Impact of long-term storage on multi-scale structures and physicochemical properties of starch isolated from rice grains

Effects of Aspergillus flavus infection on multi-scale structures and physicochemical properties of maize starch during storage

This study systematically analyzed the effect of Aspergillus flavus infection on the maize starch multi-scale structure, physicochemical properties, processing characteristics, and synthesis regulation. A. flavus infection led to a decrease in the content of starch, an increase in the content of reactive oxygen species (ROS) and malondialdehyde (MDA), a significant decrease in the activities of peroxidase (POD) and superoxide dismutase (SOD). In addition, A. flavus infection had a significant destructive effect on the double helix structure, relative crystallinity and lamellar structure of starch, resulting in the reduction of starch viscosity, affecting the viscoelastic properties of starch, and complicating the gel formation process. However, the eugenol treatment group significantly inhibited the growth of A. flavus during maize storage, protecting the multi-scale structure and processing characteristics of maize starch from being damaged. Transcriptome analysis showed that genes involved in carbohydrate synthesis in maize were significantly downregulated and genes involved in energy synthesis were significantly upregulated, indicating that maize converted its energy storage into energy synthesis to fight the invasion of A. flavus. These results of this study enriched the mechanism of quality deterioration during maize storage, and provide theoretical and technical support for the prevention of A. flavus infection during maize storage.

Changes in the starch quality of adlay seed varieties (Coix lacryma-jobi L.) from different regions in China after high-temperature storage

The effects of high-temperature storage at 37 °C on the crystallinity, pasting, rheological, and thermal properties of adlay seed starches from three famous Chinese varieties were studied. The results showed that high-temperature storage altered the natural structure of adlay seed starch, resulting in increased peak viscosity for all starch pastes after one month of storage at 37 °C. Jinsha adlay seed starch (JSC), which had the highest amylose content (11.21 %), showed increased D50, relative crystallinity and OD values, demonstrating strong regrowth ability and hydrophobicity, with starch gels having greater hardness and gumminess after storage. In contrast, Pucheng adlay seed starch (PSC) and waxy Ninghua adlay seed starch (WSC), with similar amylose proportions, showed distinct starch gel properties. PSC (with an amylose content of 3.35 %) exhibited better starch gel properties, whereas WSC (amylose content of 5.74 %) demonstrated improved gumminess and chewiness after storage and exhibited stronger anti-starch regrowth capabilities. This study provides valuable insights into the selection of future starches based on their specific processing requirements.

Impact of flaxseed gum on the aggregate structure, pasting properties, and rheological behavior of waxy rice starch

This study examines the effects of flaxseed gum (FG) on the aggregate structure, pasting and rheological properties of waxy rice starch (WRS). Results display an increase in the ordered molecular structure (R1047/1024), relative crystallinity (RC), compactness (α), and microphase heterogeneity (ε, density degree of nanoaggregates, from 3.52 to 4.23) for WRS-FG complexes. These suggested FG facilitated the development of more organized molecular and crystalline structures of WRS, accompanied by the formation of ordered nanoaggregates with higher density (i.e., nano-aggregation structure). Also, FG addition resulted in the formation of enhanced gel network structure characterized by thicker layer walls and more uniform pores. These structural transformations contributed to a rise in gelatinization temperature (To, from 56.90 °C to 62.10 °C) and enthalpy (ΔH), as well as alterations in paste viscosities (PV, from 1285.00 mPa·s to 1734.00 mPa·s), and the rigidity of network structure (e.g., decreased loss tangent). These results indicate that FG could effectively regulate the techno-functional properties of WRS by rationally controlling the starch intrinsic structures of starch. And this study may improve the pasting and gelling properties of starch, thus driving the development of high-quality starchy foods and prolonging their shelf life, especially for glutinous rice flour products.

Rheological properties of indica rice determined by starch structure related enzymatic activities during after-ripening

The processing quality of indica rice must undergo ripening after harvest to achieve stability and improvement. However, the mechanism underlying this process remains incompletely elucidated. Starch, the predominant component in indica rice, plays a crucial role in determining its properties. This study focused on analyzing the rheological properties and starch fine structure, as well as the related biosynthetic enzymes of indica rice during the after-ripening process. The results showed that after-ripened rice exhibited increased elastic modulus (G') and viscous modulus (G″), accompanied by a decrease in the loss tangent (Tan δ), indicating an enhancement in viscoelasticity and the gel network structure. Moreover, the proportions of amylopectin super long chains (DP 37-60) decreased, while those of medium chains (DP 13-24 and DP 25-36) or short chains (DP 6-12) of amylopectin increased. Additionally, the activities of starch branching enzyme (SBE) and starch debranching enzyme (DBE) declined over the after-ripening period. Pearson correlation analysis revealed that the rheological properties of after-ripened rice were correlated with the chain length distribution (CLD) of starch, which, in turn, was associated with its related endogenous enzymes. These findings provied new insights into understanding the quality changes of after-ripened indica rice.

