Effects of Postharvest Elevated‐Temperature Exposure on Rice Quality and Functionality

Rapid drying with high‐temperature air has gained interest in the rice industry, but the effects of elevated‐temperature exposure on physicochemical properties of rice are of concern. This study investigated the effects of exposing rough rice to elevated temperatures for various durations without removing moisture. Physicochemical property response was evaluated in terms of head rice yield (HRY), germination rate (GR), milled‐rice yellowing, pasting properties, and gelatinization temperatures. Two long‐grain cultivars (pure‐line Wells and hybrid CL XL729) at initial moisture contents (IMCs) of 17.9 and 18.6%, respectively, and dried moisture content (DMC) of 12.5%, were hermetically sealed and exposed to 40, 60, and 80°C for various durations. Exposure to 80°C of IMC samples of Wells and CL XL729 resulted in a significant (2.3–2.5 percentage point) reduction in the HRYs. A 2 hr exposure of both cultivars at IMC level to 60°C completely inhibited GR, and exposure to 80°C of the cultivars at both moisture content (MC) levels immediately inhibited GR. Exposure to 80°C for almost all durations and 60°C for durations over 4 hr produced significant yellowing in both cultivars at IMC. Significant yellowing in both cultivars at DMC was also observed during a 28 day storage following 80°C exposure. In general, peak viscosities of both cultivars at IMC increased only after extended exposure to 40 and 60°C, but peak viscosities of the cultivars exposed to 80°C increased sharply and immediately upon exposure. No significant differences were observed in gelatinization temperatures of either cultivar at either MC level from elevated‐temperature exposure. Results from this study suggest that extreme‐temperature exposure of rough rice affects HRY, GRs, yellowing, and pasting properties of rice, but the extent of impact is MC dependent.     

Molecular and Gelatinization Properties of Rice Starches from IR24 and Sinandomeng Cultivars

The differences in pasting properties involving gelatinization and retrogradation of rice starches from IR24 and Sinandomeng cultivars during heating‐cooling processes were investigated using a Rapid Visco Analyser (RVA)and a dynamic rheometer. The results were discussed in relation to the molecular structure, actual amylose content (AC), and concentration of the starches. Generally, both starches possessed a comparable AC (≈11 wt%), amylose average chain length (CL), iodine absorption properties, and dynamic rheological parameters on heating to 95°C at 10 wt% and on cooling to 10°C at higher concentrations. In contrast to Sinandomeng, IR24 amylose had a greater proportion of high molecular weight species and number‐average degree of polymerization (DP_n). IR24 amylopectin possessed a lower DP_n and greater CL, exterior CL (ECL), and interior CL (ICL). Comparing the results of RVA analysis and dynamic rheology, the gelatinization properties and higher retrogradation tendencies of IR24 starch can be related to the structural properties and depend on starch concentration. In addition, the exponent n of starch concentration for storage moduli at 25°C (G′₂₅ ∝ Cⁿ) increased linearly with increasing AC.     

Effect of Drying Temperature on Physicochemical Properties of Starch Isolated from Pasta

Semolina from four durum wheat genotypes (cvs. Ben, Munich, Rugby, and Vic) were processed into spaghetti that was dried by low (LT), high (HT), and ultrahigh (UHT) temperature drying cycles. Starch was isolated from dried pasta and unprocessed wheat and semolina references. Pasta-drying cycles had no significant effect on the amylose content of starches. Significant increases in enzyme-resistant starch were observed in HT- and UHT-dried pasta (2.27 and 2.51%, respectively) compared with LT-dried pasta (1.68%). Differential scanning calorimetry (DSC) gelatinization characteristics of pasta starches showed a significantly narrow range (T_r), but no changes in onset and peak temperatures (T_o and T_p, respectively) and gelatinization enthalpy (ΔH₁) were observed. When compared with unprocessed reference samples (wheat and semolina), all pasta starches shifted to higher gelatinization T_o and T_p, with narrow T_r and no changes in δH₁. The second endothermic DSC peak indicated no increase in amylose-lipid complexation (δH₂) due to drying cycle. Starches isolated from LT and HT pasta exhibited lower peak viscosities than those from UHT-dried pasta. Genotypes Ben and Rugby demonstrated higher pasting temperature and lower peak and breakdown viscosities than Vic and Munich.     

