Effect of polysaccharide emulsifiers on the fabrication of monodisperse oil-in-water emulsions using the microchannel emulsification method

The microchannel emulsification method was used to prepare monodisperse soybean oil-in-water emulsions, with polysaccharides as the sole emulsifier. The effects of different types (sodium alginate, carboxymethyl cellulose, pectin, gum arabic) and concentrations (0.1, 0.5, 1.0%) of polysaccharide on the droplet size, droplet size distribution and stability of the emulsions were investigated. The droplet diameters of the resulting emulsions were in the range of 35 ± 2 to 47 ± 3 μm, with coefficient of variations (CV) of below 6.6%. Generally, the droplet size increased as the concentration of the polysaccharides increased. The stability of emulsions prepared using 0.5% of sodium alginate, carboxymethyl cellulose and gum arabic was also evaluated in situ. Sodium alginate- and gum arabic-stabilized emulsions were stable for at least 6 h

Utjecaj lecitina iz soje i natrijevog kazeinata na stabilnost i in vitro biološku raspoloživost nanodisperzija likopena

Research background. Various approaches have been used to present functional lipids including lycopene in a palatable food form to consumers. However, being highly hydrophobic, lycopene is insoluble in aqueous systems and has a limited bioavailability in the body. Lycopene nanodispersion is expected to improve the properties of lycopene, but its stability and bioaccessibility are also affected by emulsifier type and environmental conditions such as pH, ionic strength and temperature. Experimental approach. The influence of soy lecithin, sodium caseinate and soy lecithin/sodium caseinate at 1:1 ratio on the physicochemical properties and stability of lycopene nanodispersion prepared using the emulsification-evaporation methods before and after treatment at different pH, ionic strength and temperature were investigated. The in vitro bioaccessibility of the nanodispersions was also studied. Results and conclusion. Under neutral pH conditions, nanodispersion stabilized with soy lecithin had the highest physical stability and the smallest particle size (78 nm), the lowest polydispersity index (PDI) value (0.180) and highest zeta potential (-64 mV) but the lowest lycopene concentration (1.826 mg/100 mL). Conversely, nanodispersion stabilized with sodium caseinate had the lowest physical stability. Combining the soy lecithin with sodium caseinate at 1:1 ratio resulted in a physically stable lycopene nanodispersion with the highest lycopene concentration (2.656 mg/100 mL). The lycopene nanodispersion produced by soy lecithin also had high physical stability under different pH range (pH=2-8) where the particle size, PDI and zeta potential remained fairly consistent. The nanodispersion containing sodium caseinate was unstable and droplet aggregation occurred when the pH was reduced close to the isoelectric point of sodium caseinate (pH=4-5). The particle size and PDI value of nanodispersion stabilized with soy lecithin and sodium caseinate mixture increased sharply when the NaCl concentration increased above 100 mM, while the soy lecithin and sodium caseinate counterparts were more stable. All of the nanodispersions showed good stability with respect to temperature changes (30–100 °C) except for the one stabilized by sodium caseinate, which exhibited an increased particle size when heated to above 60 °C. The combination of soy lecithin and sodium caseinate was found to increase the bioaccessibility of the lycopene nanodispersion. The physicochemical properties, stability and extent of the lycopene nanodispersion digestion highly depend on the emulsifier type. Novelty and scientific contribution. Producing a nanodispersion is considered one of the best ways to overcome the poor water solubility, stability and bioavailability issues of lycopene. Currently, studies related to lycopene-fortified delivery systems, particularly in the form of nanodispersion, are still limited. The information obtained on the physicochemical properties, stability and bioaccessibility of lycopene nanodispersion is useful for the development of an effective delivery system for various functional lipids.Pozadina istraživanja. Različitim se pristupima nastoji potrošače opskrbiti funkcionalim lipidima, uključujući likopen, u obliku prikladnom za jelo. Međutim, zbog svoje izuzetne hidrofobnosti likopen nije topljiv u vodenim otopinama i ima ograničenu biološku raspoloživost u organizmu. Pretpostavlja se da bi nanodisperzije likopena mogle poboljšatie njegova svojstva, ali odabir emulgatora i uvjeti okoline, kao što su pH-vrijednost, ionska jakost i temperatura, utječu na njegovu stabilnost i biološku raspoloživost. Eksperimentalni pristup. Ispitan je utjecaj lecitina iz soje, natrijevog kazeinata, te njihove mješavine u omjeru 1:1 na fizikalno-kemijska svojstva i stabilnost nanodisperzija likopena dobivenih kombinacijom metoda emulgiranja i uparavanja prije i nakon obrade pri različitim pH-vrijednostima, ionskoj jakosti i temperaturama. Također je ispitana biološka raspoloživost dobivenih nanodisperzija. Rezultati i zaključci. Pri neutralnoj pH-vrijednosti, najbolja stabilnost i najmanja veličina čestica (78 nm) nanodisperzija, te najniži indeks polidisperzije (0,180) i najveći zeta-potencijal (–64 mV), ali i najniža koncentracija likopena (1,826 mg/100 mL) dobiveni su pomoću lecitina iz soje. Nasuprot tome, nanodisperzije stabilizirane pomoću natrijevog kazeinata imale su najmanju fizičku stabilnost. Kombinacijom lecitina iz soje i natrijevog kazeinata u omjeru 1:1 dobivene su fizički stabilne nanodisperzije s najvećom koncentracijom likopena (2,656 mg/100 mL). Nanodisperzije likopena dobivene pomoću lecitina iz soje bile su vrlo stabilne pri različitim pH-vrijednostima (pH=2–8), uz stabilnu veličinu čestica, indeks polidisperzije i zeta-potencijal. Nanodisperzije koje su sadržavale natrijev kazeinat bile su nestabilne, te je pri pH-vrijednosti blizu izoelektrične točke natrijevog kazeinata (pH=4-5) došlo do agregacije kapljica. Veličina čestica i indeks polidisperzije nanodisperzija stabiliziranih pomoću mješavine lecitina iz soje i natrijevog kazeinata naglo su se povećali pri koncentracijama natrijevog klorida većim od 100 mM, dok su one stabilizirane samo lecitinom iz soje ili natrijevim kazeinatom bile stabilnije. Sve su nanodisperzije bile stabilne pri promjenama temperature u rasponu od 30 do 100 °C, osim one stabilizirane pomoću natrijevog kazeinata, kojoj se veličina čestica povećala pri temperaturama iznad 60 °C. Kombinacijom lecitina iz soje i natrijevog kazeinata povećala se biološka raspoloživost nanodisperzija likopena. Fizikalno-kemijska svojstva, stabilnost i probavljivost nanodisperzija likopena u potpunosti su ovisila o tipu emulgatora. Novina i znanstveni doprinos. Proizvodnja nanodisperzija smatra se jednim od najboljih rješenja problema male topljivosti, te loše stabilnosti i biološke raspoloživosti likopena. Trenutno su istraživanja o načinu apsorpcije likopena, osobito u obliku nanodisperzija, još uvijek limitirana. Dobiveni podaci o fizikalno-kemijskim svojstvima, stabilnosti i biološkoj raspoloživosti nanodisperzija likopena korisni su za razvoj učinkovitog sustava opskrbe organizma različitim funkcionalnim lipidima

