Quality Evaluation of Rice Crackers Based on Physicochemical Measurements

110931 (137)

Biosci. Biotechnol. Biochem., 76 (4), 110931-1–11, 2012

y Sumiko NAKAMURA, Dai SUZUKI, Ryota KITADUME, and Ken’ichi OHTSUBO1;

Graduate School of Natural Sciences, Niigata University, 8050 Ikarashi-ninocho, Nishi-ku, Niigata 950-2181, Japan

Received December 5, 2011; Accepted January 10, 2012; Online Publication, April 7, 2012 [doi:10.1271/bbb.110931]

The processing suitability as a material for rice Australia and China. Rice crackers have been accepted crackers was characterized in the present study, based by many consumers because they are palatable, low in on physicochemical measurements and sensory testing of calorie, and can be preserved for a long time. The high-quality premium rice, low-amylose rice, Japonica- revision of the Act of JAS (Japanese Agricultural Indica hybrid rice, and red rice as the rice cultivar Standards) in 2003 and the enforcement of the ‘‘Rice samples. Puffed rice crackers were prepared and the Traceability Law’’ in 2011 makes it obligatory for the relationship between the physicochemical properties of rice cultivars, location and year of production to be the rice grains and the quality of the resulting products described on a the packaging of milled rice, brown rice, was investigated. It was possible to estimate the physical rice flour, and various kinds of processed rice products properties of a rice cracker by using multiple-regression including rice crackers. It is therefore indispensable to analysis based on the chemical components, pasting have techniques, to identify or differentiate them by properties and physical properties of the constituent objective methods.6) rice.Advance A formula for estimating the amylose View content of Traditional baked Japanese rice crackers include the constituent rice was developed from the results of senbei and arare.7–9) Arare is a cracker made from physicochemical measurements of the rice crackers. We boiled waxy rice, pounded into rice cake with a mochi assayed the quality of commercial rice crackers and pounding machine and stored at 2–5 C for 2–3 d to examined the deterioration during the storage by harden, before cutting, drying to 20% moisture content, measuring the physicochemical properties. The hardness and baking at 200–260 C. Sesame seeds, pieces of dried and fat acidity of crackers increased markedly during seaweed, peanuts, pulverized shrimp, cheese, or spices storage for 20 d at 35 C. The novel method of a one-bite can be mixed with the rice dough if desired. Senbei is a test with a Tensipresser was useful to assay. The quality cracker-like snack made from cooked non-waxy rice of a rice cracker and made it possible to evaluate the flour, which is kneaded and rolled into sheets, cut, dried quality deterioration of the rice cracker during storage. at 70–75 C to aProofs 10–12% moisture content, and finally baked at 200–260 C.7–9) The degree of starch gelatini- Key words: rice cracker; Tensipresser; physical property; zation expansion rate and degree of starch retrogradation sensory test; quality are important factors for the quality of rice crackers.10) Arare expands more than senbei during baking and Rice is one of the most important crops in the world produces a softer texture, and can be easily dissolved together with wheat and corn. World rice production is while eating. Senbei is harder and rougher than arare. expected to be 450 million metric tons (milled basis) in The classification of rice crackers based on quality 2011/2012, with Japan producing 7.68 million metric shows-Uki-type crackers to have a higher specific tons. Rice is used as table food and for various food volume (above 4.0 mL/g), and Shime-type ones to have processing applications such as sake wine, rice snacks a lower specific volume ratio (3.5–4.6 mL/g).7–9) and rice cake. About 10% of the total rice production in Japanese rice crackers are produced by many proce- Japan is consumed as the material after rice processing. dures, and the development of novel techniques to 223 thousand tons of rice crackers being produced in stabilize the quality of rice crackers therefore important. Japan in 2010.1) Saito et al. have conducted research into the character- The rice-based foods have also been diversified and istics of rice starch by an X-ray analysis for its change such convenient products, as frozen cooked rice, retort- during the manufacturing procedures, by X-ray analysis, pouched cooked rice and aseptic cooked rice, have and the degree of for its change during the manufactur- increased markedly. However, the total rice consump- ing procedures and by an amylograph for the degree of tion is decreasing year by year in Japan. It is necessary gelatinization.10,11) The degree of retrogradation of to provide new characteristic rice cultivars or high- starch, during and after the manufacturing operation quality rice products which can satisfy the requirements has also been evaluated by amylography.10) of the food industry and consumers, and lead to As examples of rice crackers produced in Asian increased rice consumption.2–5) countries, Malao (a rice-based snack in Taiwan),9) Rice crackers are one of the traditional rice products gangjung (a traditional Korean oil-puffed snack),12) in Japan and other Asian countries and their consump- and fried rice-black gram dough13) have been reported tion has recently been increasing in USA, Europe, to be popular in each country.