Effects of fermented and unfermented aging corn on ruminal fermentation, bacterial communities, lactation performance and plasma metabolites in Holstein cows

Aging reduces the nutritional value of corn grain, which may be improved by fermentation prior to use. This study investigated the effects of replacing conventional corn (CC) with aging corn (AC) and fermented aging corn (FAC) in the diets of lactating Holstein cows. Six healthy third-parity Holstein cows were used in a replicated 3 × 3 Latin square experiment with 21-day periods. Cows were fed twice and milked twice daily. The cows were randomly divided into three treatment groups: (1) CC diet: a diet with 23.6% starch in diet DM containing 24.0% conventional corn; (2) AC diet: a diet with 23.5% starch in diet DM containing 24.0% aging corn replacing conventional corn; and (3) FAC diet: a diet with 23.2% starch in diet DM containing 24.6% fermented aging corn replacing conventional corn. The diets were formulated to be isonitrogenous and contained identical roughage. The FAC treatment increased the starch digestibility compared with AC. Feeding FAC increased the concentrations of total volatile fatty acid compared with CC and AC and decreased the molar proportion of acetate compared with AC. At the family level, the relative abundance of Prevotellaceae was higher on FAC than CC. The relative abundance of Succinivibrionaceae was lower on FAC than on CC and AC. Besides, at the genera level, the relative abundance of Succinivibrionaceae_UCG_002 in the rumen was higher on AC than CC and FAC. The relative abundance of Prevotella and Ruminococcus was higher on FAC than CC and AC. The relative abundance of Succinivibrionaceae_UCG_001 was lower on FAC than CC. The Simpson index was lower on FAC than CC and AC. The FAC treatment increased the milk yield (34.0, 33.7, and 35.2 kg/d for CC, AC, and FAC group, respectively) and protein yield, and thus, energy-corrected milk production was increased, and at the same time, decreased the somatic cell score compared with CC and AC. The AC treatment increased the malondialdehyde concentration in plasma compared with CC and FAC. The concentrations in plasma of triglyceride and malondialdehyde were lower on FAC than AC. The immunoglobulin G concentration in plasma was higher on FAC than CC and AC. Overall, feeding AC resulted in decreased plasma antioxidant capacity compared with CC, whereas feeding FAC altered the relative abundance of bacteria in the rumen and improved starch digestibility, ruminal bacterial diversity, lactation performance, plasma antioxidant capacity and immune competence compared with AC in dairy cows.

Insights into the hierarchical structure and physicochemical properties of starch isolated from fermented dough

Understanding the hierarchical structure and physicochemical properties of starch isolated from fermented dough with different times (0-120 min) is valuable for improving the quality of fermented dough-based products. The results indicate that fermentation disrupted the starch granule surface and decreased the average particle size from 19.72 μm to 18.45 μm. Short-term fermentation (< 60 min) disrupted the crystalline, lamellar, short-range ordered molecular and helical structures of starch, while long-term fermentation (60-120 min) elevated the ordered degree of these structures. For example, relative crystallinity and double helix contents increased from 23.7 % to 26.8 % and 34.4 % to 37.2 %, respectively. During short-term fermentation, the structural amorphization facilitated interactions between starch molecular chains and water molecules, which increased the peak viscosity from 275.4 to 320.6 mPa·s and the swelling power from 7.99 to 8.52 g/g. In contrast, starches extracted from long-term fermented dough displayed the opposite results. Interestingly, the hardness and springiness of starch gels gradually decreased as fermentation time increased. These findings extend our understanding of the starch structure-property relationship during varied fermentation stages, potentially benefiting the production of better-fermented foods.