Comparing the formation of lutein nanodispersion prepared by using solvent displacement method and high-pressure valve homogenization: effects of formulation parameters

In this study, we compared the effect of formulation parameters on the physicochemical properties of lutein nanodispersions prepared using a low- and high-energy approach, i.e., solvent displacement (SD) and high-pressure valve homogenization (HPH), respectively. The lutein concentration had a significant effect on the particle size (PS) and particle size distribution (PSD) of nanodispersions that were prepared by using both methods. However, Tween 80 concentration and organic-phase-to-aqueous-phase volume ratio (OAR) only had a significant effect on the PS of nanodispersions prepared by SD. Under all the variations in the formulation parameters, the PSs and PSDs of nanodispersions prepared by SD and HPH were not significantly different. At 0.1% lutein concentration, 0.1% Tween 80 concentration and OAR of 1:9, the nanodispersions prepared by using both methods displayed minimum PS and excellent lutein retentions (>90%). This study showed that SD is a suitable alternative to HPH for preparing lutein nanodispersions

Extraction of phenolic antioxidants from four selected seaweeds obtained from Sabah

Algal have attracted attention from biomedical scientists as they are a valuable natural source of secondary metabolites that exhibit antioxidant activities. In this study, single-factor experiments were conducted to investigate the best extraction conditions (ethanol concentration, solid-to-solvent ratio, extraction temperature and extraction time) in extracting antioxidant compounds and capacities from four species of seaweeds (Sargassum polycystum, Eucheuma denticulatum, Kappaphycus alvarezzi variance Buaya and Kappaphycus alvarezzi variance Giant) from Sabah. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used to determine the phenolic and flavonoid concentrations, respectively, while 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picylhydrazyl (DPPH) radical scavenging capacity assays were used to evaluate the antioxidant capacities of all seaweed extracts. Results showed that extraction parameters had significant effect (p < 0.05) on the antioxidant compounds and antioxidant capacities of seaweed. Sargassum polycystum portrayed the most antioxidant compounds (37.41 ± 0.01 mg GAE/g DW and 4.54 ± 0.02 mg CE/g DW) and capacities (2.00 ± 0.01 μmol TEAC/g DW and 0.84 ± 0.01 μmol TEAC/g DW) amongst four species of seaweed