y To whom correspondence should be addressed. Tel/Fax: +81-25-262-6360; E-mail: [email protected] Abbreviations: Max vis, maximum viscosity; Min vis, minimum viscosity; Final vis, final viscosity; Max stress, maximum stress 110931-2 S. NAKAMURA et al. Extrusion cooking is another dominant processing companies in Niigata prefecture and were purchased in the local method for snack foods, particularly, in Europe and market. North America, which is used to modify the functional Measurement of the moisture content. Milled rice grains for puffing and digestible characteristics of cereal grains due to its and the hand-made rice crackers were pulverized with an IFM-100 14–18) low cost and capability for continuous processing. coffee mill, (Iwatani, Tokyo, Japan), and the moisture content of the Such extruded cereal grains, as wheat, corn, millet, flours was measured by an oven-drying method,25) drying 2 g of flour at and rye have been tested for their digestibility and 135 C for 1 h described in the previous reports.7–9) Commercial rice palatability. crackers were crushed with a coffee mill, and the moisture content of The ease of ingestion and palatability of rice crackers the broken granules was measured by an oven-drying method, drying 2 g of the flour at 135 C for 3 h. for aged people have been studied by compression testing, electromyographe (EMG) recording of the Amylose content. The amylose content of the milled rice was masticatory muscles and sensory evaluation.19) Although measured by the iodine colorimetric method of Juliano.26) Type III several attempts have been made to classify the hardness potato amylose (Sigma Chemical Co., St. Louis, MO, USA) and waxy of rice crackers based on their physical properties and rice starch (with the fat and proteins removed from waxy rice) were sensory evaluation, such attempts have revealed that the respectively used as standard amylose and standard amylopectin for the physical properties of rice crackers evaluated by a single amylose determination. physical measurement did not completely match the 19,20) Protein content. The nitrogen content was measured by theofficial result of the sensory evaluation. Takahashi et al. AOAC (Kjeldahl) method, and the protein content was then calculated have combined two kinds of measurement, of density by multiplying by the nitrogen-protein conversion coefficient of measured as the specific volume and of maximum 5.95.27) rupture force measured with a creep-meter, which showed high correlation with the rating by a sensory Measurement of the pasting properties of the rice flour samples. evaluation.20) The pasting properties of the rice flour samples were measured with an Nakagawa et al. have studied the method of sun RVA Super 4 model rapid-visco-analyzer (New-port Scientific Warrie- Advance Viewwood, New South Wales, Australia). As sample (3.5 g based on 14% drying rice crackers, and reported that the flavor and moisture) was added to 25 mL of water. The sample cup was fitted to texture of rice crackers were both influenced by the the rotor of the RVA and heated at 50 C for 1 min and then to 93 Cin 21) drying method (sun drying or artificial drying). It 4 min. The sample temperature was held at 93 C for 7 min, and then therefore, seems very important and meaningful to cooled from 93 Cto50C in 4 min, before finally being allowed to develop a novel and simple method to evaluate the stand for 3 min at 50 C. The programmed heating and cooling cycle 28) quality of rice crackers, which matches well with the was followed as outlined by Toyoshima et al. results of a sensory evaluation. Yamada et al. have studied the suitability of newly- Measurement of the physical properties of cooked rice grains. Each rice grain sample (10 g) for hand-made rice crackers was put into a developed rice cultivars for processing rice crackers pudding cup, water (16 g) was added, and the sample soaked for 1 h at and proposed that the pasting properties could be good 25 C. Five of these pudding cups (5 cups) were transferred to an RC3 indices for the expansion of rice crackers.22) It is electric rice cooker (Toshiba,Proofs Tokyo, Japan) and cooked as described necessary to elucidate the relationship between the in our previous report.24,29) The physical properties of the cooked rice properties of the rice material and the qualities of the grains were measured by the high-compression/low-compression rice cracker product to enhance the consumption of rice method with a My Boy Tensipresser (Taketomo Electric, Co., Tokyo, Japan) under the same conditions as those reported in our previous crackers by using newly-developed rice cultivars. paper.29) Although it is well known that rice crackers can be stored for a long period because of their low moisture Measurement of the physical properties of the rice crackers. The content, their palatability gradually deteriorates during physical properties of the rice crackers were measured by the one-bite storage. We carried out a storage test commercial rice test with the MyBoy Tensipresser (Taketomo Electric, Co., Tokyo, crackers and examined their quality deterioration during Japan) under the following; Plunger (13 mm diameter), saucer (80 mm storage. We have already reported novel methods to length, 80 mm width), bite speed 2 mm/s; distance, 30 mm; clearance, measure the fat acidity23) and physical properties24) of 3 mm; thickness, 15 mm; Base line, 3; Load cell, 10 kg. Measurements were taken five 5 times and the data were statistically treated by using rice during and we used these methods for detecting the the software provided with the Tensipresser (Fig. 1), which gave the quality deterioration of rice crackers during storage. H1, A1, A2, A3, L1, L2, L3, S1, fracture, inflection, and Max stress of the rice crackers. H shows the compression force of the plunger, L Materials and Methods shows the moving distance of the plunger, A shows as the area surrounded by the stress profile and abscissa (workload), fracture Materials. Japonica and Indica hybrid rice, and Hoshiyutaka high- shows the peak subtracted from the bottom, inflection is shows INF1, amylose rice, were cultivated in an experimental field of Kyushu INF2 and INF3, and Max stress shows the maximum compression load. University in 2008. Koshihikari high-quality premium rice and Yumetoiro high amylose Indica rice were cultivated in an experimental Sensory evaluation. The sensory test was carried out by the method field of Hokuriku Research Center in Joetsu in 2008. Benisarasa red reported in our previous paper for wheat/rice bread.30) The handmade rice, Natsugumo and Akigumo low-amylose rice, Koshinomenjiman puffed rice crackers were subjectively scored by 10 trained taste high-amylose rice, and Takanari Indica rice, were cultivated at the panelists. Five ranking were used to evaluate the appearance, aroma, Niigata Prefectural Agricultural Research Institute in 2008. hardness, taste and overall liking. Puffed rice crackers for the sensory test were prepared by the above-mentioned method from milled grains Commercial rice cracker and handmade rice cracker samples. of Koshihikari and Hoshiyutaka rice, a puffed rice cracker made from Milled grains (7 g) of Hoshiyutaka, Koshihikari, Yumetoiro, Benisarasa, Hoshiyutaka rice being used as a control (3 points). The commercial Natsugumo, Akigumo, Koshinomenjiman and Takanari rice were rice crackers were scored subjectively by the 10 trained taste panelists baked with a puffing grain machine (Tatibanakikou, Co., Ltd.) at for very soft (10 points), soft (20 points), a little soft (30 points), 220 C for 10 s. The pressures during the steady state was 10.0 MPa. neither soft nor hard (40 points), a little hard (50 points), hard (60 Commercial rice crackers were made by several confectionery points), and very hard (70 points) with the focus on hardness. Physical Properties of Rice Crackers 110931-3

F A, C, E : Inflection E F : Max Stress B: First Max Fracture Point Fracture Fracture = Peak -Bottom B A C G : Max Negative Compressive stress Point D

H 1 : Peak

Bottom A 2 A 1

L 3

A 3 L 2 S 1

L 1 G

Fig. 1. Texture Proﬁle of a Rice Cracker Measured by the One-Bite Method with a Tensipresser. A, C, and E, Inﬂection; F, Max stress; B, First max fracture point; Fracture, peak-bottom; G, Max negative compressive stress point. The physical properties of the rice crackers were measured by the one-bite method with a My Boy Tensipresser (Taketomo Electric, Co., Tokyo, Japan). The following conditions were used; plunger (13 mm diameter), saucer (80 mm length and 80 mm width), bite speed (2 mm/s), distance (30 mm), clearance (3 mm), thickness (15 mm), base line (3), load cell (10 kg).

Table 1. Main Chemical Components and Physical Properties of Milled Rice

Balance Balance AdvanceMoisture SD Amylose SD Protein SD ViewH1 SD H2 SD S1 SD S2 SD L3 SD A1 SD A2 SD 2 2 2 2 % % % gw/cm gw/cm gw/cm [gw/cm ] [mm] (A3/A1) (A6/A4) Koshihikari 12.5a 0.06 17.6a 0.21 5.5a 0.06 68.3a 16.0 1499.0a 190.3 7.1a 4.2 365.2a 61.3 2.9a 0.7 0.17a 0.1 0.10a 0.0 Hoshiyutaka 11.2b 0.10 29.9b 0.15 6.3b 0.10 88.5a 19.0 2093.0b273.3 3.0b 1.5 141.1b 52.8 2.6a 0.9 0.07b 0.0 0.04b 0.0 Yumetoiro 12.3a 0.06 32.0c 0.10 6.9b 0.10 99.3a 19.3 2291.0b175.5 0.9b 0.1 9.1c 12.3 2.7a 0.7 0.04b 0.0 0.04b 0.0 Takanari 13.3c 0.05 19.0a 1.02 5.5a 0.05 62.4a 11.0 2148.0b210.2 4.6b 1.3 285.0d 61.8 2.5a 0.9 0.20a 0.1 0.08a 0.0 Benisarasa 13.2c 0.39 15.7d 0.24 5.4a 0.05 60.9a 12.3 1864.7b199.5 7.4a 2.9 362.7a 55.2 2.9a 0.6 0.41c 0.2 0.11a 0.0 Koshinomenjiman 13.8c 0.31 28.4b 0.19 5.4a 0.05 82.0a 17.2 2281.3b235.8 4.3b 1.6 201.4d 48.6 2.8a 0.7 0.19a 0.1 0.05b 0.0 Akigumo 13.4c 0.20 11.0e 0.06 5.5a 0.05 55.1b 11.3 1716.7a 161.8 10.8c 3.7 355.5a 35.4 2.8a 0.6 0.60d 0.3 0.18c 0.1 Natugumo 13.2c 0.09 7.2f 0.09 6.1b 0.05 54.0b 11.1 1621.3a 207.7 10.5c 3.6 341.3a 51.6 2.9a 0.5 0.64d 0.3 0.18c 0.1 Correlation significant at 5% by the method of Tukey. same letter means not significantly different. Proofs Moisture: Oven-dry method Amylose: Iodine colorimetric method Protein: New Infra-red reflectance method H1, H2, S1, S2, L3, Balance A1, Balance A2; Measured one-bite test with a Tensipresser

