Eckhard Flöter

Organogel-Emulsions with Mixtures of β-Sitosterol and γ-Oryzanol: Influence of Water Activity and Type of Oil Phase on Gelling Capability

In this study, water-in-oil emulsions were prepared from water containing different salt concentrations dispersed in an oil phase containing a mixture of β-sitosterol and γ-oryzanol. In pure oil, the β-sitosterol and γ-oryzanol molecules self-assemble into tubular microstructures to produce a firm organogel. However, in the emulsion, the water molecules bind to the β-sitosterol molecules, forming monohydrate crystals that hinder the formation of the tubules and resulting in a weaker emulsion-gel. Addition of salt to the water phase decreases the water activity, thereby suppressing the formation of sitosterol monohydrate crystals even after prolonged storage times (∼1 year). When the emulsions were prepared with less polar oils, the tubular microstructure was promoted, which significantly increased the firmness of the emulsion-gel. The main conclusion of this study is that the formation of oryzanol and sitosterol tubular microstructure in the emulsion can be promoted by reducing the water activity and/or by using oils of low polarity.

Foods with a High Fat Quality Are Essential for Healthy Diets

Fat is generally a highly valued element of the diet to provide energy, palatability to dry foods or to serve as a cooking medium. However, some foods rich in fat have a low fat quality with respect to nutrition, i.e., a relative high content of saturated (SFA) as compared to unsaturated fatty acids, whereas others have a more desirable fat quality, i.e., a relative high content of unsaturated fatty acids as compared to SFA. High-fat dairy products and fatty meats are examples of foods with low fat quality, whereas vegetable oils (tropical oils such as palm and coconut oil excluded) are products with a generally high fat quality. The aim of this paper is to explore the nutritional impact of products made of vegetable oils, e.g. margarines and dressings, and how they can be designed to contribute to good health. Since their first industrial production, the food industry has endeavored to improve products like margarines, including their nutritional characteristics. With evolving nutrition science, margarines and cooking products, and to a lesser extent dressings, have been adapted to contain less trans fatty acids (TFA), less SFA and more essential (polyunsaturated, PUFA) fatty acids. This has been possible by using careful fat and oil selection and modification processes. By blending vegetable oils rich in the essential PUFAs α-linolenic acid (vegetable omega–3) or linoleic acid (omega–6), margarines and dressings with both essential fatty acids present in significant quantities can be realized. In addition, full hydrogenation and fat rearrangement have enabled the production of cost-effective margarines virtually devoid of TFA and low in SFA. Dietary surveys indicate that vegetable oils, soft margarines and dressings are indeed often important sources of essential fatty acids in people’s diets, whilst providing negligible amounts of TFA and contributing modestly to SFA intakes. Based on empirical and epidemiological data, the public health benefit of switching from products with a low fat quality to products with a high fat quality can be predicted. For example, switching from butter or palm oil to a soft margarine shows a substantial improvement in the nutritional quality of the diet. These simple, practical dietary adaptations can be expected to contribute to the healthy growth and development of children and to reduce the burden of cardiovascular disease.

Developing products with modified fats.

Publisher Summary Designing products with nutritionally enhanced characteristics is a challenge. Successful products need to deliver a credible health benefit and be good products with respect to their perceivable properties. The benchmark for the perceivable properties that can be assessed by the consumer directly on usage are the generic products. Alternative attempts to provide the consumer with visible cues in healthy products have not yet been successful. The key challenge for the food scientist is to significantly change the products in their composition but to at least maintain their primary quality attributes. In practice, this means maintaining the product structure and delivering oral melting and taste sensation with a reduced fat phase that contains fewer saturated fatty acids. Additionally, it can be expected that almost all nutrition-enhancing ingredients would increase the sensitivity of the product to chemical changes. These have to be kept at a minimum. To achieve this, one either improves the raw material quality and manufacturing practices or takes chemical measures and introduces additional sequestering ingredients to inhibit oxidation.

Stability of aqueous food grade fibrillar systems against pH change

We report that the stability of an aqueous food grade fibril system upon pH change is affected by the presence of peptides that are formed during the process of fibril formation. We discuss several other relationships between food relevant properties and nano-scale characteristics, and compare these relationships for aqueous fibril systems to those of oil based fibril systems. In such fibril systems, dynamics, self-organisation, and sensitivity to external conditions, play an important role. These aspects are common to complex systems in general and define the future challenge in relating functional properties of food to molecular scale properties of their ingredients.

Edible oil organogels based on self-assembled β-sitosterol+γ-oryzanol tubules.

Publisher Summary It would be desirable to reduce the amount of crystallizing Triacylglycerols (TAGs) and increase the amount of liquid TAGs, containing predominantly Mono-Unsaturated Fatty Acids (MUFAs) and Polyunsaturated Fatty Acids (PUFAs). One way to achieve this is to replace the SAFA-rich crystalline TAGs by an alternative structuring agent. This chapter presents a concise summary of the way that crystalline TAGs structure a lipid phase consisting of liquid TAGs. The firmness of the crystalline TAG network increases with smaller crystals and with higher surface-to-volume ratio and the degree of oil exudation decreases with finer pore size of the network. Alternative structurants can be chosen to mirror this behavior and this can be achieved in a relatively straightforward way in systems for which structuring is based on the crystallization behavior of fatty acids. One can also try to base structuring on fundamentally different modes of molecular assembly. An alternative food structurant should comply with a number of other restrictions. A number of recent reviews have considered the question to what extent currently known systems satisfy these two sets of requirements. The structuring system based on mixtures of a plant sterol and a plant sterol ester, β-sitosterol and γ-oryzanol, seems to emerge amongst the most interesting candidates. The chapter shows that these mixtures form a slightly hazy transparent gel in triglyceride oil, whereas the single components do not. The structure of the mixture bears little resemblance to that of the pure components. The chapter provides a comprehensive review of this system and a number of closely related systems. It describes the single components and the kinetics and structure of the self-assembled structures, discusses the rheology of the (water-free) organogels and the behavior of this type of structuring in the presence of water and further presents a number of potential applications of the oryzanol + sterol mixture.

