Glycemic and Insulinemic Responses of Fresh, Freeze-Dried, and Cooked Apples: As Single Food or Preload

The aim of this study was to investigate the impact of raw, cooking, and freeze-drying on the postprandial glycemic and insulinemic responses and preloading effect of apples. Three fruit products containing 50 g available carbohydrates, including raw apple (RA), freeze-dried apple (FA), and cooked apple (CA), were tested in fourteen healthy subjects. The result showed that the FA elicited both the mildest glycemic and insulinemic responses in terms of early postprandial glucose rise, hypoglycemia risk, insulin peak, and insulin sensitivity among all samples. Compared with CA, the FA induced lower postprandial glycemic amplitude. Compared with its uncooked counterparts, the FA led to lower postprandial insulin excursion. When eaten as a preload prior (containing 15 g available carbohydrates) to a rice meal, all apple preload groups reduced the postprandial glycemic peak, compared with the water preload group. Apple preload enhanced insulin recruitment in the first 30 min after preloading but did not increase the total amount of postprandial insulin secretion. The FA had a higher retention of total phenolic compounds and higher viscosity of the digesta than the RA. This study showed that freeze-dried apples have a potential advantage in terms of glycemic and insulinemic properties. Further investigation on the micro-structure and the rheological properties of the digesta are needed to understand the disparity of glycemic properties between the freeze-dried fruits and the other fruit products.