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.     

Changes in Rice with Variable Temperature Parboiling: Thermal and Spectroscopic Assessment

Rapid visco analysis (RVA) and differential scannning calorimetry (DSC) provided overall assessments of the effects of variable temperature soaking at 30, 50, 70, and 90°C and steaming at 4, 8, and 12 min. Calculation of the relative parboiling index (RPI) and percent gelatinization provided good metrics for determining the overall effects of partial parboiling. FT‐Raman and solid‐state ¹³C CP‐MAS NMR spectroscopies provided insight to conformational changes in protein and starch of paddy rice under various parboiling conditions. RVA showed lower pasting curves and DSC showed lower ΔH with increased temperature and steaming times. A large decrease in viscosity occurred with only the 30‐4 treatment as opposed to raw rice. This observation was consistent with FT‐Raman results that indicated substantial conversion of the protein from α‐helix to other conformations. DSC indicated incomplete gelatinization of starch, even with 90°C soaking and 12 min of steaming. Solid‐state ¹³C CP‐MAS NMR spectroscopy confirmed this result. However, it indicated the percent of V_h/amorphous plus the remaining crystalline starch in the 90‐12 treatment was equal to the amorphous and partially‐ordered starch in commercially parboiled rice. These results suggest that partial parboiling, 90°C soaking, and more than 8 min of steaming (ideally ≈12 min) of paddy rice is sufficient to induce changes that inactivate enzymes and provide enough starch gelatinization to prevent kernel breakage.     

Effect of Variable Parboiling on Crystallinity of Rice Samples

Rice parboiled at various combinations of soaking temperature and steaming time were analyzed by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Generally, gelatinization enthalpy decreased as the soaking temperature increased from 30°C to 50°C and 70°C to 90°C, and gelatinization enthalpy decreased as steaming times increased from 4 and 8 min to 12 min. As expected, a distinctive A‐pattern was observed in the XRD of raw rice. The most severely parboiled laboratory sample (90°C for 12 min), showed no discernable change toward the V‐pattern. Crystallinity decreased from the raw rice (24.6%) with increased cooking temperature.     

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.     

Physicochemical Properties of Rice Starch Modified by Hydrothermal Treatments

Rice starches of long grain and waxy cultivars were annealed (ANN) in excess water at 50°C for 4 hr. They were also modified under heat-moisture treatment (HMT) conditions at 110°C with various moisture contents (20, 30, and 40%) for 8 hr. The modified products were analyzed by rapid-viscosity analysis (RVA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Generally, these hydrothermal treatments altered the pasting and gelling properties of rice starch, resulting in lower viscosity peak heights, lower setbacks, and greater swelling consistency. The modified starch showed increased gelatinization temperatures and narrower gelatinization temperature ranges on ANN or broader ones on HMT. The effects were more pronounced for HMT than for ANN. Also, the typical A-type XRD pattern for rice starch remained unchanged after ANN or HMT at low moisture contents, and the amorphous content increased after HMT at 40% moisture content.     

Physicochemical Properties of Starch in Extruded Rice Flours

The effects of extruding temperatures and subsequent drying conditions on X‐ray diffraction patterns (XRD) and differential scanning calorimetry (DSC) of long grain (LG) and short grain (SG) rice flours were investigated. The rice flours were extruded in a twin‐screw extruder at 70–120°C and 22% moisture, and either dried at room temperature, transferred to 4°C for 60 hr, or frozen and then dried at room temperature until the moisture was 10–11%. The dried materials were milled without the temperature increasing above 32°C. XRD studies were conducted on pellets made from extruded and milled flours with particle sizes of 149–248 μm; DSC studies were conducted from the same material. DSC studies showed that frozen materials retrograded more than the flours dried at room temperature. The LG and SG samples had two distinct XRD patterns. The LG gradually lost its A pattern at >100°C, while acquiring V patterns at higher temperatures. SG gradually lost its A pattern at 100°C but stayed amorphous at the higher extruding temperatures. DSC analysis showed that retrograded flours did not produce any new XRD 2θ peaks, although a difference in 2θ peak intensities between the LG and SG rice flours was observed. DSC analysis may be very sensitive in detecting changes due to drying conditions, but XRD data showed gradual changes due to processing conditions. The gradual changes in XRD pattern and DSC data suggest that physicochemical properties of the extruded rice flours can be related to functional properties.     