Measurement of the fat acidity of the rice crackers. The fat acidity Results and Discussion of the rice crackers was measured by the colorimetric method of 23) Ohtsubo et al. The flour sample of crushed rice crackers (100 mg) Moisture content was put into a stoppered test tubes (10 mL, Sibata, Science Co., Saitama, Japan), and 6 mL of toluene was added and mixed well to Rice and processed rice quality is greatly affected by extract the free fatty acid for 30 min at 30 C. The solution was passed the moisture content; the higher the amount of moisture, through a no. 2 filter paper (110 mm diameter, Advantec, Tokyo, the faster the quality of a rice crackers deteriorates. Japan). One mL of the filtrate solution was put into a different The moisture content of rice and processed rice stoppered test tube, and 4 mL of chloroform and 2.5 mL of a copper therefore needs to be kept at a low level. Table 1 shows reagent (90 mL of 1 M triethanolamine 90 mL, 10 mL of 1 N acetic acid, that Hoshiyutaka, the Japonica and Indica hybrid rice and 100 mL of 0.45% copper nitrate) were added and mixed well. After had a low moisture content (11.2%), while the other rice centrifugation (1500 g, 5 min, 4 C), this solution was separated into a copper solution (the water phase) and chloroform solution (the organic samples had a moisture content the range of 12.3%– solvent phase). The copper solution was removed, 3 mL of the 13.8%. The moisture content of the constituent rice was chloroform solution was put into a different stoppered test tube, and adjusted to about 10% before baking and the moisture 0.5 mL of a coloring reagent (0.1% sodium diethyldithiocarbamate in content of the rice cracker was kept at about 3%–5% isobutyl alcohol) was added, mixed well and the tube stood for 30 min after baking as reported in the previous references.7–9) at 20 C. The absorbance of the solution was measure at 440 nm with a UV-1600 spectrophotometer (Shimadzu, Kyoto, Japan). A calibration Apparent amylose content curve was made with linoleic acid, and the amount of free fatty acid was calculated according to this calibration. The fat acidity ratio is Amylose is a non-branched 1, 4 glucan, which is one expressed as the volume of potassium hydroxide to neutralize the free of the components of rice starch and greatly affects the fatty acid in 100 g of rice flour (dry matter). quality and gelatinization properties of cooked rice.25,29) Low-amylose rice generally becomes soft and sticky Statistical analyses. All the results, including the significance of regression coefficients, were subjected to a statistical analysis by the upon cooking, while high-amylose rice becomes hard 29) t-test and one way ANOVA according to the method of Tukey, with the grains separated. The starch of low-amylose provided in Excel Statistics (ver. 2006, Microsoft Corporation, Tokyo, rice is not easily retrograded as Takami et al. have Japan). reported.31) The quality of rice crackers is affected by 110931-4 S. NAKAMURA et al. their amylose content.22) Table 1 shows that the amylose (4.3 gw/cm2) had lower values than Takanari (4.6 gw/ contents of Yumetoiro (32.0%), Hoshiyutaka (29.9%) cm2). In contrast, Koshihikari, rice with good eating and Koshinomenjiman (28.4%) were high, not endowing quality showed the highest value for overall stickiness them with good eating characteristics, but they were (365.2 gw/cm2, S2) and the lowest value for overall suitable for processing rice flour, rice noodles, pilaf and hardness (1499.0 gw/cm2, H2), while Yumetoiro, a curry rice. Takanari (19.0%) is characterized as having a high-amylose cultivar, showed the lowest value for medium amylose content, making it suitable for the hard overall stickiness (0.9 gw/cm2, S2) and the highest type of rice crackers, dumplings, brown rice tea and value for overall hardness (2291.0 gw/cm2, H2). The rice bread.2–5) The red rice, Benisarasa, showed a low values of Balance A1 (the ratio of work for adhesiveness amylose content (15.7%) and, seemed to be suitable for to work for hardness of the surface layer of the cooked the soft type of rice cracker. It would also be useful for rice grains, A3/A1) and Balance A2 (the ratio of work unpolished rice food, unpolished rice porridge and rice for adhesiveness to work for hardness of the overall snacks, because the red pigment is localized only in the layer of the cooked rice grains, A6/A4) are important outer layer of the kernel. Koshihikari (17.6%) showed indices in evaluating the palatability of rice.29) For a low amylose content and has the best eating quality balance A (A3/A1), Akigumo (0.60) and Natsugumo in Japan.6,29) Akigumo low-amylose rice (11.0%) and (0.64) showed higher values than Koshihikari (0.17) and Natsugumo (7.2%) are characterized as having an Benisarasa (0.41), while Yumetoiro (0.04) showed lower exceptionally low amylose content, their starches is values than Hoshiyutaka (0.07), Takanari (0.20) and therefore not easily retrogradad and maintains high Koshinomenjiman (0.19). Among these textural analy- stickiness well. These two cultivars are expected to be ses, the degrees of change in the hardness and stickiness suitable for rice crackers (soft type), box lunches and obtained by the low-compression test could well express rice balls.5,22) Low-amylose rice was found generally the degree of staling of cooked rice, and Akigumo and suitable for soft-type rice crackers because it expanded Natsugumo, low-amylose cultivars, were found to be well, while high-amylose rice was suitable for hard-type stale-resistant rice cultivars as Takami et al. have Advance View22) rice crackers because it did not expand well. Among previously reported for the staling characteristics of the components, increasing the amylose content of the the cooked low-amylose rice cultivar, Snowpearl.31) The starch decreased the expansion rate of rice crackers as palatability and acceptability of rice are greatly affected reported by Yamada et al.22) by the physical properties of hardness and stickiness. Koshihikari, Benisarasa, Akigumo and Natsugumo, Protein content as low-amylose cultivars, showed good eating qualities Protein is the second most abundant constituent of due to their physical properties of low hardness and milled rice after starch. The amount of protein affects high stickiness, while Yumetoiro, Hoshiyutaka and the physical properties of cooked rice grains, the higher Koshinomenjiman with high-amylose content, exhibited the protein content, the harder and less sticky the rice a hard texture with high hardness and low stickiness. grains become upon boiling.32) The protein content of Takanari, a softProofs type of Indica cultivar, showed a soft Japonica milled rice is generally 6.8%.31) Table 1 shows texture after cooking, for example, low surface hardness that the protein contents of Koshihikari (5.5%), Takanari and medium overall stickiness. (5.5%), Benisarasa (5.4%), Koshinomenjiman (5.4%) and Akigumo (5.5%) were low, while Yumetoiro Pasting properties of rice the flour samples from the (6.9%), Hoshiyutaka (6.3%) and Natsugumo (6.1%) various cultivars had intermediate protein contents. Since the pasting properties also influence rice eating quality, it is meaningful to conduct a gelatinization test Physical properties of cooked rice grains for a quality assay of rice crackers. Break down The measured physical properties of the cooked rice indicates the ease with which the starch granules were grains by low-compression (25%) and high-compression disintegrated.11) High-amylose cultivars had a higher (90%) methods24,29) with the Tensipresser are shown in final viscosity than low-amylose cultivars, the final Table 1. A clear difference was detected by the LC viscosity being related to the degree of starch retro- (low-compression) test for H1 (surface hardness). There gradation upon cooling.22) The expansion rate of rice was a difference in H1 between Natsugumo (54.0 gw/ crackers upon roasting has showned a highly negative cm2) and Akigumo (55.1 gw/cm2) as cultivars with very correlation with the ratio of Final viscosity to Max. low amylose content and Koshihikari (68.3 gw/cm2) and viscosity and the ratio of Consistency to Break down on Benisarasa (60.9 gw/cm2) with low amylose content. an amylogram.22) Table 2 shows that consistency value There was also a difference in H1 among Yumetoiro for Koshinomenjiman, a high-amylose cultivar, was (99.3 gw/cm2), Hoshiyutaka (88.5 gw/cm2) and very low for Akigumo (78.9 RVU) and Natsugumo Koshinomenjiman (82.0 gw/cm2) as cultivars with high (64.6 RVU), both low-amylose cultivars, was low, while amylose content, while Takanari had a medium value for Koshihikari (144.2 RVU), Takanari (120.8 RVU) (62.4 gw/cm2), being the soft type of Indica rice. and Benisarasa (118.2 RVU) was a medium value. Cooked rice grains with higher amylose contents On the other hand, Yumetoiro (293.8 RVU) and generally have a harder texture.29) The surface stickiness Hoshiyutaka (232.6 RVU), high-amylose cultivars, in- (S1) data show higher values for Akigumo (10.8 gw/ dicated a high value. The ratio of consistency to cm2) and Natsugumo (10.5 gw/cm2) than Koshihikari breakdown (consistency/breakdown) of Yumetoiro (7.1 gw/cm2) and Benisarasa (7.4 gw/cm2). Yumetoiro (1.8) was very high, that of Hoshiyutaka (1.4) was high, (0.9 gw/cm2), a high-amylose rice, had the lowest value, while those of Koshihikari (0.5), Benisarasa (0.5), while Hoshiyutaka (3.0 gw/cm2) and Koshinomenjiman Takanari (0.5) and Koshinomenjiman (0.5) were low, Physical Properties of Rice Crackers 110931-5 Table 2. Pasting Properties of Milled Rice Flour

