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This study investigated the effects of extrusion on the physical properties of glutinous rice and addressed the challenges associated with its hardened texture and reduced taste in glutinous rice products by adding extruded glutinous rice to assess their anti‐retrogradation effect compared with different improvers. Glutinous rice flour with different gelatinization degrees was obtained by changing the initial moisture content of glutinous rice grains before extrusion, and their physicochemical properties and the effect of adding them to rice products were analyzed. Results showed that with the increase in moisture content, the viscosity, water absorption index of extruded glutinous rice flour, and product viscosity increased, while the gelatinization degree, water solubility index, and product elasticity decreased, and the hardness of the rice products showed a trend of first decreasing and then increasing. Twenty percent moisture content of glutinous rice products showed the best properties mentioned above. The effects of adding different improvers on retrogradation degree, quality characteristics, microstructure, and moisture migration of glutinous rice products were analyzed by texture profile analysis, sensory evaluation, scanning electron microscopy, and low‐field nuclear magnetic resonance. It was found that soybean polysaccharides, xanthan gum, and extruded glutinous rice flour had better anti‐retrogradation effects, while colloid and soybean polysaccharides provided a tighter and more three‐dimensional internal structure to the rice products. Our study showed that extruded glutinous rice flour had good anti‐retrogradation properties and little effect on flavor and taste, but it would increase the roughness and viscosity of the products, which had advantages and disadvantages compared with other improvers. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effects of sucrose (0%–30%, w/w) on the pasting properties, retrogradation, freeze–thaw stability, texture, and the possible interaction with corn starch–tamarind seed polysaccharide (CS–TSP) mixtures. Sucrose increased the gelatinization temperature (from 76.4 ± 0.1 to 87.6 ± 0.0°C), peak viscosity (from 3358.0 ± 1.4 to 7732.5 ± 44.5 cP), and final viscosity (from 3514.0 ± 31.1 to 7724.5 ± 142.1 cP) of CS–TSP mixtures. Further, sucrose limited the increase in the storage modulus of the mixture pastes, transfer of bound water to free water, and water syneresis during the freeze–thaw process. Additionally, sucrose resulted in a more complete gel structure with stronger resistance. Scanning electron microscope and fluorescence labeling analysis showed that the presence of sucrose helped in tight entanglement or cross‐link between amylose or between amylose and TSP. Thus, these results in this study could help to improve physicochemical properties of starch‐based products, such as glue pudding and other starch desserts. [ABSTRACT FROM AUTHOR]

Semi‐waxy rice, a low‐amylose content (8%–13%) rice variety, can resist retrogradation. It is becoming more and more popular and widely cultivated in East China where consumers prefer cooked rice with soft and tender texture. In this study, water migration, texture and oral processing properties of cooked rice during retrogradation were investigated in order to characterize semi‐waxy rice. The results confirmed that the water mobility and migration of semi‐waxy rice during retrogradation is weaker than that of waxy rice and stronger than that of nonwaxy rice. Simultaneously, the hardness of semi‐waxy rice was higher than that of waxy rice and lower than that of nonwaxy rice. The oral processing properties confirmed that freshly waxy rice was too adhesive and needed more work to breakdown slow breakdown structure (Type Ⅱ structure) compared to freshly semi‐waxy rice. Meanwhile, nonwaxy rice was too hard, and more work was needed to break both fast breakdown structure (Type I structure) and slow breakdown structure (Type Ⅱ structure). The oral processing properties confirmed that retrograded semi‐waxy rice generated more reducing sugar than retrograded waxy rice and nonwaxy rice. Thus, semi‐waxy rice can retard retrogradation, and the texture of cooked semi‐waxy rice is neither too adhesive as waxy rice nor too hard as nonwaxy rice. Practical Application: Semi‐waxy rice cultivars have been widely cultivated in East China and well accepted by the consumers. This study aims to characterize semi‐waxy rice and provide theoretical basis for semi‐waxy rice study. [ABSTRACT FROM AUTHOR]

Retrogradation affects acceptability of starchy foods; however, it is preferred in some products such as rice noodles. Amylose content, gelatinization temperature, and storage condition were reported to affect retrogradation but with disputed data. The joint effects of these parameters were interested in this study. Rice starch was gelatinized using different temperatures (77, 81, 95, and 121 °C) and stored isothermally with temperature cycles for 10 days. Results showed that the most important parameter that affected retrogradation was storage time followed by storage condition and gelatinization temperature. The recrystallization rate constant (k) and Avrami exponent (n) of retrograded starches stored under temperature cycle were higher than isothermal storage. All samples showed similar polymorphs of a mixture of B and V types. High‐temperature gelatinized starch gel stored under temperature cycle condition produced higher yield of resistant starch. The study provided useful information on how to apply these parameters to control the retrogradation of starchy foods, especially rice noodle. Practical Application: Retrogradation is found to be more prominent at higher gelatinization temperature and longer storage time. Resistant starch produced from retrograded starch depended largely on storage time than storage condition. This finding can be applied to improve rice noodle qualities (by increasing retrogradation) with lower digestibility (by producing higher resistant starch). [ABSTRACT FROM AUTHOR]