Relationship of Gelatinization and Recrystallization of Cross‐Linked Rice to Glass Transition Temperature

Nonwaxy rice starch was cross‐linked with sodium trimetaphosphate and sodium tripolyphosphate to obtain different degrees of cross‐linking (9.2, 26.2, and 29.2%). The objective was to investigate the influence of cross‐linking on thermal transitions of rice starch. Starch suspensions (67% moisture) were heated at 2°C/min using differential scanning calorimetry (DSC) to follow melting transition of amylopectin. Biphasic transitions were observed at ≈60–95°C in all samples. Melting endotherms of amylopectin shifted to a higher temperature (≤5°C) with an increasing degree of cross‐linking, while there was no dramatic change in enthalpy. Recrystallization during aging for 0–15 days was significantly suppressed by cross‐linking. The delayed gelatinization and retrogradation in crosslinked starch were evident due to restricted swelling and reduced hydration in starch granules. Glass transition temperature (T_g) measured from the derivative curve of heat flow was ‐3 to ‐4°C. No significant change in T_g was observed over the storage time studied.     

Thermomechanical Behavior of Concentrated Starch-Water Preparations

The rheological behavior of concentrated starch preparations from various origins was studied by dynamic mechanical thermal analysis (DMTA). Four types of starch were used: wheat, potato, normal, and waxy corn adjusted to moisture contents in the 42–49% (w/w) range. The thermal treatments of the starch-water mixtures consisted of heating to 85°C and cooling to room temperature, both at a rate of 1°C/min. During heating, the storage modulus (E′) appearance was first characterized by an increase with a maximum at ≈70°C (or potato starch at 63°C) followed by a decrease to 85°C. During cooling, storage modulus increased steadily down to room temperature. The magnitude of these variations depended on the starch type. Despite some differences, all the loss tangent curves showed a decrease during heating from 60–70°C to 85°C, followed by a plateau during cooling. To propose an interpretation for the DMTA results, we measured, by laser-light diffraction, the influence of heating (up to the maximum E′ peak) on the distribution of the granule sizes of the different starches. Moreover, differential scanning calorimetry (DSC) was used to measure the temperature range where the melting of starches ordered regions occurred. Partial melting enthalpies were plotted against temperature. The hypothesis of a relationship between swelling and an increase in rigidity during heating seemed to be confirmed by laser-light diffraction, whereas DSC indicated the decrease in rigidity was caused predominantly by order-disorder transitions. During cooling, amylose gelation plays a major role in the rigidity increase, but a contribution of amylopectin is not excluded.     

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.     

Retrogradation of Maize Starch After Thermal Treatment Within and Above the Gelatinization Temperature Range

Studies of starch retrogradation have not considered the initial thermal treatment. In this article, we explore the effect of heating to temperatures within and above the gelatinization range on maize starch retrogradation. In the first experiment, 30% suspensions of waxy (wx) starch were initially heated to final temperatures ranging from 54 to 72°C and held for 20 min. On reheating in the differential scanning calorimeter immediately after cooling, the residual gelatinization endotherm peak temperature increased, the endotherm narrowed, and enthalpy decreased. Samples stored for seven days at 4°C showed additional amylopectin retrogradation endotherms. Retrogradation increased dramatically as initial holding temperature increased from 60 to 72°C. In a second experiment, wx starch was initially heated to final temperatures from 54 to 180°C and rapidly cooled, followed by immediate reheating or storage at 4°C. Maximum amylopectin retrogradation enthalpy after storage was observed for initial heating to 82°C. Above 82°C, retrogradation enthalpy decreased as initial heating temperature increased. A similar effect for ae wx starch was observed, except that retrogradation occurred more rapidly than for wx starch. These experiments show that heating to various temperatures above the range of gelatinization may profoundly affect amylopectin retrogradation, perhaps due to varying extents of residual molecular order in starch materials that are commonly presumed to be fully gelatinized. This article shows that studies of starch retrogradation should take into account the thermal history of the samples even for temperatures above the gelatinization temperature range.     

Starch Retrogradation in Cooked Pasta and Rice

Effect of cooking time on starch retrogradation and water distribution was studied in pasta (spaghetti) and rice (parboiled and arborio) using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) Optimum cooking times (OCT) were 8, 16, and 18.5 min for spaghetti, parboiled, and arborio rice, respectively. Swelling was observed by image analysis. OCT spaghetti and rice showed various starch retrogradation rates at various aging times and temperatures. Based on the classical Avrami function, the retrogradation rate at 5°C followed the order spaghetti > parboiled rice > arborio rice, while extent was in the opposite order. At higher temperature (20°C), the rates decreased by 20× in all cases. Thermogravimetric analysis (TGA) investigations were undertaken to check the distribution of water within these products and its relationship to starch retrogradation. During heating, water was released in two distinguishable steps at ≈80 and 100°C. Results supported the conclusion that the more tightly bound water might not participate or facilitate starch retrogradation. In this study, the overall water content did not change during storage, and water appeared to migrate from sites of stronger binding to sites of weaker binding. The temperature dependence of the Avrami constant was described with the Vogel‐Tamman‐Fulcher empirical expression.     

