Effects of amylose and amylopectin chain-length distribution on the kinetics of long-term rice starch retrogradation

Freezing rate's impact on starch retrogradation, ice recrystallization, and quality of water-added and water-free quick-frozen rice noodles

The study evaluated the effect of freezing rate on the quality of water-added quick-frozen rice noodles and water-free quick-frozen rice noodles. Results indicated that the retrogradation enthalpy, relative crystallinity, freezable water content, and cooking loss of water-added quick-frozen rice noodles were higher than those of water-free quick-frozen rice noodles with increasing storage time. Furthermore, ice recrystallization accelerated the deterioration of the quality of the rice noodles, resulting in the enlargement of the pores within the rice noodles and the formation of many pores on the surface. This phenomenon was particularly evident in the rice noodles of Y-40 °C (freezing with water at -40 °C) and Y-60 °C (freezing with water at -60 °C). After 28 days of frozen storage, the hardness increased by 83.83 % for rice noodles of Y-20 °C (freezing with water at -20 °C), while the hardness decreased by 51.68 % and 45.80 %, respectively, for rice noodles of Y-40 °C and Y-60 °C. Consequently, the impact of the freezing rate on the quality of water-added quick-frozen rice noodles is more pronounced than that of water-free quick-frozen rice noodles. Moreover, a higher freezing rate can delay the deterioration of the quality of frozen rice noodles by postponing starch retrogradation and inhibiting ice recrystallization.

Effect of Different Fertilizer Types on Quality of Foxtail Millet under Low Nitrogen Conditions

In order to clarify the effect of different fertilizers on foxtail millet quality under low nitrogen conditions, we used JGNo.21 and LZGNo.2 as experimental materials and set up five treatments, including non-fertilization, nitrogen, phosphorus, compound, and organic fertilizers, to study the regulation of different fertilizer types on agronomic traits, nutrient fractions, and pasting characteristics of foxtail millet under low nitrogen conditions. Compared with the control, all of the fertilizers improved the agronomic traits of JGNo.21 to a certain extent. Nitrogen and compound fertilizer treatments reduced the starch content of JGNo.21; the starch content was reduced by 0.55% and 0.07% under nitrogen and compound fertilizers treatments. Phosphorus and organic fertilizers increased starch content, and starch content increased by 0.50% and 0.56% under phosphorus and organic fertilizer treatments. The effect of each fertilizer treatment on protein content was completely opposite to that of starch; different fertilizer treatments reduced the fat content of JGNo.21 and increased the fiber content. Among them, nitrogen and phosphorus fertilizers increased the yellow pigment content; the yellow pigment content increased by 1.21% and 2.64% under nitrogen and phosphorus fertilizer treatments. Organic and compound fertilizers reduced the content of yellow pigment; the yellow pigment content was reduced by 3.36% and 2.79% under organic and compound fertilizer treatments. Nitrogen and organic fertilizers increased the fat content of LZGNo.2; the fat content increased by 2.62% and 1.98% under nitrogen, organic fertilizer treatment. Compound and phosphorus fertilizer decreased the fat content; the fat content decreased by 2.16% and 2.90% under compound and phosphorus fertilizer treatment. Different fertilizer treatments reduced the cellulose and yellow pigment content of LZGNo.2. The content of essential, non-essential, and total amino acids of JGNo.21 was increased under compound and nitrogen fertilizer treatments and decreased under organic and phosphorus fertilizer treatments. The content of essential, non-essential, and total amino acids of LZGNo.2 was significantly higher under compound, nitrogen, and organic fertilizer treatments compared with control and significantly decreased under phosphorus fertilizer treatments. Nitrogen and compound fertilizer treatments significantly reduced the values of peak viscosity, trough viscosity, breakdown viscosity, final viscosity, setback viscosity, and pasting time of each index of JGNo.21; phosphorus and organic fertilizer treatments improved the values of each index. In contrast, the pasting viscosity of LZGNo.2 increased under phosphorus fertilizer treatment and decreased under nitrogen fertilizer treatment. Reasonable fertilization can improve the quality of foxtail millet, which provides a scientific theoretical basis for improving the quality of foxtail millet.

