Baking using oleogels

Abstract

Food Science and TechnologyVolume 37, Issue 1 p. 23-25 FeaturesFree Access Baking using oleogels First published: 08 March 2023 https://doi.org/10.1002/fsat.3701_6.xAboutSectionsPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Vincenzo Di Bari from the University of Nottingham explains fat functionality in food applications and provides reformulation strategies that could be used to reduce food products’ saturated and trans-fat content via oleogelation. Fat functionality and reformulation strategies Edible lipids are a broad class of biological molecules, generally characterized by poor solubility in water and referred to as ‘hydrophobic’ materials. In food sciences, lipids are usually classified into ‘fats’ and ‘oils’, with the difference dictated by their physical state at ambient temperature: fats appear solid, oils are liquid. This classification is empirical since ambient temperature values differ depending on several environmental factors. Furthermore, some ‘oils’, e.g., palm and coconut oil, appear as solids at ambient temperature (20°C-25°C) and are considered ‘fats’ from a functionality standpoint. When formulating a product, the type of lipids chosen is strongly dictated by the functionality required during processing, storage, and consumption. The following sections discuss fats functionality in bakery applications and examples of reformulation strategies to reduce saturated and trans-fats. Fats functionality in bakery applications The underlying reason why fats are solid at ambient temperature lies in their chemical composition: fats are made up to triglycerides rich in saturated fatty acids. At sufficiently low temperatures these molecules can establish intermolecular hydrophobic interactions leading to the formation of crystals, which aggregate into a semisolid three-dimensional network[1]. Fats are unique food ingredients that play several functional properties: on cooking they are a medium for heat transfer, perform a shortening role in pastries and biscuits[2], aid aeration in cakes and puff pastry, and regulate lubrication, organoleptic properties such as mouthfeel and flavours release profile[3]. In some cases can present resistance to oxidative stress and spoilage[4, 5]. In pastries and biscuits, where the fat content can exceed 30% (wt%), the shortening property is crucial to product quality. The term 'shortening’ refers to the ability to limit the hydration and interaction of gluten proteins and starch granules of the flour limiting structure formation, resulting in a crumbly, tender, uniform and light texture[6-9]. To obtain quality baked goods, fat physicochemical characteristics need to be considered; solid fat content (SFC), polymorphic form, melting point, plasticity and consistency[10]. Fat chemical composition, processing history and post-processing conditions (storage temperature, transportation, mixing with other ingredients, etc.) affect the physicochemical properties, with SFC and crystal polymorphic form being key parameters. The SFC, i.e., the percentage of fat in a solid state, and its temperature-dependent variation are key properties considered for puff pastry applications[11]. The SFC of commercial fats and margarines play a significant role in shortening as the high melting points enable the shortening to withstand high baking temperatures leading to a more stable batter emulsion[12]. Fat polymorphism is another property that is important in determining its functionality and behaviour when used in food matrices. There are different polymorphic forms labelled as α, β′ and β crystals[13, 14], with the α and β forms being the most unstable and stable, respectively. Research suggests that the β′ is most suitable for bakery products because it provides good shortening properties, ideal for pastry[15], and in bakery applications where the crystals stabilise the incorporated air cell (until melting during baking)[7](Figure 1) Figure 1Open in figure viewerPowerPoint Example of cake manufactured using baking margarine. Current commercial fats are produced by the hydrogeneration of vegetable oils. This process involves the addition of hydrogens aiming for the conversion of cis-double bonds, typical of unsaturated fatty acids (FA), to form saturated ones, determining a conversion from liquid to solid. This process also involves the production of trans-isomers, which are commonly known as ’trans-fats’. Trans-isomers of FA, produced in the partial hydrogenation of vegetable oils, display a straight hydrocarbon chain that can pack together tightly, improving the fat functionality and quality of the products[16]. However, data also suggests that industrially produced trans-fats are more detrimental to health than natural saturated fats, as they increase LDL (bad) cholesterol, reduce HDL (good) cholesterol[17] while also increasing lipoprotein and triglyceride levels, which are associated with coronary heart diseases development[18]. Coconut oil and palm oil are both saturated-rich fats of plant origin and are often used in the food industry to replace trans-fats. The World Health Organisation recommends that saturated fat content should not exceed 10% of total fat intake with the total fat content not exceeding 30% of the total calories for a healthy diet[12]. Increasing environmental and sustainability concerns associated with tropical fat farming and health concerns associated with saturated-rich fats are strong drivers for their replacement. With more people consuming high-fat food products[19], eliminating trans-fats and reducing the saturated fat content of foods has become a global health objective, which to date has seen limited success due to the challenge of identifying valuable alternatives. In order to address such issues, a new formulation approach known as ‘oleogelation’ could be a solution. Trans- and Saturated fat replacement in bakery products: Oleogels Saturated and trans-fats are difficult to replace due to their unique structures and functional properties that allow them to coat flour particles, giving rise to the shortening properties. In shortcrust pastry the selection of fat is important: if the fat is too soft then it will not mix with the flour properly, while if the fat is too hard the pastry will be too tough[20]. In puff pastry fats are necessary to separate the dough layers and trap water vapour on baking, resulting