The impact of temperature on the hydrolysis of potato starches into simple sugars

Potatoes, underground tubers of the plant Solanum tuberosum, are staple foods in many cultures across the globe. In temperate climates, potatoes are harvested and stored throughout the cold season. In commercial storage facilities, they often undergo cold-induced sweetening (CIS), which negatively affects their taste. We aimed to determine why potatoes can also turn sweet during short-term storage in consumers’ houses—especially when peeled and pre-cut—and to assess the impact of storage temperatures on this process. Specifically, we aimed to determine the effect of different storage temperatures on the breakdown of starches into simple sugars, which causes the undesirable sweet taste. To this end, we used a blood glucometer to measure sugar contents of juices squeezed from the tubers peeled, sliced, and exposed for 96h to three different temperatures: cold (4°C/39°F), ambient (approximately 20°C/68°F), and hot (37°C/98.6°F). Our initial hypothesis was that the hotter the storage temperature, the faster the rate of starch hydrolysis and the greater the content of simple sugars. Surprisingly, our data indicated that the highest levels of simple sugars were achieved during storage at the ambient temperature, while both the cold and hot storage conditions prevented the breakdown of starches, and the tubers remained relatively unsweetened. Thus, the rate of enzymatic breakdown as a function of temperature is not linear but follows a bell curve, with peak values achieved at the room temperature. Our findings suggest keeping freshly peeled potatoes in household refrigerators, where prolonged effects of CIS are unlikely to be a factor.