Sang-Gi Min

Effect of Freeze-Drying Process Conditions on the Stability of Nanoparticles

Abstract The purpose of this study was to optimize the freeze-drying processes of nanoparticles in order to improve their end-used properties and their stability. Polycaprolactone (PCL) nanoparticles were prepared by the emulsification-diffusion method and then were frozen at different freezing rates. Finally, the nanoparticles were freeze-dried under different operating conditions by using a laboratory-made freeze-dryer. Then, the average particle size was analyzed by using a Coulter® LS 230 apparatus firstly after the freezing step and finally after the sublimation step. The surface morphology and the thermophysical characteristics of the nanoparticles were determined by SEM and by DSC, respectively. It was observed that, the freezing process can break the nanoparticles and cause the leakage of their contents during the freeze-drying step. The higher the freezing rate, the larger the size of nanoparticles during the freezing process. From the results DSC data, it could be assumed that the nanoparticles in the nanosuspensions may have been broken not by water crystallization in the external phase, but by the solidification of the oil (miglyol) in the internal phase.

Release characteristics of freeze-dried eugenol encapsulated with β-cyclodextrin by molecular inclusion method

The study investigated the thermo-physical properties of eugenol encapsulated with β-cyclodextrin (β-CD) by molecular inclusion and eugenol release characteristics at various relative humidities and storage temperatures. Particle size, Zeta-potential, thermal transition and morphology of β-CD-Eugenol complex after freeze-drying measured using Nanosizer®, differential scanning calorimeter (DSC) and transmission electron microscopy (TEM), respectively. The particle size, Zeta-potential and inclusion efficiency of encapsulated eugenol presented ∼340 nm, −34.5 mV and 91.7% after freeze-drying, respectively. The relationship between retention rate of eugenol and time during release was described by a mathematical model of Avrami equation. In these events, the parameter of release mechanism and the release rate constant were rapidly elevated with increasing relative humidity and storage temperature. Furthermore, the Arrhenius activation energy for the release of eugenol decreases with increasing relative humidity and storage temperature.

Variability in temperature distribution and cooking properties of ground pork patties containing different fat level and with/without salt cooked by microwave energy.

This study was carried out to evaluate the cooking effects of fat level (10% and 20%) with and without NaCl (1.5%) on the microwave cooking pattern and properties of ground pork patties. Each patty was cooked from a thawed state to 76.7°C in a microwave oven with full power (900W). Cooking rate in patties produced without salt was not affected by fat level, but the addition of salt in pork patties decreased cooking rate, regardless of fat levels. The temperatures at the edges of the patties increased faster than those at the center or the mid-way positions. In the patties with NaCl, the temperature of the center position was higher than that of the mid-way position. Patties containing salt within the same fat level had higher moisture content and lower fat content than those without salt, although no significant differences in compositional properties were observed between the center, midway, or edge positions. Total cooking loss, drip loss, and reduction in diameter and thickness were higher in patties with 20% fat compared to those with 10% fat, but the addition of salt resulted in reduction, regardless of fat level. Also, the addition of salt increased the redness and reduced yellowness of the cooked products.

Effect of glucono-δ-lactone and κ-carrageenan combined with high pressure treatment on the physico-chemical properties of restructured pork.

In this study, response surface methodology (RSM) was used to evaluate the combined effects of NaCl, glucono-δ-lactone (GdL), and κ-carrageenan concentration (0.25%, 0.5%, and 0.75%) on the binding properties of restructured pork under hydrostatic pressure. All the generated RSM models showed no lack-of-fit and significance at the 0.001 level. The addition of both NaCl and GdL had a significant effect on color. A significant decrease in pH was shown when the GdL level increased, and subsequently led to a decrease in WHC. However, increasing the GdL level increased the binding strength. Therefore, the results indicate that a reduction in the NaCl level during meat restructuring, under pressure treatment, can be achieved by using GdL; and even a low GdL concentration allows for palatable binding properties in meat restructuring when κ-carrageenan is added.

Emulsion properties of pork myofibrillar protein in combination with microbial transglutaminase and calcium alginate under various pH conditions.

In this study, the effects of microbial transglutaminase (MTG) and calcium alginate (CA) systems in combination with soybean oil on the emulsion properties of porcine myofibrillar protein (MP) were evaluated under various pH conditions. MTG was shown to improve emulsifying capacity and creaming stability, which increased with increasing pH values up to 6.5. The CA did not influence emulsifying capacity, but it improved the creaming stability of the MP-stabilized emulsions. Both MTG and CA enhanced the rheological properties, but their effects on the physical characteristics of the protein evidenced an opposite trend in relation to pH, i.e., the MTG system improved both the emulsion and gelling properties with increasing pH, whereas the CA system was effective when the pH was lowered. By combining the two MP gelling systems, a stable and pH-insensible emulsion could be produced.

Physicothermal Properties of Freeze-Dried Fish Oil Nanocapsules Frozen under Different Conditions

This research compared the effects of vacuum freeze drying (VFD) and conventional freeze drying (CFD) processes on the stability of fish oil–loaded nanocapsules (NCs). For CFD, the NCs showed aggregation that was dependent on the freezing temperature. The encapsulation efficiency of CFD was greater than that of VFD, except at the freezing temperature of −30°C. From differential scanning calorimetry (DSC) analysis and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, it was concluded that the CFD process was more effective in the oxidative stability of the fish oil–loaded NCs. In addition, the vacuum-freezing process may affect the fragility of the poly-ϵ-caprolactone membrane due to its low encapsulation efficiency and aggregation of particles. No differences in Z-potential values between the CFD samples were observed, whereas in the VFD samples, it became increased in the negative charge when decreasing the cooling temperature of the fish oil–loaded nanocapsules for the freeze-drying procedure. Regarding the observation of surface tension, CFD samples presented lower values than VFD samples at given freezing temperature.