Infrared Drying Characteristics of Long‐Grain Hybrid,Long‐Grain Pureline,and Medium‐Grain Rice Cultivars

The objective for this study was to investigate the effectiveness of scaled‐up infrared (IR) heating followed by tempering steps to dry freshly harvested rough rice. An industrial‐type, pilot‐scale, IR heating system designed to dry rough rice was used in this study. The heating zone of the equipment had catalytic IR emitters that provided heat energy to the sample as it was conveyed on a vibrating belt. The sample comprised freshly harvested rough rice of long‐grain pureline (Cheniere), long‐grain hybrid (6XP 756), and medium‐grain (CL 271) cultivars at initial moisture contents of 23, 23.5, and 24% wb, respectively. Samples at a loading rate of 1.61 kg/m² were heated with IR of radiation intensity 5.55 kW/m² for 30, 50, 90, and 180 s followed by tempering at 60°C for 4 h, at a product‐to‐emitter‐gap size of 450 mm, in one‐ and two‐pass drying operations. Control samples were gently natural air dried in an equilibrium moisture content chamber set at relative humidity of 65% and temperature of 26°C to moisture content of 12.5% wb. The effects of IR treatments followed by tempering on percentage points of moisture removed, head rice yield, energy use, rice color, and pasting characteristics were evaluated. For all cultivars, percentage point moisture removed increased with increase in IR drying duration. For all rice cultivars, one‐pass IR treatments for 180 s resulted in head rice yield significantly lower than that of rice dried with natural air in the controlled‐environment conditions (P < 0.05). Energy required to dry rice increased with increase in drying duration. Viscosity values of all the experimental samples were significantly greater (P value < 0.05) than that of the control samples for all the cultivars, except those treated with IR for 180 s. There was a significant difference (P < 0.05) in the color index (ΔE ) of treated milled samples and the controls. In conclusion, the study provided information crucial to understanding the effects of scaled‐up radiant heating and tempering of rough rice on drying rates and rice quality for long‐grain pureline, long‐grain hybrid, and medium‐grain rice cultivars.     

Effect of Moisture Content on Thermomechanical Behavior of Concentrated Wheat Starch-Water Preparations

The rheological behavior of wheat starch preparations at intermediate moisture contents (25–60%, w/w) was studied by dynamic mechanical thermal analysis (DMTA). Differential scanning calorimetry (DSC) and electron spin resonance (ESR) experiments were also performed in parallel. Upon heating wheat starch preparations from 25 to 85°C, DMTA showed first a slight decrease in storage modulus (G′) to 45–60°C, then an increase of the shear modulus (predominant effect of swelling) to 68–74°C, followed by a decrease (predominant effect of melting-softening) to 85°C. In this 25–85°C temperature range, the initial swelling and subsequent softening were less pronounced with decreasing moisture content. The 45% moisture content level appeared critical, since there was a radical change in the thermomechanical behavior below this concentration. DSC showed that gelatinization did not appear as a single endotherm but as two endotherms. Whatever the moisture content, the melting started within a quite narrow temperature range, while the end of melting shifted progressively to higher temperatures as moisture content was decreased. ESR showed first a slight decrease in the water-soluble probe (Tempol) mobility as temperature was increased to 47–50°C, followed by a pronounced decrease to 57–60°C. Then, a progressive increase in probe mobility was observed to 85°C. These changes in probe mobility suggest some modifications of the kinetic and thermodynamic properties of the aqueous phase associated with changes in the starch physical state. For the lowest moisture contents, the probe mobility was quite stable during heating.     

