Erlenbusch, Nelli

Matthäus, Bertrand

Nikolay, Sharline

Schubert, Madline

Smit, Inga

Weber, Lydia

English

OA OpenAgrar repository

Oleogels as alternatives for frying fats andoilsDeep-fat frying is one of the most popular applications for thepreparation of food. It is fast, simple to handle, and results in highlyaccepted products due to the typical smell, taste, and palatability offried food. One pivotal aspect in the production of high-quality friedfood is the selection of an appropriate frying medium. During the fryingprocess, oil or fat serves as a medium that transfers heat from theheating source to the food [1]. Another important task of the fryingmedium is to enhance food’s  avor, which is responsible for the typicalsmell and taste of fried products. The selection of a suitable fryingmedium is also crucial for the quality of the  nal product. This isbecause a lot of fat or oil is taken up by the food, and the high amountsof fat in fried food in uence its shelf life, aroma, texture, and surfaceproperties.Bertrand Matthäus Madline Schubert Nelli Erlenbusch Inga Smit Lydia Weber andSharline NikolayOleogels are structured vegetable oils that behave like solid fats but have the samenutritional properties of liquid vegetable oils.Our research group recently did the first promising experiments to evaluate the use ofoleogels in deep-fat frying.This article describes the first initial results.Over the last 50 years, the trends for using fats and oils in food processing have changed severaltimes, driven especially by consumer awareness about nutritional quality. Fifty years ago, animal fatswere very popular due to their technological properties and high storage stability. Later, animal fatswere replaced by partially hydrogenated oils (PHO) due to concerns about the high cholesterolcontents of animal fats. Then, PHO was banned in many countries because they contain trans-fattyacids, which are suspected to cause cardiovascular heart diseases [2].Palm oil or modified fats became the replacement, but this has prompted strong discussion aboutenvironmental impacts and the high content of saturated fatty acids. Today, the use of highly stableliquid high-oleic oils or blends of different vegetable oils are preferred as a frying medium. Theydisplay some advantages with respect to nutritional aspects due to low amounts of saturated fattyacids, high contents of monounsaturated fatty acids, and an oxidative stability that is comparable withsolid fats. On the other side, the application of liquid oils gives fried food a greasy surface andcauses oil leakage during long-term storage.WHAT ARE OLEOGELS?Thus, the search for alternative fats or oils for food processing is an ongoing story. One promisingalternative to conventional frying media are oleogels. Oleogels have technological properties that aresimilar to those of solid triacylglycerol structured fats, but they display the nutritional properties ofliquid vegetable oils. While the structure of solid fats results from saturated fatty acids, which have amore-or-less linear structure and therefore allow a compact assembly of fatty acids, oleogels mainlyconsist of liquid oil and a small amount of a structuring agent known as an organogelator.Therefore, oleogels contain a high amount of unsaturated triacylglycerols, but the solid structure isprovided by the organogelator, which forms a 3-dimensional network in which the liquid oil isincorporated. Since the unsaturated fatty acids in the oleogel are not changed, the nutritional value ofthe liquid oil is preserved [3]. Many different structuring agents are applicable, such as ethyl cellulose,monoacylglycerols, fatty acids, phytosterols, alcohols, or waxes. Ethyl cellulose andmonoacylglycerols, for example, are already approved as food additives, waxes, such as sunflowerwax (SFW), have not been approved yet. The preparation of oleogels is a simple process thatincludes heating and stirring of the liquid oil in combination with the organogelator, just above itsmelting point. Finally, the mixture is cooled down to allow the formation of a gel-like structure, inwhich the liquid phase is embedded [4].OLEOGELS AS PROMISING ALTERNATIVES FORCONVENTIONAL FRYING MEDIAThe application of oleogels for food processing has been presented in the literature for someproducts [5-7], especially for bakery goods [8-10]. Only one scientific study has been published on theapplication of oleogels as an alternative to high saturated-fat frying media [11]. In this work, soybeanoil-based oleogels with carnauba wax as organogelator, were used to prepare instant fried noodles.The resulting products had a similar texture and more favorable fatty acid composition than noodlesfried in saturated fat.An alternative to carnauba wax obtained from leaves of the palm Copernicia prunifera, SFW is anatural constituent of sunflower seeds. This wax forms a protective layer on the seed surface, andnoticeable levels are extracted with the oil during oil processing. These high-melting waxes solidify atroom temperature, causing a visible white precipitation that is unappealing to consumers. Therefore,waxes are removed from the oil during oil processing by winterization, leading to a large quantity ofSFW that is readily