Pasting Consis/ Final vis/ Sample Max vis Min vis Break down Final vis Setback Consistency temp B.D Max vis (RVU) SD (RVU) SD (RVU) SD (RVU) SD (RVU) SD (RVU) SD CSD SD SD Koshihikari 436.7a 16.7 160.0a 2.8 276.6a 14.0 304.2a 6.0 132:5a 10.8 144.2a 3.2 63.9a 0.5 0.5a 0.0 0.7a 0.0 Hoshiyutaka 341.7b 49.9 179.8b 20.7 161.9b 29.2 412.5b 43.0 70.8b 7.0 232.6b 22.2 66.1a 0.6 1.4b 0.1 1.2b 0.0 Yumetoiro 401.9c 8.5 249.1c 18.0 152.8c 9.5 517.5c 6.1 115.6b 2.41 293.8c 5.8 70.2b 0.5 1.8a 0.1 1.3b 0.0 Takanari 382.1b 4.9 142.8a 3.2 239.3a 3.9 263.6d 5.4 118:5a 7.0 120.8a 3.3 67.2b 2.0 0.5a 0.8 0.7a 1.1 Benisarasa 400.2c 3.5 179.6b 7.3 220.5a 5.6 297.8d 5.8 102:3a 4.1 118.2a 1.7 68.3a 1.9 0.5a 0.3 0.7a 1.7 Koshinomenjiman 246.4d 4.8 136.8a 5.0 109.7d 5.7 204.6e 2.8 49.7b 4.1 49.7d 4.1 62.8a 0.7 0.5a 0.7 0.8a 0.6 Akigumo 399.9b 3.1 113.5d 1.8 286.4a 3.0 192.5e 2.1 207:5c 3.1 78.9d 1.3 67.6b 3.6 0.3a 0.4 0.5a 0.7 Natsugumo 392.1b 3.3 93.3d 1.4 298.7a 2.2 157.9f 0.8 234:2c 2.6 64.6d 0.6 68.0b 4.6 0.2a 0.3 0.4a 0.2

Correlation significant at 5% by the method of Tukey. Same letter are not significantly different

Table 3. Correlation between Chemical Components and Physical Parameters of Milled Rice Samples

Max Min Final Cons/ Final/ Moisture Amylose Protein H1 H2 S1 S2 L3 Bal.A1 Bal.A2 B.D Setback Consis Past.T vis vis vis B.D Max Moisture 1.00 Amylose 0:49 1.00 Protein 0:63 0.53 1.00 H1 0:57 0.96 0.70 1.00 H2 0:08 0.81 0.38 0.71 1.00 S1 0.49 0:95 0:62 0:91 0:82 1.00 Advance View S2 0.49 0:88 0:79 0:94 0:80 0.87 1.00 L3 0.39 0:65 0:34 0:54 0:72 0.75 0.62 1.00 Balance A1 0.57 0:90 0:48 0:85 0:62 0.93 0.71 0.71 1.00 Balance A2 0.45 0:94 0:46 0:86 0:78 0.96 0.75 0.70 0.95 1.00 Max vis 0:22 0:48 0.08 0:35 0:63 0.33 0.33 0.25 0.23 0.44 1.00 Min vis 0:56 0.74 0.63 0.79 0.51 0:80 0:73 0:40 0:74 0:72 0.14 1.00 Break. down 0.20 0:91 0:37 0:84 0:87 0.82 0.78 0.48 0.70 0.86 0.73 0:57 1.00 Final vis 0:76 0.75 0.74 0.82 0.47 0:81 0:77 0:50 0:77 0:70 0.19 0.96 0:50 1.00 Setback 0:48 0.99 0.58 0.97 0.81 0:93 0:90 0:57 0:84 0:92 0:49 0.77 0:94 0.76 1.00 Consistency 0:82 0.67 0.79 0.77 0.39 0:74 0:76 0:52 0:70 0:61 0.27 0.89 0:38 0.98 0.67 1.00 Pasting.T 0:13 0:14 0.46 0:02 0.08 0:01 0:23 0:04 0.22 0.21 0.54 0.35 0.20 0.37 0:06 0.43 1.00 onsis/B.D 0:78 0.81 0.82 0.89 0.58 0:83 0:89 0:56 0:75 0:72 0.00 0.88 0:60 0.96 0.83 0.96 0.34 1.00 Proofs Final/Max 0:70 0.93 0.70 0.95 0.70 0:92 0:89 0:60 0:86 0:87 0:22 0.88 0:78 0.92 0.95 0.87 0.13 0.96 1.00