Water plays a significant role in the gelatinization and retrogradation (crystallization) of starch. Amylopectin crystalline regions can adopt several hydrated polymorphic forms; however, reports differ on the migration of water during retrogradation. The objectives of this study were to determine the moisture sorption patterns of gelatinized starch lyophiles during retrogradation in controlled relative humidity (RH) environments and document the amylopectin polymorph(s) formed. Starches from different botanical sources containing A‐type and B‐type amylopectin polymorphs were studied. Suspensions of starch were heated and then frozen and freeze‐dried to make primarily amorphous matrices. Moisture sorption profiles of the dried samples were collected from 5% RH to 95% RH at 25 °C. To capture the retrogradation event, sample masses were also monitored at constant RHs over time (95%, 92.5%, and 90% RH). Powder X‐ray diffraction was used to document the physical state of the samples, including the amylopectin polymorph formed upon retrogradation, and differential scanning calorimetry was used to determine glass transition temperatures (Tgs). In all lyophiles, water was first absorbed (mass gain), and if a critical water content was reached (at ≥92.5%RH), sample Tgs dropped below room temperature and concurrent retrogradation and water expulsion (mass loss) occurred, regardless of starch botanical source and whether A‐ or B‐type polymorphs were formed. Overall, retrogradation and water expulsion increased as storage RH increased. These results offer further knowledge into the role of water in amylopectin retrogradation and the relationship among starch type, environmental RH, moisture sorption prior to retrogradation, and water redistribution during retrogradation. Practical Application: Starch gelatinization and retrogradation require molecular mobility, which is facilitated by water. Limited retrogradation occurred in lyophiles in the glassy state (90% RH, 25 °C), but increasing the storage RH (to ≥92.5% RH) resulted in increasing amylopectin retrogradation (note: many baked products have water activities in this range). Regardless of starch type (botanical source and amylose content), when the storage RH was high enough, the starch lyophiles first absorbed water, which depressed the Tg below the storage temperature, and then exhibited concomitant retrogradation and water expulsion. The water expelled during amylopectin retrogradation was not (fully) retained in the amorphous starch fraction, which is why samples lost weight. Water leaving the starch matrix during retrogradation could pose challenges for quality, texture, and shelf‐life of starch‐based products. [ABSTRACT FROM AUTHOR]

Amylomaltase (α-1,4-glucanotransferase, AM; EC 2.4.1.25) from Corynebacterium glutamicum expressed in Escherichia coli was used to prepare the enzyme-modified cassava starch for food application. About 5% to 15% (w/v) of cassava starch slurries were incubated with 1, 3, or 5 units of amylomaltase/g starch. Apparent amylose, amylopectin chain length distribution, thermal properties, freeze-thaw stability, thermo-reversibility, and gel strength of the obtained modified starches were measured. The apparent amylose content and retrogradation enthalpy were lower, whereas the retrogradation temperatures, freeze-thaw stability, and thermo-reversibility were higher than those of the native cassava starch. However, when amylomaltase content was increased to 20 units of amylomaltase/g starch and for 24 h, the modified starch showed an improvement in the thermo-reversibility property. When used in panna cotta, the gel strength of the sample using the 20 units/24 h modified cassava starch was similar to that of using gelatin. [ABSTRACT FROM AUTHOR]

Retrogradation in cooked starch-based products is a significant hindrance in extending the shelf life of these products as they become progressively hard to bite over short time periods (say 1 or 2 months). In this study, the effects of tea polyphenols (TPs) on cooked amylopectin-rich cassava starch have been investigated. Cassava starch was mixed with TPs and then gelatinized to form starch gels. The obtained gels were stored for up to 80 d and characterized by X-ray diffraction (XRD), hardness test, color analysis, and Fourier transform infrared spectroscopy (FT-IR). The results of XRD show that the formation of long-range ordered structure of amylopectin was retarded by the interaction of TPs with amylopectin via hydrogen bond. The results of hardness test show that the accelerating increase in the hardness of cassava starch gel was retarded by the addition of TPs. The increase in hardness versus time can be correlated well using a single-parameter exponential equation. The increase in hardness, variations in color, and FT-IR spectrum of the TPs treated samples during storage with TPs were relatively small, suggesting that the retrogradation of starch is inhibited by TPs. This work presents an opportunity of antiretrogradation in the related products. [ABSTRACT FROM AUTHOR]

Albumins, globulins, gliadins, and glutenins were isolated from wheat flour and the effects of those proteins on retrogradation of wheat starch were investigated. The results showed that only glutenins retarded retrogradation of wheat starch and other 3 proteins promoted it. The results of IR spectra proved that no S-S linkage formed during retrogradation of wheat starch blended with wheat proteins. Combination of wheat starch and globulins or gliadins through glucosidic bonds hindered the hydrolysis of wheat starch by a-amylase. The melting peak temperatures of retrograded wheat starch attached to different proteins were 128.46, 126.14, 132.03, 121.65, and 134.84 °C for the control with no protein, albumins, glutenins, globulins, gliadins groups, respectively, and there was no second melting temperature for albumins group. Interaction of wheat proteins and starch in retrograded wheat starch greatly decreased the endothermic enthalpy (H) of retrograded wheat starch. Retrograded wheat starch bound to gliadins might be a new kind of resistant starch based on glycosidic bond between starch and protein. [ABSTRACT FROM AUTHOR]