Self-assemblies of lecithin and a-tocopherol as gelators of lipid material

Amongst the different mechanisms that have been proposed and used to structure organogels, self-assembly of the gelators into supramolecular structures linked through non-covalent bonds is the most interesting. The gelator activity of LMGOs is often found most effective when micellar or lamellar phases are obtained, which is dependent on the gelator geometry and the specific packing parameter. Gelation can therefore be induced by altering the packing parameter of different gelators, but due to the law restrictions there are only a few edible gelators that can be used to structure edible lipids. Here, we show that a combination of a-tocopherol and phosphatidylcholine (PC) can be used to alter the packing geometry to provide supramolecular structures needed for the organogelation. We have observed that when the gelators were combined at 1:1 ratio in sunflower oil, edible organogels were obtained. The firmness of the solid-like material was enhanced when 1.0 wt% of water was added. The proposed mechanism for this assembly is that most likely cylindrical micellar structures are formed, due to combined assembly of the a-tocopherol and phosphatidylcholine, stabilized through physical interactions. Since these interactions, and the accompanied packing geometry, depends on temperature and application of external stresses, the formation of the organogels showed reversibility when the organogels were subjected to shear or when the temperature was increased to values above 35 oC. Polarized microscopy along with small angle X-ray scattering were used to provide a hypothesis for the mechanism behind the gelation

Efficient single-step rapeseed oleosome extraction using twin-screw press

Oil in seeds is encapsulated in oleosomes, which are small lipid droplets surrounded by a phospholipid-protein monolayer. The currently proposed method to extract intact oleosomes includes mixing seeds with alkaline media in a ratio 1:7, batch blending and filtering. In this work, we propose the use of a twin-screw press to perform the oleosome extraction at pH 7. The results show that similarly to blender extraction, twin-screw press recovers ⁓60% of the oleosomes; however the twin-screw press is able to achieve this yield even when just pure water is used. While in the blender extraction, the yield depends on ionic strength and pH of the extraction media, when using twin-screw press, the oleosome extraction yield predominantly depends on the mechanical forces. These shear forces are able to break the cell walls and release the cellular material while maintaining the integrity of oleosomes. The oleosomes extracted with twin-screw press have similar characteristics than those obtained by the blending process. Overall, twin-screw press seems a promising alternative to scale-up the oleosome aqueous extraction, especially as neutral pH can be used and the water usage is significantly reduced. Additionally, preliminary results showed that the yield can increase up to 90 wt%.</p

High internal phase emulsion gels (HIPE-gels) created through assembly of natural oil bodies

A natural emulsion was used to create a high internal phase emulsion (HIPE) gel with elastic properties, indicated by shear elastic moduli between 102 and 105 Pa. The elasticity of the gel network was provided from a 2D-gel network of proteins which were naturally adsorbed at the interface of an oil-in-water emulsion formed after aqueous extraction of oil bodies from sunflower seeds. Extensive centrifugation of the obtained emulsion resulted in a stable ultrahighly concentrated emulsion with an oil volume fraction of 0.91 and a protein content of 2.5 wt% only. This high volume fraction of the emulsion cream was achieved due to the large deformability (low rigidity) of the oil body surface. After formation of the HIPE, the rigidity of the interfacial network was increased by addition of small concentrations of Ca2+ and heating at 72 °C for 10 min. This led to aggregation of the interfacial proteins, thereby forming a 2D interfacial gel providing a space-spanning network. The behaviour of the self-supporting gel exhibited increased elastic behaviour, determined by the increased elastic modulus of the interfacial network. The balance between the low rigidity upon formation and the increased rigidity after formation offers a tempting strategy to produce structured solid matter that contains edible hydrophobic liquids. Additionally, the followed procedure is cost-effective and friendly to the environment

Polymer organogelation with chitin and chitin nanocrystals

In this paper, we show that biodegradable and biocompatible organogels can be formed with chitin as the filler material and triglycerides as the continuous hydrophobic phase. When crude chitin was used, a large degree of aggregation was observed that prevented the formation of stable organogels. Two approaches were used to diminish this degree of aggregation and increase the stability. Either surfactants were used to increase the dispersability of the crude chitin, or the crude chitin was transformed into smaller rod-like nanocrystals by acid hydrolysis. Both approaches led to the formation of stable organogels with storage moduli up to 106 Pa for high chitin concentrations (20 wt%). Three different types of surfactants were used, namely phosphatidylcholine, enzymatically modified phosphatidylcholine and sorbitan monostearate (Span 60). The choice of surfactant has a large influence on the gel strength and the temperature sensitivity of the gels. With chitin nanocrystals, in the presence of surfactants, larger gel strengths were observed for lower concentrations (1-10 wt%), indicating more efficient packing of the particles. Gels were stable even after addition of considerable amounts of water up to 25 wt%. The increase in gel strength in the presence of water (storage modulus) was most likely an effect of the water absorption ability of chitin that increased the effective volume fraction of the fillers

