Effects of Ultrasound Combined with Preheating Treatment to Improve the Thermal Stability of Coconut Milk by Modifying the Physicochemical Properties of Coconut Protein

The composition, extraction, functional property, quality, and health benefits of coconut protein: A review

Coconut is widely appreciated for its distinctive flavor and is commonly utilized in the production of a variety of goods. Coconut protein, a by-product derived from coconut oil and coconut milk cake, is frequently underutilized or discarded. This study provides a comprehensive overview of the distribution and composition of coconut protein. Analyses reveal that coconut protein, specifically 11S globulin and 7S globulin, is predominantly found in coconut flesh. Furthermore, various extraction techniques for coconut protein, such as chemical, enzymatic, and physical methods, are discussed. The alkali dissolution and acid precipitation methods are widely utilized for extracting coconut protein, with the potential for enhancement through the incorporation of physical methods such as ultrasound. The evaluation of functional properties, quality, and health benefits of coconut protein is essential, given the limitations imposed by its solubility. Modification may be necessary to optimize its functional properties. Coconut presents a promising source of food protein, characterized by balanced amino acid composition, high digestibility, and low allergenic potential. In conclusion, this study provides a comprehensive overview of the extraction methods, functional properties, quality, and nutritional benefits of coconut protein, offering insights for potential future research directions in the field. Additionally, the information presented may serve as a valuable reference for incorporating coconut protein into plant-based food products.

Effect of Dry Processing of Coconut Oil on the Structure and Physicochemical Properties of Coconut Isolate Proteins

The effects of the dry processing of coconut oil on the amino acid composition, molecular weight, secondary structure, solubility, surface hydrophobicity, microstructure, total sulfhydryl and free sulfhydryl content, free amino acid content, thermal properties, and water-holding, oil-holding, foaming, and emulsifying properties of coconut isolate protein were investigated. The results showed that the dry processing altered the amino acid composition of coconut isolate proteins as well as resulted in fewer irregular structural regions and more homogeneous particle sizes, leading to an improvement in the thermal stability of the proteins. SDS-PAGE analysis showed that globular proteins located at ~34 kDa in coconut isolate proteins underwent slight degradation during the dry processing of coconut oil. The dry processing reduced the surface hydrophobicity, total and free sulfhydryl groups, solubility, and free amino acid content of coconut isolate proteins. In addition, the water-holding capacity, oil-holding capacity, and foam stability of coconut isolate proteins were improved to different degrees after the dry processing. Therefore, the development and utilization of copra meal protein is of great significance to increase its added value.

The potential of pulsed electromagnetic field-generated shock waves for reducing microbial load and improving homogenization in raw milk

Milk is a highly nutritious food essential for human consumption. However, traditional thermal processing methods can reduce its nutritional value and cause unwanted changes. The use of shock waves produced by pulsed electromagnetic fields (PEMFs) has been explored as a means to reduce pathogenic microorganisms. The effect of shock wave treatment on microbial load and particle distribution in packaged fresh cow's milk was investigated. Additionally, the impact of shock wave treatment on Salmonella enterica counts in a bacterial suspension of phosphate-buffered saline (PBS) was evaluated, as this bacterium is a significant milkborne pathogen. Treatment with 1000 impulses from an electromagnetic shock wave generator resulted in a 0.7-log reduction in the total bacterial count of milk. In a separate experiment, a 300-impulse shock wave treatment applied to a Salmonella enterica suspension achieved a 3-log reduction in bacterial counts. Furthermore, shock wave treatment resulted in a decrease in milk particle size compared to untreated milk. Notably, the volume of milk used in this study aligns with commercially available packaged products, enhancing the experiment's industrial relevance. The use of PEMF to generate shock waves could provide a novel approach for future studies focused on reducing the microbial load of milk and improving its homogenization.

