Glycemic Index of Sweet Potato as Affected by Cooking Methods

Abstract

Understanding the effect of cooking on glucose availability will aid in the recommendation for including sweet potatoes as a regular component in American diets. Heating breaks down starch granules to allow amylopectin and amylose to be more readily digested by pancreatic amylase, which theoretically should increase the glycemic index of sweet potato. Twelve volunteers consumed 25 g of available carbohydrate from Beauregard sweet potato skin and flesh separately that were subjected to conventional cooking methods: baking at 163 °C for 1 hour; microwaving for five minutes in a 1000 watt microwave; dehydrating at 60°C for 16 hours; and steaming at 100°C for 45 minutes. Available carbohydrate was determined by difference from proximate analysis of protein, lipid, total dietary fiber, moisture, and ash. Fasted participants measured blood glucose levels at 0, 30, 60, 90, and 120 minutes after consuming 25 g of carbohydrate from test foods or glucose. Glycemic indices calculated from these methods for steamed, baked and microwaved sweet potato flesh were 63 ± 3.6, 64 ± 4.3 and 66 ± 5.7, respectively, indicative of a moderate glycemic index food. However, dehydrated and raw sweet potato flesh had a low glycemic index (41 ± 4.0 and 32 ± 3.0, respectively). Steamed skin, baked skin, and dehydrated flesh did not have a statistically different glycemic index (P> 0.05) from that of raw sweet potatoes. A second experiment confirmed the low glycemic index of raw sweet potato, especially the skin, and showed that a commercial extract of the sweet potato cortex, Caiapo, tended to lower the glycemic index of white potato to a level that was not different from the raw sweet potato peel. The physiological mechanism for the lower glycemic index was not due to a greater release or a greater clearance of insulin during the glycemic response. Depending on cooking methods, "Beauregard" sweet potato flesh and skin may be considered low and medium glycemic index foods, which may prove beneficial for diabetic or insulin-resistant consumers.

The Nutritional Value of Sweet Potato Tubers [Ipomoea batatas (L.) Lamb.] Consumed by Infants and Children of Dani Tribe in Kurulu District, Baliem-Jayawijaya

“…Carbohydrate of sweet potato tubers constitute of low glycemic index (54). According to Allen et al (2012), dehydrated and raw sweetpotato flesh had a low glycemic index (41±4.0 and 32±3.0, respectively). In addition, steamed skin, baked skin, and dehydrated flesh did not have a statistically different glycemic index from raw sweet potatoes (Allen et al, 2012).…”

“…According to Allen et al (2012), dehydrated and raw sweetpotato flesh had a low glycemic index (41±4.0 and 32±3.0, respectively). In addition, steamed skin, baked skin, and dehydrated flesh did not have a statistically different glycemic index from raw sweet potatoes (Allen et al, 2012). Low glycemic index tend to slow the rate of glucose absorption, therefore maintaining the low level of blood glucose.…”

Quality evaluation of gnocchi pasta prepared with orange-fleshed sweet potato

“…This cultivar can be consumed in the same way as any other sweet potato cultivars (MELO, 2011). In addition, this variety has a low glycemic index when raw (32 ± 3.0) and a moderate index (66 ± 5.7) when cooked in a microwave (ALLEN et al, 2012), playing an important role in the age of obesity and diabetes growth.…”

Ultrastructural and Starch Digestibility Characteristics of Sweet Potato Spaghetti: Effects of Edible Gums and Fibers

“…[12] Nevertheless, cooking methods were reported to affect the GI of SP, with baked and microwaved SP having GI of 64 and 66, respectively. [13] The possibility of producing low glycaemic pasta from SP was investigated by various workers. [6,7,14,15] SP starch noodles are a popular food in China and Japan and its quality enhancement through fortification has been attempted.…”