Correlation is significant or at 5% or 1%, respectively by the method of t-test. and those of Akigumo (0.3) and Natsugumo (0.2) were final viscosity to maximum viscosity (r ¼ 0:93), setback very low. The ratios of final viscosity to maximum (r ¼ 0:99), and with ratio of consistency/break-down viscosity (Final vis/Max vis) for Yumetoiro (1.3) and (r ¼ 0:81), and negative correlations with S1 (r ¼ Hoshiyutaka (1.2) were very high, for Koshinomenjiman 0:95), S2 (r ¼0:88), balance A1 (r ¼0:90) and (0.8) was high, while for Koshihikari (0.7), Benisarasa balance A2 (r ¼0:94) at the level of 1%. Since the (0.7) and Takanari (0.7) were medium values, and for cooked high-amylose rice samples were hard and tough, Akigumo (0.5) and Natsugumo (0.4) were very low. As it seemed that they could not be suitable as a material for a result, Koshinomenjiman, a high-amylose cultivar, is soft-type rice crackers, due to their higher ratio of final suitable for rice flour, rice noodles, the index of starch viscosity to maximum viscosity and the higher ratio of retrogradation indicating a low value. Akigumo and consistency to break down. Natsugumo, both low-amylose cultivars, are suitable for The protein content was positively correlated with rice crackers (the soft type) because their expansion rate Final vis (r ¼ 0:74), consistency (r ¼ 0:79), with the index had a high value; moreover, Akigumo and ratio of consistency/breakdown (r ¼ 0:82), and nega- Natsugumo are also suitable for box lunches, rice balls tively correlated with S2 (r ¼0:79) at the level of 5%. and rice blending, because their indices of low-amylose The surface hardness (H1) could distinguish the differ- starch retrogradation were low.31) Yumetoiro and ence in protein content among rice samples of the same Hoshiyutaka are suitable for the hard-type of rice cultivar.33) The value for H1 (surface hardness) was found cracker because their expansion rate indices had low to have a positive correlation with the protein content. values, and they tended to expand less than the other rice The results of this study show, H1 (surface hardness) cultivars. to be positively correlated with the ratio of consistency/ break down (r ¼ 0:89), the ratio of Final vis/Max vis Correlation among the physicochemical and pasting (r ¼ 0:95), and with setback (r ¼ 0:97) at the level of properties of the rice samples 1%, and negatively correlated with S1 (r ¼0:91), S2 Significant correlations among the physicochemical (r ¼0:94), balance A1 (r ¼0:85), balance A2 (r ¼ properties are shown in Table 3. The apparent amylose 0:86) and break down (r ¼0:84) at the level of 1%. contents showed positive correlations with the ratio of The surface hardness (H1) had a higher negative 110931-6 S. NAKAMURA et al. Table 4. Correlation among Physical Properties of Rice Crackers Measured by One-Bite Method a Tensipresser

H1 L1 A1 L2 A2 MAX MAX FRACTURE INF1 INF2 INF3 (rice.c) (rice.c) (rice.c) (rice.c) (rice.c) (rice.c) Stress H1 (rice.c) 1.00 L1 (rice.c) 0:36 1.00 A1 (rice.c) 0.16 0.56 1.00 L2 (rice.c) 0.82 0.04 0.60 1.00 A2 (rice.c) 0.97 0:41 0.26 0.84 1.00 MAX(rice.c) 0.57 0.13 0.85 0.85 0.66 1.00 FRACTURE 0:14 0:38 0.10 0:06 0:05 0.23 1.00 INF1 0.43 0:53 0.34 0.45 0.58 0.68 0.64 1.00 INF2 0.51 0:14 0.72 0.72 0.66 0.94 0.46 0.88 1.00 INF3 0.58 0.05 0.82 0.82 0.70 0.98 0.21 0.73 0.96 1.00 MAX Stress 0.88 0:58 0.22 0.71 0.94 0.64 0.26 0.73 0.72 0.67 1.00 Moisture 0.44 0.60 0.49 0.67 0.37 0.41 0:66 0:30 0.11 0.37 0.07 Amylose 0:06 0:37 0.20 0.07 0.06 0.26 0.87 0.57 0.47 0.28 0.34 Protein 0:25 0:22 0.19 0:28 0:14 0.19 0.68 0.59 0.40 0.26 0.10 H1 0:20 0:29 0.26 0:03 0:06 0.28 0.92 0.63 0.51 0.31 0.23 H2 0.39 0:28 0.33 0.44 0.43 0.50 0.66 0.56 0.58 0.51 0.62 S1 0.08 0.30 0:21 0.03 0:02 0:21 0:80 0:48 0:39 0:24 0:32 S2 0.09 0.25 0:28 0:03 0:01 0:35 0:91 0:66 0:54 0:37 0:28 L3 0.02 0.36 0.26 0.21 0.06 0.23 0:51 0:07 0.10 0.19 0:16 Balance A1 0.30 0.29 0:04 0.24 0.19 0.05 0:69 0:26 0:15 0.01 0:09 Balance A2 0.00 0.39 0:16 0:03 0:11 0:18 0:70 0:46 0:38 0:24 0:38 Max vis 0:60 0.41 0:20 0:69 0:68 0:50 0:22 0:57 0:58 0:57 0:65 Min vis 0:28 0:08 0.30 0:17 0:19 0.21 0.81 0.39 0.35 0.17 0.13 AdvanceBreak. down 0:31 0.39 0:37 View0:46 0:43 0:56 0:74 0:74 0:72 0:59 0:63 Final vis 0:38 0:22 0.08 0:37 0:30 0.02 0.86 0.38 0.22 0.00 0.04 Setback 0.02 0:39 0.27 0.15 0.15 0.38 0.89 0.69 0.59 0.40 0.43 Consistency 0:45 0:24 0:04 0:49 0:39 0:10 0.84 0.33 0.11 0:11 0:05 Pasting.T 0.03 0.16 0.16 0:10 0:05 0.17 0.23 0.11 0.12 0.09 0.05 onsis/B.D 0:28 0:35 0.05 0:28 0:19 0.09 0.94 0.55 0.33 0.10 0.15 Final/Max 0:15 0:43 0.11 0:12 0:03 0.18 0.95 0.61 0.43 0.19 0.30

