The effect of different cooking methods and different fat types on the estimated glycemic index value of potatoes

Food and Agriculture Organization/World Health Organization (FAO/WHO) Expert Advisory states that the concept of glycemic index (GI) is a useful tool for selecting carbohydrate-containing foods to maintain health and treat various diseases. The GI value of foods is affected by different cooking and preparation methods as well as the botanical origin of the food. Potatoes are one of the most important sources of carbohydrates worldwide. High consumption of fried foods is associated with negative health outcomes. There is not enough evidence regarding the GI value of potatoes prepared with the alternative methods and by added to different types of oil. This study aimed to investigate the effect of using different cooking methods and different fat types on the GI value of potatoes. The potatoes were prepared by deep-fried (12 min at 190°C), cooked with an airfryer (30 min at 200°C) and baked in an oven (30 min at 180°C), using sunflower oil (SO), canola oil (CL), olive oil (OO), and butter (B). Butter was not used in deep-fried samples due to the hydrolysis of triglycerides. Starch types (rapid digestible starch (RDS), slow digestible starch (SDS), total digestible starch (TDS), resistant starch (RS), total starch (TS)) and estimated GI (eGI) of cooked potatoes were evaluated. The according to glucose eGI values of the samples deep-fried with SO, CO, OO were respectively 65,37; 65,53; 68,92 (p=0,124). The according to glucose eGI values of the samples air fried with SO, CO, OO, B were respectively 59,91; 67,24; 65,67; 66,91 (p=0,009). The according to glucose eGI values of the samples baked with SO, CO, OO, B were respectively 63,47; 70,00; 72,64; 74,96 (p=0,000). It was determined that the potatoes using sunflower oil had a lower eGI value compared to other oil types in the air fried and oven-baked samples (p<0.05). When other oil types except CO were used, air frying resulted in lower eGI values compared to other cooking methods (p<0.05). It was found that the RDS, SDS and RS contents of the samples were between 50,02-64,32%, 4,05-17,33%, 1,49-2,45% in deep-fried potatoes; 49,15-61,81%, 4,38-18,79%, 1,83-3,08% in potatoes cooked with airfryer; 51,07-66,05%, 1,38-14,43%, 0,81-2,39% in oven-baked potatoes, respectively (p<0,05). It was determined that the eGI values of the test foods significantly correlated with positively the RDS content, and negatively the SDS and RS contents (p<0.05). When all test foods were compared, the lowest eGI value was observed in potatoes cooked with an airfryer by adding SO, and the highest eGI value was observed in potatoes baked by adding B. A difference of 15 units was detected between the eGI values of potatoes cooked in an airfryer with the addition of SO and those baked in the oven with the addition of B. In low GI diets, adding sunflower oil as the oil type and cooking with an airfryer may be recommended when preparing fried potatoes.