Cooking Increased the Postprandial Glycaemic Response but Enhanced the Preload Effect of Air-Dried Jujube

Abstract

Randomised controlled trials involving healthy participants were conducted to investigate the impact of cooking and ingestion patterns on the physiological response and preloading effect of air-dried jujube (AJ). The participants' postprandial glycaemic and insulinemic responses were tested after ingestion of cooked or uncooked air-dried jujube containing 50 g (as a sole food source) or 15 g (as a preload food prior to a rice meal) of available carbohydrates. Compared with the uncooked AJ, the cooked air-dried jujube (CAJ) induced a 34.5% higher glycaemic peak, 57.1% greater glycaemic variability, and a 159.1% larger negative area under the glycaemic response curve when ingested as the only food in a meal. When eaten as a preload prior to a rice meal, the CAJ reduced the postprandial glycaemic peak by 25.17%. The CAJ preload enhanced insulin production in the 15 min after preloading but did not increase the total amount of postprandial insulin secretion. The result suggests that when taken as preload, the loose matrix of cooked fruits may exhibit glycaemic benefits by eliciting early insulin production and may therefore be conducive to the blood glucose management of a carbohydrate-laden meal.

Keywords: food matrix; glycaemic response; insulin; jujube; preload.

Figure A1

Flow diagram of the study subjects from the glucose and insulin response trial. Notes: “*” means multiplication, “-” means subtraction.

Figure A2

Flow diagram of the study subjects from the preload trial. Notes: “*” means multiplication, “-” means subtraction.

Figure 1

The procedure of the trials examining postprandial glycaemic and insulinaemic responses after consuming raw and cooked air-dried jujubes. Notes: “✔” means at the current time point, blood glucose testing or blood sample collection (for insulin analysis) are required.

Figure 2

The procedure for the preload trial study. Notes: “✔” means at the current time point, blood glucose testing or blood sample collection (for insulin analysis) are required.

Figure 3

The total phenolic and flavonoid contents of air-dried jujube and cooked air-dried jujube. Note: * indicates that there is a significant difference between air-dried jujubes and cooked dried jujubes, p < 0.05.

Figure 4

α-amylase and α-glucosidase inhibitory activity. Note: “a, b, c” are used to indicate comparisons of differences between groups.

Figure 5

Power law parameters of the different digesta of air-dried jujube and cooked air-dried jujube. Note: * indicates that there is a significant difference between air-dried jujubes and cooked dried jujubes, p < 0.05.

Figure 6

The postprandial glycaemic response curves after ingesting raw and cooked air-dried jujubes. Note: * denotes significant difference between raw and cooked air-dried jujubes, p < 0.05. Group*Time means interaction effect between group and time.

Figure 7

The postprandial insulinemic response curves of raw and cooked air-dried jujubes. Note: * denotes significant difference between raw and cooked air-dried jujubes, p < 0.05. Group*Time means interaction effect between group and time.

Figure 8

The postprandial glycemic response curves of preload test meals. AJ+R: air-dried preload and rice; CAJ+R: cooked air-dried preload and rice; W+R: water preload and rice as control. Note: “a, b” are used to indicate comparisons of differences between groups. Group*Time means interaction effect between group and time.

Figure 9

The postprandial insulinemic response curves of the preload test meals. AJ+R: air-dried preload and rice; CAJ+R: cooked air-dried preload and rice; W+R: water preload and rice as control. Note: “a, b, c” are used to indicate comparisons of differences between groups. Group*Time means interaction effect between group and time.