Impact of starch chain length distributions on physicochemical properties and digestibility of starches

Changing starch structure at different levels is a promising approach to promote desirable metabolic responses. Chain length distribution (CLD) is among the starch structural characteristics having a potential to determine properties of starch-based products. Therefore, the objective of the current review is to summarize recent findings on CLD and its impact on physicochemical properties and digestion. Investigations undertaken to enhance understanding of starch structure have shown clearly that CLD is a significant determining factor in modulating starch digestibility. Enzymatic modifications and processing treatments alter the CLD of starch, which in turn affects the rate of digestion, but the underlying molecular mechanisms have yet to be fully elucidated. Even though advances have been made in manipulating CLD using different methods and to correlate the changes with various functional properties, in general the area needs further investigations to open new awareness for enhancing healthiness of starchy foods.

Effects of oat β-glucan on the retrogradation behavior of rice starch and its potential mechanism

In this study, to minimize the quality deterioration caused by the retrogradation of starch-based food, the effect and mechanism of oat β-glucan (OG) on the retrogradation of rice starch was investigated. OG effectively decreased storage modulus (G'), syneresis, and retrogradation enthalpy, indicating the inhibition of short-term and long-term retrogradation of rice starch. The competition for water molecules between the OG and rice starch resulted in partial swelling of the starch granules, consequently reducing particle size, lowering amylose leaching, and decreasing the proportion of short-amylose chains. The microstructure characterization showed that the OG-treated rice starch group (ST-OG) exhibited a smoother and denser surface. Particularly, no notable alterations were observed in the structure of the ST-OG sample during storage, owing to the improved water-holding capacity of starch gel and reduced proportion of free water caused by OG. Furthermore, the ordered structure results confirmed the occurrence of hydrogen bonding between OG and rice starch, which hindered the rearrangement of starch molecules. Therefore, OG is an effective natural additive for controlling the retrogradation of starch-based foods.

A Comprehensive Study on the Influence of Superheated Steam Treatment on Lipolytic Enzymes, Physicochemical Characteristics, and Volatile Composition of Lightly Milled Rice

Enzyme inactivation is crucial for enhancing the shelf life of lightly milled rice (LMR), yet the impact of diverse superheated steam (SS) treatment conditions on lipolytic enzyme efficiency, physicochemical properties, and volatile profiles of LMR remains unclear. This study investigated varying SS conditions, employing temperatures of 120 °C, 140 °C, and 160 °C and exposure times of 2, 4, 6, and 8 min. The research aimed to discern the influence of these conditions on enzyme activities, physicochemical characteristics, and quality attributes of LMR. Results indicated a significant rise in the inactivation rate with increased treatment temperature or duration, achieving a notable 70% reduction in enzyme activities at 120 °C for 6 min. Prolonged exposure to higher temperatures also induced pronounced fissures on LMR surfaces. Furthermore, intensive SS treatment led to a noteworthy 5.52% reduction in the relative crystallinity of LMR starch. GC/MS analysis revealed a consequential decrease, ranging from 44.7% to 65.7%, in undesirable odor ketones post-SS treatment. These findings underscore the potential of SS treatment in enhancing the commercial attributes of LMR.

Impact of molecular structure of starch on the glutinous taste quality of cooked chestnut kernels

Chestnuts are a starchy food with a characteristic glutinous taste that is often used to assess their quality. In this study, our findings indicated that chestnuts with higher glutinous taste quality had lower amylose content and microcrystalline structures, as well as higher subcrystalline structures and relative crystallinity in both the raw and steamed starches. In the leached starch, chestnuts with higher glutinous taste quality had lower amylopectin B1 chains and microcrystalline structure, but higher amylopectin B2 chains, subcrystalline structure and relative crystallinity. These results suggest that amylose content, relative crystallinity, and amylopectin chain length distribution are important factors determining the glutinous taste quality of chestnuts. To further enhance our understanding of these factors, an sensory evaluation model was developed based on textural profile analysis parameters. This study provides valuable insights into the relationship between molecular structure of starch and the glutinous taste quality of starchy foods.

Structural and Physicochemical Properties of a Chinese Yam Starch-Tea Polyphenol Complex Prepared Using Autoclave-Assisted Pullulanase Treatment

Interactions between food components have a positive impact in the field of food science. In this study, the effects of tea polyphenol on the structural and physicochemical properties of Chinese yam starch using autoclave-assisted pullulanase treatment were investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, rapid visco analysis, differential scanning calorimetry, and the 3,5-dinitrosalicylic acid method were applied in this study. The results showed that the Chinese yam starch-tea polyphenol complex formed a structural domain with higher thermal stability along with lower pasting viscosities than native starch. The in vitro digestibility of Chinese yam starch decreased with the addition of the tea polyphenol, and the amount of resistant starch content in the complex was 56.25 ± 1.37%, significantly higher than that of native starch (p < 0.05). In addition, the complex showed a B+V-type crystalline structure, which confirmed that the interaction modes between the starch and tea polyphenol include hydrogen bonding and hydrophobic interactions. Moreover, the appearance of an irregular sponge network structure of the complex further supported the interactions between the starch and tea polyphenol. This study provides a theoretical basis for the development of functional foods using Chinese yam starch.