The Phase Behavior of γ-Oryzanol and β-Sitosterol in Edible Oil

The phase behavior of binary mixtures of γ-oryzanol and β-sitosterol and ternary mixtures of γ-oryzanol and β-sitosterol in sunflower oil was studied. Binary mixtures of γ-oryzanol and β-sitosterol show double-eutectic behavior. Complex phase behavior with two intermediate mixed solid phases was derived from differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) data, in which a compound that consists of γ-oryzanol and β-sitosterol molecules at a specific ratio can be formed. SAXS shows that the organization of γ-oryzanol and β-sitosterol in the mixed phases is different from the structure of tubules in ternary systems. Ternary mixtures including sunflower oil do not show a sudden structural transition from the compound to a tubule, but a gradual transition occurs as γ-oryzanol and β-sitosterol are diluted in edible oil. The same behavior is observed when melting binary mixtures of γ-oryzanol and β-sitosterol at higher temperatures. This indicates the feasibility of having an organogelling agent in dynamic exchange between solid and liquid phase, which is an essential feature of triglyceride networks.

Solid immiscibility in milk fat fractions and methods to determine their occurrence

In this work, the occurrence of solid phase immiscibility during the fractionation process of milk fat is documented. It is shown that solid phase immiscibility occurs in normal fractionation procedures, upon crystallisation at low temperatures and in particular on further fractionation of narrow melting fractions. This phenomenon results in distinct phases of crystallisation. In some cases, the initial phase yields intermediate solid levels independent of increasing supersaturation. The subsequent increase of solids content is solely a contribution of a second, independent crystallisation event. Furthermore, it could be shown that the induction time for the second crystallisation event is not influenced by the presence or absence of the first triacylglyceride group. These results clearly indicate the independence of the crystallisation of the different immiscible fractions in terms of kinetics and thermodynamics. The different processes during the crystallisation process are monitored simply by viscosimetry.

Effect of quality and origin of technical sucrose solutions on the inclusion of colourants into the sugar crystal matrix

BACKGROUND Due to the liberalisation of the European sugar market the pressure to improve factory utilisation is growing. Currently, beet and cane as sucrose sources are produced in isolation, according to geography. Co-production of sugar from beet and cane origin in one stream is a promising option. However, the knowledge base for production sugar is practically non-existent. This paper is part of our contribution to this field and specifically addresses effects of raw material quality. RESULTS This framework formulated for the colouring of sugars crystallised from mixed syrups is also valid for different raw material qualities: raw cane sugars: colour values 1221 to 2505 IU, dextran levels 50 to 1200 mg kg-1 ; beet syrups: 1509 to 2058 IU. Co-crystallisation is the main colour incorporation mechanism. Colour due to liquid inclusion increases strongly at cane inclusion levels in excess of 60%. The prediction of final sugar colour based on characteristics of pure mixture constituents is verified and indicates significant differences to current recommendations. CONCLUSION A first comprehensive description of the colour values in sugars produced from mixed cane and beet syrups is presented. Prediction of colour values from data on sugar colour of single sources marks a major contribution to future applications of co-production.

CHAPTER 5:Structuring Edible Oil Phases with Fatty Acids and Alcohols

The properties of edible oil gels structured with fatty acids, fatty alcohols or their mixtures are reviewed in terms of the polymorphism (X-ray scattering) and crystal morphology (microscopy) of the structurants and the texture (small and large deformation rheology) of the gels. A number of potential applications presented in the patent literature are assessed against criteria that can be used to score the likelihood of success of the oil structuring technology in the market.

Non-triglyceride structuring of edible oils and emulsions

The structure of oil-continuous products, such as margarine or butter, is based on a network of small crystallites of triglycerides (also known as triacylglycerols or TAGs). Low molecular weight structuring agents that can serve as an alternative to crystallising triglycerides in edible oils have raised considerable interest in recent years. The requirement that potential structurants should at least hold the promise to be allowed in food applications is a severe limitation. Nevertheless, several systems have been identified [1], amongst which the class of γ-oryzanol + sterol organogelators is the most intriguing representative [2]. Small-angle X-ray scattering (SAXS) studies demonstrated that mixtures of β-sitosterol and γ-oryzanol form tubules in triglyceride oil with a diameter of 7.2±0.1 nm and a wall thickness of 0.8±0.2 nm [3]. Mixtures of β-sitosterol and γ-oryzanol in emulsions at 16% total sterols show scattering data containing reflections of mainly β-sitosterol monohydrate crystals. Evidence for the formation of tubules is not found in these emulsion systems, indicating that transitions from anhydrous and hemi-hydrate to monohydrate formation prevent this self-assembled supra-molecular ordering. Intermolecular hydrogen bonding is playing an important role in the formation of the tubules and hydration of sterols might exclude the appearance of this bonding [4]. The stability of the tubules in the presence of water is critical for the applicability of these organogelling systems in the structuring of food emulsions. A decrease of the water activity by salt suppresses the hydration of sterols and promotes tubule formation.