拔节期追氮对春播和秋播糯玉米淀粉胶凝和回生特性的影响

以垦粘1号、苏玉糯1号和苏玉糯5号为材料,研究了拔节期追氮量(N 01、50和300 kg/hm2)对春播和秋播糯玉米淀粉胶凝和回生特性的影响,试验于扬州大学实验农牧场进行。结果看出,播期、品种和拔节期追氮量单因素及其互作对淀粉胶凝和回生主要特征值存在显著影响。糯玉米淀粉胶凝和回生特征值在拔节期追氮150 kg/hm2时和秋播条件下较优,即原淀粉具有较低的峰值温度、较高的热焓值,回生淀粉具有较低的回生值,且以垦粘1号表现较好。糯玉米淀粉胶凝和回生特征值之间存在一定的相关性。回生值分别与回生淀粉的热焓值、原淀粉的终值温度显著正相关,相关系数分别为0.82(P0.01)和0.47(P0.05);原淀粉的热焓值与峰值指数显著正相关,相关系数为0.53(P0.05),与原淀粉峰值温度、回生淀粉的终值温度显著负相关,相关系数分别为-0.53(P0.05)和-0.52(P0.05);回生淀粉的热焓值分别与回生淀粉起始温度、终值指数显著正相关,相关系数分别为0.46(P0.05)和0.66(P0.01)。综合考虑淀粉胶凝和回生特性在不同处理下的变化趋势,以秋播糯玉米淀粉在拔节期追N 150 kg/hm2处理下较优。     

拔节期追氮对鲜食糯玉米粉糊化和热力学特性的影响

以苏玉糯1号、苏玉糯5号和渝糯7号为材料,研究了拔节期追氮量（N 0、150和300 kg/hm2）对鲜食糯玉米粉糊化和热力学特性的影响。结果表明,随着拔节期追氮量的增加,峰值黏度和崩解值下降,糊化温度升高,而谷值黏度、终值黏度和回复值呈先降后升趋势; 热力学特征参数中,回生值、终值温度、糊化范围和峰值指数受拔节期追氮量影响较小。原样品热焓值和回生后样品热焓值均表现为随着拔节期追氮量的增加呈先降后升趋势。糊化和热力学特征值对拔节期追氮量的响应不同品种间存在差异。鲜食糯玉米粉的理化特性存在显著的基因型差异,峰值黏度以苏玉糯5号最高,苏玉糯1号最低; 峰值温度苏玉糯1号和苏玉糯5号无显著差异,但均高于渝糯7号; 热焓值、回生值、糊化范围和峰值指数不同品种间相对稳定。相关分析表明,峰值黏度与原样品热焓值和峰值指数呈显著正相关; 崩解值与糊化温度及转变温度,回生值与淀粉的终值黏度和回复值呈显著负相关。在本试验条件下,拔节期追氮总体上使糯玉米食用品质降低,其中以苏玉糯5号在不追氮处理下的糊化和热力学特性较优,即峰值黏度、崩解值和热焓值较高,回生值较低。     

Physicochemical Properties of Rice Dried in a Single Pass Using High Temperatures

This study evaluated the physicochemical properties of high‐temperature, single‐pass dried rough rice. Pureline cultivars Wells (long grain) and Jupiter (medium grain) and hybrid cultivar CL XL729 (long grain), at initial moisture contents of 17.9–18.1% were dried in a single pass to approximately 12.5% moisture content with drying air temperatures of 60, 70, and 80°C and relative humidities of 13–83%. Immediately after drying, the samples were tempered for 1 h at the drying air temperatures in sealed plastic bags. Color, degree of milling, pasting viscosity, and thermal properties of the milled rice were evaluated. Results showed that color, degree of milling, and thermal properties were not affected by drying treatments. However, peak and final viscosities increased with increasing drying air temperatures in all three cultivars.     

