in DS of OSA-starch and increase in the initial water content, whereas the particle size increased significantly (P<0.05) with the increase in the concentration of OSA-starch. These OSA-starch nanospheres can be preferentially used to microencapsulate hydrophobic drugs.