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ISSN : 1225-8504(Print)
ISSN : 2287-8165(Online)
Journal of the Korean Society of International Agriculture Vol.35 No.4 pp.235-242
DOI : https://doi.org/10.12719/KSIA.2023.35.4.235

Comparison of the Physicochemical and Structural Properties of Grain Starch from the Main and Ratooned Rice

Jong-Hee Shin†, Chae-Min Han, Young-Un Song, Sang-Kuk Kim, Jung-Gi Ryu
Division of Crop Research, Gyeongsangbuk-do Provincial Agricultural Research and Extension Services, Daegu 41404, Korea
† Corresponding author (Phone) +82-53-320-0271 (E-mail) szzong91@korea.kr
August 1, 2023 September 26, 2023 September 26, 2023

Abstract


Rice ratooning is the cultural practice that easily produces secondary rice from the stubble left behind after harvesting the main crop. ‘Daol’ is an extremely early growing rice variety. Planting this variety early allows for an additional ratoon harvest after the primary rice harvest. The plant growth and yield of ratoon rice were very low compared to those of main rice. Protein, amylose content, and head rice rate were higher in ratoon rice than in main rice. The distribution by the rice flour particle size of main and ratoon rice was similar. The damaged starch content in ratoon rice was relatively high at 6.1%. Ratoon rice required a longer time and higher temperature for pasting than main rice. Compared to the original rice, peak viscosity (PV), hot paste viscosity (HPV), cool paste viscosity (CPV), and breakdown (BD) were very low, and setback (SB) was high. As a result of analyzing the gelatinization properties of main and ratoon rice using differential calorimetry, it was found that the onset (To), peak (Tp), and conclusion (Tc) of ratoon rice starch were processed at a lower temperature than those of main rice. The gelatinization enthalpy of both samples was similar. The distribution of amylopectin short chains in ratoon rice was higher than that in main rice.


rice starch , ratoon rice , pasting property

조생 벼와 이로부터 발생한 움벼 전분의 이화학적, 구조적 특성 비교

신종희†, 한채민, 송영운, 김상국, 류정기
경상북도농업기술원 작물연구과

초록

    INTRODUCTION

    Ratooning is the practice of allowing the crop to regenerate after cutting in order to harvest a second crop. Its benefit is that there is no costs and labor involved in growing seedlings in a nursery or in preparatory cultivation of the land. In Korea climate condition, ratoon rice cultivation is unusual agricultural practice. In previous study in Korea, Shin et al. (2015) confirmed the ratooning potential of several early-ripening rice varieties and compared milling and quality properties of the main and ratoon rice (Shin et al., 2021).

    In some genotype, the seed quality of the ratoon crop is equivalent to that of the main crop (Nagaraju and Mahadevappa, 1985). Although there was significant difference in protein content, it tended to be considerably higher in the grain of the ratoon crop compared to the main crop. Moreover, gelatinization temperature and viscosity values were lower in the ratoon crop samples. Babaeean Jelodar and Tavasoli (2009) reported that the alkali-spreading value in ratoon rice was higher than that of the main crop, but no significant differences were observed in the amylose content and gel consistency. In another study, the milling quality, uniformity and appearance, size and weight of ratoon rice grains were lower than those of the main crop (Bollich et al., 1988;Calendakion et al., 1992).

    The physicochemical properties of rice starches are highly depending on rice variety, environment, and agronomic conditions. Air temperature conditions during the ripening period affect the yield and quality of rice. Due to the high and low temperatures during the ripening period, the quantity and quality deteriorate (Tetlow et al., 2004;Lee et al., 2012;Ko et al., 2014;Kim et al., 2016;Baek et al., 2018;Kwak et al., 2018). Main and ratoon rice are matured under different temperature conditions.

    The specific objectives of this study were to: (a) compare the difference in growth and yield properties of rice produced by the ratoon system and the main crop method; and (b) investigate the difference in structural and physicochemical properties of starch between the main rice and ratoon rice. This reports may help you better understand the variation in ratoon rice quality in Korea.