Relationships Between Some Structures and Functionalities of Starches from Wheat Cultivars Grown in East China

Starches separated from 30 wheat cultivars grown in East China were studied for granule size, amylose content, degree of crystallinity, thermal, pasting, and gel textural properties. Average granule size and amylose content of wheat starches were 15.08–20.8 μm and 29.43–34.19%, respectively. The degree of crystallinity and enthalpy of gelatinization of samples was 29.54–42.12% and 5.2–9.95 J/g, respectively. The gelatinization temperature and pasting temperature were 59.45–62.2°C and 75.40–83.95°C, respectively. There was a wide range of gel hardness values (208.5–426 g). Various significant correlations between functionality and structural parameters were observed. Highly positive correlations were found between the gelatinization temperatures. Gelatinization peak temperature was significantly correlated to hardness of starch gels (r = –0.374, P < 0.05). Significant correlations were observed between amylose content and breakdown viscosity (r = –0.483, P < 0.01), hardness (r = 0.373, P < 0.05), and cohesiveness (r = 0.378, P < 0.05). Many significant correlations between the various pasting parameters were observed. The average granule size was positively correlated to peak viscosity, trough viscosity, and final viscosity (r = 0.369, 0.381, and 0.398, respectively, P < 0.05).     

Effects of Annealing and Concentration of Calcium Salts on Thermal and Rheological Properties of Maize Starch During an Ecological Nixtamalization Process

The objective of the present work was to study the effect of annealing and concentration of Ca(OH)₂ (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (T_o, T_p, and T_f) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl₂ > CaSO₄ > Ca(OH)₂ ≈ CaCO₃. This behavior was because of the dissociation of each salt or lime in water. Anions (OH⁻) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns.     

Physicochemical Properties of Common and Tartary Buckwheat Starch

Physicochemical properties of starch of three common (Fagopyrum esculentum) and three tartary (F. tataricum) buckwheat varieties from Shanxi Province, China, were compared. Starch color, especially b*, differed greatly between tartary (7.99–9.57) and common (1.97–2.42) buckwheat, indicating that removal of yellow pigments from tartary buckwheat flour may be problematic during starch isolation. Starch swelling volume in water of reference wheat starch (2.8% solids and 92.5°C) was 20.1 mL; for the three common buckwheat starches it was 27.4–28.0 mL; and for the three tartary buckwheat starches it was 26.5–30.8 mL. Peak gelatinization temperature (T_p) in water was 63.7°C for wheat starch, 66.3–68.8°C for common buckwheat and 68.8–70.8°C for tartary buckwheat. T_p of all samples was similarly delayed (by 4.0–4.8°C) by 1% NaCl. Enthalpy of gelatinization (ΔH) was higher for all six buckwheat starches than it was for wheat starch. However, one common buckwheat sample had significantly lower ΔH than the others. Starch pasting profiles, measured by a Rapid Visco-Analyzer, were characteristic and similar for all six buckwheat starches, and very different from the reference wheat starch. A comparison of pasting characteristics of common and tartary buckwheat starches to wheat starch indicated similar peak viscosity, higher hot paste viscosity, higher cool paste viscosity, smaller effect of NaCl on peak viscosity, and higher resistance to shear thinning. Texture profile analysis of starch gels showed significantly greater hardness for all buckwheat samples when compared to wheat starch.     

Comparison of Flour Starch Properties in Half‐Sib Families of Opaque‐2 Maize (Zea mays L.) from Argentina

Since the discovery of the o2 mutation in maize, many studies have reported the characterization of the protein quality of opaque‐2 genotypes. However, few have reported the properties of their starch. The objective of this study was to characterize flour starch properties of 12 half‐sib families of opaque‐2 maize from Argentina. Chemical composition and thermal and pasting properties of whole grain flour were determined. Nonopaque genotypes were used as a control. Starch content of opaque‐2 genotypes did not show significant differences compared with nonopaque genotypes, yet amylose content was significantly lower. A high variability in pasting and thermal properties was observed in genotypes. Opaque samples showed a significantly higher peak viscosity and a lower pasting temperature compared with nonopaque samples, probably owing to larger and less compact starch granules in the floury endosperm. The higher the gelatinization enthalpy of opaque‐2 genotypes was, the lower the amylose content in relation to nonopaque varieties. Two retrogradation endotherms were observed in DSC analysis: one corresponding to amylopectin crystallization and the other to melting of amylose‐lipid complex. Both enthalpies were considered total starch retrogradation (ΔH _RT). A wide range of variation was obtained in ΔH _RT in opaque‐2 genotypes, but no significant differences between opaque and nonopaque genotypes were observed. The differences in starch properties found in this study would make it possible to identify opaque‐2 families with particular characteristics for the development of starchy food items adapted to specific processing traits.     

