The Suppression of the Changes in Physical Properties of Rice Gruel Consumed by Patients with Mastication or Swallowing Disorders

Abstract

[Objective] Rice gruel is the staple food of people with impaired mastication or swallowing; however, its physical properties tend to change at lower temperature. Addition of gelatin to rice gruel is known to inhibit these changes, and yet few studies have reported on the change in characteristics of rice gruel with the addition of gelatin. We therefore decided to determine these changes in the physical properties of rice gruel.

[Method] Rice gruel was prepared by cooking water and raw rice (raw rice : water＝1 : 5) in a rice cooker. Then, we added gelatin dissolved in hot water to the rice gruel. Gelatin is derived from three sources: bovine bone, porcine skin, and fish, and are available with gel strengths of 150 g and 200 g; we used all three types of gelatin with both gel strengths (6 gelatin samples in total). The concentrations of gelatin were 1.0%, 2.0%, and 3.0%. The physical properties of rice gruel immediately after addition of gelatin (0 min), and 30 and 60 min after incubation at 20℃ were measured by a creep meter. Hardness and adhesiveness were determined from the measurements. In the sensory test, we determined the taste, flavor, and ease of swallowing of rice gruel immediately after gelatin was added and 60 min after it was added.

[Results] Changes in hardness and adhesiveness with decreasing temperature were most inhibited in the rice gruel to which 3.0% fish gelatin (gel strength, 150 g) was added. In the sensory test, the rice gruel to which 3.0% fish gelatin (gel strength, 150 g) was added was easy to swallow compared to the control gruel to which gelatin was not added. Moreover, the addition of fish gelatin had hardly any effect on the flavor.

[Discussion] The physical properties of the rice gruel to which fish gelatin was added were hardly affected as the temperature of the rice gruel decreased till it reached room temperature. We think that the increase in hardness and adhesiveness was inhibited because the gelling point of fish gelatin is low, which was also why the ease of swallowing was significantly higher in the case of fish gelatin compared to the control. These results suggest that adding 3.0% fish gelatin (gel strength, 150 g) to rice gruel will be useful for patients with mastication or swallowing disorders who take a long time to eat.