Knowing Your Roots

Blog 5

Sugars are a major concern for the potato industry. As consumers, we demand a year-round supply of high quality potatoes to eat.  When processed, we expect the perfect, blond chips and French fries we are addicted to. However, to ensure this year-round supply, tubers must be stored at carefully controlled temperatures and humidity’s for up to 9 months to maintain the balance of sugars needed to ensure acceptable processing quality. This is a major challenge for the industry, as potato tubers are living, breathing entities that seem to have their own agendas when it comes to storing them for longer than they are designed to be kept.

If we store potatoes at temperatures that are too high, the tubers soon realize that it is time for a new year to begin and within a few months they adjust their internal physiology and sugar balance to produce sprouts and start to grow. On the other end of the scale, if we store potatoes at temperatures that are too low, we can slow everything down and store tubers for long periods without sprouting, but only at the expense of disrupting the balance among the complex of sugars that give tubers their characteristic flavors and, worse yet, cause chips and fries to turn dark brown when they are processed! To find the middle ground where we can have long term storage without disrupting the delicate balance of sugars needed for taste and processing, we need tools that enable us to monitor what sugars are present and how these change under different storage conditions.  

I’d like to shed some light on some of the research I have been working on at the University of Wisconsin to address this need. Specifically, I would like to talk about how I hope to use near infrared light (that is light above the wavelengths that are visible to us!) and how I hope to use it to study the complex of sugars in potato tubers and their genetic regulation in storage.  The expense and time required to accurately measure sugar content in tubers during storage, which allows breeders to select lines with desired characteristics and food processors to fine tune storage conditions to avoid problems, are major challenges to the potato industry. Currently, the tools available to accurately measure the sugar content of potatoes are limited to expensive laboratory procedures that can take many hours to complete and there is an urgent need for faster and less expensive approaches that can retain the desired accuracy.

This is where Near Infrared Spectroscopy (NIRS) comes in. When infrared light is focused on a potato sample, light is reflected and recorded which is unique and dependent on the specific chemical makeup of the sample. NIRS technology is already used to determine grain quality at storage mills, in processing plants, and by grain breeders. However, this not yet a reality for potatoes because we are currently not able to link infrared reflectance to concentrations of specific sugars in potato tissues. In my research, I am working on a model to provide this linkage. The model will be calibrated for the complex of sugars in potato tubers and, after sufficient samples have been processed, we will be able to determine the sugar content of a potato samples accurately, quickly (in under 3 seconds) and for a fraction of a penny per sample. We anticipate that this tool will have wide applicability among potato breeders, allowing them to select desirable breeding lines rapidly, and food processors who will be able to adjust storage conditions to provide consumers with the flawless chips and fries they demand.

For more information contact Curtis Frederick : Curtis is a PhD student in the Plant Breeding and Genetics Program at the UW, Madison under the direction of Dr. Paul Bethke.

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