Correlation is significant or at 5% or 1%, respectively by t-test. correlation by RVA with the factor for the expansion breakdown, amylose content, surface hardness (H1), rate of rice crackers similar to overall hardness H2. The final viscosity andProofs setback as a very useful indicator to surface stickiness (S1) showed positive correlations with distinguish the expansion rate of rice crackers. S2 (r ¼ 0:87), balance A1 (r ¼ 0:93) and balance A2 (r ¼ 0:96) at the level of 1%, and negative correlations Physical properties of the rice crackers with setback (r ¼0:93), ratio of consistency/break Young’s modulus can be experimentally determined down (r ¼0:83) and ratio of Final vis/Max vis from the slope of the stress-strain curve created during a (r ¼0:92) at the level of 1%. The surface stickiness compression test conducted on a sample of material. (S1) had a higher positive correlation by RVA with the Young’s modulus for anisotropic materials, may have factor for the expansion rate of rice crackers, similar to different values depending on the direction of the the overall stickiness (S2). The ratio of stickiness/ applied force with respect to the material’s structure. hardness (the balance degree) is an important index in As shown in Table 4, H1 showed positive correlation evaluating the palatability of rice in Japan. Balance A1 with A2 (r ¼ 0:97) at the level of 1%. L2 showed (the surface ratio of stickiness/hardness) showed a positive correlation with A2 (r ¼ 0:84) and Max stress positive correlation with balance A2 (r ¼ 0:95) at the (r ¼ 0:85) at the level of 1%. Max stress, one of the level of 1%, and a negative correlation with setback factors related the quality and characteristics of rice (r ¼0:84) and the ratio of Final vis/Max vis crackers, showed positive correlation with H1 (r ¼ 0:88) (r ¼0:86) at the level of 1%, similar to the overall and A2 (r ¼ 0:94) at the level of 1%. The profile of the ratio of stickiness/hardness (balance A2). physical properties of puffed rice crackers is shown in As a result, Min vis, which had a high correlation with Fig. 2A. The results, Max stress values of the high- ratio of Final vis/Max vis and with the ratio of amylose rice cultivars to be higher than those of low consistency/breakdown, was a more useful indicator to amylose rice. distinguish the expansion rate of rice crackers than the Figure 3 shows the indices of H1, A2 and Max stress Max vis value. Consistency was positively correlated for Koshinomenjiman to be higher than those for with the ratio of Final vis/Max vis (r ¼ 0:87) and with Yumetoiro and Hoshiyutaka, while the fracture value the ratio of consistency/breakdown (r ¼ 0:96) at the was lower than that for Yumetoiro and Hoshiyutaka. level of 1%. The ratio of consistency/breakdown was The amylose contents of Yumetoiro (32.0%), positively correlated with the ratio of Final vis/Max vis Hoshiyutaka (29.9%) and Koshinomenjiman (28.4%) (r ¼ 0:96) at the level of 1%. were for the overall stickiness (S2) of Koshinomenjiman We therefore propose the ratio of Final vis/Max vis, (201.4 gw/cm2) was higher than that for Yumetoiro which had high correlation with the ratio of consistency/ (9.1 gw/cm2) and Hoshiyutaka (141.1 gw/cm2). And the Physical Properties of Rice Crackers 110931-7

A E B F b B G ) ) ) 2 2 2 CD

a Load (gw/ cm Load (gw/ cm Load (gw/ cm A H

Distance (mm) Distance (mm) Distance (mm)

Fig. 2. Texture Proﬁles of Various Crackers Measured by the One-Bite Method with a Tensipresser. A: Puﬀed rice crackers. A, Koshihikari; B, Hoshiyutaka; C, Yumetoiro; D, Takanari; E, Benisarasa; F, Koshinomenjiman; G, Akigumo; H, Natsugumo. The high-amylose rice cultivars showed higher Max stress values than the low amylose rice cultivars. B: Commercial rice crackers. a, fresh commercial rice cracker; b, stale rice cracker (7 months after production). The stale commercial rice crackers showed higher H1 and Max stress values than the fresh commercial rice crackers.

2 (gw/cm2) (gw·cm/cm ) A 2 H 1 1400 20000 d d b b 1208 1241 18000 16070 1200 b 15720 b 16000 b b b 13650 b 13350 1000 927 14000 12660 882 b 11850 833 12000 c 800 c 9708 c 637 10000 a 586 600 8000 6436 a 6000 400 4000 249 200 Advance2000 View 0 0 1 2 3 4 5 6 7 8 1 2 3 4 5678

2 (gw/cm ) MAX Stress (gw/cm2) FRACTURE 20000 1200 b b b 1060 18000 b b c 16090 15760 941 15120 1000 16000 c c 13700 14000 13250 c 13420 800 a 11920 12000 a 10070 572 10000 600 a a 451 448 8000 a a 357 6000 400 338 c 4000 201 200 2000 Proofs 0 0 12345678 12345678

Fig. 3. Physical Properties of Handmade Rice Crackers Measured by the One-Bite Method with a Tensipresser. 1, Koshihikari; 2, Hoshiyutaka; 3, Yumetoiro; 4, Takanari; 5, Benisarasa; 6, Koshinomenjiman; 7, Akigumo; 8, Natsugumo. The significance of correlation (at the level of 5%) was examined by the method of Tukey. The same letter shows no significant difference. Among the high- amylose rice cultivars, Koshinomenjiman (28.4% amylose content), showed higher H1, A2 and Max stress values, and lower fracture than Yumetoiro (32.0% amylose content) and Hoshiyutaka (29.9% amylose 29.9%). value for the final viscosity, which is related to the 0:81), Final vis (r ¼ 0:86), setback (r ¼ 0:89), consis- degree of starch retrogradation, of Koshinomenjiman tency (r ¼ 0:84), ratio of consistency/breakdown (r ¼ (49.7 RVU) was lower than the values for Yumetoiro 0:94) and ratio of Final vis/Max vis (r ¼ 0:95) at the (293.8 RVU) and Hoshiyutaka (232.6 RVU) while the level of 1%. As suitable indices for evaluating the rice ratio of consistency/breakdown, which is related to the cracker texture, such as the parameters for the cooked low expansion rate of rice crackers,22) of Koshinomenji- rice palatability, of H1 (surface hardness) and S2 man (0.5) was lower than the ratios for Yumetoiro (1.8) (overall stickiness), we selected the main chemical and Hoshiyutaka (1.4), similar to the ratio of Final vis/ components of the rice grains, comprising the amylose Max vis. Although the amylose contents of these three content and the pasting properties of rice flour (the rice cultivars were about same, the pasting properties of rations of Final vis/Max vis and of consistency/break the rice flour samples and the physical properties of the down), from all the measured parameters. cooked rice grains were different, the latter values being Calibration models to estimate fracture of the rice in good agreement with the physical properties of the crackers are shown in Fig. 4. We developed a multiple- rice cracker products. It is be noteworthy that the pasting regression equation for fracture of the puffed rice properties of the rice flour samples and the physical crackers as a function of five physical or chemical properties of the cooked rice grains could be better parameters of the rice flour samples and grains. The indices than the amylose content to evaluate the formula for estimating fracture was as follows; 2:66 processing suitability for rice crackers as shown in the H1 0:71 S2 10:19 amylose content + 27.30 case of Koshinomenjiman. Table 4 shows that fracture consistency/breakdown + 743.75 Final vis/Max vis + was positively correlated with the amylose content 136.28. The multiple regression coefficient was found (r ¼ 0:87), protein content (r ¼ 0:92), Min vis (r ¼ to be 0.93. 110931-8 S. NAKAMURA et al.

