Fatty acid and sterol composition of frozen and freeze-dried New Zealand green lipped mussel (Perna canaliculus) from three sites in New Zealand

In view of previously reported anti-inflammatory bioactivity of the New Zealand Green Lipped Mussel (NZGLM), the overall lipid profile and fatty acid and sterol composition of the NZGLM from various sites in New Zealand (Hallam Cove, Port Ligar, Little Nikau) were investigated using thin layer  chromatography (TLC) and gas liquid chromatography (GLC). Samples were either frozen (F) or freeze-dried (FD) soon after collection. It was also thought prior to the study, there may be differences in the dietary sources of phytoplankton between the sites, responsible for the bioactivity, however data collected in New Zealand reported no difference in the type of phytoplankton, but a difference in the quantity. There were no major significant differences in the major components of the lipid, fatty acid and sterol composition between FD or frozen samples, nor were there any significant differences in the major composition between sites. The only major difference was between total lipid composition of the freeze-dried and frozen samples due to the removal of water during freeze-drying. Total lipid content on a dry weight basis in FD samples was 8.4 g/100g tissue and was significantly higher than frozen samples (P < 0.05) and there was no significant site variation. The lipid class content between sites was also not significantly different as judged by TLC. Triglyceride (TG) lipid fraction appeared to be the most prominent in the frozen and FD samples. The free fatty acid (FFA) band was the next most prominent band and was visually more prominent in the frozen samples. Sterol esters (SE) were detected in higher amounts in the frozen samples compared with the FD samples. Phospholipid (PL) and sterols (ST) were distributed throughout all samples. Polyunsaturated fatty acids (PUFA) were the main group of fatty acids in both FD and frozen samples (45-46%), most of which were omega-3 (n-3) fatty acids (40-41%). Saturated fatty acids (SFA) accounted for approximately one quarter of total fatty acids, with little variation between FD and frozen samples. The major fatty acids of the NZGLM were docosahexaenoic acid (DHA; 22:6n-3) (19% in both FD and frozen samples), eicosapentaenoic acid (EPA; 20:5n-3) and palmitic acid (16:0) (15% in both FD and frozen samples). Cholesterol was the most prominent sterol (31% of total sterols). Other major sterols included desmosterol/ brassicasterol (co-eluting), 24-methylenecholesterol, trans-22-dehydrocholesterol, 24- nordehydrocholesterol and occelasterol. This study is unique as it compares the lipid composition of the NZGLM from three sites in New Zealand with the additional effect of processing. This is the second comparative study investigating the lipid, fatty acid and sterol composition of the NZGLM with added interest in the effect of freeze drying on the lipid content of the mussel. This study showed that there were no major significant differences in lipid, sterol and fatty acid composition between the FD and frozen samples of the NZGLM for three sites in New Zealand. Food chain studies and further research is warranted to investigate the presence and role of major and minor lipid.
components of the NZGLM.

Fabrication of carbon nanofiber by pyrolysis of freeze-dried cellulose nanofiber

The possibility of fabricating carbon nanofibers from cellulose nanofibers was investigated. Cellulose nanofiber of ~50 nm in diameter was produced using ball milling in an eco-friendly manner. The effect of the drying techniques of cellulose nanofibers on the morphology of carbon residue was studied. After pyrolysis of freeze-dried cellulose nanofibers below 600 °C, amorphous carbon fibers of ~20 nm in diameter were obtained. The pyrolysis of oven-dried precursors resulted in the loss of original fibrous structures. The different results arising from the two drying techniques are attributed to the difference in the spatial distance between cellulose nanofiber precursors.

Seasonal variations of lipid content and composition in perna viridis

The total lipid content, composition of main lipid classes, composition of sterols and composition of fatty acids in the main glycerolipids of Perna viridis were analyzed through four seasons using TLC-FID and GLC. Mussel samples were collected during different seasons between 2003 and 2004 from Shengsi Island, Zhejiang Province, China and stored frozen prior to freeze-drying and lipid extraction. Ten grams of dried mussel powder of each season were analyzed. Total lipid content ranged from 14.5 g/100 g in spring month to 7.8 g/100 g dried mussel powder in autumn month. The predominant lipid in spring month was triacylglycerol (TAG), however, in the other three seasons the phospholipids (PL) was the main lipid class. The most abundant fatty acid in TAG, PL and phosphatidylcholine (PC) was 16:0, with the summer samples having the highest proportion (24-30% of total fatty acid) and winter the lowest (14-22%). In phosphatidylethanolamine (PE), the spring samples had the highest proportions of 16:0. The predominant polyunsaturated fatty acids (PUFA) were 22:6n-3 and 20:5n-3 in TAG, PL, PE and PC (25-40%). The proportions of 22:6n-3 and 20:5n-3 were higher in spring than in other seasons in PL and PE. There were nine sterols identified, with cholesterol being the predominant sterol, and other main ones were desmostersol/brassicasterol and 24-methylenecholesterol. Proportions of other fatty acids in different lipid fractions and the sterol compositions as well also varied seasonally. There were subject to the seasonal variations. Differences in lipid content and composition, fatty acid composition in different lipid fractions may be caused by multiple factors such as lifecycle, sex, variation of plankton in different seasons and temperature, which could influence physiological activities and metabolism.

