Texture Evaluation of Cooked Rice Prepared from Japanese Cultivars Using Two‐Bite Instrumental Test and Electromyography

Abstract

The objective of this study was to determine the effects of texture of cooked rice on the natural chewing behavior of people who habitually consume rice. Eight Japanese cultivars varying in amylose content and protein content were selected and cooked rice samples with various texture were prepared. Instrumentally measured textural parameters were highly correlated with the amylose content but not with protein content. Electromyography (EMG) from both masseter muscles was recorded during natural eating for 10 men. The number of chews, mastication time and sum of muscle activities were significantly higher in the harder rice samples from high amylose cultivars. The burst duration and muscle activities per chew were also high; however, the interburst duration was low in rice with a high amylose content. EMG variables per chew were compared in the early, middle and late stages of mastication. The amplitude and muscle activities decreased in the late stage, whereas the interburst duration and cycle time increased for all cultivars and the burst duration was similar. No significant correlations between EMG variables and protein content were found. Amylose content influences the texture of cooked rice and also chewing behavior, but the effects of amylose content were diminished at the late stage of mastication. EMG was useful for analyzing natural eating behavior as well as dynamic changes in texture during mastication of cooked rice. Practical Applications The texture of cooked rice is due to the amylose content in starch contained in rice grains. Many parameters obtained from instrumental and electromyography (EMG) measurements were significantly correlated with the amylose content. EMG is useful for analyzing eating behavior and dynamic changes in texture during mastication. Raw EMG variables analyzed through repeated‐measure analysis of variance (ANOVA) and standardized EMG variables using a control sample followed by ANOVA provided similar results for different cultivars. Both raw and standardized EMG variables correlated with instrumentally measured parameters. Standardization of EMGs is not necessary if the number of chews, time for oral processing, chewing cycle are of interest. These absolute values are useful for designing the texture of foods and optimizing the cooking method if there is not a good control material. The standardized EMGs clearly indicate degree of texture effects on each variable.

Supporting young researchers in food texture studies

“…My first EMG study, which was published in the JTS , was about the effects of different rice cultivars on the texture of cooked rice (Kohyama et al, ). I have also published more recent studies on rice texture (Kohyama et al, ).…”

“…Kohyama et al () selected eight rice cultivars (1–8) whose apparent amylose levels were 0.45, 2.2, 8.5, 10.7, 17.6, 20.0, 31.2, and 33.3%, respectively. EMG of both masseter muscles from 10 subjects who freely consumed a spoonful (6 g) of cooked rice was performed, and EMG variables were evaluated during each chewing motion (Figure ).…”

“…The variables from both the entire mastication process and the early stage of mastication correlated to PC1, whereas those from the middle and late stages of mastication more strongly correlated with the second principal component (PC2). We measured many physico‐chemical properties of the original rice and cooked rice samples (Kohyama et al, ), but PC2 was not characterized in terms of the rice cultivars.…”

“…Mean and standard deviation values of EMG measurements for 10 subjects. Cultivars 1 and 2 are waxy (blue bars), 3 and 4 have low amylose levels (green bars), 5 and 6 have normal amylose levels (orange bars), and 7 and 8 have high amylose levels (red bars) (Calculated from original data by Kohyama et al, )…”

Comparison of a Double Compression Test for the Prediction of Sensory Texture Attributes of Cooked Rice to a Single Compression Test

“…Instrumental methods found in the literature include the General Foods Texturometer (Okabe, 1979;Szczesniak and Hall, 1974), the Instron Food Tester (Juliano et al, , 1984Juliano, 1979, 1981), the Haake Consistometer (Kumar et al, 1976), various uniaxial compression tests (Champagne et al, 1998;Li et al, 2016;Sesmat and Meullenet, 2001), the Ottawa texture measuring system Perez and Juliano, 1979;Rousset et al, 1995;Sitakalin and Meullenet, 2000), the Kramer shear cell , the dynamic rheological testing (Li et al, 2016), and the two-bite instrumental test and Electromyography (Kohyama et al, 2016).…”