Effects of Salt Stress on Grain Yield and Quality Parameters in Rice Cultivars with Differing Salt Tolerance

Rice yield and grain quality are highly sensitive to salinity stress. Salt-tolerant/susceptible rice cultivars respond to salinity differently. To explore the variation in grain yield and quality to moderate/severe salinity stress, five rice cultivars differing in degrees of salt tolerance, including three salt-tolerant rice cultivars (Lianjian 5, Lianjian 6, and Lianjian 7) and two salt-susceptible rice cultivars (Wuyunjing 30 and Lianjing 7) were examined. Grain yield was significantly decreased under salinity stress, while the extent of yield loss was lesser in salt-tolerant rice cultivars due to the relatively higher grain filling ratio and grain weight. The milling quality continued to increase with increasing levels. There were genotypic differences in the responses of appearance quality to mild salinity. The appearance quality was first increased and then decreased with increasing levels of salinity stress in salt-tolerant rice but continued to decrease in salt-susceptible rice. Under severe salinity stress, the protein accumulation was increased and the starch content was decreased; the content of short branched-chain of amylopectin was decreased; the crystallinity and stability of the starch were increased, and the gelatinization temperature was increased. These changes resulted in the deterioration of cooking and eating quality of rice under severe salinity-stressed environments. However, salt-tolerant and salt-susceptible rice cultivars responded differently to moderate salinity stress in cooking and eating quality and in the physicochemical properties of the starch. For salt-tolerant rice cultivars, the chain length of amylopectin was decreased, the degrees of order of the starch structure were decreased, and pasting properties and thermal properties were increased significantly, whereas for salt-susceptible rice cultivars, cooking and eating quality was deteriorated under moderate salinity stress. In conclusion, the selection of salt-tolerant rice cultivars can effectively maintain the rice production at a relatively high level while simultaneously enhancing grain quality in moderate salinity-stressed environments. Our results demonstrate specific salinity responses among the rice genotypes and the planting of salt-tolerant rice under moderate soil salinity is a solution to ensure rice production in China.

Moderate Reduction in Nitrogen Fertilizer Results in Improved Rice Quality by Affecting Starch Properties without Causing Yield Loss

The quality and starch properties of rice are significantly affected by nitrogen. The effect of the nitrogen application rate (0, 180, and 230 kg ha^-1) on the texture of cooked rice and the hierarchical structure and physicochemical properties of starch was investigated over two years using two japonica cultivars, Bengal and Shendao505. Nitrogen application contributed to the hardness and stickiness of cooked rice, reducing the texture quality. The amylose content and pasting properties decreased significantly, while the relative crystallinity increased with the increasing nitrogen rates, and the starch granules became smaller with an increase in uneven and pitted surfaces. The proportion of short-chain amylopectin rose, and long-chain amylopectin declined, which increased the external short-range order by 1045/1022 cm^-1. These changes in hierarchical structure and grain size, regulated by nitrogen rates, synergistically increased the setback viscosity, gelatinization enthalpy and temperature and reduced the overall viscosity and breakdown viscosity, indicating that gelatinization and pasting properties were the result of the joint action of several factors. All results showed that increasing nitrogen altered the structure and properties of starch, eventually resulting in a deterioration in eating quality and starch functional properties. A moderate reduction in nitrogen application could improve the texture and starch quality of rice while not impacting on the grain yield.

Unveiling the retrogradation mechanism of a novel high amylose content starch-Pouteria campechiana seed

The research of starch retrogradation have been attracting interest. Thereby, the long-term retrogradation mechanism (0-21 days) of Pouteria campechiana seed starch (PCSS) was investigated. The results showed that crystal type was changed from A- to B + V-type during retrogradation. The retrogradation PCSS (RPCSS) exhibited faster retrogradation rate and more compact internal ultra-structure compared to rice, wheat and maize starch. Pearson correlation indicated that, as retrogradation days increased, values of α-1,4-glycosidic bond, A chains, double helix, V-type polymorphism, Mw, relative crystallinity (Rc) and short-range order gradually significantly increased, and B1 chains, B3 + chains values gradually significantly dropped (p < 0.05). These inferred an increasing peak temperature and compactness of morphology with increasing retrogradation days. Compared to native starch, RPCSS α-1.4-glycosidic bond was increased, which indicated that its quick molecules degradation including decreased Mw, B3 + chains, Rc, semicrystalline order, and ΔH. These might provide a theoretical direction for preparation of starch-basis food.