available. SFW has not been approved as food additive yet, but since itsmolecular structure is similar to that of carnauba wax, SFW is likely to pass through the digestivetract unaltered as well—and to be approved in the coming years.Compared to frying with conventional fats, the application of rapeseed oil-based oleogels with SFWas an organogelator for the preparation of potato crisps or French fries offers several advantages:optimized surface properties, improved multi-sensory perception, and a more healthful fatty acidprofile that is lower in saturated fat and higher in unsaturated fatty acids but has comparabletechnological properties. Another important aspect in this context is that oleogels become solid againafter deep-frying, when the fried food cools down. This should result in a significantly less oily surfaceand, possibly, a lower fat uptake. In a first experiment, these aspects were proven by using a SFW-based oleogel as a frying medium for commercially available par-fried French fries.iSUNFLOWER WAX-BASED OLEOGELS (5% SFW) IN THEFRYING PROCESSParameters for the evaluation of ready-to-eat French fries are texture, color, and oil content. Inaddition to sensory quality, these parameters determine the acceptance of products by consumers.Thus, when using an oleogel-based frying medium, it is paramount that these parameters arecomparable with that of conventional frying media. Furthermore, the application of the organogelatorshould not impair frying performance of the frying medium.Chemical resultsNo significant differences in the chemical parameters used to assess frying oil quality (such aspolymer triacylglyerols or total polar compounds) were observed after 20 frying cycles with rapeseedoil-based oleogels versus rapeseed oil. Therefore, it can be concluded that the use of SFW does notsignificantly influence the frying performance of rapeseed oil.ColoriThe color of fried French fries gives some indication of reactions in the context of the non-enzymaticbrowning (Maillard reaction), which takes place in the crust at higher temperatures when the moisturecontent of the product decreases in the presence of reducing sugars and asparagine as amino acid.When measuring the color of fried French fries, the amount of reflected light on the surface of thefood is recorded, and the results are given in a color space. A common standard for a color space isthe L*a*b* color space established by the International Commission for Eclairage (CIE) in 1976. Thethree parameters of this model represent the brightness of the color (L*), its position between red andgreen (a*), and its position between yellow and blue (b*) 13. The CIE-L*a*b* color system is basedon the spectral range of the sensitivity of human vision. A comparison between French fries fried inrapeseed oil or in 5% SFW oleogel showed no significant difference between the three parameters ofthe CIELAB color room, so an influence of the frying medium on the color development can beexcluded (Fig. 1). It can be assumed that the quality of the raw material and processing conditionshave a stronger influence on the formation of Maillard reaction products and, therefore, on the color.FirmnessThe firmness of French fries strongly influences consumer acceptance. It is determined by chemicaland physical changes that take place during the frying process in the product, e.g., release ofintracellular materials, starch gelatinization, dehydration, crust formation, breakdown of adhesiveforces between cells, water evaporation, and tissue expansion [12]. Firmness of French fries wasmeasured by a texture analyzer and gives some impression of the crispness or hardness of theFrench fries with special consideration to the crust. Ten French fry sticks of nearly the same sizewere placed close together on the base platform of the texture analyzer, and the force needed topress a knife 5 mm deep into the sticks was measured. The results showed that the French fries friedwith rapeseed oil were a little less firm than the French fries prepared with 5% SFW-based rapeseedoil oleogel. However, the difference was not significant (Fig. 2).Fat content and fatty acid compositionDepending on the frying temperature, type of fryer, and quality of the raw material, fried French friescontain between 12 and 18% fat. From a nutritional point of view, a lower fat content isrecommended to reduce fat intake. Frying with a 5% SFW oleogel resulted in 1% less fat intake(11.3%) compared to 12.4% fat intake for frying with rapeseed oil (Fig. 2). However, the differencebetween the two frying media was not significant.Today, the fatty acid composition of food influences consumer purchasing decisions. The optimalfatty acid composition should have low levels of saturated fatty acids, a high level ofmonounsaturated oleic acid, and a ratio of linoleic to linolenic acid of 2:1. The proportion of trans-fattyacids should not exceed 2 grams per 100 g of fat [14]. Figure 3 shows the fatty acid compositions ofrapeseed oil and 5% SFW oleogel compared to conventional frying media. There was no significantdifference in fatty acid composition between rapeseed oil and 5% SFW oleogel. The content of trans-fatty acids was low for the different oils except for partially hydrogenated oil, which