Study of Structural and Thermal Changes in Endosperm of Quality Protein Maize During Traditional Nixtamalization Process

This work presents the study of the structural changes of the endosperm of Quality Protein Maize (QPM H-368C), modified by alkaline cooking at two different temperatures (72 and 92°C) and steeping time of 0–7 hr. Structural changes in the outermost 10% layers, the subsequent 10%, and the remaining 80% of the endosperm as a function of the steeping time were studied using scanning electron microscopy (SEM), X-ray diffraction, and differential scanning calorimetry (DSC) techniques. SEM images revealed that soft and hard endosperm have different shapes and packing factors. The X-ray diffraction patterns of the hard and soft endosperm from raw corn suggest that the hard endosperm consists mainly of amylopectin and has a bigger relative crystallinity quality than the soft endosperm. Samples cooked at 72 and 92°C with and without the (Ca(OH)₂ and steeped for 0, 3, and 7 hr, showed structural changes, X-ray diffraction patterns from the outermost 10% layers and subsequent 10% of the endosperm were completely amorphous. This fact is related to the total or partial gelatinization of the starch. The crystallinity in the internal layers of endosperm (remaining 80%) did not have significant changes after the treatments and exhibited the characteristic patterns of crystalline amylose and amylopectin. DSC measurements in the outermost layers of the endosperm did not exhibit the characteristic endothermic peak of starch (from 64 to 81°C) compared with the raw sample, while the endotherm peak for 80% of the endosperm internal layers appears in all cases (72 and 92°C). According to these results, a new definition of the nixtamalization process can be developed as follows. During the nixtamalization process there is a total gelatinization of the starch granules from the most external layers, and a partial gelatinization of the innermost internal layers of the endosperm.     

Effects of Modulated Differential Scanning Calorimetry (MDSC) Variables on Thermodynamic and Kinetic Characteristics During Gelatinization of Waxy Rice Starch

The total, reversing, and nonreversing thermal properties during gelatinization of waxy rice starch (starch-to-water ratio = 1:2, w/w) were examined by modulated differential scanning calorimetry (MDSC). The effect of MDSC operating variables (i.e., the amplitude and frequency of temperature modulation and the underlying heating rate) on these thermal properties was determined by response surface methodology (RSM) and statistical analysis. The frequency of temperature modulation and the underlying heating rate significantly influenced the gelatinization temperatures and enthalpy changes in total and nonreversing endotherms. In addition, the combination of 0.025Hz and 4–8°C/min with a properly low degree of oscillation was suitable for characterization of starch gelatinization by MDSC. The enthalpy changes in the reversing (thermodynamic) endotherms increased, but those in the nonreversing (kinetic) endotherms decreased with increasing periods (i.e., decreasing frequencies) and underlying heating rates. However, the total enthalpy changes were only slightly influenced by the MDSC variables studied. In addition, the activation energies for the total and nonreversing events were 281.8–417.3 and 386.3–739.7 kJ/mol, respectively, depending on the MDSC conditions. From the compensation relationship between the activation energy and frequency factor, we concluded that the total and nonreversing endotherms were linked to the same single transition.     

Retrogradation Mechanism of Rice Starch

The non‐Newtonian behavior and dynamic viscoelasticity of rice starch (Akihikari, 18.8% amylose content) solutions after storage at 25 and 4°C for 24 hr were measured with a rheogoniometer. The flow curves, at 25°C, of Akihikari starch showed plastic behavior >3.0% (w/v) after heating at 100°C for 30 min. The dynamic viscoelasticity of the starch increased after storage at 25 and 4°C for 24 hr and stayed at a constant value with increasing temperature. A small dynamic modulus of rice starch was observed upon addition of urea (4.0M) at low temperature (0°C), but it produced a sigmoid curve when plotted against increasing temperature. A small dynamic modulus was also observed in 0.05M NaOH solution. However, it increased rapidly after the temperature reached 70°C. Possible models of retrogradation mechanism of rice starch were proposed.     

Chemical and Physicochemical Properties of Maize Starch After Industrial Nixtamalization

Processing conditions similar to traditional nixtamalization are now used by the industry in the production of dry maize flours (DMF). The objective of this investigation was to evaluate the effect of industrial nixtamalization on maize starch. Thus, dent maize grains were sampled from storage silos and the starch isolated (S). From the same batch of maize, DMF was obtained and the starch isolated (S‐DMF). The amylose content in the starches was quite similar (21.5–23.4%) and characteristic of a dent maize. However, nixtamalization increased the calcium content in S‐DMF. The starches investigated exhibited the typical A‐type diffraction pattern after 40 days of storage at 11–84.1% rh. However, the differential scanning calorimetry (DSC) results showed that annealing of maize starch occurred during storage at 30°C. On the other hand, industrial nixtamalization has both a melting and annealing effect on maize starch. Thus, the operative glass transition temperature (T_g), and the DSC parameters that define starch gelatinization (T_p and ΔH) showed that the proportion between crystalline and amorphous regions within the starch granule and the extent of physical damage to starch were modified by nixtamalization. As an example, T_g for S was between 60 and 62.5°C, while the S‐DMF had a T_g of 45–55°C for damaged starch and 65–70°C for annealed starch. Additionally, the extraction of the nonconstitutive starch lipids provided starches with more consistent thermal properties, particularly in the behavior of gelatinization at different water content. This last observation might have important implications in the consistency of starch physicochemical properties and, consequently, in the quality of maize products such as tortillas.     

