Is Your Food Healthy?
Measuring Total Sugar (Glucose and Fructose) in Potatoes Using Mobile Reflectometry

Saskia Schröter, Product Manager Mobile and Analytical Workflows

Measuring Total Sugar in PotatoesWho doesn’t love golden, hot French fries or a steaming baked potato? In fried or baked goods, much of the savory taste and aroma can be attributed to the Maillard reaction. It is what creates the brown compounds that give many cooked foods this flavor. Unfortunately, the reaction between asparagine and reducing sugars (e.g., fructose or glucose) can also produce acrylamide, which is considered toxic and potentially carcinogenic: In the body, acrylamide is converted into glycidamide, which can bind to DNA and cause mutations. High levels of acrylamide can be found in starchy foods, such as potatoes and bread, when cooked at temperatures over 120 °C. This potentially dangerous acrylamide formation can be minimized by ensuring that the levels of reducing sugars are within safe limits, thereby ensuring the quality and nutritional value in processed food.

Precise in-process results - directly on-site

Reflectometry, or remission photometry, is a rapid, sensitive method for quantitating a wide variety of organic and inorganic parameters in water, food, beverages, and environmental samples. Using test strips in combination with a reflectometer, readings can be taken in the laboratory, on the production line, or in the field.

The total free sugar in potatoes can be determined in minutes with the simple Reflectoquant® Total Sugar Test and the RQflex® 20 reflectometer:

Reflectometric determination after enzymatic reaction with glucose6-phosphate dehydrogenase and diaphorase

Sample preparation

Homogenize the potato in a blender (e.g. Ultraturrax). Weigh 10-20 g of the mashed sample into a 50 mL volumetric flask, and note down the exact sample weight. Add approx. 40 mL distilled water and stir for 10 minutes. Afterwards, make up to the mark with distilled water. Filter through a folded filter.

Analysis

Reflectometer

Place 10 mL distilled water, 5 drops of reagent TS-1 and 1 mL filtrated sample in the test vessel and swirl. Press the reflectometer START key and simultaneously dip the test strip into the measurement sample (23 ± 3 °C) for ca. 2 s, ensuring that both reaction zones are immersed. Allow excess liquid to run off via the long edge of the strip on to an absorbent paper towel. Insert the strip immediately into the strip adapter. After 60 s the strip is measured in the reflectometer. The value [mg/L] will be stored automatically. The total sugar content can then be calculated as [g/kg] = Measured value [mg/L] x 50 mL / Sample weight [g] x 100.

 

 

Sample Total Sugar [g/kg] Reflectoquant® method Total Sugar [g/kg] Enzymatic method
1 15.4 17.3
2 5.7 6.4
3 0.4 0.4
4 <0.2 0.1

 

Results and comparison with classic enzymatic method

From Potatoes with 0.2–1.0 g/kg reducing sugar, roasted products of optimum culinary quality can be prepared and, if prepared under conditions minimizing acrylamide formation, acrylamide contents remain below 500 µg/kg.1

 

References

  1. How much reducing sugar may potatoes contain to avoid excessive acrylamide formation during roasting and baking? Biedermann-Brem, S., Noti, A., Grob, K. et al. Eur Food Res Technol (2003) 217:369. https://doi.org/10.1007/s00217-003-0779-z

 

 

Materials