Multi-Scale Comparison of Physicochemical Properties, Refined Structures, and Gel Characteristics of a Novel Native Wild Pea Starch with Commercial Pea and Mung Bean Starch

In the present study, the morphology, refined structure, thermal properties, and dynamic rheological, texture, and digestive properties of common vetch starch, a potential new type of legume starch, were systematically investigated, and compared with commercially available pea and mung bean starch. The results showed that the composition and chemical structure of common vetch starch were similar to the pea and mung bean starch. However, the amylose content (35.69), A-chain proportion (37.62), and relative crystallinity (34.16) of common vetch starch were higher, and the particle size and molecular weight (44,042 kDa) were larger. The value of pasting properties and enthalpy change (ΔH) of gelatinization of common vetch starch was lower and higher than mung bean and pea starch, respectively, and a lower swelling power and pasting index indicate that common vetch starch had higher hot-paste and cold-paste stability. In addition, common vetch starch gel exhibited good rheology, cohesiveness, and anti-digestive properties. These results provide new insights into the broader application of common vetch starch.

Combination of NIR spectroscopy and algorithms for rapid differentiation between one-year and two-year stored rice

Storage is necessary for rice to ensure the year-round consumption of rice. With the increase in storage time, the taste quality and commercial value of rice gradually decrease. The accurate determination of the freshness of rice is critical to the rice trade. However, it is difficult to distinguish aging rice from fresh rice, so a quick and simple method is needed to identify the freshness of the rice. In this study, a combination of near-infrared spectroscopy (NIR) and various algorithms, such as partial least squares discriminant analysis (PLS-DA), support vector machines (SVM), and classification and regression trees (CART), were used to differentiate the freshness of rice. PLS-DA and SVM demonstrated excellent classification ability in identifying the freshness of rice, with sensitivity and specificity of 1. The original spectra were used with 100% accuracy in the test set to determine the freshness of the rice. As a result, PLS-DA and SVM can be used to determine the freshness of the rice.

Identification of aged-rice adulteration based on near-infrared spectroscopy combined with partial least squares regression and characteristic wavelength variables

The long-term storage of rice will inevitably be involved in the deterioration of edible quality, and aged rice poses a great threat to food safety and human health. The acid value can be employed as a sensitive index for the determination of rice quality and freshness. In this study, near-infrared spectra of three kinds of rice (Chinese Daohuaxiang, southern japonica rice, and late japonica rice) mixed with different proportions of aged rice were collected. The partial least squares regression (PLSR) model with different preprocessing was constructed to identify the aged rice adulteration. Meanwhile, a competitive adaptive reweighted sampling (CARS) algorithm was used to extract the optimization model of characteristic variables. The constructed CARS-PLSR model method could not only reduce greatly the number of characteristic variables required by the spectrum but also improve the identification accuracy of three kinds of aged-rice adulteration. As above, this study proposed a rapid, simple, and accurate detection method for aged-rice adulteration, providing new clues and alternatives for the quality control of commercial rice.

Effects of Extraction Methods on Physicochemical and Structural Properties of Common Vetch Starch

Three extraction methods: water extraction, lactic acid bacteria fermentation, and back-slopping fermentation were applied to extract a new type of legume starch, common vetch starch. Our results showed that the lactic acid bacteria fermented starch had the highest amylose content (35.69%), followed by the back-slopping fermented starch (32.34%), and the water-extracted starch (30.25%). Furthermore, erosion surface, lower molecular weight, smaller particle size, larger specific surface area, and a higher proportion of B1 chain were observed in the fermented starch, especially in the back-slopping fermented starch. All the extracted starches showed a type C structure, but a type C_B structure was observed in the back-slopping fermented starch. In addition, the relative crystallinity of the lactic acid bacteria fermented starch (34.16%) and the back-slopping fermented starch (39.43%) was significantly higher than that of the water-extracted starch (30.22%). Moreover, the swelling power, solubility, pasting, and thermal properties of the fermented starches were also improved. In conclusion, the fermentation extraction method, especially back-slopping fermentation, could improve the quality of the extracted common vetch starch when compared with the traditional water extraction method.