Extraction, characterization, and utilization of mung bean starch as an edible coating material for papaya fruit shelf-life enhancement

This research was aimed to investigate the utilization of mung bean starch as an innovative edible coating material to enhance the shelf-life of cut papaya fruits. The study focused on the extraction process of mung bean starch and its subsequent characterization through various analyses. Particle size (142.3 ± 1.24 nm), zeta potential (-25.52 ± 1.02 mV), morphological images, Fourier transform infrared (FTIR) spectra, and thermal stability (68.36 ± 0.15°C) were assessed to determine the mung bean starch properties. The functional properties, such as bulk density (0.51 ± 0.004 g/cm3) and tapped density (0.62 ± 0.010 g/cm3), angle of repose (21.61°), swelling power (12.26 ± 0.25%), and minimum gelation concentration (4.01 ± 1.25%), were examined to detect its potential as a coating base material. Subsequently, the prepared mung bean starch coating solution (1%, 2%, 3%, 4%, and 5%) was applied to papaya fruits and the coated fruits' physicochemical characteristics evaluated during storage. These characteristics encompassed color, weight loss, pH shifts, total soluble solids, titratable acidity, vitamin C content, fruit firmness, microbial analysis, and sensory attributes. The results revealed that starch coating on papaya maintained its color, reduced weight loss, preserved vitamin C, and delayed firmness loss, enhancing shelf-life when compared to control sample. These findings demonstrated the effectiveness of mung bean starch coatings in preserving papaya fruits. The research made a significant contribution to the use of mung bean starch as a potential coating material for improving the shelf-life of papaya fruits. This finding has great promise for the field of food preservation and quality control.

3D printed arrowroot starch-gellan scaffolds for wound healing applications

Skin, the largest organ in the body, blocks the entry of environmental pollutants into the system. Any injury to this organ allows infections and other harmful substances into the body. 3D bioprinting, a state-of-the-art technique, is suitable for fabricating cell culture scaffolds to heal chronic wounds rapidly. This study uses starch extracted from Maranta arundinacea (Arrowroot plant) (AS) and gellan gum (GG) to develop a bioink for 3D printing a scaffold capable of hosting animal cells. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction analysis (XRD) prove that the isolated AS is analogous to commercial starch. The cell culture scaffolds developed are superior to the existing monolayer culture. Infrared microscopy shows the AS-GG interaction and elucidates the mechanism of hydrogel formation. The physicochemical properties of the 3D-printed scaffold are analyzed to check the cell adhesion and growth; SEM images have confirmed that the AS-GG printed scaffold can support cell growth and proliferation, and the MTT assay shows good cell viability. Cell behavioral and migration studies reveal that cells are healthy. Since the scaffold is biocompatible, it can be 3D printed to any shape and structure and will biodegrade in the requisite time.

Effects of different proportions of erythritol and mannitol on the physicochemical properties of corn starch films prepared via the flow elongation method

In this study, corn films based on corn starch were fabricated through the casting method, and various plasticizers (namely, erythritol and d-mannitol) were incorporated. The study delved into the gelatinization and physicochemical characteristics of these corn starch-based films. Additionally, the impact of different ratios of plasticizers on reductive gelatinization was assessed using RVA analysis. The investigation also encompassed the effects of varying plasticizer ratios on starch granule expansion, amylose dissolution, and amylopectin melting. Interestingly, as the proportion of d-mannitol increased, there were gradual increases in film thickness, water content, and water contact angle, alongside decreases in water vapor permeability, crystallinity, and water solubility of the corn starch-based films. In essence, this research provides a fundamental basis for potential industrial applications of corn starch-based films.

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.

Effect of starch and protein on eating quality of japonica rice in Yangtze River Delta

This study examined four types of japonica rice from Yangtze River Delta, categorized based on amylose content (AC) and protein content (PC): high AC with high PC, high AC with low PC, low AC with high PC, and low AC with low PC. It systematically explored the effect of starch, protein and their interactions on eating quality of japonica rice. Rheological analysis revealed that increased amylose, long chains amylopectin or protein levels during cooking strengthen starch-protein interactions (hydrogen bonding), forming a firm gel network. Scanning electron microscopy showed that increased amylose, long chains amylopectin or protein levels made protein and starch more stable in combination during cooking, limiting starch structure cleavage. Therefore, the eating quality of high AC in similar PC japonica rice and high PC in similar AC japonica rice were poor. Further, correlation and random-forest analysis (RFA) identified amylose as the most influential factor in starch-protein interactions affecting rice eating quality, followed by amylopectin and protein. RFA also revealed that in high AC japonica rice, the interactions of Fb3 and albumin with amylose were more conducive to forming good eating quality. In low AC japonica rice, the interactions of Fb2 and prolamin with amylose were more beneficial.