    MATERIAL AND METHOD

    1. Sample preparation and experimental design

    The studies were conducted on field at Gyeongsangbukdo Provincial Agricultural Research and Extension Services, Daegu, Korea during the cropping season of 2021~2022. The field experiment was carried between the month of May and November. The site is located on longitude 128° 34'E, latitude 35° 58'N and an altitude of 50 m. The annual rainfall and daily temperature in Daegu is an average of about 1,061 mm and 14.6?. The average daily temperature during the cropping season for the year 2021 and 2022 was 22.3?, and 23.0? respectively. For estimate rice ratooning, early ripening rice variety ‘Daol’, a new rice variety developed in Gyeongsangbuk-do’, was used. Sowing date was April 15th. The seedlings were transplanted 25 days after seeding at a spacing of 30 cm between rows and 15 cm between hills using 2~3 seedlings per a hill in a split plot design with 3 replications. The main crop was fertilized with 90 kg ha-1 of N, 45 Kg ha-1 of P2O5, and 57 kg ha-1 of K2O. The plots were weeded regularly to minimize weed infestation. The main crop was harvested at mass maturity, after which the tillers were hand mowed to stubbles of 10 cm tall. These were then left without any further input, until the ratooned plants were ready for harvest.

    2. Milled rice quality

    The husked grain was milled by uniformly placing pressure, achieving 92% milled (SY94+RTA2+2400, Ssangyong Machinery Industry Co., LTD, Korea) rice per brown rice ratio. Milled rice quality such as head rice and chalky kernel ratio were measured in a Grain Analyzer (Cervitec Grain Inspector 1625, Foss, Sweden). Rice endosperm protein and amylose contents were measured using Near-Infrared Grain Tester (Infratec 1241, Foss, Sweden).

    3. Starch isolation

    Starch was isolated through alkaline treatment after soaking the rice grains in water (Yamamoto and Shirakawa, 1999). After drying the soaked rice, it was pulverized using a blender, and then the sample was steeped in 0.2% NaOH solution. Alkaline treatment was repeated until the yellowish color disappeared and the biuret reaction was no longer observed. Thereafter, the precipitate was washed with deionized water, neutralized with 1N HCl, washed repeatedly with deionized water, and centrifuged at room temperature at 1,300 × g for 10 min. The isolated starch was dried at room temperature and sieved (100 mesh).

    4. Granule size distribution and damaged starch contents

    A laser diffraction particle size analyzer (Malvern Mastersizer 2000, Malvern Instruments Ltd., UK) was used to measure the granule size distribution of flour from each experimental sample (main and ratoon rice). Powder samples were then immersed in ethyl alcohol for 30 s after sonication (Sochan et al., 2012). Damaged starch content was measured using the Megazyme kit (Megazyme International Ireland, Wicklow Ireland) according to the American Association of Cereal Chemists (AACC) method 76- 31 (AACC,76-31). Absorbance was measured at 510 nm. The percentage of damaged starch was calculated as; % Damaged starch (W/W) = Absorbance (sample) × (150/ Glucose standard absorbance)/Sample weight (mg) × 8.1.

    5. Gelatinization properties

    A. Pasting properties

    Pasting properties of rice flours were measured with a Rapid visco analyzer (RVA, Model 4, Newport Scientific, Australia). Briefly, 3 g rice flour sample and 25 mL of deionized water were added in the sample canister and then rotated at 960 rpm for 10 s to produce rice flour suspensions. Then, the rotation speed was maintained at 160 rpm until the analysis was completed. The heating temperature was maintained at 50 ? for 1 min; The sample was then heated at a rate of 12 °C per min to 95 °C, held at 95 °C for 2.5 min, then cooled to 50 °C and held at this temperature for 2 min.

    B. Differential scanning calorimetry (DSC)

    The gelatinization properties of starch were evaluated using Differential scanning calorimetry (DSC). Briefly, 3.0 mg of rice flour and deionized water (1:2, v/v) were poured into an aluminum pan using a micro-syringe; the aluminum pan was scaled, left for 1 h and then heated from 30 ? to 100 ? at a rate of 10 ?/min using a DSC (DSC 8500, Perkin Elmer, Waltham, MA, USA). The gelatinization onset temperature (To), gelatinization peak temperature (Tp), gelatinization conclusion temperature (Tc), and gelatinization enthalpy (ΔH) were measured in triplicate.