Mechanism for improving the in vitro digestive properties of coconut milk by modifying the structure and properties of coconut proteins with monosodium glutamate

In this paper, the effect of monosodium glutamate (MSG) on coconut protein (CP) solubility, surface hydrophobicity, emulsification activity, ultraviolet spectroscopy and fluorescence spectroscopy was investigated. Meanwhile, the changes in the in vitro digestive properties of coconut milk were also further analyzed. MSG treatment altered the solubility and surface hydrophobicity of CP, thereby improving protein digestibility. Molecular docking showed that CP bound to pepsin and trypsin mainly through hydrogen bonds and salt bridges. And MSG increased the cleavable sites of pepsin and trypsin on CP, thus further improving the protein digestibility. In addition, MSG increased the Na+ concentration in coconut milk, promoted flocculation and aggregation between coconut milk droplets, which prevented the binding of lipase and oil droplets and inhibited lipid digestion. These findings may provide new ideas and insights to improve the digestive properties of plant-based milk.

Effects of protein concentration, ionic strength, and heat treatment on the interfacial and emulsifying properties of coconut (Cocos nucifera L.) globulins

This research aimed to investigate the effects of protein concentration (0.2 %-1.0 %), ionic strength (100-500 mM NaCl), and heat treatment (temperature: 80 and 90℃; time: 15 and 30 min) on the interfacial and emulsifying properties of coconut globulins (CG). When protein concentration was set at 0.2-0.6 %, the interfacial adsorption increased with the increasing of protein concentration. However, the lowest interfacial viscoelasticity was found when CG concentration was 0.6 %. When the protein concentration was higher than 0.6 %, the dilatational viscoelasticity increased with the increasing of protein concentration. The protein concentration showed positive effect on the emulsion stability of CG. The ionic strength showed positive effect on the interfacial adsorption but negative effects on the interfacial viscoelasticity and emulsion stability. Higher temperature and longer heating time brought worse interface behavior. The heated CG (90℃, 30 min) had the worst interfacial behavior but the best emulsion stability.

Regulation of Protein Flexibility and Promoting the Cod Protein Gel Formation Using Ultrasound Treatment

In order to obtain a soft-textured protein gel suitable for the elderly, the cod protein gel was prepared by improving the protein flexibility under ultrasound treatment. It has been found that the increase in ultrasonic power, protein flexibility, particle size, ζ-potential, surface hydrophobicity, and α-helix content of preheated cod protein exhibited an increasing trend. The improvement of protein flexibility promoted uniformity and density of the gel network, water retention, and texture properties. The flexibility of preheated cod protein increased to 0.189, the water holding capacity of the gel reached up to 99.41%, and the hardness increased to 49.12 g, as the ultrasonic power level increased to 400 W. Protein flexibility was correlated well with the cohesiveness of the gel. The storage modulus (G') initially decreased and then increased during the heating-cooling process. The attractive forces forming between the flexible protein molecules during cooling in the ultrasound treatment groups promoted protein self-assembly aggregation and formed the cod protein gel. The gel obtained at 100-400 W could be categorized as Level 6─soft and bite-sized according to the International Dysphagia Diet Standardization Initiative (IDDSI) framework, indicating that the cod protein gel has potential as an easy-to-swallow diet for the elderly.

Preparation of high complex concentration emulsion stabilized by soy protein/dextran sulfate composite particles

BACKGROUND

Soy protein isolate (SPI) could be used as an emulsifier to stabilize emulsions, while SPI is unstable under low acidic conditions. The stable composite particles of SPI and dextran sulfate (DS) could be formed by the electrostatic interaction at the pH was 3.5. And the SPI/DS composite particles were used to prepare the high complex concentration emulsion. The stabilization properties of high complex concentration emulsion were investigated.

