Mastication Effort Estimated by Electromyography for Cooked Rice of Differing Water Content

Abstract

The objective of this study was to quantify the mastication effort for cooked rice. We analyzed mastication patterns while normal subjects ate a spoonful of cooked rice that had been prepared by cooking with different amounts of water (1.5, 2.0, 3.0, and 4.0 times the water to rice weight). The rice samples were served with the same weight, same volume and same solid content, and electromyography (EMG) of the masticatory muscles was measured. The texture of the four cooked rice samples was instrumentally analyzed by the two-bite method. The number of chews, masticatory time, and jaw-closing muscle activities per chew evaluated by EMG were higher in the rice sample cooked with least water, which exhibited a high firmness value in the instrumental test. Rice cooked with 4.0 times the amount of water exhibited the longest jaw-opening duration, which was related to the adhesiveness value in the instrumental test. The ratio of jaw-opening muscle activity to the preceding jaw-closing muscle activity was lower for the rice containing least water, this corresponding to the area ratio (balance degree) in the instrumental test. Softer rice containing more water reduced the total mastication effort until swallowing because it required a shorter mastication time. It was not difficult for the softer rice with high density to be ingested in greater weight, decreasing the mastication effort for a certain amount.

Mouthful Size Effects on Mastication Effort of Various Hydrocolloid Gels Used as Food Models

“…Observed significant differences among five samples were smaller in T2 than in T1 because the mass of gel samples was small after the first swallow. There are two reasons for that: first, original gel properties were weakened during T1 (Kohyama et al, 1998(Kohyama et al, , 2005b(Kohyama et al, , 2007bKohyama and Mioche, 2004), and second, the amount of samples remained in the oral cavity after the first swallow was much smaller, varied greatly, and unknown as majority of the gel bolus was transported from the mouth. The amount left in the mouth after the first swallow may be related to original gel size;…”

“…However, the changes in oral processing time and number of chews and/or swallows were less than the proportional value to the sample mass. Mastication effort is estimated from the activities of masseter muscles (Kohyama et al, 2005b(Kohyama et al, , 2007b. The mastication effort per mass of the large gels was about 0.7.…”

“…We can evaluate the mastication effort using an indicator, the total muscle activity of both masseter muscles until swallowing (Kohyama et al, 2005b). Mastication of more adhesive foods such as caramels and rice cakes (mochi) leads to greater activity of the suprahyoid muscles, which act in the jaw-opening phase (Sakamoto et al, 1989;Kohyama et al, 1998Kohyama et al, , 2005bKohyama et al, , 2007bÇakir et al, 2012).…”

“…We can evaluate the mastication effort using an indicator, the total muscle activity of both masseter muscles until swallowing (Kohyama et al, 2005b). Mastication of more adhesive foods such as caramels and rice cakes (mochi) leads to greater activity of the suprahyoid muscles, which act in the jaw-opening phase (Sakamoto et al, 1989;Kohyama et al, 1998Kohyama et al, , 2005bKohyama et al, , 2007bÇakir et al, 2012). Soft foodstuffs such as jellies are eaten through compression between the tongue and the hard palate without chewing with the back teeth, where the masseter activity is very weak, while the suprahyoid activity is observed more significantly (Nakazawa and Togashi, 2000;Ishihara et al, 2011).…”

“…A larger size of sample often results in a longer period of oral processing, larger number of chewing, and higher EMG amplitude (Dantas and Dodds, 1990;Palmer et al, 1999;Miyawaki et al, 2000;Kohyama et al, 2005bKohyama et al, , 2007aWoda et al, 2006;Miyaoka et al, 2010;Ashida et al, 2010). We compared EMG variables during free eating of rice gruel (5 g and 10 g), and found that 10 g gruel exhibited significantly higher EMG variables corresponding to mastication time such as number of chews, chewing time, and total muscle activity than 5 g. However there were no significant differences between 5 g and 10 g in EMG variables per chew such as EMG amplitude, duration, muscle activity or muscle work, and chewing cycle (Kohyama and Nakayama, 2004).…”