The present study aimed to examine the effects of rice particles in test foods and their visual appearance on oral textural perceptions. One original and three filtered Amazake (a traditional Japanese beverage made from malted rice) preparations were used as test foods. Three physical measurements of the test foods were conducted at room temperature: linear spread test, viscosity, and concentration of rice particles. Results of these three measurements formed two groups with lesser and more filtered test foods. Sensory evaluation experiments using a paired comparison test in 32 healthy young participants revealed the following: 1) the estimates of “grittiness in the mouth” (mouth feel) and “grittiness at a glance” of the test foods also comprised two groups, similar to the results of the physical measurements, 2) estimates of textural “smoothness” resulted in two groups, with a half-range of two items of “grittiness”, and 3) estimates of “sweetness” and “odor intensity” were similar to each other than to the other three items. Functional relationships between physical properties and characteristics of the test foods and sensory evaluation of their grittiness (oral, textural, and visual) of Amazake are discussed.
A keystone study classified textural parameters of foods and proposed three main categories [
Amazake is a Japanese food produced from malted rice or sake lees. Because both types of Amazake are nutritious and flavorsome, they are recommended to people of all age groups. However, the presence of rice particles owing to malted rice apparently renders people hesitant to consume it [
To the best of our knowledge, few studies have examined oral perceptions using natural particle products in suspension. In the present study, we examined the effects of particles in Amazake test foods prepared using malted rice and visual observation of the test foods on oral textural perceptions. The results showed that the concentration of particles did not simply reflect grittiness or smoothness, and that visual observation strongly affected these perceptions.
A commercially available bottled Amazake (Houraiya Ltd., Niigata, Japan) was used as basic test food in the present study. The test food was filtered (under gravity) using three different sieves of pore diameters 1.5, 3.0, and 5.0 mm (
Test food | #1 | #2 | #3 | #4 |
---|---|---|---|---|
Pore diameter (mm) | 1.5 | 3.0 | 5.0 | -a |
Weight after filtration (g) | 3.8 (0.3) | 5.1 (0.7) | 8.9 (0.5) | 10.0 (0.0) |
Values of weights are means (SD in parentheses). aThe original and non-filtered test food. See the text for details.
Length | Width | Height | |
---|---|---|---|
Size (mm) | 3.3 (0.87) | 2.3 (0.47) | 1.6 (0.35) |
Values of dimensions are means (SD in parentheses).
The Brix value and pH of the test foods were 21.3% (n = 5) and 5.2 (n = 5), respectively. The overall intensity of odor of the four test foods was measured mechanically (XP-329III, New Cosmos Electric CO., LTD, Osaka, Japan). One-way analysis of variance (ANOVA) of the measured values revealed that average intensities were not statistically different among the four test foods.
Three physical measurements of the four test foods were conducted at room temperature (i.e., 25˚C) as reference for the results of sensory evaluation. First, linear spread test [
Second, the viscosity of test foods was determined using a single cylinder rotational viscometer (TVB-10M, TOKI SANGYO CO., LTD, Tokyo, Japan). A 500 mL glass beaker (inner diameter 85 mm) was filled with one of the test foods and placed under a measurement rotor with a diameter of 25 mm. The rotor was selected for lower viscosity samples, such as the present test foods, and was vertically immersed in the test food three times. Rotational speed and time were determined according to the manufacturer’s instructions: 1) rotational speed of 20 rpm was determined as the lowest speed that could avoid both over- and under-scale errors due to excessive over- and under-torquing, and 2) the time point 60 s after the start of measurements was determined as the minimum time at which measurement values were stabilized. Rotational viscosity was measured as stress applied to the rotor (measured in mPa・s).
Finally, the concentration of rice particles was determined: 1) 7 g of each filtered test food was leveled off using a spoon, 2) the sample was spread evenly on a paper sheet, and 3) number of clear (i.e., countable) rice particles (see
Thirty-two healthy young adults [16 males and 16 females, 20.5 ± 2.9 (mean ± SD) years old] participated in this study. The participants received remuneration and were undergraduate students of Niigata University of Health and Welfare, and were not trained for sensory evaluations in this study. None of the participants had any subjective problems with gustatory and olfactory functions. Informed consent was obtained from all participants.
The experiment was conducted in an air-conditioned room maintained at 25˚C. An experimental set consisted of eight participants simultaneously, with four such sets in total. Participants were comfortably seated on chairs. After instructions were delivered by the experimenter, participants were invited to ask any questions about the experiment. During the experiment, participants were required not to talk to the others concerning any matters related to the experiment. Subsequently, participants were asked to rinse their mouths with tap water and were instructed to repeat rinsing whenever the test foods were changed. A session consisted of 12 [4 × (4 − 1)] trials for each participant, with a 1-min break between trials. A 5-min rest period was also introduced after the first half of each session to prevent participant fatigue.
A modified method of Scheffe’s paired comparison was used. Each participant was provided with two foods (10 mL each), which were randomly selected in each trial, and they were asked to compare the perceived intensity of the latter with that of the former. Five items were adopted for evaluation: 1) “grittiness at a glance”, 2) “overall intensity of the odor”, 3) “grittiness in the mouth”, 4) “smoothness”, and 5) “sweetness.” The former two items were evaluated before ingestion and the latter three items after ingestion. The comparison of intensity was quantified on a seven-step graded scale (from −3 to +3).
After Bartlett’s test for examining homogeneity of variances, physical measurements were analyzed using one-way ANOVA for parametric variables (linear spread test [LST] and viscosity) and using Kruskal-Wallis test for non-parametric variables (the concentration of rice particles). Confidence intervals between pairs of test foods were estimated to detect specific differences. Scores obtained from sensory evaluation were statistically analyzed using three-way ANOVA using “main effect (the five items)”, “participant”, and “main effect × participant”, based on the design of the modified Scheffe’s method. Differences were regarded as statistically significant where P < 0.05.
As seen in
the four test foods, and specific differences were also identified between four of the 12 possible pairs of test foods for LST values (
Particle concentration is one of the major determinants of grittiness of food in the mouth [
Estimates of “grittiness at a glance” (
The average LST (
Estimates of the two chemical sensory items, the overall intensity of odor and sweetness, of the test foods were much more similar to each other (
The first major limitation of the present study is associated with the test foods used. Three of the four test foods were filtered using three different sieves (
The concentration of Amazake’s particles does not simply reflect oral grittiness or smoothness, and visual observation of the particles strongly affects these perceptions.
The authors would like to thank Enago (https://www.enago.jp/) for the English language review.
Ajiro, M., Araki, M., Ishikawa, M., Kobayashi, K., Ashida, I. and Miyaoka, Y. (2017) Analysis of Functional Relationships between Rice Particles and Oral Perception Using Amazake: A Traditional Japanese Beverage of Malted Rice. Food and Nutrition Sciences, 8, 901-911. https://doi.org/10.4236/fns.2017.810065