Sugar is the number two enemy when making fresh cut French fries. Number one is low solids or starch. Low solids will make your fries soggy. That’s why a low solid potato, such as a waxy red, just won’t fry up properly. High sugars will mask the problems, as it can ruin a perfectly good potato with high solids by tricking you into thinking it is fully cooked. Too much sugar causes the potato to change color prematurely… but it is not fully cooked.
The final color is directly related to the quantity of sugars in the tuber. Storage (before you get the potato) is important. But storage, especially in a cool refrigerator or walk in at your operation is also important. Remember this guideline… below 40° Fahrenheit, the starch in the potato will start to turn to sugar. As a potato matures and sizes up, the sugars in that potato are reduced to a low level (depends on the variety). Long term storage at cooler temps raises the sugar level. Stresses in storage such as low temperature, low oxygen or physical damage all can increase sugars.