in the desirable expanded structure. Key requirements for alternatives to be considered and adopted by the food industry are: better health, sustainability, and environmental profile than conventional fats; be manufactured easily and at comparable costs; display the same functional properties as fats. Several examples are reported in the literature where carbohydrates and proteins structured hydrogels are discussed. Here we focus on a formulation technology approach called ‘oleogelation’ to produce oil-based gels, e.g., oleogels. Oleogels are semi-solid structures, where the gelator, i.e. the gel-forming molecule, entraps the liquid oil within a self-supporting three-dimensional network providing a solid-like consistency and plasticity similar to that of fats. This technology relies on the blending of ingredients (oil and oleogelator) with different and complementary physical properties and does not involve any chemical modification of the oil. Oleogelations offers the opportunity to improve the functionality of healthy unsaturated oils by structuring them into a physical state that mimics the functionality of fats, without the production of trans-fats, and reducing the saturated fats content. Different oleogelators have been investigated and discussed in the literature[21, 22], among which waxes have emerged as one of the most promising class of compounds[23]. This is due to their ability to structure large amounts of unsaturated oils into a semi-solid gel at low concentrations (1-5%, wt/wt)[24, 25]. Waxes are underutilised by-products of the food industry meeting the demand for sustainable ingredients and a circular economy approach. The concentration of oleogelator and manufacturing conditions directly impact these systems’ appearance (Fig. 2) and functional properties. Whilst oleogels are already used in drugs and cosmetics, they have seen limited application in the food industry. Food-grade oleogelators include rice bran wax (RBW). RBW-based oleogels are made by heating the oil-wax blend above the wax melting point, followed by cooling to a final temperature allowing the crystals to form[21]. Wax-based oleogels are thermo-reversible gels: they can be heated and cooled without affecting the oleogelator functionality and can be tailored to obtain shape (Fig. 3) and desirable properties. Figure 2Open in figure viewerPowerPoint Appearance of rice bran wax-based oleogels at concentrations ranging from 0% (left-hand side) to 7% (wt/wt) (right-hand side) wax concentration. Figure 3Open in figure viewerPowerPoint Example of rice bran wax based-oleogels produced to mimic margarine shape and functionality. Work in Food Sciences at the University of Nottingham has focused on the research and development of RBW-based oleogels for shortcrust pastry and baking applications. Data suggest it is possible to formulate RBW-based oleogels with comparable functionality to palm oil in pastries. Confocal laser scanning (CLS) imaging allows to gain an insight on lipid functionality. In Figure 4 the microstructure of the investigated products is shown. In both products, i.e., the reference containing palm oil and the reformulated containing a RBW-based oleogel, the lipid phase (stained in red) coats the flour particles (of which only the edges are visible in Fig. 4), providing shortening functionality. No difference in the pastry's mechanical properties resulted from the fat type change (data not shown). Figure 4Open in figure viewerPowerPoint Confocal laser scanning image of pastry samples with fat stained in red. Fat phase is (left-hand side panel and sample) palm oil; (right-hand side panel and sample) rice-bran wax-based oleogel. Scale bar: 100 μm. Figure 5 shows the appearance of cakes prepared using butter (left-hand side panel) and a rice bran wax-based oleogel (right-hand side panel) as fat type. In both cases, the structure is well developed with air cells visible. This indicates that the lipid phase in both products was able to stabilise the air cell and support volumetric expansion. Texture profile analysis of the cakes revealed no difference in hardness and springiness between the two products (data not shown). These data suggest that oleogels can provide a feasible functional replacement for palm oil in bakery food applications. Figure 5Open in figure viewerPowerPoint Figure 5: Example of cakes baked using (left-hand side panel) butter and (right-hand side panel) a wax-based oleogel Conclusions Developing healthier, sustainable, and low-environmental impact alternatives to saturated and trans-fats is an area of active research interest, which requires immediate action to mitigate the global health and climate crisis we are facing. Due to the technological functionality and contribution to consumer acceptability, reducing fat content is a complex challenge, especially in food products that are high in fat[12]. While it is key to gain a deeper understanding of conventional fats behaviour in foods and of how processing affects their functionality, synergies between industry players across the supply chain, academic institutions, and food policy makers need to be developed quickly to identify, validate, and implement new and safe formulation approaches to tackle such challenge. Among those, the olegelation technology, which relies on the use of natural, underutilised sustainable ingredients, could provide the long-sought solution. Establishing nutritional reference values, validating technological functionality at the industrial scale, and determining consumer acceptability are key milestones to healthier products with low environmental impact, which can be delivered only by the concerted effort of all players in the sector Dr Vincenzo Di Bari, Assistant Professor in Food Structure and Processing, Faculty of Science, University of Nottingham email vincenzo.dibari@nottingham.ac.uk web nottingham.ac.uk/biosciences/people/vincenzo.Dibari References 1Marangoni, A. G., Acevedo, N., Maleky,a, F., Co, E., Peyronel, F. et al. 2012. Structure and Functionality of Edible Fats. Soft Matter 8: 1275- 1200. Available from: https://pubs.rsc.org/en/content/articlelanding/2012/sm/c1sm06234d 2Mamat, H., Hill. S. E. 2014. Effect of Fat Types on the Structural and Textural Properties of Dough and Semi-Sweet Biscuit. Journal of Food Science and Technology 51: 1998- 2005. 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