Influence des procédés de cuisson sur la composition nutritionnelle et la digestibilité de la pomme de terre

Potatoes are a healthy food choice because they are nutrient dense and low in calories; they contain ample amounts of pertinent micronutrients including potassium and ascorbic acid. Despite this, potato consumption continues to decline in several countries possibly due to their purported high glycemic index (GI). The GI is a classification system that ranks foods based on their blood glucose raising potential. High GI diets have been associated with an increased risk of developing type 2 diabetes and cardiovascular disease. A major factor determining the GI of foods is the rate of starch digestion. The starch in raw potatoes is highly resistant to digestion. However, upon cooking, starch becomes gelatinized and is readily broken down by digestive enzymes. Conversely when cooled the starch in potatoes undergoes the process of retrogradation which once again causes it to become resistant to digestion. The GI values for various potato varieties show a wide variation from as low as 23 to as high as 111. Several factors affect the GI of potatoes including variety, cooking method, maturity and processing. Freshly cooked potatoes have a higher GI than potatoes that have been cooked and then cooled prior to consumption, but the magnitude of this effect varies in different potato varieties. The degree of amylopectin branching is reduced in immature (new) potatoes which have a lower GI than those harvested at maturity. Potatoes can be processed into different food products such as instant potatoes, French fries, potato chips and gnocchi which also influences their GI. Further work is needed to examine the effects of various cooking processes on the GI of potatoes and processed potato products.