Architecture of macromolecular network of soft functional materials : from structure to function

An enhanced macromolecular nanofiber network and its implications have been developed by employing the understanding of its formation with an emphasis on its topological aspect. Using agarose aqueous solution as a typical example, the macromolecular nanofiber network of soft functional materials has been clearly visualized for the first time using the developed technique of field emission scanning electronic microscopy coupled with flash-freeze-drying. Both the systematic kinetic study and the image evidence indicates that the nanofiber network in soft functional materials such as agarose turns out to form through a self-expitaxial nucleation-controlled process. This new understanding enables us to engineer ultra functions of soft materials via nanofiber network architecture, which in turn opens up a new direction in nano fabrication.

Porous carbon nanotube/polyvinylidene fluoride composite material: Superhydrophobicity/superoleophilicity and tunability of electrical conductivity

Porous carbon nanotube/polyvinylidene fluoride (CNT/PVDF) composite material can be fabricated via formation and freeze-drying of a gel. The field emission scanning electron microscopy, nitrogen adsorption-desorption and pore size distribution analysis reveal that the introduction of a small amount of carbon nanotubes (CNTs) can effectively increase the surface roughness and porosity of polyvinylidene fluoride (PVDF). Contact angle measurements of water and oil indicate that the as-obtained composite material is superhydrophobic and superoleophilic. Further experiments demonstrate that these composite material can be efficiently used to separate/absorb the insoluble oil from oil polluted water as membrane/absorbent. Most importantly, the electrical conductivity of such porous CNT/PVDF composite material can be tuned by adjusting the mass ratio of CNT to PVDF without obviously changing the superhydrophobicity or superoleophilicity. The unique properties of the porous CNT/PVDF composite material make it a promising candidate for oil-polluted water treatment as well as water-repellent catalyst-supporting electrode material.

Complex coacervation with whey protein isolate and gum arabic for the microencapsulation of omega-3 rich tuna oil.

Tuna oil rich in omega-3 fatty acids was microencapsulated in whey protein isolate (WPI)-gum arabic (GA) complex coacervates, and subsequently dried using spray and freeze drying to produce solid microcapsules. The oxidative stability, oil microencapsulation efficiency, surface oil and morphology of these solid microcapsules were determined. The complex coacervation process between WPI and GA was optimised in terms of pH, and WPI-to-GA ratio, using zeta potential, turbidity, and morphology of the microcapsules. The optimum pH and WPI-to-GA ratio for complex coacervation was found to be 3.75 and 3 : 1, respectively. The spray dried solid microcapsules had better stability against oxidation, higher oil microencapsulation efficiency and lower surface oil content compared to the freeze dried microcapsules. The surface of the spray dried microcapsules did not show microscopic pores while the surface of the freeze dried microcapsules was more porous. This study suggests that solid microcapsules of omega-3 rich oils can be produced using WPI-GA complex coacervates followed by spray drying and these microcapsules can be quite stable against oxidation. These microcapsules can have many potential applications in the functional food and nutraceuticals industry.

Carbon nanotube based elastomer composites-an approach towards multifunctional materials

The current study focuses on giving a basic understanding of tubular graphene sheets or carbon nanotubes (CNTs) and points towards their role in fabricating elastomer composites. Since the properties and the performance of CNT reinforced elastomer composites predominantly depend on the rate of dispersion of fillers in the matrix, the physical and chemical interaction of polymer chains with the nanotubes, crosslinking chemistry of rubbers and the orientation of the tubes within the matrix, here, a thorough study of these topics is carried out. For this, various techniques of composite manufacturing such as pulverization, heterocoagulation, freeze drying, etc. are discussed by emphasizing the dispersion and alignment of CNTs in elastomers. The importance of the functionalization technique as well as the confinement effect of nanotubes in elastomer media is derived. In a word, this article is aimed exclusively at addressing the prevailing problems related to the CNT dispersion in various rubber matrices, the solutions to produce advanced high-performance elastomeric composites and various fields of applications of such composites, especially electronics. Special attention has also been given to the non-linear viscoelasticity effects of elastomers such as the Payne effect, Mullin's effect and hysteresis in regulating the composite properties. Moreover, the current challenges and opportunities for efficiently translating the extraordinary electrical properties of CNTs to rubbery matrices are also dealt with.

Optimisation of the microencapsulation of tuna oil in gelatin-sodium hexametaphosphate using complex coacervation.

The microencapsulation of tuna oil in gelatin-sodium hexametaphosphate (SHMP) using complex coacervation was optimised for the stabilisation of omega-3 oils, for use as a functional food ingredient. Firstly, oil stability was optimised by comparing the accelerated stability of tuna oil in the presence of various commercial antioxidants, using a Rancimat™. Then zeta-potential (mV), turbidity and coacervate yield (%) were measured and optimised for complex coacervation. The highest yield of complex coacervate was obtained at pH 4.7 and at a gelatin to SHMP ratio of 15:1. Multi-core microcapsules were formed when the mixed microencapsulation system was cooled to 5 °C at a rate of 12 °C/h. Crosslinking with transglutaminase followed by freeze drying resulted in a dried powder with an encapsulation efficiency of 99.82% and a payload of 52.56%. Some 98.56% of the oil was successfully microencapsulated and accelerated stability using a Rancimat™ showed stability more than double that of non-encapsulated oil.