Impact of using whole chestnut flour as a substitute for cake flour on digestion, functional and storage properties of chiffon cake: A potential application study

Developing fresh cake product with rich nutrition and high quality has become a hot spot in food industry. In this study, whole chestnut flour as a high-quality dietary source was successfully substituted for cake flour in the production of chestnut chiffon cake with 40-55% substitution rate, and its application prospects were further evaluated through studying nutritional and storage properties. The results showed that chestnut chiffon cake with 45% and 50% substitution rate could significantly increase the resistant component, scavenging activity and ferric reducing antioxidant power, surprisingly decrease predicted glycemic index to 54.05-57.28, and reduce the acetate/propionate ratio and Firmicutes/Bacteroidetes value for human gut microbiota as well. Comparatively, chestnut chiffon cake with 45% substitution rate had more application potential due to its higher free water retention at day 7 and higher resilience throughout the storage time. Overall, this study could provide valuable information for the development of modern nutritional cake industry.

Mechanism of action of three different glycogen branching enzymes and their effect on bread quality

Bread staling adversely affects the quality of bread, but starch modification by enzymes can counteract this phenomenon. Glycogen branching enzymes (GBEs) used in this study were isolated from Deinococcus geothermalis (DgGBE), Escherichia coli (EcGBE), and Vibrio vulnificus (VvGBE). These enzymes were characterized and applied for starch dough modification to determine their role in improving bread quality. First, the branching patterns, activity on amylose and amylopectin, and thermostability of the GBEs were determined and compared. EcGBE and DgGBE exhibited better thermostable characteristics than VvGBE, and all GBEs exhibited preferential catalysis of amylopectin over amylose but different degrees. VvGBE and DgGBE produced a large number of short branches. Three GBEs degraded the starch granules and generated soluble polysaccharides. Moreover, the maltose was increased in the starch slurry but most significantly in the DgGBE treatment. Degradation of the starch granules by GBEs enhanced the maltose generation of internal amylases. When used in the bread-making process, DgGBE and VvGBE increased the dough and bread volume by 9 % and 17 %, respectively. The crumb firmness and retrogradation of the bread were decreased and delayed significantly more in the DgGBE bread. Consequently, this study can contribute to understanding the detailed roles of GBEs in the baking process.

Importance of amylose chain-length distribution in determining starch gelatinization and retrogradation property of wheat flour in the presence of different salts

Although starch gelatinization and retrogradation properties of wheat flour have been studied with respect to their relations to starch structures, it remains less understood how starch structure and salt (a common food additive) together determine these properties. Gelatinization and retrogradation properties of seven wheat flours with distinct starch structures were thus investigated after adding different salts. NaCl most efficiently increased starch gelatinization temperatures, while KCl showed highest efficiency in retarding the retrogradation degree. Both gelatinization and retrogradation parameters were significantly affected by amylose structural parameters and types of salts. E.g., wheat flours with longer amylose long chains had more heterogeneous amylopectin double helices during gelatinization, while this relationship disappeared after adding NaCl. More amylose short chains increased the heterogeneity of retrograded short-range starch double helices, while the relationship was opposite after adding NaCl. These results help a better understanding of the complex relationship between starch structure and physicochemical property.

Variation in Wheat Quality and Starch Structure under Granary Conditions during Long-Term Storage

As a globally distributed cereal, wheat is an essential part of the daily human dietary structure. Various changes in nutrient composition and starch structure can reflect the quality of wheat. In this study, we carried out a series of measurements to reveal the levels of wheat quality during long-term storage. We found that the deterioration of wheat was apparent after two years of storage: (1) the content of fatty acid increased from 12.47% to 29.02%; (2) the malondialdehyde content increased to 37.46%; (3) the conductivity significantly increased from 35.71% to 46.79%; and (4) other indexes, such as the amylopectin content, peak viscosity, and disintegration rate, increased noticeably during storage. Moreover, SEM images revealed a certain degree of damage on the surface of starch granules, and an X-ray diffraction (XRD) analysis showed A-type crystalline starch of wheat. Additionally, FTIR spectra suggested that the ratio of amylose and amylopectin decreased with a decreasing content of amylose and increasing content of amylopectin. The ratio of amylose and amylopectin can lead to variations in wheat machining characteristics. Therefore, wheat should be kept at an average of 20 °C with safe water content for less than two years to maintain reasonable quality.

