Use of X-Ray Scattering for Food Characterization

One active research area is the development of nanocarriers for functional food delivery. Information on the influence of nutrient loading and processing conditions on the final structure and stability of nanocarriers, as well as their dispersion in food, can be provided by characterization techniques. This information is required for both the development and the production process. An essential technique for functional food characterization is small-angle X-ray scattering (SAXS). This article outlines why.

Food that delivers extra health benefits on top of basic nutrients such as fat, proteins and carbohydrates is known as functional food. Such foods include fortified breakfast cereals and probiotics. Functional food is now one of the most active topics in nutritional science research due to rapid growth in the health and wellness market and an increase in health-conscious customers.^1-3

Nature Provides Functional Foods that are Stable and Bioavailable

More recently, research has focused on preserving the integrity of functional ingredients while at the same time making sure they are readily available to the body. Food scientists are particularly interested in the properties of naturally occurring vesicles and micelles found in plants or animals. To release and absorb these contents, our digestive system has evolved.

Naturally occurring bio-architectures and how they self-assemble are now better understood thanks to recent developments in characterization techniques. This has enabled the creation of synthetic liposomes that closely resemble those found in nature.^4-7

Nanocarriers Designed for Functional Food Delivery

Food scientists currently face many challenges, including the need for new functional food protection solutions, controlled release, and increased bioavailability of compounds such as vitamins, minerals, antioxidants, aroma compounds, and oils. ^5,9-13

The design of a wide variety of self-assembled nanocarriers for food delivery has been a primary focus for research in recent times. These include lipid and protein-based microemulsions, liquid crystalline phases, and nanostructured dispersions.

The composition and structure of nanocarriers dictate their ability to stabilize functional food compounds and release their contents when required.

One essential part of designing systems for functional food delivery is the characterization of self-assembled nanostructures and learning how nutrient loading and assembly conditions impact on their final structure and properties. Small-angle X-ray scattering (SAXS) is one analysis technique used with functional foods to characterize nanocarriers and dispersions.¹⁴

Small-Angle X-Ray Scattering (SAXS) Provides Essential Information About Nanocarriers and Their Dispersions

SAXS analytical technique makes it possible to characterize nanocarrier dispersions in their intended environment. Unlike other characterization methods, SAXS requires no sample preparation such as drying, freezing and staining. This means that samples are analyzed under the same conditions as those in food products.

Nanoscale differences in density are determined with SAXS analysis through the scattering of X-ray photons from electrons in the sample. This provides nanoscale structural information about mesophases, nanostructures, and dispersions. The impact of synthesis or external factors on the final structure and properties of the nanocarriers can be observed with SAXS. Such factors include nutrient loading and external conditions such as dilution and pH changes.^14-16

One example where SAXS can be used is the characterization of the liquid crystalline phases of nanostructured lipid miniemulsions (submicron particles) when formulating mixture, including food-grade ingredients.

A SAXS characterization study was carried out by scientists from the University of Orleans to examine miniemulsions of food flavor compounds. The results are shown in the figures below. A significant finding of this study is that when the flavor amount is changed, the emulsions show a different structural or phase behavior, even though they have a very similar chemical composition. This could impact their release characteristics. Furthermore, no major structural change of the self-assembled miniemulsions is observed when up to 20% or 25% of flavor compound (depending on its type) is added. Less stable structures and increased risk of flavor compound leaks are indicated by a drastic loss of order.¹³

Figure 1. SAXS patterns from DU (commercial grade form of monolinolein) based dispersions with varying type and content of γ-lactone type (γL) flavor compounds (left: γ-nonalactone , right: γ-decalactone) evidencing phase transitions depending on the ratio of flavor to lipid content δ (δ=100xDU/(DU+үL)). Measurements performed using a Xeuss instrument show the following phases: L₂: emulsified micro emulsion, H₂: hexagonal phase, V₂ phase: bicontinuous cubic phase. Adapted with permission from Tidu et al¹³, Langmuir 2018, 34(44), pp 13283-13287, Copyright 2018 American Chemical Society.

Use of SAXS to Characterize Nanostructured Liposomes

Liposomes provide another example of where SAXS can be used for characterization. A seemingly ideal target for nutrient delivery is to deliver functional food compounds through the use of liposomes that mimic those found in nature. However, precise process conditions and undesirable solvents such as chloroform are usually required to synthesize liposomes with controlled size and nutrient loadings making this practice challenging^5,8 As such, a huge amount of research is being carried out to find new routes to synthesize nature resembling liposomes and to develop non-natural liposomes with simpler and safer production routes.

A team of Brazilian scientists recently carried out research to explore a system designed to deliver Vitamin D₃ and curcumin co-encapsulated in liposomes. The structure and properties of the final liposomes were investigated under the effects of temperature and nutrient loading using SAXS.

Their results demonstrate that co-encapsulation can be used to load both nutrients into one liposome and that the final structure is hardly affected by nutrient loading and co-encapsulation. This confirms that daily recommended amounts of curcumin and vitamin D₃ can be met by delivering the two together.¹² Moreover, a great indicator of the stability during transport to the customer is that these liposomes are stable at temperatures ranging from 20 to 60 ˚C.

Figure 2. a) Electron density profiles of lipid bilayers obtained by fitting of SAXS patterns of liposome dispersions loaded with curcumin (FC) alone, with 0.002 wt% vitamin (F8V) or with 0.002 wt% vitamin + curcumin (FC8V) and measured at different temperatures.¹² 3b) parameters extracted using SAXS data analysis and c) schematic representation of the formed structures and the parameters that can be found using SAXS. Data courtesy of Professor Cristiano Oliveira (USP) measured with a Xeuss instrument.