Shelf life determination of durian (Durio zibethinus) paste and pulp upon high pressure processing

Globally, there has been an increase in demand for durian. Therefore, it is important to extend the shelf life and at the same time, maintain the quality of durian. This study investigated the effect of high-pressure processing (HPP) on the shelf life of durian paste and pulp. Specifically, HPP treatments of 500 MPa for 5 min on nylon- and skin film-packed durian pulp, and 600 MPa for 5 min on nylon-packed durian paste were applied. It was found that throughout the 56-day storage period, the total soluble solids (TSS), pH and titratable acidity of durian paste and pulp showed no significant changes (p>0.05). The colour (L* values) of nylon-packed untreated durian pulp showed no significant changes (p>0.05), while the untreated durian paste and skin film-packed durian pulp showed significant changes (p0.05) throughout the storage period. The microbial levels of all the high- pressure (HP)-treated durian samples remained below the detection limit till the end of the storage study. HP-treated durian samples showed lower enzymatic (polygalacturonase and pectin methyl esterase) activities compared to untreated sample throughout the storage period. Sensory evaluation showed no significant difference (p>0.05) between untreated and HP-treated samples. In summary, HPP effectively maintained the overall quality of durian for a minimum of 56 days

Physical properties and stability evaluation of fish oil-in-water emulsions stabilized using thiol-modified β-lactoglobulin fibrils-chitosan complex

Fish oil-in-water emulsions containing fish oil, thiol-modified β-lactoglobulin (β-LG) fibrils, chitosan and maltodextrin were fabricated using a high-energy method. The results showed that chitosan coating induced charge reversal; denoting successful biopolymers complexation. A significantly (p < 0.05) larger droplet size and lower polydispersity index value, attributed to the thicker chitosan coating at the oil-water interface, were observed. At high chitosan concentrations, the cationic nature of chitosan strengthened the electrostatic repulsion between the droplets, thus conferring high oxidative stability and low turbidity loss rate to the emulsions. The apparent viscosity of emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex was higher than those stabilized using β-LG fibrils alone, resulting in the former's higher creaming stability. Under thermal treatments (63 °C and 100 °C), emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex possessed higher heat stability as indicated by the consistent droplet sizes observed. Chitosan provided a thicker protective layer that protected the oil droplets against high temperature. Bridging flocculation occurred at low chitosan concentration (0.1%, w/w), as revealed through microscopic observations which indicated the presence of large flocs. All in all, this work provided us with a better understanding of the application of protein fibrils-polysaccharide complex to produce stable emulsion

Physicochemical, morphological and cellular uptake properties of lutein nanodispersions prepared by using surfactants with different stabilizing mechanisms

In this study, we prepared a series of lutein nanodispersions via the solvent displacement method, by using surfactants with different stabilizing mechanisms. The surfactants used include Tween 80 (steric stabilization), sodium dodecyl sulfate (SDS; electrostatic stabilization), sodium caseinate (electrosteric stabilization) and SDS–Tween 80 (electrostatic–steric stabilization). We then characterized the resulting lutein nanodispersions in terms of their particle size, particle size distribution, zeta potential, lutein content, flow behavior, apparent viscosity, transmittance, color, morphological properties and their effects on cell viability and cellular uptake. The type of surfactant used significantly (p < 0.05) affected the physical properties of the nanodispersions, but the chemical properties (lutein content) remained unaffected. Transmission electron microscopy (TEM) images obtained from this study demonstrated that the solvent displacement method was capable of producing lutein nanodispersions containing spherical particles with sizes ranging from 66.20–125.25 nm, depending on the type of surfactant used. SDS and SDS–Tween 80 surfactants negatively affected the viability of the HT-29 cells used in this study. Thus, for the cellular uptake determination, only Tween 80 and sodium caseinate surfactants were used. The cellular uptake of the lutein nanodispersion stabilized by sodium caseinate was higher than that which was stabilized by Tween 80. All things considered, the type of surfactant with different stabilizing mechanisms did produce lutein nanodispersions with different characteristics. These findings would aid in future selection of surfactants in order to produce nanodispersions with desirable properties

Modification of physicochemical and mechanical properties of a new bio-based gelatin composite films through composition adjustment and instantizing process