Study of the Plasticization Effect of 1-Ethyl-3-methylimidazolium Acetate in TPS/PVA Biodegradable Blends Produced by Melt-Mixing

The first step towards the production and marketing of bioplastics based on renewable and sustainable materials is to know their behavior at a semi-industrial scale. For this reason, in this work, the properties of thermoplastic starch (TPS)/polyvinyl alcohol (PVA) films plasticized by a green solvent, as the 1-ethyl-3-methylimidazolium acetate ([Emim⁺][Ac^-]) ionic liquid, produced by melt-mixing were studied. These blends were prepared with a different content of [Emim⁺][Ac^-] (27.5-42.5 %wt.) as a unique plasticizer. According to the results, this ionic liquid is an excellent plasticizer due to the transformation of the crystalline structure of the starch to an amorphous state, the increase in flexibility, and the drop in T_g, as the [Emim⁺][Ac^-] amount increases. These findings show that the properties of these biomaterials could be modified in the function of [Emim⁺][Ac^-] content in the formulations of TPS, depending on their final use, thus becoming a functional alternative to conventional polymers.

The Role of Amylose in Gel Forming of Rice Flour

In this study, Glutinous rice (GR), Japonica rice (JR), and Indica rice (IR), with amylose contents at 1.57 ± 0.18%, 15.88 ± 1.16%, and 26.14 ± 0.25%, respectively, were selected to reveal the role of amylose in the gel forming of rice flours. The strength and elasticity of the associated gels were found in an ascendant order with the increase in amylose content. For the retrograded gels (at 4 °C for 7 days), the peak temperature (Trp) was positively related to the amylose content. In general, Trp of IR increased to 63.21 ± 0.13 °C, and the relative crystallinities of IR were in the top ranking at 10.67 ± 0.16%, followed by those of JR and GR. The relative amounts of short-range ordered structures to amorphous regions in JR and IR were also higher than that of GR, and the number of compact network structure were positively related to the amylose content. These results indicated that amylose can enhance the strength and elasticity of gels by facilitating the formation of crystalline, short-range ordered, and compact network structures. These results can provide a reference for the development of rice products.

Main factors affecting the starch digestibility in Chinese steamed bread

Chinese steamed bread (CSB) is one of the staple foods in China, although it has a high glycemic index (GI) value. Development of CSB with a slower starch digestibility is thus of great importance for the improvement of human health. Many factors are related to the starch digestibility in CSB. Most currently available strategies are focusing on the incorporation of other whole flours with high dietary fiber or polyphenols to reduce the starch digestibility. Although successful in reducing starch digestibility, the incorporation of these flours also deteriorated textural attributes and sensory characteristics of CSB. Much more strategies have been applied for the reduction of starch digestibility in breads, which should be further explored to confirm if they are applicable for CSB. This review contains important information, that could potentially turn CSB into a much healthier food product with slower starch digestibility.

Effects of Konjac Glucomannan on Retrogradation of Amylose

The effect of konjac glucomannan (KGM) on the retrogradation of amylose was explored during storage. The color, rheological properties, texture, water-holding capacity (WHC), low-field nuclear magnetic resonance (LF-NMR), and X-ray diffraction (XRD) were investigated. Results of color and rheological measurements showed that with the increasing amount of KGM, the L value of the system decreased, but the elastic modulus, viscous modulus, and tangent value of loss angle increased. The textural result presented that KGM obviously inhibited the growth rate of gel strength of amylose. Results from WHC and XRD suggested after 14 days of storage, when the concentration of KGM increased from zero to 0.3% in the mixture, the WHC grew from 80% to 95% and the crystallinity degree declined from 35.3% to 25.6%. The LF-NMR result revealed that KGM limited the conversion of free water to bound water in the system. In general, a small amount of KGM in a mixed system could inhibit the short-term and long-term retrogradation of amylose. This research could provide a theoretical reference for the influence of hydrophilic colloids on the retrogradation of starch, and it could also provide support for the processing and production of starch-based food.