Physicochemical Properties and In Vitro Starch Digestibility of Cooked Rice from Commercially Available Cultivars in Canada

The influence of amylose content, cooking, and storage on starch structure, thermal behaviors, pasting properties, and rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) in different commercial rice cultivars was investigated. Long grain rice with high‐amylose content had a higher gelatinization temperature and a lower gelatinization enthalpy than the other rice cultivars with intermediate amylose content (Arborio and Calrose) and waxy type (glutinous). The intensity ratio of 1047/1022 cm^–1 determined by Fourier Transform Infrared (FT‐IR), which indicated the ordered structure in starch granules, was the highest in glutinous and the lowest in long grain. Results from Rapid ViscoAnalyser (RVA) showed that the rice cultivar with higher amylose content had lower peak viscosity and breakdown, but higher pasting temperature, setback, and final viscosity. The RDS content was 28.1, 38.6, 41.5, and 57.5% in long grain, Arborio, Calrose, and glutinous rice, respectively, which was inversely related to amylose content. However, the SDS and RS contents were positively correlated with amylose content. During storage of cooked rice, long grain showed a continuous increase in pasting viscosity, while glutinous exhibited the sharp cold‐water swelling peak. The retrogradation rate was greater in rice cultivars with high amylose content. The ratio of 1047/1022 cm^–1 was substantially decreased by cooking and then increased during storage of cooked rice due to the crystalline structure, newly formed by retrogradation. Storage of cooked rice decreased RDS content and increased SDS content in all rice cultivars. However, no increase in RS content during storage was observed. The enthalpy for retrogradation and the intensity ratio 1047/1022 cm^–1 during storage were correlated negatively with RDS and positively with SDS (P ≤ 0.01).     

Calibration of Hargreaves–Samani and Priestley–Taylor equations in estimating reference evapotranspiration in the Northwest of Iran

Accurate estimation of reference evapotranspiration (ET_o) is essential for water resources management and irrigation systems scheduling, especially in arid and semiarid regions such as Iran. In the present research, constant coefficients of Hargreaves–Samani (C_H–S) and Priestley–Taylor (C_P–T) equations were locally calibrated to estimate the ET_o based on the FAO–Penmen–Monteith (PM) method as standard method. For this purpose, meteorological data of eight synoptic stations located in the northwest of Iran were used during the period of 1997–2008. The outcomes showed that the values of C_H–S and C_P–T were 0.0026 (instead of 0.0023) and 1.68 (instead of 1.26), respectively. Also, at stations with high wind speed, the values of calibrated coefficients of C_H–S and C_P–T were maximum. Then, the estimated ET_o values using adjusted C_H–S and C_P–T coefficients were compared to the obtained actual ET_o values by PM method using root mean square error and mean bias error indices. The results indicated that the new calibrated H–S and P–T equations have good agreement with the PM method for estimation of the ET_o. Moreover, the equation of Ravazzani et al. was calibrated in the studied region. It was concluded that in general, the mentioned equation was shown better performance than original H–S equation.     

Optimization of Near‐Infrared Reflectance Model in Measuring Gelatinization Characteristics of Rice Flour with a Rapid Viscosity Analyzer (RVA) and Differential Scanning Calorimeter (DSC)

This study compared the calibration models generated by combinations of different mathematical and preprocessing treatments as well as regression algorithms to optimize the analysis of gelatinization properties of rice flour by using near‐infrared spectroscopy, in comparison with conventional techniques of differential scanning calorimetry (DSC) and rapid viscosity analysis (RVA). A total of 220 milled rice flours were used for model construction. A model generated by the modified partial least squares regression (MPLS) with mathematical treatment “2, 8, 8, 2” (second‐order derivative computed based on eight data points, and eight and two data points in the second smoothing, respectively) and detrend preprocessing was identified as the best for simultaneously measuring onset temperature (T_o), peak temperature (T_p), and conclusion temperature (T_c) of DSC. MPLS/“2, 8, 8, 2”/weighted multiplicative scattering correction preprocessing was identified as the best for RVA properties. The results indicated that near‐infrared reflectance spectroscopy could be used to rapidly predict gelatinization properties of rice flour for the purposes of quality evaluation of germplasm and selection of intermediate lines in breeding programs.     