The production of a new bio-based bovine gelatin (BG) film with incorporation of pea protein isolate (PPI), psyllium gum (PSY) and tragacanth (TRA) gum, and plasticized with glycerol, was completed via a two-stage fluidized bed agglomeration and casting techniques. Fluidization technique was used as a novel method to prepare instant film-forming powder (IFFP) in order to improve the films’ physicochemical, mechanical and handling properties. The incorporation of PSY, TRA, and PPI greatly improved the physicochemical, thermal and mechanical properties of the film as compared to control films. Composite films containing high glycerol concentration displayed significant (p < 0.05) reductions in tensile strength (TS) and melting point (Tm) values. The FTIR and DSC results showed that PSY, TRA and PPI interacted effectively with gelatin. In addition, scanning electron microscopy (SEM) showed film surfaces without any cracks. The results demonstrated the miscibility and compatibility of the employed plasticizer (glycerol), polysaccharides (PSY and TRA) and protein (PPI) in composite films. Gelatin-based composite film containing 0.65 g glycerol (w/w, based on 5 g IFFP), 15.0 g gelatin, 3.0 g PPI, and 1.0 g of TRA/PSY (30:70 ratio, mL/mL) possessed the best characteristics in terms of MC, TS, Tm, and swelling properties as determined by response surface methodology

Health System for Dengue Control in Singapore

Dengue fever/dengue haemorrhagic fever (DF/DHF) first appeared in Singapore in an outbreak in 1960. In 1966, the Ministry of Health established the Vector Control Unit which was charged with the responsibility of controlling the dengue vector mosquitoes, Aedes aegypti and Aedes albopictus. The Unit immediately launched an Aedes control programme based on source reduction and public health education. To obtain reliable statistics on disease incidence, DF/DHF was made administratively notifiable in 1966, and finally, legally notifiable in 1977. It was also recognized early in the control programme that long-term and active participation by the community was essential for its implementation. A new legislation called the Destruction of Disease-Bearing Insects Act was thus enacted in 1968. The Act empowers vector control officers to enter and examine houses for mosquito breeding, to take appropriate control measures, and to serve offenders with orders and summonses which carry a fine or imprisonment by the court. With the new legislation in force, the Aedes control programme adopted an integrated approach of source reduction, public health education and law enforcement. When the new Ministry of the Environment was formed in 1972 to take over the responsibility of environmental health, its Vector Control and Research Department and the Quarantine & Epidemiology Department became responsible for the surveillance and control of DF/DHF in the country. Surveillance of disease incidence and Aedes vectors is important in the prevention and control of DF/DHF outbreaks. Disease surveillance is conducted by officers of the Quarantine & Epidemiology Department based on notifications on clinically diagnosed cases as well as on the number of blood specimens submitted by hospitals, clinics, and private practitioners to the Virology Division of the Department of Pathology in the Ministry of Health and the Department of Microbiology of the National University of Singapore for laboratory confirmation of dengue infection. Aedes surveillance depends on regular surveys of mosquito larvae and adults in designated DF/DHF-sensitive areas. In addition to destruction of breeding habitats, fogging is carried out when the Aedes house index is 2% and above, or when a potential outbreak situation arises such as the occurrence of a focus of two or more DF/DHF cases in an area

Epidemiology of Dengue in Singapore-Current Situation

There has been a resurgence of dengue fever/dengue haemorrhagic fever (DF/DHF) cases in Singapore in recent years. Following the large outreak in 1973 with 1,187 cases and 27 deaths, the incidence of DF/DHF declined with minor bi-annual outbreaks occurring in 1978, 1980 and 1982. Beginning from 1986, however, the DF/DHF situation changed for the worse when outbreaks of increasing size occurred almost annually. In the past 3 years, there were 1,733 cases in 1990, 2,179 cases in 1991 and 2,878 cases in 1992. In the 1991 and 1992 outbreaks, 93-95% of the notified cases required hospitalization and 92-95% of them were serologically confirmed by the IgM capture ELISA and/or the commercial Dengue Blot assay. The number of fatal cases, however, remained low with 3-6 reported deaths in the three outbreaks. All age groups were affected with the highest morbidity rate in children and young adults between 15 and 24 years of age. In contrast, in the earlier 1973 and 1978 outbreaks, more patients below the age of 15 years were observed. There was a slight predominance among males and Chinese had the highest morbidity rate compared with Malays and Indians. The recent outbreaks occurred mainly in highly populated urban and suburban areas in the eastern, northeastern and southeastern parts of the island. Patients living in landed property such as compound houses had a 9X higher morbidity rate than those living in high-rise flats. Cases were reported throughout the year and the number increased during May and June. The increased DF/DHF incidence was preceded by an increase in the Aedes mosquito population. In the 1991 and 1992 outbreaks, although the overall Aedes house index was<1 for both Ae aegypti and Ae albopictus higher indices were detected in localized areas with high dengue transmission. The proportion of compound houses found breeding Ae aegypti was 3-4 times and Ae albopictus 7-10 times higher than that of flats. The major breeding habitats were ornamental and domestic containers and discarded receptacles