Characterization and application of a coating of starch extracted from avocado (Persea americana L. cv. Hass) seeds as an alternative to reduce acrylamide content in French fries

The starch extracted from avocado (Persea americana L. cv. Hass) seeds was characterized and used in the preparation of an edible coating to reduce the oil uptake and acrylamide content in French fries. Starch characterization was carried out using Differential Scanning Calorimetry, Fourier transform infrared spectrophotometry, gelatinization, and scanning electron microscopy. Uncoated (UFF) and coated (CFF) French fries were compared and evaluated for moisture, water activity (Aw), fat, color, firmness, acrylamide content, and sensorial analysis. The extracted starch presented a high crystalline structure and good stability to mechanical work and heat treatments. The CFF French fries showed significantly higher Aw, color parameter a*, but lower luminosity and acrylamide content than UFF samples. Similarly, the CFF samples tended to decrease the fat content, although without statistical differences. Avocado seed starch can be an economical and technically feasible alternative to the food industry as an effective coating to reduce acrylamide content in French fries.

Structural, physicochemical and long-term retrogradation properties of wheat starch treated using transglucosidase

To reduce the wheat-flour-based food texture and flavor deterioration caused by starch retrogradation, herein wheat starch, the most ingredient in wheat flour, was modified by transglucosidase to delay long-term retrogradation of wheat starch. The study proposed promising data of transglucosidase-treated starch about structure, crystallinity and retrogradation kinetics. Structural properties showed that transglucosidase treatment shortened the average chain length from 19.49 to 16.10 and induced the dominance of amorphous state. Moreover, branching degree increased from 14.11% to 17.97% after transglucosidase treatment, resulting in higher water mobility. Amylose content increased from 25.33% to 59.00% due to the hydrolysis ability of transglucosidase. Relative crystallinity of the retrograded starches decreased from 24.33% to 14.50%. Furthermore, the Avrami parameters demonstrated that transglucosidase treatment significantly retarded the retrogradation rate of wheat starch due to the decrease of re-crystalline rate. The outcoming would supply a solid theory foundation for exploring the wheat staple foods with higher qualities.

Combined effects of starch fine molecular structures and water content on starch digestibility of cooked white rice

Although the starch digestibility of cooked white rice has been investigated with regard to its relation to starch structure, it is not yet clear how starch molecular structure and water content affect its digestion rate. To investigate this, the in vitro starch digestibility and molecular structure of 10 rice varieties with a range of rice-to-water cooking ratios were investigated. As expected, starch digestibility varied with different conditions. Typically, a higher amylose content resulted in a lower maximum digestion extent for a given water content. Having relatively more and longer amylopectin intermediate chains caused a slower starch digestion rate, but only with rice-to-water ratios between 1:1 and 1:1.2. These results could prove useful to find combinations of starch fine molecular structures and water contents to produce cooked rice with low glycemic index.

Testing the Linearity Assumption for Starch Structure-Property Relationships in Rices

Many properties of starch-containing foods are significantly statistically correlated with various structural parameters. The significance of a correlation is judged by the p-value, and this evaluation is based on the assumption of linear relationships between structural parameters and properties. We here examined the linearity assumption to see if it can be used to predict properties at conditions that are not close to those under which they were measured. For this we used both common domesticated rices (DRs) and Australian wild rices (AWRs), the latter having significantly different structural parameters and properties compared to DRs. The results showed that (1) the properties were controlled by more than just the amylopectin or amylose chain-length distributions or amylose content, other structural features also being important, (2) the linear model can predict the enthalpy ΔHg of both AWRs and DRs from the structural parameters to some extent but is often not accurate; it can predict the ΔHg of indica rices with acceptable accuracy from the chain length distribution and the amount of longer amylose chains (degree of polymerization > 500), and (3) the linear model can predict the stickiness of both AWRs and DRs to acceptable accuracy in terms of the amount of longer amylose chains. Thus, the commonly used linearity assumption for structure-property correlations needs to be regarded circumspectly if also used for quantitative prediction.