    6. Amylopectin branch-chain-length distribution

    The chain-length distribution of amylopectin was analyzed with a High-performance anion-exchange chromatography system equipped with pulsed amperometric detection (HPAEC-PAD). The HPAEC system (Dionex DX500, Sunnyvale, CA, USA) consists of a GP50 gradient pump, an LC20-1 chromatography organizer, an ED40 electrochemical detector, a CarboPac PA-1 guard column (4 × 50 mm), a CarboPac PA-1 analytical column (4 × 250 mm), and an AS40 automatic sampler (Kim et al., 2016). Filtered (0.45 μm pore size) samples were separated with gradient elution from 100% eluent A (150 mM NaOH) to 100% eluent B (500 mM NaOH in 150 mM NaOH).

    RESULT AND DISCUSSION

    1. Yield and growth

    ‘Daol’ is an extremely early-growing rice variety. If planted early, additional ratoon plants can be harvested after harvesting the main rice plant. Rice transplanted on May 10th blooms on July 5th, matures for 45 days, and can be harvested at the late August (Figure 1). Additional ratoon plants were generated from the stubble remaining after harvesting the main crop, which bloomed in mid-tolate September and could be harvested again in early November. At this time, the time it took for the main crop to heading was 57 days, and it took about 32 days for ratoon rice to heading after harvesting the main crop (Table 1). In previous study by Shin et al. (2015), among domestic early-maturing rice varieties, ratoon performance ranged from 0% (‘Unkwang’, ‘Jopeyong’, ‘Odae’, ‘Nokyang’) to 33%(‘Jinbuol’) in grain yield. The maximum yield of ratoon rice was ‘Jinbuol’ and ‘Joun’ at 202 and 203 kg/10a, followed by ‘Junamjoseng’ at 174 kg/10a.

    The growing season climatic conditions of main and ratoon rice were compared (Table 2). Although the ratoon plant grows at a high temperature during the growing stage, the growth period was shorter than those of the main plant, so the cumulative temperature was about 60% of main plants, and the cumulative sunshine durations is 129 hours, resulting the significant different in quantity (Figure 2). While major rice matured at 26.9?, ratoon rice matured at a lower temperature of 17.3?. There was no difference in cumulative sunlight hours between the two life cycles.

    Ratoon rice had shorter culm, shorter panicle, less tiller, and less grain per panicle than main rice (Table 3). The weight of brown rice was also 10.2% less than that of the main rice, resulting in a decrease in rice production (Figure 2). In previous study by Shin et al. (2015), in the three early-maturing varieties producing ratoon rice, the culm length was about 51 to 56% of the main plant, and the pan-icle length was short, at 65 to 75%. The spikelet number of panicles was 40-48% of the main plant.

    2. Milled rice quality

    The protein and amylose contents of the ratoon rice were higher than those of main rice (Table 4). The head rice ratio was high, because ratoon rice was matured at a lower temperature than main rice. In some genotype, the seed quality of the ratoon crops is equivalent to that of the main crop (Nagaraju and Mahadevappa, 1985). In another study, milling quality, uniformity and appearance, size and weight of ratoon rice grains were lower than the main crop (Bollich et al., 1988;Calendakion et al., 1992). Ratoon rice is characterized by high grain quality, which is mainly associated with the decrease in temperature after the heading stage (Huang et al., 2020;Wang et al., 2020). It has been well proven that ratoon rice improves rice milling and appearance qualities by increasing head rice ratio and reducing the chalkiness ratio (Wang et al., 2020). Ratoon rice also increase the amylose content (Deng et al., 2021).

    3. Granule size distribution and damaged starch contents

    The size distribution of rice flour granules directly affects gel consistency (Juliano et al., 1985;Hsieh & Luh, 1991). The particle size distribution and damaged starch content of each samples are reported in Figure 3 and Table 5. The particle size distribution of main and ratoon rice was similar, and the particle size corresponding to D50 was about 82.5~86.6 μm. The damaged starch content of ratoon rice was relatively high of 6.1% (Table 5). Rice flour with high damaged starch is not suitable for highquality food production (Chiang and Yeh, 2002).