Sources of Variation for Starch Gelatinization,Pasting, and Gelation Properties in Wheat

The starch of wheat (Triticum aestivum L.) flour affects food product quality due to the temperature-dependent interactions of starch with water during gelatinization, pasting, and gelation. The objective of this study was to determine the fundamental basis of variation in gelatinization, pasting, and gelation of prime starch derived from seven different wheat cultivars: Kanto 107, which is a partial waxy mutant line, and six near-isogenic lines (NILs) differing in hardness. Complete pasting curves with extended 16-min hold at 93°C were obtained using the Rapid Visco Analyser (RVA). Apparent amylose content ranged from 17.5 to 23.5%; total amylose content ranged from 22.8 to 28.2%. Starches exhibited significant variation in onset of gelatinization. However, none of the parameters measured consistently correlated with onset or other RVA curve parameters that preceded peak paste viscosity. Peak paste viscosity varied from 190 to 323 RVA units (RVU). Higher peak, greater breakdown, lower final viscosity, negative setback, and less total setback were associated with lower apparent and total amylose contents. Each 1% reduction in apparent or total amylose content corresponded to an increase in peak viscosity of about 22 and 25 RVU, respectively, at 12% starch concentration. Of the seven U.S. cultivars, the lower amylose cultivars Penawawa and Klasic were missing the granule-bound starch synthase (GBSS; ADPglucose starch glycosyl transferase, EC 2.4.4.21) protein associated with the Waxy gene locus on chromosome 4A (Wx-B1 locus). Kanto 107 was confirmed as missing both the 7A and 4A waxy proteins (Wx-A1 and Wx-B1 loci). The hardness NIL also were shown to be null at the 4A locus. Apparent and total amylose contents of prime starch generally corresponded well to the number of GBSS proteins; although the hardness NIL tended to have somewhat higher amylose contents than did the other GBSS 4A nulls. We concluded that reduced quantity of starch amylose due to decreased GBSS profoundly affects starch gelatinization, pasting, and gelation properties.     

Noodle Quality as Related to Sorghum Starch Properties

Starch was extracted from 10 sorghum genotypes and physicochemical properties (amylose content and pasting, textural, and thermal properties) were evaluated. The amylose content was 24–30%. DC‐75 starch had the highest peak viscosity (380 Rapid Visco Analyser units). Gelatinization peak temperature occurred over a narrow range (67–69°C). Genotypes Kasvikisire and SV2 produced white starches. Starches from other genotypes were different shades of pink. The starch noodles prepared were, accordingly, either white or pink. Cooking enhanced the pink coloration of noodles. Cooking loss, noodle rehydration, and elasticity were evaluated. Cooking loss was low (mean 2.4%). Noodle elasticity was highly correlated with starch pasting properties of hot paste viscosity (HPV) (r = 0.81, P < 0.01) and cold paste viscosity (CPV) (r = 0.75, P < 0.01). Noodle rehydration was significantly correlated to the initial swelling temperature of starch (T_i) (r = ‐0.91, P < 0.001) and gelatinization peak temperature (T_p) (r = 0.69, P < 0.05). The findings suggest a potential area of food application for sorghum genotypes of different grain colors. Evaluation of starch properties could be a good starting point for selecting sorghum genotypes with superior noodle‐making properties.     

Quantitative Genetic Basis of Gelatinization Temperature of Rice

Gelatinization temperature of rice starch plays an important role in grain quality. We mapped eight loci responsible for the gelatinization parameters of rice: onset temperature (T_o), peak temperature (T_p), conclusion temperature (T_c) and enthalpy (ΔH) using a population of 242 recombinant inbred lines (RIL). Eight quantitative trait loci (QTL) were mapped onto the chromosome regions where starch‐synthesis related genes are located. The Wx gene (granule‐bound starch synthase [GBSS]), and the region of chromosome 11 played major roles in gelatinization trait determination; and other loci were starch‐branching enzyme (SBE) genes that modify the two major loci by epistasis. High‐level interactions were also detected indicating a trans mode of action of the genes. The genetic basis for these parameters was consistent with the relationship between the thermal properties and the structure of the starch granule. This information can be helpful for the improvement of starch‐producing crops, including the improvement of rice grain quality, both for food and industrial uses.     