Co-encapsulation and characterisation of omega-3 fatty acids and probiotic bacteria in whey protein isolate-gum Arabic complex coacervates

Omega-3 fatty acids and probiotic bacteria were co-encapsulated in a single whey protein isolate (WPI)-gum Arabic (GA) complex coacervate microcapsule. Tuna oil (O) and Lactobacillus casei 431 (P) were used as models of omega-3 and probiotic bacteria, respectively. The co-microcapsules (WPI-P-O-GA) and L.casei containing microcapsules (WPI-P-GA) were converted into powder by using spray and freeze drying. The viability of L.casei was significantly higher in WPI-P-O-GA co-microcapsules than in WPI-P-GA. The oxidative stability of tuna oil was significantly higher in spray dried co-capsules than in freeze dried ones.

Hierarchical Nafion enhanced carbon aerogels for sensing applications

This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m(-1), and a specific capacity of 136.8 F g(-1) after reduction. Therefore, NECAG monoliths performed well as a gas sensor and as a biosensor with high sensitivity and selectivity. The remarkable sensitivity of 8.52 × 10(3)μA mM(-1) cm(-2) was obtained in dopamine (DA) detection, which is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template. These outstanding properties make the NECAG a promising electrode candidate for a wide range of applications. Further in-depth investigations are being undertaken to probe the structure-property relationship of NECAG monoliths prepared under various conditions.

Survival and fermentation activity of probiotic bacteria and oxidative stability of omega-3 oil in co-microcapsules during storage

Tuna oil (O) and probiotic bacteria Lactobacillus casei (P) were co-microencapsulated in whey protein isolate (WPI)-gum Arabic (GA) complex coacervate. The co-microcapsules (WPI-P-O-GA), L. casei microcapsules (WPI-P-GA) and tuna oil microcapsules (WPI-O-GA) were converted into powder using spray and freeze drying. The interaction between probiotic bacteria and omega-3 oil in co-microcapsules, particularly in terms of oxidative stability of omega-3 oil and vitality/viability of probiotic bacteria and any synergistic outcome, was studied. The effect of storage temperature (5 and 25 °C) and time (90 days) on the survival and fermentation activity of L. casei and oxidative stability of tuna oil in the microcapsules/co-microcapsules was determined. A synergism between oxidative stability of omega-3 oil and vitality of probiotic bacteria was observed, when they were co-microencapsulated and spray dried. These co-microcapsules will likely have utility in functional food formulations due to simple and cost effective stabilisation and delivery of two important functional ingredients.

Drying front in a sloping aquifier: nonlinear effects

The profiles for the water table height h(x, t) in a shallow sloping aquifer are reexamined with a solution of the nonlinear Boussinesq equation. We demonstrate that the previous anomaly first reported by Brutsaert [1994] that the point at which the water table h first becomes zero at x = L at time t = t c remains fixed at this point for all times t > t c is actually a result of the linearization of the Boussinesq equation and not, as previously suggested [ Brutsaert, 1994 ; Verhoest and Troch, 2000 ], a result of the Dupuit assumption. Rather, by examination of the nonlinear Boussinesq equation the drying front, i.e., the point x f at which h is zero for times t ≥ t c , actually recedes downslope as physically expected. This points out that the linear Boussinesq equation should be used carefully when a zero depth is obtained as the concept of an “average” depth loses meaning at that time.

Zooplankton dynamics from inundation to drying in a complex ephemeral floodplain-wetland

Ecological responses to wetting and drying in dryland river floodplain systems are often described in terms of “boom” and “bust”. We suggest that patterns in floodplain species abundances and assemblage structures will be closely linked to the changes in spatial habitat heterogeneity that accompany flooding and drying phases. This study examined the responses of zooplankton through a wetting and drying cycle in a complex floodplain-wetland system in semi-arid Australia, the Narran Lakes. We illustrate the complexity of the zooplankton “boom” and “bust” response. Total densities of zooplankton varied considerably over time and patterns were very dissimilar between sites with abundances varying from <30 animals/L to over 4000 animals/L. We detected different patterns in the proportion of variance in abundances of the broad taxonomic groups (rotifers, cladocerans, ostracods, calanoid copepods, cyclopoid copepods and nauplii) explained by time and space. Site explained the highest proportion of variation in cladoceran and ostracod abundances,whereas variance in calanoid abundances was explained predominantly by time since inundation. Variation in the abundances of the remaining groups was explained largely by the site by time interaction. Zooplankton assemblages were observed to diverge during drying with highest between-site dissimilarities in assemblage structure occurring during the later stages of drying. Such high spatial and temporal variability in zooplankton abundances and community composition could have important consequences for consumers such as fish and some wetland birds that utilize these ephemeral systems for feeding and breeding while they are inundated.