    4. Gelatinization properties of grains

    A. Pasting properties

    As a result of comparing the amylograms of each sample (Figure 4), ratoon rice requires longer time and higher temperature than main rice to be pasted. PV, HPV, CPV, and BD were very low and SB was high compared to main rice (Table 6). These characteristics act as a factor that reduces the taste of Japonica type rice. Pasting is a phenomenon resulting from gelatinization in the dissolution of a starch and involves granular swelling, exudation of molecular components from the granules, and finally total disruption of the granules (Thomas and Atwell, 1999). In general, Japonica-type varieties with high taste value are known to have low pasting temperatures, HPV, BD, and low final viscosity (Choi et al., 2006). In a previous research report by Nagaraju and Mahadevappa (1985), the gelatinization temperature and viscosity of ratoon rice were low.

    B. Thermal properties

    The gelatinization properties of main and ratoon rice are shown in Table 7. To, Tp, and Tc of ratoon rice starch were processed at lower temperature than those of original rice. The ΔT value, which represents the range of To and Tc, was larger in ratoon rice than in main rice. The gelatinization enthalpies of both samples were similar. DSC is a thermal analysis that can thermodynamically describe the gelatinization process by measuring enthalpy from an endothermic reaction of the gelatinization pasting because it can measure heat absorption or release by chemical reactions during phase changes, such as melting (Lee et al., 1993). Furthermore, the thermal properties of rice are closely associated with its textural properties. For example, a higher gelatinization temperature has been found to increase the hardness of cooked rice (Zhang et al., 2016).

    5. Amylopectin branch-chain-length distribution

    The amylopectin branch chain-length distribution is shown in Table 8, and Figure 5, where an increase in the A chains (DP ≤ 12) but a decrease in the long chains of the ratoon rice grain is evident as compared to the main crop. In general, the elevated air temperature led to a decrease in the proportion of the short chains of amylopectin and a corresponding increase in the proportion of the long chains (Asaoka et al., 1985). Kim et al. (2017) also suggested that the amylopectin structure of high-temperature-ripening grains seemed to have an increased amount of long B chains but reduced quantity of short chains of amylopectin. In the previous report by Shin et al. (2021), the distribution of amylopectin short chains in ratoon rice was higher than that in main rice. Numerous studies have shown that short amylopectin A chain (DP 6-12) was negatively correlated with gelatinization temperature (To, Tp, Tc) and enthalpy (ΔHg) during flour gelatinization (Nakamura et al., 2002;Vandeputte et al., 2003).

    CONCLUSION

    If ‘Daol’, an extremely early-growing rice variety, planted early, additional ratoon plants can be harvested after harvesting the main rice plant. The structural and physicochemical properties of starch, and the yield and quality of rice showed significant differences between main rice and ratoon rice. Compared to the main rice, the amylose content of ratoon rice was significantly increased. Ratoon rice also resulted in changes in starch structures. Short-chain amylopectin increased, but also increased the damaged starch. The amylose content is the major factor that affecting rice quality (Fan et al., 2019; Zhu et al., 2021), and it is positively related to the hardness of cooked rice. In previous study by Shin et al. (2015) showed that the palatability of ratoon rice was reduced, but seed viability was not affected. This rice ratooning system requires a short duration, creating possibility for growing another crop in the same cropping year and offers an opportunity to increase cropping intensity per unit of cultivated area.

    적 요

    움벼는 수확된 벼의 그루터기에서 2차 분얼이 발생하여 새 로운 수확물을 얻어내는 것으로, 평균기온이 높은 대구지역에 서 극 조생종 벼의 움벼 재배가 가능하다. 경북농업기술원에 서 개발한 ‘다올’ 품종의 경우 조기 재배시 7월 7일 출수하는 극조생종 품종으로 생산된 움벼의 품질 및 전분 특성을 분석 하였다.