Thermal Modifications of Starch During High‐Temperature Drying of Pasta

Changes in starch at the molecular level during high‐temperature (HT) drying of pasta were studied with differential scanning calorimetry (DSC). Pasta was manufactured from durum wheat semolina into the shape of spaghetti on a pilot‐plant installation. The HT phase (100°C) was applied at relatively high (27 g/100 g, wb), intermediate (20 g/100 g), and low (15 g/100 g) product moisture, respectively. Spaghetti dried at 55°C served as reference samples. The changes in the thermal properties of starch during drying were dependent on the drying conditions. The gelatinization enthalpy of pasta dried at 55°C was reduced by 30% during drying, which indicates a partial melting of the starch crystallites. With the beginning of the HT phase, the gelatinization enthalpy increased to final values that were close to or higher than those of freshly extruded pasta. In general, HT drying of pasta induced a broadening of the gelatinization range. Starch crystallinity remained unchanged during extrusion and drying at HT. Based on a state diagram of starch and on DSC measurements of pasta during drying, it is hypothesized that HT drying favors molecular rearrangements of starch polymers at the double helical level.     

Retrogradation of du wx and su2 wx Maize Starches After Different Gelatinization Heat Treatments

Retrogradation of du wx and su2 wx starches after different gelatinization heat treatments was studied by differential scanning calorimetry. Suspensions of 30% (w/w) starch were initially heated to final temperatures of 55–180°C. Gelatinized starch was cooled and stored at 4°C. Starch retrogradation in the storage period was influenced by initial heat treatments. Retrogradation of du wx starch was rapid: when initially heated to 80–105°C, retrogradation enthalpy was ≈10 J/g after one day at 4°C. The retrogradation enthalpy was ≈15 J/g after 22 days of storage, and reached a maximum of 16.2 J/g after 40 days of storage. For du wx starch, application of the Avrami equation to increases in retrogradation enthalpy suggests retrogradation kinetics vary with initial heating temperature. Furthermore, starch retrogradation may not fit simple Avrami theory for initial heating ≤140°C. Retrogradation of su2 wx starch was slow. After 30 days of storage at 4°C, the maximum retrogradation enthalpy for all initial heating temperatures tested was 7.0 J/g, for the initial heating to 80°C. This work indicates that gelatinization heat treatment in these starches is an important factor in amylopectin retrogradation, and that the effect of initial heat treatment varies according to the genotype.     

Two- and multi-step annealing of cereal starches in relation to gelatinization

Two- and multi-step annealing experiments were designed to determine how much gelatinization temperature of waxy rice, waxy barley, and wheat starches could be increased without causing a decrease in gelatinization enthalpy or a decline in X-ray crystallinity. A mixture of starch and excess water was heated in a differential scanning calorimeter (DSC) pan to a specific temperature and maintained there for 0.5-48 h. The experimental approach was first to anneal a starch at a low temperature so that the gelatinization temperature of the starch was increased without causing a decrease in gelatinization enthalpy. The annealing temperature was then raised, but still was kept below the onset gelatinization temperature of the previously annealed starch. When a second- or third-step annealing temperature was high enough, it caused a decrease in crystallinity, even though the holding temperature remained below the onset gelatinization temperature of the previously annealed starch. These results support that gelatinization is a nonequilibrium process and that dissociation of double helices is driven by the swelling of amorphous regions. Small-scale starch slurry annealing was also performed and confirmed the annealing results conducted in DSC pans. A three-phase model of a starch granule, a mobile amorphous phase, a rigid amorphous phase, and a crystalline phase, was used to interpret the annealing results. Annealing seems to be an interplay between a more efficient packing of crystallites in starch granules and swelling of plasticized amorphous regions. There is always a temperature ceiling that can be used to anneal a starch without causing a decrease in crystallinity. That temperature ceiling is starch-specific, dependent on the structure of a starch, and is lower than the original onset gelatinization of a starch.