had more than10% trans-fatty acids. In the other oils, transfatty acids are formed to a low-level during refining,which today should be below 1%. Palm oil is characterized by a high content of palmitic acid, whilerapeseed oil shows the highest content of polyunsaturated fatty acids.Sensory evaluationAnother important factor that influences consumer purchasing decisions is the sensory quality offood. Products that do not meet consumer expectations will not have a chance on the market. Acommon method of comparing products is the pairwise comparison test with consumers known asDIN EN ISO 5495:2007. In this test method, the examiner is given two samples and asked to identifythe sample with the most pronounced characteristic.The results of the sensory evaluation (Fig. 4, page 26) show that the surface of French fries wasassessed by testing the French fry sticks between the thumb and index finger. Those sticks fried in5% SFW oleogel were determined to be less oily. The mouthfeel of French fries fried in 5% SFWoleogel was also characterized as less oily, demonstrating that the use of oleogel as frying mediumresulted in the perception that the fried product was less oily. Finally, there was no significantdifference in the taste of French fries fried in different types of frying media, indicating that the use ofSFW-based oleogels did not impair the taste of the final product.iWERBUNGThese initial results of our frying experiment indicate that oleogels based on rapeseed oil with SFWas an organogelator are a promising alternative for solid fats rich in saturated fatty acids. The finalproducts were comparable with respect to texture and color but had a slightly lower fat content, whichis desirable from a nutritional point of view. Most important is that products fried in 5% SFW rapeseedoil-based oleogels were perceived to be less oily than French fries fried in liquid oil. This means thatithe solid structure of the oleogel improved the quality of the French fries. However, for the industrialapplication of SFW-based oleogels in food to move forward, it is essential to advance the approval ofSWF. In addition, further work is necessary to evaluate different types and amounts oforganogelators to optimize the frying process.Bertrand Matthäus, Madline Schubert, Nelli Erlenbusch, Inga Smit, Lydia Weber, and SharlineNikolay are all working at the Max Rubner-Institut, Department of Safety and Quality of Cereals, inDetmold, Germany. Bertrand Matthäus can be contacted at bertrand.matthaus@mri.bund.de.References1. Vitrac, O., G. Trystram, and A.-L. Raoult-Wack, Deep‐fat frying of food: heat and mass transfer, transformations, andreactions inside the frying material, Eur. J. Lipid Sci. Technol. 102: 529–538, 2000.2. Mozaffarian, D., M.B. Katan, A. Ascherio, M.J. Stampfer, and W.C. Willett, Trans-fatty acids and cardiovasculardisease, N. Engl. J. Med. 354: 1601–1613, 2006.3. Stortz, T.A., A.K. Zetzl, S. Barbut, A. Cattaruzza, and A.G. Marangoni, Edible oleogels in food products to helpmaximize health benefits and improve nutritional profiles, Lipid Techn. 24: 151–154, 2012.4. Patel, A.R. and K. Dewettinck, Edible oil structuring: an overview and recent updates, Food Func. 7: 20–29, 2016.5. Botega, D.C.Z., A.G. Marangoni, A.K. Smith, and H.D. Goff, Development of Formulations and processes toincorporate wax oleogels in ice cream, J. Food Sci. 78 :C1845-C1851, 2013,.6. Huang, H.D., R. Hallinan, and F. Maleky, Comparison of different oleogels in processed cheese products formulation,Int. J. Food Sci. Tech. 53: 2525–2534, 2018.7. Martins, A.J., A.A. Vicente, R.L. Cunha, and M.A. Cerqueira, Edible oleogels: an opportunity for fat replacement infoods, Food Funct. 9: 758–773, 2018.8. Giacomozzi, A.S., M.E. Carrin, and C.A. Palla, Muffins elaborated with optimized monoglycerides oleogels: from solidfat replacer obtention to product quality evaluation, J. Food Sci. 83: 1505–1515, 2018.9. Jang, A., W. Bae, H.-S. Hwang, H.G. Lee, and S. Lee, Evaluation of canola oil oleogels with candelilla wax as analternative to shortening in baked goods, Food Chem. 187: 525–529, 2015.10. Mert, B. and I. Demirkesen, Reducing saturated fat with oleogel/shortening blends in a baked product, Food Chem.199: 809–816, 2016.11. Lim, J., S. Jeong, I.K. Oh, and S. Lee, Evaluation of soybean oil-carnauba wax oleogels as an alternative to highsaturated fat frying media for instant fried noodles, Lwt-Food Sci. Technol. 84: 788–794, 2017.12. Pedreschi, F. and P. Moyano, Effect of pre-drying on texture and oil uptake of potato chips, Lwt-Food Sci. Technol.38: 599–604, 2005.13. Yam, K.L. and S.E. Papadakis, A simple digital imaging method for measuring and analyzing color of food surfaces,J. Food Eng. 61: 137–142, 2004.14. Anon., Commission Regulation (EU) 2019/649 of 24 April 2019 amending Annex III to Regulation (EC) No 1925/2006of the European Parliament and of the Council as regards trans fat, other than trans fat naturally occurring in fat ofanimal origin, Official Journal of the European Union L 110: 17–20, 2019.

Oleogels as alternatives for frying fats and oils

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Oleogels as alternatives for frying fats and oils

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