The role of Tween in inhibiting heat-induced destabilization of yolk-based emulsions

The process of heat-induced destabilization of yolk-based emulsions and the role of Tween addition in inhibiting droplet aggregation/coalescence in the thermally treated emulsions were investigated. The aim of the study was to understand the mechanism behind yolk emulsion destabilization during the application of processes such as pasteurization/sterilization and/or cooking. Data on emulsion particle size distribution were combined with results on yolk protein adsorption to clarify the role of the unadsorbed yolk protein fraction in the destabilization of the thermally treated emulsion. Surface tension measurements were also conducted to investigate yolk protein-Tween interactions at the air/water interface and their effect on emulsion stability. The presence in the emulsion continuous phase of unadsorbed yolk protein is crucial for the thermal destabilization of the system. Tween addition inhibits droplet flocculation/coalescence phenomena by shielding the reactive groups of protein molecules adsorbed at the droplet surfaces and those of unadsorbed proteins in the emulsion continuous phase which become available for interaction following heating and protein denaturation

Composition, properties and potential food applications of natural emulsions and cream materials based on oil bodies

Oil bodies are micron- or submicron-sized organelles found mainly in parts of plants such as seeds, nuts or some fruits and their main role is to function as energy stores. Their structure is made up of a core of triglycerides covered by a protein–phospholipid layer which protects the oil bodies against external chemical/mechanical stresses. Following treatment with aqueous media of the rich-in-oil raw materials, an extract of oil bodies, dispersed in a solution of exogenous plant proteins, is obtained. Effective recovery of oil droplets from the initial extract, which is in effect a relatively dilute natural emulsion, leads to the preparation of either a more concentrated natural emulsion with a composition in terms of oil and protein close to that of animal milk or, alternatively, to a concentrated oil droplet-based “cream”. Both the natural emulsion and the “cream” can be exploited in the development of a number of novel food products by suitably substituting the oil/fat droplets of the traditionally-prepared food product with natural oil droplets

Organogel formation via supramolecular assembly of oleic acid and sodium oleate

To create materials with novel functionalities, the formation of gels within hydrophobic media has become popular. This is often accomplished through the assembly of low molecular weight organogelators into a variety of complex phases through intermolecular interactions. In the case of edible materials, the assembly of saturated fatty acids to form fat crystal networks is often used for structuring. Here, the first example of structuring with unsaturated fatty acids is reported, namely mixtures of oleic acid and sodium oleate, to structure edible lipid phases. Small-angle scattering demonstrates that the resultant structures, which vary with oleic acid and sodium oleate molar ratio, comprise either inverse micellar or lamellar phases, combined with the formation of crystalline space-filling networks. Network formation was found for filler concentrations above 10 wt%. Rheological measurements show that gel strength depends on the ratio of oleic acid to sodium oleate, and is greater when only oleic acid is used. The addition of up to 1.5 wt% of water enhanced the strength of the organogels, probably through supplementary hydrogen bonding but, for concentrations greater than 2.0 wt%, the assembly was inhibited leading to collapse of the gel

Potential use of Rosemary, Propolis and Thyme as Natural Food Preservatives

The use of preservatives in food stuffs and beverages is essential in order to prevent spoilage due to microbial growth or undesirable chemical changes. However, the use of synthetic additives has been associated with various health problems. Therefore, consumers have turned suspicious and obverted towards ingredients from natural sources. This tendency has driven food industry in further search and development of “natural preservatives”, to extend the shelf life of its products and maintain their safety. This report is focused on the current status of the natural derived preservatives and potential use of propolis, thyme and rosemary as sources for the development of effective preservatives

Quality characteristics of egg-reduced pound cakes following WPI and emulsifier incorporation

The effect of partial (50 wt%) or total liquid egg replacement by whey proteins in combination with emulsifiers, i.e. hydroxypropylmethylcellulose (HPMC) and sodium stearoyl-2-lactylate (SSL), on the quality of pound cakes was investigated. Cakes containing whey protein isolate (WPI) solutions of varying concentrations (i.e. 20, 17 and 14% w/v) were first prepared. Complete egg replacement by WPI led to the preparation of cake batter of increased specific gravity as well as to final cake products of inferior quality with regard to volume, texture and hardness increase upon storage, compared to the control. In the case of partial liquid egg replacement by WPI solutions, cakes with acceptable sensory and quality characteristics were obtained, which were further improved following the addition of emulsifiers. During a storage period of four days the egg-reduced cakes exhibited a significantly lower staling rate depending mainly on the concentration of WPI and the presence of emulsifiers. Finally, the analysis of cake microstructure confirmed the positive effect of the co-addition of whey proteins and emulsifiers in egg-reduced cakes. This work made it possible to develop an alternative, egg-reduced cake of satisfactory quality, by using a combination of whey proteins with two common baking additives