Starch crystal seed tailors starch recrystallization for slowing starch digestion

Crystal seed significantly affected polymers homogeneous or heterogeneous crystallization. However, how starch crystal seed affected recrystallization of gelatinized starch and in turn digestibility were not clearly understood. Herein, effects of endogenous crystal seed on starch recrystallization and digestibility were herein investigated. Structures of retrograded starches characterized by Fourier transform infrared spectroscopy and X-ray diffraction indicated that endogenous A-type crystal seed significantly promoted starch reassociation to form well-defined crystalline structure. Notably, starch crystal seed-mediated retrograded starch contained more compact structures after cooking in comparison with that of retrograded starch mediation without the crystal seed, and therefore the crystal seed-mediated retrograded starch exhibited a lower digestibility. This study preliminarily indicated starch endogenous crystal seed significantly modulate starch retrogradation and digestibility, nevertheless, how recrystallization temperature, the content and crystalline structure of the crystal seed affect recrystallization behaviors of crystal seed-containing starch are part of future work.

Understanding the Changes in Quality of Semi-Dried Rice Noodles during Storage at Room Temperature

The changes in semi-dried rice noodles during storage at room temperature (25 ± 2 °C) in terms of microbial growth, cooking quality, color, textural properties, thermal properties, crystallinity, and moisture content, and moisture distribution was examined. Total plate count, cooked broken rate, cooking loss, and b* value increased, while rehydration ratio, L* value, and moisture content decreased during storage. The hardness, adhesiveness, and chewiness of semi-dried rice noodles increased significantly, according to textural properties. DSC and XRD showed that the enthalpy of thermal absorption and crystallinity of semi-dried rice noodles increased from 1.67 J/g and 3.48% to 4.21 J/g and 18.62%, respectively. LF-NMR showed that the weakly bound water content in semi-dried rice noodles decreased by 3.71%, and the bound water content and free water content increased by 3.20% and 0.51%, respectively. The results of correlation analysis showed that the changes in quality during storage of semi-dried rice noodles were influenced by the combination of microbial growth, aging of rice noodles, and moisture migration.

Changes in structures and digestibility of amylose-oleic acid complexes following microwave heat-moisture treatment

Amylose-oleic acid complexes (AOA) were exposed to microwave heat-moisture treatment (M-HMT) with different moisture content (MC), and the variations in structures and digestibility were investigated. M-HMT caused the dissociation of helical structures and destruction of short-range molecular order of AOA. Meanwhile, the molecules of amylose and oleic acid rearranged and more amylose-oleic acid complexes were formed during M-HMT, the complexing index of AOA was increased from 25.41 % to 41.20 % when treating at 35 % MC. Moreover, the relative content of single helix increased with increasing MC, resulting in higher V-type relative crystallinity. With ≥30 % MC, the treated complexes showed greater thermostability than that of original AOA. The treatment increased the enzymatic digestibility of AOA, and sample treated with 35 % MC had the highest resistant starch content of 82.33 %, which was 17.96 % higher than that of native AOA. The improved enzyme resistance should be correlated to increased molecular interplay and formation of amylose-oleic acid complexes.

Differences in starch multi-layer structure, pasting, and rice eating quality between fresh rice and 7 years stored rice

With the continuous improvement of rice production capacity and the accumulation of reserves year by year, rice sometimes has to be stored for a long time. However, long-term storage of rice has poor sensory properties, which may be related to the structural changes of starch. Different from the previous studies on short-term storage of rice (often 3–12 months), the focus of this study was to understand the differences in starch multi-layer structure, pasting, and rice eating quality between 7 years stored rice and fresh rice. Our research indicated that 7 years stored rice showed higher hardness and lower stickiness compared to fresh rice, which ultimately led to poorer eating quality. These bad changes were related to differences in starch multi-layer structure. The 7 years stored rice had lower amylose content, a lower thickness of crystalline lamellae and short-range ordered structure of starch, and more large starch granules. In particular, the volume mean diameter of 7 years starch was more than 4 times that of fresh starch. 7 years stored rice had more large granular starch and unstable crystal structure, which led to the increase of pasting temperature and the decrease of gelatinization enthalpy during starch gelatinization, and ultimately reduced the eating quality of the rice.

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7 years stored rice had higher hardness and poorer eating quality.

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Volume mean diameter of 7 years stored starch was 4 times larger than fresh starch.

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7 years stored rice had lower short-range order structure of starch.

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The pasting temperature of 7 years stored starch was higher than fresh starch.

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Higher pasting temperature and lower gelatinization enthalpy reduced the eating quality.