(gw/cm2) We could also estimate the fracture characteristics 1200 of a rice cracker, which are closely related to the 3 R2 = 0.9285 palatability of the rice cracker based on the physico- 1000 2 chemical properties of the rice material and we could as

800 well estimate the amylase content, which is closely related to the expansion and retrogradation of a rice 6 600 cracker based on the product’s physical properties. 5 7 However, this estimate would only be valid when the 400 1 4 manufacturing conditions and storage period are same, Observation of fracture 8 because these conditions aﬀect the physical properties 200 of a rice cracker.

0 200 300 400 500 600 700 800 900 1000 1100 1200 Relationship between physical the properties and fat Predictor of fracture acidity of rice crackers during storage Fig. 4. Fracture Calibration for the Puffed Rice Crackers Measured The physical properties of six kinds of commercial with a Tensipresser. rice cracker were measured by the novel method of a 1, Koshihikari; 2, Hoshiyutaka; 3, Yumetoiro; 4, Takanari; one-bite test with a Tensipresser as shown in Fig. 6. 5, Benisarasa; 6, Koshinomenjiman; 7, Akigumo; 8, Natsugumo. , Observation; ——, Theoretical value. Fracture ¼ 2:66 Rice cracker A was the hard type, rice crackers B, C and H1 0:71 S2 10:19 amylose content + 27.30 consistency/ D were the soft type, and rice crackers E and F were the breakdown + 743.75 Final vis/Max vis + 136.28. The multiple rather hard type rice. Rice crackers C (H1) and E (H1), regression coefficient was found to be 0.9285. As suitable indices for and F (H1) were significantly different at the respective the multiple-regression analysis as textural parameters related to the levels of 1% and 5%. Rice crackers D (H1), and E (H1), palatability of cooked rice grains to estimate the fracture (one of the important textural parameters for rice crackers), H1 (surface F (H1) were respectively different at the level of 1% and hardness) and S2 (overall stickiness), the amylose contents (one of 5%. Rice crackers A (A1), B (A1), C (A1), D (A1), and Advancethe main chemical components of rice grains), and Final View vis/Max vis F (A1), and rice cracker E (A1) were significantly and consistency/break down (parameters for the pasting properties different at the level of 1%. H1 showed positive of the rice flour samples) were selected from among the parameters correlation with Max stress (r ¼ 0:96) at the level of analyzed in each test. 1% and with A1 (r ¼ 0:83) at the level of 5%. To summarize, rice crackers E and F were harder than

35 rice crackers C and D. Rice cracker A was the hard type, 2 showing that the degree of expansion of air bubbles was 30 R2=0.9252 6 3 associated with the physical properties of the rice 25 crackers. The physical properties of the soft type of 4 20 1 rice cracker could be evaluated more easily than the hard 5 15 type by our novelProofs method of the one-bite test with a 7 10 8 Tensipresser. Such textural parameters, as Max stress,

5 A1, and H1, are proposed to be suitable for classifying

Observation of amylose content of amylose Observation rice crackers according to their hardness. These param- 0 5101520253035 eters are simple and useful, because only physical Predictor of amylose content measurement is necessary to evaluate or classify

Theoretical value commercial rice crackers. The physical properties of six kinds of commercial Fig. 5. Calibration for the Amylose Content of Material Rice Based rice crackers after storage were also measured. Fat on a Multiple-Regression Analysis, Using Several Physical Param- acidity has been reported to be one of the important eters as Independent Variables. 24) 1, Koshihikari; 2, Hoshiyutaka; 3, Yumetoiro; 4, Takanari; indices for the quality deterioration of rice, so we 5, Benisarasa; 6, Koshinomenjiman; 7, Akigumo; 8, Natsugumo. tried to use it to check the quality deterioration of rice , Observation; ——, Theoretical value. Amylose content ¼ crackers during storage. We adopted the colorimetric 6:35 fracture 13:27 L2 þ 17:19 A2 0:96 H1 0:73 method23) for measuring the fat acidity, the results for þ Max stress 0:60 INF1 112:43. The multiple regression coef- the commercial rice crackers before and after storage ficient was found to be 0.9252. It was possible to determine amylose contents of a rice material with a physical measurement, and one- (for 20 d at 35 C, packed in plastic bags) being shown bite test on puffed rice crackers with a Tensipresser, instead of in Fig. 7. The fresh rice crackers showed less fat chemical analysis. acidity than after storage, when it increased by 1.5–4.0 times. Commercial rice cracker D showed a particularly high increase of fat acidity. The variation of fat It was slso possible to easily estimate the amylose acidity with the physical properties of commercial rice content of the rice material by using the one-bite test crackers during storage is shown in Fig. 8. The values with a Tensipresser on a puffed rice cracker, using a of the physical properties increased between 1.2 times– physical method instead of a chemical analysis. Cali- 9.1 times during the storage of rice crackers. A2 of the bration models to estimate the amylose content of the physical parameters showed a particularly high rate of raw material in a rice cracker are shown in Fig. 5. The increase. The increase of H1 and increase of Max formula for estimating the amylase content was as stress were significantly correlated at the level of 1%, follows; 6:35 fracture 13:27 L2 þ 17:19 A2 the increase of fat acidity and H1 were significantly 0:96 H1 0:73 Max stress 0:60 INF1 þ 112:43. correlated at the level of 5%. Figure 2 (B shows the The multiple-regression coefficient found to be 0.93. profiles for a) fresh commercial rice crackers and b for Physical Properties of Rice Crackers 110931-9

(gw/cm2) (gw/cm2) H 1 A 1 18000.0 7000.0 b c 16000.0 5653.0 a 14150.0 c 6000.0 14000.0 13370.0 a 5000.0 12000.0 11300.0 a 10210.0 4030.0 b b 4000.0 a a 10000.0 a a 8499.0 8511.0 3178.0 3194.0 2969.0 2968.0 8000.0 3000.0 6000.0 2000.0 4000.0 1000.0 2000.0

0.0 0.0 ABCDE F ABCDE F

2 2 (gw/cm ) MAX stress (gw/cm ) FRACTURE 18000.0 2500.0 c a 16000.0 a 14600.0 c a 14000.0 a 13470.0 2000.0 1705.0 c 12090.0 1646.0 12000.0 11420.0 b b 1500.0 1260.0 10000.0 8638.0 8706.0 b 8000.0 1000.0 b 769.3 b 6000.0 643.3 544.9 4000.0 500.0 2000.0 0.0 0.0 AB CDE F ABCDEF

Fig. 6. Physical Properties of Commercial Rice Crackers Measured by One-Bite Method Using a Tensipresser. A, Rice cracker A; B, Rice cracker B; C, Rice cracker C; D, Rice cracker D; E, Rice cracker E; F, Rice cracker F. Correlation is significant at 5% respectively by the method of Tukey. Same letter means not significantly different. Rice cracker E and F were harder than rice cracker C and AdvanceD. The soft type rice crackers were more suitable than View hard type ones for the measurement of physical properties by the novel method of one bite test with a Tensipresser.