RESULTS

Compared to uncompounded SPI, the particle size of SPI/DS composite particles was smaller at 1.52 μm, and the absolute value of the potential increased to 19.9 mV when the mass ratio of SPI to DS was 1:1 and the pH was 3.5. With the DS ratio increased, the solubility of the composite particles increased to 14.44 times of the untreated protein at pH 3.5, while the surface hydrophobicity decreased. Electrostatic interactions and hydrogen bonds were the main forces between SPI and DS, and DS was electrostatically adsorbed on the surface of SPI. The emulsion stability significantly enhanced with the increase of complex concentration (38.88 times higher than at 1% concentration), the emulsion average droplet size was the lowest (9.64 μm), and the absolute value of potential was the highest (46.67 mV) when the mass ratio of SPI to DS was 1:1 and the complex concentration of 8%. The stability of the emulsion against freezing was improved.

CONCLUSION

The SPI/DS complex has high solubility and stability under low acidic conditions, and the SPI/DS complex' emulsion has a well stability. This article is protected by copyright. All rights reserved.

Effects of ultrasonic-assisted pH shift treatment on physicochemical properties of electrospinning nanofibers made from rapeseed protein isolates

Electrospinning nanofibers (NFs) made from natural proteins have drawn increasing attention recently. Rapeseed meal is a by-product that rich in protein but not fully utilized due to poor properties. Therefore, modification of rapeseed protein isolates (RPI) is necessary to expand applications. In this study, pH shift alone or ultrasonic-assisted pH shift treatment was adopted, the solubility of RPI, along with the conductivity and viscosity of the electrospinning solution were detected. Moreover, the microstructure and functional characteristics of the electrospinning NFs, as well as the antibacterial activity of clove essential oil loaded-NFs were investigated. The tested parameters were remarkably improved after different treatments compared with the control, and synergistic effects were observed, especially under alkaline conditions. Hence, pH_12.5 + US showed the maximum value of solubility, conductivity, and viscosity, which was more than 7-fold, 3-fold, and almost 1-fold higher than the control respectively. Additionally, SEM and AFM images showed a finer and smoother surface of NFs after treatments, and the finest diameter of 216.7 nm was obtained after pH_12.5 + US treatment in comparison with 450.0 nm in control. FTIR spectroscopy of NFs demonstrated spatial structure changes of RPI, and improved thermal stability and mechanical strength of NFs were achieved after different treatments. Furthermore, an inhibition zone with a diameter of 22.8 mm was observed from the composite NFs. This study indicated the effectiveness of ultrasonic-assisted pH shift treatment on the physicochemical properties improvement and functional enhancement of NFs made from RPI, as well as the potential antibacterial application of the composite NFs in the future.

Effect of Multi-Mode Thermosonication on the Microbial Inhibition and Quality Retention of Strawberry Clear Juice during Storage at Varied Temperatures

Strawberry juice, which is rich in nutrients and charming flavor, is favored by consumers. To explore whether multi-mode thermosonication (MTS) can ensure the quality stability of strawberry clear juice (SCJ) during storage, the effects of microbial inhibition, enzyme activity, and physicochemical properties of SCJ pretreated by MTS were evaluated during storage at 4, 25, and 37 °C in comparison with thermal pretreatment (TP) at 90 °C for 1 min. The MTS, including dual-frequency energy-gathered ultrasound pretreatment (DEUP) and flat sweep-frequency dispersive ultrasound pretreatment (FSDUP), were conducted at 60 °C for 5 and 15 min, respectively. Results showed that the total phenols, flavonoids, anthocyanins, ascorbic acid, and DPPH free radical scavenging ability of SCJ decreased during the storage period. The control sample of SCJ was able to sage for only 7 days at 4 °C based on the microbiological quality, while the FSDUP and DEUP group extended the storage period up to 21 and 14 days, respectively. The polyphenol oxidase in SCJ pretreated by MTS did not reactivate during the storage period. The MTS remarkably (p < 0.05) reduced the color deterioration, browning degree, and nutrient degradation during the storage period. Moreover, the FSDUP group exhibited the maximum shelf life with a minimum loss of quality, demonstrating that it was the most suitable processing method for obtaining high-quality SCJ. It can be concluded that the MTS has the potential to inhibit enzymatic browning, inactivating microorganisms, preserve original quality attributes, and prolong the shelf life of SCJ.