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Plant Particle based Hybrid Bicontinuous Oleogels

Periodic Reporting for period 1 - PlantOleogels (Plant Particle based Hybrid Bicontinuous Oleogels)

Reporting period: 2018-11-01 to 2020-10-31

Dietary intake of excess trans fatty acids and to a lesser extent, excess saturated fatty acids along with insufficient n-6 polyunsaturated fatty acids, has been estimated to increase coronary heart disease (CHD) mortality worldwide. Over the years, almost entire removal of hardstock trans fats has been achieved; whereas full substitution of hardstock long-chain saturated fatty acids (e.g. palmitic acid) by unsaturated fatty acids (i.e. liquid oil) has proven elusive. Substitution of saturated fats brings unprecedented industrial challenges, as their removal affects adversely physical properties, functionality, stability and sensory attributes of oil-based suspensions, leading to food products poor in quality and consumer acceptability. Furthermore, in addition to address the technological challenges brought about by the subsitution of saturated fats, it is desirable that any oil-structuring alternative to be “clean label” or free of additives, to boost their acceptability and commercialization. Currently, there are limited commercially-viable strategies to formulate healthier fats within the field of gelled oils or oleogels. None of the current ‘oleogel’ are suitable for food applications as they do only meet partially the following criteria: 1) being food grade, natural, 2) complement physical characteristics of fats such as temperature induced melting, 3) mimic or complement the rheology and texture of solid saturated lipids. Besides this criteria, it is of paramount important to establish links between the mesoscopic structure and mechanics of the developed oleogel systems. To address this grand industrial and fundamental challenge, we proposed to design novel hybrid ‘oleogels’ using a biomimetic approach based on edible plant particles along with economical solid fat sources, and understand the underlying structure, physical properties, and texture. To achieve this goal, we specifically met the following objectives: (1) Developed oil continuous colloidal gels and colloidal glasses based on individual/binary mixtures of plant derived edible colloidal nanoscale particles, (2) Developed new hybrid systems: bicontinuous glass-gel networks and bicontinuous gel networks, comprising individual/binary mixtures of colloidal particles along with the fat particles to introduce temperature melting and (3) Established structure and rheology relationships in (1) and (2), and (4) Extended findings from specific goals 1-3, to develop commercially-viable hybrid oleogel systems. Overall, we arrived to the following conclusions: 1) the mechanics of model suspensions of glass-gel and gel-gel comprising starch or micro fibrillated cellulose, and lipid particles can be closely described by phenomenological models for particle-filled yield stress fluids, and micromechanical models proposed for interpenetrating multiphase composites, 2) the mechanics of the previously mentioned systems depend on two main observables: total volume fraction, and mixture composition or the relative concentrations of colloidal species, 3) Bonding and caging mechanics, dependent on the observables, define static structures and dynamic properties and 4) The model glass-gel and gel-gel oil-continuous soft materials can be realized with commercially-relevant food-grade ingredients.
We processed plant colloidal particles: cellulose and starch by mechanical deagglomeration and dispersed them in oil, or oil was dispersed in the present of these particles (emulsion-based approach). We devised two strategies to create oleogel systems with starch and cellulose. The first approach consisted in creating attractive capillary interactions in starch, whereas the second approach consisted in designing a cellulose-based emulsion followed by its water removal. Additional fundamental studies were conducted using model food-grade particles: silica colloids. Our results showed that depending on volume fraction and mixture composition (ratio of colloidal particle-to-solid lipid particle), silica-lipid bigels stiffen, and toughen, bearing larger deformations prior to yielding or material fluidization. We exploited these systems in 3D-printing of edible soft constructs. By studying silica-lipid model systems, we anticipated the effects of variables: volume fraction and mixture composition on the structure and mechanics of gel-glass and bicontinuous interpenetrated gel networks bigels from cellulose microfibrils and starch nanoparticles and fat crystal networks. In these systems, we found scaling laws based on volume fraction that describe the reinforcement of plant particles devoid of any physical interaction, in lipid gels. Remarkably, we found analogues between the mechanical reinforcement of plant particle fillers and that of passive rigid spherical fillers embedded in model yield fluids. Our results can be generalized to dense and concentrated oil-continuous suspensions found in consumer products industries. We also elucidated the effect of attractive interactions, the elastic modulus of starch or cellulose-lipid bigels, which can be described by additive effects of the individual elastic gel constants. Building upon this knowledge, we translated our findings to more complex oleogel systems using industrial relevant fat base stocks and the creation of plant-based ingredients such as fat mimetics sought to be exploited in the fabrication of plant-based meat analogues. For all systems developed links between structure and mechanics were established using the following main techniques: microscopy (light, confocal, SEM), mechanical (tensile and oscillatory shear rheology).
All the results have been reported in internal meetings and internal reports (confidential according to the contract) within the host institute. Inventions are being identified and two patent applications are being prepared within the host institute (Unilever R&D, Wageningen). All results are publishable and are under review and in preparation for submission in international peer-reviewed journals, as indicated, and provided on the online platform.
Through this research proposal and its execution, we have advanced understanding of hybrid oleogels where attractive or glassy colloidal or granular gels coexist with a fat crystal network gel, which is relevant to the scientific community. The expected results until the end of this project is the expansion of the design oleogel toolbox to structure oils with reduced amounts of solid saturated fats, while attaining textural and melting characteristics similar to 'pure' solid fat gels. The socio-economical of this project is evident through the creation of proprietary oil-structuring technologies that aim to support the creation of "healthier" oil-based food products, as well as support and offer dietary alternatives through plant-based foods within the European community.
Mixed particle-fat crystal gesl (intepenetrating networks with particles)