90.0 degree of quality deterioration of the rice crackers by 81.7 b 80.0 the physical method of the one-bite test with a Tensipresser. The fat acidity could also be a useful 70.0 chemical index of quality deterioration during the 60.0 storage of rice crackers. 49.6 b 50.0 KOH / 100g.d.w)

· Sensory evaluation 40.0 The objectiveProofs of this study was to investigate the 30.0 various methods for measuring the physical and chemi- 20.7 18.7 a Fat acidity (mg 20.0 b cal properties of rice crackers and to propose method for 13.2 13.1 a b 9.0 evaluating the quality of rice crackers in accordance 8.5 a 7.4 a 10.0 5.8 5.7 6.3a a a a with the sensory evaluation. 0.0 abcdef Several attempts have been made to classify the Rice crackers hardness of rice crackers based on their mechanical properties and a sensory evaluation.19,20) However, such Fig. 7. Change in Fat Acidities of Various Commercial Rice reports have revealed that the mechanical properties of Crackers Before and After Storage. , Fresh rice crackers; , Stale rice crackers (stored at 35 C for rice crackers did not completely match the results of the 19,20) 20 d). a, Rice cracker A; b, Rice cracker B; c, Rice cracker C; d, Rice sensory evaluation. Our sensory test shown in Fig. 9 cracker D; e, Rice cracker E; f, Rice cracker F. Same letter means indicates that hardness by the sensory analysis and H1 not significantly different. Values are the average of triplicate (from the physical properties) and Max stress (from the measurements. The bar showed standard deviation. After the physical properties) were significantly correlated at the storage, fat acidities of rice crackers increased 1.5 times–4.0 times those of fresh crackers. Commercial rice cracker D showed level of 1%. particularly high ratio of increase. The results of the sensory evaluation of six kinds of commercial rice cracker given in Fig. 10 show a rice crackers whose expiration date had passed seven significant correlation between the sensory analysis, months before. After storing for a long period, the rice and the values for physical parameters commercial rice crackers lost their brittleness as shown by the profiles crackers. The hardness by the sensory analysis, and the in Fig. 2. The reason for the hardening of rice crackers values for H1 (physical properties), Max stress (physical during storage is not clear. The results of our previous properties) and A1 (physical properties) were signifi- study on the storage of rice grains,23,24) have shown cantly correlated at the level of 1%. It was found that H1 that the combination of amylose and free fatty acids, and Max stress, by the physical measurements were the denaturation of proteins, or the cross-linkage of the useful parameters to classify rice crackers according cell wall may each play a roles in the hardening of rice to their hardness, because these factors significantly crackers during storage. In conclusion, H1 and Max affected the hardness of rice crackers by the sensory test. stress of the stale rice crackers showed very high It seems relevant that these physical parameters showed values, similar to the other parameters during storage significant correlation for both hand-made rice crackers (for 20 d at 35 C). It was possible to estimate the and rice crackers. One of the reasons for this high 110931-10 S. NAKAMURA et al.

14.0

12.0

b 10.0

a a 8.0 a a

6.0

Ratio of parameters after to before storage after to before Ratio of parameters a a b a a 4.0 b b b a b a a a a b b a a a a b a b b a a b b a 2.0 b b b b a a a a a b a b a aa aaa a a a b b a a a a a a b b a a a a a a

0.0 Fat Acidity H 1 L 1 A 1 L 2 A 2 MAX FRACTURE INF1 INF2 INF3 MAX Stress

Fig. 8. Changes in Fat Acidity and Physical Parameters of Various Commercial Rice Crackers during the Storage. Correlation is significant at 5% respectively by the method of Tukey. Means with same letter are not significantly different. , Rice cracker A; , Rice cracker B; , Rice cracker C; , Rice cracker D; , Rice cracker E; , Rice cracker F. For during storage, value of physical properties parameters of rice crackers showed increase of 1.2 times–9.1 times. A2, one of physical property parameters, showed particularly high increasing ratio during the storage.

1234 5 1234 5 a 6 Rice cracker A Appearance Bad Good Soft Hard

123c 4 5 6 1 234 5 Rice cracker B Soft Hard Aroma Bad Good Advance View 123cd 4 5 6 Rice cracker C Soft 1234 5 Hard Hardness Hard Soft 123cd 4 5 6 Rice cracker D Soft 1234 5 Hard * Taste Bad Good 1234 b 5 6 Rice cracker E Soft Hard 123* *4 5 Overall evaluation Bad Good 1 23bd 4 5 6 Rice cracker F Soft Hard Fig. 9. Result of Sensory Test of the Puffed Rice Crackers. , Puffed rice cracker of Koshihikari. p < 0:05, p < 0:01 Fig. 10. Result of Sensory Test of the Commercial Rice Crackers. Control (3 points) is a puffed rice cracker of Hoshiyutaka Sensory Correlation is significant at 5% respectively by the method of 28) test was carried out as reported in our previous report by 10 Tukey. Means withProofs same letter are not significantly different. trained taste panelists. Correlation is significant at 1%, 5% Sensory test was carried out as reported in our previous report28) by respectively by the method of Tukey. Hardness (Sensory analysis) 10 trained taste panelists. Sensory analysis (Hardness) and H1 showed significant correlation with H1 (physical property) and Max (physical properties), Max stress (physical properties) and A1 Stress (physical properties) at the level of 1%. (physical properties) were shown to be correlated significantly at the level of 1%. correlation would be the high sensitivity of the Tensi- grains used and the quality of the resulting products was presser when used with a plunger of large diameter investigated. (13 mm) and rapid bite speed (2 mm/s) when compared It was found possible to estimate the physical proper- with other reports.19,20) ties by using a multiple-regression analysis based on the chemical components, pasting properties and physical Conclusions properties of the rice used. A formula for estimating the amylose contents of the rice samples was developed by The degree of swelling is one of the criteria for high using the results of physicochemical measurements of quality rice crackers, and while it varies, depending the rice crackers. upon the rice cultivar, genealogy, and manufacturing We assayed the quality of commercial rice crackers conditions, the cause-and-effect relationship has not and examined their deterioration during storage by been clearly defined.28,34,35) measuring the physicochemical properties. The hardness The objective of this present study is to examine and fat acidity of the crackers increased markedly several advanced methods for measuring the physical storage for 20 d at 35 C. properties of rice crackers and to propose a novel The novel method of the one-bite test with a method for evaluating rice crackers based on the Tensipresser was useful for a quality assay of the rice hardness in the sensory evaluation. crackers, and made it possible to evaluate the quality The suitability for processing of eight kinds of rice deterioration of the rice crackers during storage. variety was characterized according to the results of physicochemical quality assays. The novel one-bite test Acknowledgment with a Tensipresser was proposed for evaluating rice crackers focusing on their hardness. Part of this research was supported by the Agriculture, Puffed rice crackers were prepared, and the relation- Forestry and Fisheries Ministry of Japan for research ship between the physicochemical properties of the rice and development projects for promoting new policies. Physical Properties of Rice Crackers 110931-11 We express our gratitude to Professor Hikaru Satoh 17) Dahlin KM and Lorenz KJ, Cereal Chem., 70, 329–333 (1993). of Kyushu University, Niigata Prefectural Agricultural 18) Chen C-M and Yeh An-I, J. Cereal Sci., 32, 137–145 (2000). Research Institute, and Hokuriku Research Center for 19) Takahashi H, Itou A, Egawa H, Watanabe T, Inoue M, Inoue M, Arai E, and Yamada Y, Japanese Society for Mastication kindly presenting the rice samples. Science and Health Promotion (in Japanese with English abstract), 16, 69–82 (2006). 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