To investigate the effects of cold storage and vinegar addition on glycemic and insulinemic responses to a potato meal in healthy subjects, researchers studied 13 healthy subjects who volunteered for the study; tests were performed at Applied Nutrition and Food Chemistry, Lund University, Sweden. The study included four meals; freshly boiled potatoes, boiled and cold stored potatoes (8°C, 24 h), boiled and cold stored potatoes (8°C, 24 h) with addition of vinaigrette sauce (8 g olive oil and 28 g white vinegar (6% acetic acid)) and white wheat bread as reference. All meals contained 50 g available carbohydrates and were served as a breakfast in random order after an overnight fast. Capillary blood samples were collected at time intervals during 120 min for analysis of blood glucose and serum insulin. Glycemic (GI) and insulinemic indices (II) were calculated from the incremental areas using white bread as reference.

They found: “Cold storage of boiled potatoes increased resistant starch (RS) content significantly from 3.3 to 5.2% (starch basis). GI and II of cold potatoes added with vinegar (GI/II=96/128) were significantly reduced by 43 and 31%, respectively, compared with GI/II of freshly boiled potatoes (168/185). Furthermore, cold storage per se lowered II with 28% compared with the corresponding value for freshly boiled potatoes.”

The researchers concluded: “Cold storage of boiled potatoes generated appreciable amounts of resistant starch. Cold storage and addition of vinegar reduced acute glycemia and insulinemia in healthy subjects after a potato meal. The results show that the high glycemic and insulinemic features commonly associated with potato meals can be reduced by use of vinegar dressing and/or by serving cold potato products.”

Source: Diabetes In Control: European Journal of Clinical Nutrition (2005) 59, 1266–1271. doi: 10.1038/sj.ejcn.1602238. November 2005. Vinegar dressing and cold storage of potatoes lowers postprandial glycemic and insulinemic responses in healthy subjects, M Leeman, E Östman and I Björck.