    1. 5월 10일 이앙된 극조생종 ‘다올’은 이앙 후 57일경 출 수하여 8월 중순경 1차 수확이 가능하였으며, 수확한 그루터 기에서 자란 움벼는 32일이면 출수하여 움벼로부터 쌀 생산이 가능하였다.

    2. 움벼는 본식물체보다 생육 기간이 짧아 식물체가 작고, 수량이 본 수확의 30% 정도로 적었다.

    3. 고온 등숙된 본포 쌀 시료보다 움벼의 완전미율, 단백질 함량, 아밀로스 함량이 높았다.

    4. 전분 입자 크기별 분포는 본포 생산 벼와 움벼가 비슷하 였으나 손상전분 함량은 움벼에서 높게 나타났다.

    5. 쌀가루의 호화특성은 움벼의 경우 호화하는데 높은 온도 와 시간이 소요되고 PV, HPV, CPV, BD 점도가 낮고 SB는 높았다.

    6. 움벼의 아밀로펙틴 짧은 사슬 분포가 본포 생산 벼에 비 해 증가하는 경향이었다.

    Figure

    KSIA-35-4-235_F1.gif

    Life cycle of the main and ratoon plant of ‘Daol’ variety in 2021~2022.

    KSIA-35-4-235_F2.gif

    Difference in the yield of milled and head rice between main and ratoon rice.

    * Error bar indicate standard deviation.

    KSIA-35-4-235_F3.gif

    Particle size distribution of flour granules in main and ratoon rice.

    KSIA-35-4-235_F4.gif

    Comparison of the RVA profiles of the main and ratoon rice grains.

    KSIA-35-4-235_F5.gif

    Amylopectin branch chain-length distribution of the main and ratoon rice starch.

    Table

    The days required for heading of the main and ratoon rice plants.

    † Days for heading means require days seeding to heading of main plant, and main plant harvesting to ratoon plant heading.
    ‡Different letters in the same column of each sample indicate significant differences among the samples according to Duncan’s multiple range test (<i>P</i> < 0.05).

    Air temperature and daylight hours during the growing period of the main and ratoon rice plants.

    †Ripening stage means 45 days form the heading to the harvest.

    Growth and yield components of main and ratoon rice.

    †All data represent the mean ± SD of three measurements. Different letters in the same column of each sample indicate significant differences among the samples according to Duncan’s multiple range test (<i>P</i> < 0.05).

    Protein, amylose contents, and milled rice quality of the main and ratoon rice grains.

    †All data represent the mean ± SD of three measurements. Different letters in the same column of each sample indicate significant differences among the samples according to Duncan’s multiple range test (<i>P</i> < 0.05).

    Particle size distribution (D10, D50, and D90) and damaged starch content of main and ratoon rice.

    †D10, D50, and D90 represent 10%, 50%, 90%, respectively, of the cumulative particle size distribution.
    ‡All data represent the mean ± SD of three measurements. Different letters in the same column of each sample indicate significant differences among the samples according to Duncan’s multiple range test (<i>P</i> < 0.05).

    RVA pasting parameters of the main and ratoon rice grains.

    †All data represent the mean ± SD of three measurement. Different letters in the same column indicate significant differences among the samples according to Duncan’s multiple range test (<i>P</i> < 0.05).
    ‡PV, HPV, and CPV are the peak viscosity, hot paste viscosity, and cool paste viscosity, respectively. BD and SB are the breakdown and setback, respectively. BD is equal to the difference between the peak viscosity and hot paste viscosity, consistency is equal to the difference between the final viscosity and hot paste viscosity, and SB is equal to the difference between the cool paste viscosity and peak viscosity.

    DSC parameters of the main and ratoon rice grains.

    †T<sub>o</sub>, T<sub>p</sub>, and T<sub>c</sub> are the temperatures of the onset, peak and conclusion of gelatinization, respectively. ∆<i>T</i> (T<sub>c</sub>-T<sub>o</sub>) is the temperature range of gelatinization, and ∆<i>H</i> is the enthalpy change of gelatinization.
    ‡All data represent the mean ± SD of three measurement.

    The chain-length distribution of amylopectin of rice starch of the main and ratoon rice grains.

    †All data represent the mean ± SD of three determinations.

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