Identifying Sugars in Food Products using X-ray Diffraction

The crystallinity of sugars affects the macroscopic properties (such as texture or mouthfeel) of food products to a large extent. X-ray diffraction can be used to identify sugars in food products and to investigate their crystallinity.

1        Introduction

Sugars occur naturally in many grocery products, but are also regularly added in the processing of food products. They mainly serve as sweeteners, but also affect many other properties such as flavor, color or mouthfeel1. Health concerns associated with free sugars initiated the World Health Organization (WHO) to recommend reduced sugar consumption2 and many customers look for products with reduced sugar content. The term sugar most often refers to sucrose, a disaccharide which is mostly refined from sugar beet or sugarcane. However, more generally the term covers all mono- and disaccharides including glucose, fructose, glucose, lactose, etc.

All these sugars are highly soluble in water and often occur in a dissolved state (e.g. in soft drinks). On the other hand, solid sugars can also be found in many food products. Both crystalline and amorphous polymorphs occur for most sugars. While X-ray diffraction (XRD) is of only limited use for the investigation of dissolved sugars, it can easily detect any crystalline ones. Since each type of sugar has a different crystal structure, sugars can easily be differentiated from each other using XRD. XRD has also been used to investigate the crystallization of amorphous sugars – a process that is often undesirable due to accompanying detrimental property changes3. Even quantification of crystalline and amorphous sugars using XRD is possible4.

In this application report, XRD patterns of pure sugars and of some sweet food products are recorded using the Automated Multipurpose Powder X-Ray Diffractometer XRDynamic 500 from Anton Paar. The crystalline sugars in the food products are then identified from the measured diffractograms.

 

References:

1. K.R. Goldfein, J.L. Slavin, Comprehensive Reviews in Food Science and Food Safety 14 (2015), 644-6562. World Health Organization, Guideline: sugar intake for adults and children (2015)3. K.D. Roe, T.P. Labuza, International Journal of Food Properties 8 (2005), 559-5744. D. Nicholls et al., Food Analytical Methods 11 (2018), 2673-2681

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