Xeuss and Nano-inXider: Two Solutions for Functional Food Research

Precise and predictable characterization is required for insightful research into nanocarrier dispersions for the functional food industry. The Nano-inXider from Xenocs offers compact, user-friendly, and affordable nanoscale characterization and can analyze solids, liquids, pastes, and gels at various temperatures. This makes it an ideal solution for functional food research or stability evaluation.

The Nano-inXider uses an automatic acquisition workflow to provide fast feedback to scientists with important structural information at the nano and atomic scale through simultaneous SAXS/WAXS characterization. The Nano-inXider offers simple sample loading, automatic acquisition workflow and assisted analysis of results. This makes it ideal for analyzing dispersed nanocarriers as well as a variety of other food science applications. It can be used, for example, to study the impact of crystalline phase polymorphs on food texture and its associated sensorial impact. Another application one could cite is the in-situ characterization of the crystallization state of fats to evaluate the impact of the manufacturing process.

For research groups including X-ray scattering experts looking for a solution for the characterization of their samples that is more accessible than synchrotron beamlines, Xeuss is a highly versatile X-ray scattering platform.

References and Further Reading

1. ‘Functional Foods: Benefits, Concerns and Challenges—A Position Paper from the American Council on Science and Health’ — Hasler CM, The Journal of Nutrition, 2002.
2. ‘The Role of Functional Foods, Nutraceuticals, and Food Supplements in Intestinal Health’ — Cencic A, Chingwaru W, Nutrients, 2010.
3. ‘Position of the Academy of Nutrition and Dietetics: Functional Foods’ — Crowe KM, Francis C, Journal of the Academy of Nutrition and Dietetics, 2013.
4. ‘Dietary lipids from an evolutionary perspective: sources, structures and functions’ — German JB, Maternal & Child Nutrition, 011.
5. ‘Self-assembly in food — A concept for structure formation inspired by Nature’ — Sagalowicz L, Michel M, Blank I, Schafer O, Leser ME, Current Opinion in Colloid & Interface Science, 2017.
6. ‘Food Lipids: Chemistry, Nutrition, and Biotechnology’ — Akoh CC, Min DB, Marcel Dekker, Inc., 2002.
7. ‘Analysis of biostructural changes, dynamics, and interactions – Small-angle X-ray scattering to the rescue’ — Vestergaard B, Archives of Biochemistry and Biophysics, 2016.
8. ‘Liposome: classification, preparation, and applications’ — Akbarzadeh A, Rezaei-Sadabady R, Davaran S, Joo SW, Zarghami N, Hanifehpour Y, Samiei M, Kouhi M, Nejati-Koshki K, Nanoscale Research Letters, 2013.
9. ‘Nanoencapsulation of food ingredients using lipid based delivery systems’ — Fathi M, Mozafari MR, Mohebbi M, Trends in Food Science & Technology, 2012.
10. ‘Nanoencapsulation Techniques for Food Bioactive Components: A Review’ —Ezhilarasi PN, Karthik P, Chhanwal N, Anandharamakrishnan C, Food and Bioprocess Technology, 2013.
11. ‘Lyotropic Liquid Crystalline Phases for the Formulation of Future Functional Foods’ — Sadeghpour A, Rappolt M, Journal of Nutritional Health & Food Engineering, 2016.
12. ‘Structural characterization of multilamellar liposomes coencapsulating curcumin and vitamin D₃’ — Chaves MA, Filho PLO, Garcia Jange C, Sinigaglia-Coimbra R, Oliveira CLP, Pinho SC, Colloids and Surfaces A, 2018.
13. ‘Influence of #-lactones on monolinolein/water bulk and emulsified mesophases’— Tidu A, Méducin F, Faugère A, Guillot S, Langmuir, 2018.
14. ‘Nanotechnologies for Solubilization and Delivery in Foods, Cosmetics and Pharmaceuticals’ — Garti N, Amar-Yuli I, DEStech Publications, 2012.
15. ‘Physicochemical characterization of drug nanocarriers’ — Manaia EB, Abuçafy MP, Chiari-Andréo BG, Silva BL, Oshiro JA, Chiavacci LA, International Journal of Nanomedicine, 2017.
16. ‘Nanocarriers for Drug Delivery: Nanoscience and Nanotechnology in Drug Delivery’ — Mohapatra S, Ranjan S, Dasgupta N, Mishra RK, Thomas S, Elsevier, 2018.

About Xenocs

Xenocs is a supplier of x-ray scattering equipments (SAXS/WAXS) for characterizing the nanostructure and morphology of materials at the nanoscale. Such equipments are used for research, development, and production of advanced materials in various domains such as nanoparticles & colloïds, polymer, food science, cosmetics or biostructural research.

Created in 2000 as a spin off from Institute Laue Langevin, the company started activity offering its customers innovative X-ray sources, optics and collimation solutions for X-ray characterization of nanomaterials and nanostructures.

Xenocs delivered its first x-ray scattering equipment in 2008, setting new standards for the possibilities of using SAXS in the laboratory for characterization at the nanoscale.

Working closely with both academic and corporate customers, Xenocs has continuously focused on providing value through performance and ease of use, while also creating a global sales and service organization.

In 2016, Xenocs bought Saxslab with operations in Denmark and in Massachusetts, making it the leading provider of SAXS equipments worldwide. Xenocs headquarters are located in France, and the company has subsidiaries in USA, Denmark and Singapore as well as a strong network of local contacts.

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