Classification of Rice Based on Statistical Analysis of Pasting Properties and Apparent Amylose Content: The Case of Oryza glaberrima Accessions from Africa

The diversity of 1,020 Oryza glaberrima rice accessions being kept at the Genetic Resources Unit of the Africa Rice Center with a varied range of apparent amylose content (AAC) and pasting properties was explored with cluster analysis. Rice cultivars are usually characterized according to grain dimensions, AACs, and gelatinization temperatures; however, this work focused on grouping African rice accessions based on their pasting properties and AAC. Using the Ward method of hierarchical cluster analysis, 1,020 rice accessions were initially distributed into five major clusters and further into 23 subclusters. The distribution pattern indicated that clusters I, II, III, IV, and V formed 27.6, 10.2, 15.8, 23.7, and 22.6% of the entire population, respectively. Although some of the groups had similar AAC, their pasting properties were very different, making it imperative for further investigations. Peak viscosity highly correlated (P < 0.01) with trough, breakdown, and final viscosities in all five clusters, whereas correlation between peak viscosity and AAC was not significant within clusters II and IV. Additionally, this categorization serves as a tool for exploring materials that can be employed in the development of rice cultivars for specific end uses.     

Physicochemical Properties of Normal and Waxy Job's Tears (Coix lachryma-jobi L.) Starch

Physicochemical properties of starches from eight coix (Coix lachrymajobi L.) accessions were investigated. There was considerable variation in most measured traits, generally corresponding to the separation into waxy and normal amylose types. The amylose contents of five normal coix ranged from 15.9 to 25.8%, and those of three waxy coix were 0.7–1.1%. Swelling power of waxy coix starches varied between 28.6 and 41.0 g/g, generally higher than waxy maize. Normal coix starches had significantly higher gelatinization peak temperature (T_p) than the normal maize, 71.9–75.5°C. The T_p of waxy coix starches was 71.1–71.4°C, similar to waxy maize. Rapid Visco-Analyser (RVA) pasting profiles of normal coix showed little variation and closely matched the normal maize starch profile. Pasting profiles of waxy coix showed more variation and had lower peak viscosities than waxy maize starch. Waxy coix starches formed very weak gels, while the gel hardness of normal coix starches was 11.4–31.1 g. Amylose content was the main factor controlling differences in starch properties of the coix starches.     

Effects of Rough Rice Storage Conditions on Gelatinization and Retrogradation Properties of Rice Flours

Changes in gelatinization and retrogradation properties of two rice cultivars, Bengal and Kaybonnet, during rough rice storage were studied using differential scanning calorimetry (DSC). The storage variables included two storage moisture contents (12 and 14%), three storage temperatures (4, 21, and 38°C), and four storage durations (0, 3, 9, and 16 weeks). Rough rice cultivar, storage temperature, moisture content, and duration affected (P < 0.05) the enthalpies and temperatures of gelatinization and retrogradation of rice flour. Bengal had a higher gelatinization enthalpy (P < 0.005) but lower gelatinization temperatures (P < 0.0001) than the long-grain Kaybonnet. Rice stored at 38°C exhibited higher gelatinization enthalpy and temperatures (P < 0.05) than those stored at 4 or 21°C. Storage duration affected the gelatinization and retrogradation properties through a higher order, rather than a linear, relationship.     

Heat Treatments of Milled Rice and Properties of the Flours

The effects of autoclave and oven treatments on the gelatinization of rice flour and on the rheological characteristics of its pastes were studied by differential scanning calorimetry (DSC), rapid viscoanalysis (RVA), and rotational viscometry. Flours from autoclave‐treated rice (ATR) and oven‐treated rice (OTR) were prepared, respectively, by heating at 120°C for 60 min and 160°C for 60 min followed by drying (ATR sample), and grinding at 2.2–12.9% moisture content. The rice flour dispersions were adjusted between pH 6.3 and 2.8 using 0.2M citrate buffer. The retort processing of rice flour in water pastes were done at 120°C for 20 min either once or twice. The gelatinization peak temperature (PT and T_o) and the peak temperature corresponding to the amylose‐lipid complexes (T_p3) of ATR increased at pH 6.3 and 2.8 compared with OTR and UTR flour. This indicates that the internal structures of the starch granules in ATR became more stable to heat and acid, even though the damaged starch content of ATR was 23% compared with 16 and 7%, respectively, for untreated rice flour (UTR) and OTR. The OTR flour pastes showed a gel‐like behavior at pH 4.5 after retort processing in water at 120°C for 20 min; however, the ATR mixture behaved more like a liquid paste. Decreases in the reducing sugar content of OTR and ATR pastes suggested that enzymes in the heat‐treated rice were denatured, which retarded the hydrolysis of glucose chains and the rupture of starch granules during pasting.