Physical properties of frozen pork thawed by high pressure assisted thawing process

The effects of a high pressure assisted thawing process (HPATP) at 50, 100, 150 and 200MPa at 15ºC on the physical properties of frozen pork, M. longissimus dorsi, were investigated. Treated samples increased pH significantly, compared to atmospheric thawing ones (control). HPATP samples had higher water holding capacities and lower thawing losses than the control. Cooking losses of HPATP treatment decreased at 50 and 100MPa. HPATP had no significant effect (p 0.05) on Warner-Bratzler shear force below 150MPa. There were no differences in colour at 100MPa, however, both L*-and b*-values increased significantly from 150MPa whereas a*-value decreased. According to the results, HPATP treatment improved the quality of frozen pork below 100MPa, effectively.

The effect of high pressure-low temperature treatment on physicochemical properties in milk.

This study was carried out to investigate the effect of high pressure-low temperature (HPLT) treatment on physicochemical properties and nutrients in milk. The milk was treated at 200 MPa and -4 degrees C for 10, 20, and 30 min. Protease and lipase activities of HPLT-treated milk were highly inactivated compared with that of raw milk. Among time treatments, the 30-min treatment showed the lowest activities compared with others. Absorbance of thiobarbituric acid increased with time in HLPT-treated milks; however, no difference was observed between the raw milk and milk treated for 10 min. The concentrations of short-chain fatty acids except C(4) in HPLT-treated milks increased with time. The total free amino acids in HPLT-treated milks were greater than that of the raw milk for the 30-min treatment. L-Ascorbic acid, niacin, and riboflavin in HPLT-treated milks were significantly lower compared with concentrations in raw milk. For color, the L-value of HPLT-treated milks was significantly lower than that of the raw milk; however, there was no difference in the a-value for 10 min and in the b-value at 20 min between the raw milk and the HPLT-treated milks.

Effect of Cryoprotectant and Freeze-Drying Process on the Stability of W/O/W Emulsions

In order to protect a hydrophilic drug and to prolong its further delivery, the formulation of multiple emulsions could be worthy. However, the double emulsions are not stable, their structure can change, leading to the formation of a single emulsion as the destruction of the system, and the drug can release easily from the globules in liquid state. The freeze-drying technology could be used to produce dry emulsion, the powder form being much more stable. The aim of this work was to study the influence of a cryoprotectant and a freeze-drying process on the stability of W/O/W emulsions. Samples were frozen at two different freezing rate (ν f = 0.55°C/min and 1.25°C/min) and successively dried at two different sublimation temperature (T s = − 10°C and − 20°C). The particle size distributions were measured by granulometer and UV spectrophotometer was performed to investigate the leakage of internal constituent. The glass transition temperature (T g ) of the double emulsions was analyzed by DSC. The particle sizes became even smaller after freeze drying, except when κ-carrageenan is used as a cryoprotectant. In that case, the particles became aggregated after freeze drying, whatever the process conditions. The mean size is considerably reduced when the globules are diluted at low concentration in glucose and trehalose solution. When the concentration is increased, the size distribution is not significantly affected. The leakage of the internal aqueous phase to the external one during freeze drying was measured as an indicator of the structure stability. It is affected by the nature of the cryoprotectant and the conditions of the freeze-drying process. The leakage of the internal phase was smaller when cycle III (ν f = 1.25°C/min, T s = − 10°C) was processed. From our experiments, we suppose that the water transfer from the inner phase to the outer aqueous phase results in the diminution of the globules size in double emulsion. The T g of the double emulsions diluted with trehalose and glucose were determined at − 33.8°C and − 47.1°C. In contrast, the T g of double emulsion with κ-carrageenan and HES did not appear.

Characterization of β-cyclodextrin Self-Aggregates for Eugenol Encapsulation

Abstract The application of β-cyclodextrin(CD)-assisted molecular encapsulation of neutraceutical ingredients, functional food in food products, hydrophobic drugs, and volatile substances helps protect the active ingredients against oxidation, loss of volatile compounds and light-induced decomposition and increases the solubility of hydrophobic medicines. Self-assembly aggregation of CDs has been extensively investigated from the aggregation of native CDs to high-order complex aggregates. The increasing complex order of the aggregates is dependent on some parameters such as pH, temperature, time and concentration. The aim of this study was to investigate the effects of the aggregation behaviour of β-cyclodextrin (CD)-eugenol complexes induced at shaking times on the release characteristic at various relative humidity and storage temperatures. The particle size started to increase after shaking for 8 h at 650 nm, and then, significant aggregation (1,110 nm) was observed after 24 h. The retention rate of eugenol significantly increased according to storage duration under various relative humidity and temperature conditions. Prolonged shaking time enhanced the self-aggregation of β-CD-eugenol complexes resulting in eugenol release behavior due to their effect on the aggregation mechanism, as assessed by TEM observation. The aggregation of β-CD-eugenol complexes could be attributed to the slow release of eugenol owing to the presence of a thick layer of β-CD aggregates.