Combined effects of starch fine molecular structures and storage temperatures on long-term rice amylopectin retrogradation property

Though the retrogradation property as affected by starch fine molecular structures has been widely investigated, it remains largely unexplored how concurrent starch structures and storage conditions e.g. temperature tailor the starch retrogradation property. The amylopectin long-term retrogradation for 8 different rice starches with a broad range of amylose content was thus investigated under different storage temperatures. Results showed that gelatinized starch stored at -20 °C generally had a narrower melting temperature range from differential scanning calorimetry, while larger cells and thicker cell walls in the gel matrix than that stored at 4 °C. Different linear correlations were found between starch fine molecular structures and amylopectin retrogradation parameters when starch was stored under different temperatures. For example, the melting enthalpy of retrograded starch double helices was negatively correlated with the amount of amylose intermediate chains at 4 °C, while positively correlated with the relative length of amylopectin short chains at -20 °C. Under both temperatures, rice starch R250 had the highest retrogradation enthalpy. These results could help the rice industry improve both the nutritional and textural attributes of cooked rice by selecting starch with desirable molecular structures and optimizing the storage conditions for rice after cooking.

The relationship between linear chain length distributions of amylopectin and the functional properties of the debranched starch-based films

The relationship between linear chain length distributions and the functional properties of the starch-based films after pullulanase debranching treatment of corn (CS), rice (RS) and wheat (WS) were investigated. The results indicated that the film thickness was negatively correlated with A chains content (r = -0.939) and apparent amylose content (r = -0.926), and was positively correlated with B3 chains content (r = 0.847). The tensile strength of the debranched starch-based films were positively correlated with apparent amylose content (r = 0.813), and the elongation at break were inversely proportional to B3 chains content (r = -0.817). The hydrophobicity of the starch-based films was positively and negatively correlated with the proportions of linear chains with DP 6-12 (r = 0.892) and DP 25-36 (r = -0.863), respectively. On the contrary, no significant correlation was noticed between chain length distribution of amylopectin and transparency and thermal stability.

Biodegradation behavior and digestive properties of starch-based film for food packaging - a review

Non-degradable plastic places a serious burden on the environment, so consumers and researchers are working to develop biodegradable, safe, and sustainable food packaging materials. The starch-based film has become emerging material for food packaging. Not only does it shows excellent physicochemical properties, but also provides the desired degradation characteristics after use or the digestive properties after consumption, thus needing to comprehensively evaluate the quality of starch-based food packaging materials. This review summarizes the degradation behavior of the starch-based film in different degradation environments, and compares the suitability of degradation environments. Besides, the physicochemical properties of the composite or blend film during the degradation process were further discussed. The factors affecting the digestibility of starch-based edible film were reviewed and analyzed. Finally, the application and the future trend of the biodegradable starch-based film in the food packaging field were proposed. Future studies should combine and evaluate the physical properties and biodegradability of the composite/blend film, to develop food packaging materials with good characteristics and biodegradability.

Consecutive reaction kinetics model reveals the nature of long-term rice amylopectin retrogradation characteristics

Starch retrogradation involves nucleation and crystal growth steps, while their relative contribution to the overall retrogradation kinetics and relations with starch fine molecular structures have not been elucidated. In this study, a consecutive reaction kinetics model (CRK) was developed to fit long-term retrogradation kinetics curves for 10 rice starches with distinct molecular structures. Starch chain-length distributions (CLDs) and melting enthalpy kinetics curves for these starches were obtained from our published data. It was shown that these melting enthalpy kinetics curves can be satisfactorily deconvoluted by the CRK model into a combination of nucleation and crystal growth curves. Correlation analysis between CRK model-fitted parameters with starch CLDs showed that starch retrogradation nucleation and crystal growth steps were controlled by distinct starch fine molecular structures. These results have practical applications, as it enables a separate regulation of nucleation and crystal growth steps during retrogradation process of starch-based foods for desirable nutritional properties.

Application of first-order kinetics modeling to reveal the nature of starch digestion characteristics

Mathematical modeling of in vitro starch digestograms is essential to understand starch structure-digestibility relationships as it covers all detailed information of the starch digestograms with only a few kinetics-based parameters. However, many assumptions exist for these mathematical models, which are frequently overlooked by researchers and lead to inappropriate or even wrong interpretations of the fitted parameters. This review presents a critical evaluation of four mostly applied empirical first-order kinetics models including single first-order kinetics (SK), logarithm of slope (LOS) transformed kinetics, parallel first-order kinetics (PK) and the combination of parallel and sequential (CPS) kinetics models. For homogeneous food systems, the SK model is perfectly suitable, whereas the LOS, PK and CPS models were suitably developed for food systems containing multiple digestible fractions. For the digestion of starch containing multiple digestible fractions, the LOS model assumed a sequential digestion pattern, whereas the PK model assumed a parallel pattern. In the current review, there is also emphasis on the recently developed CPS model, which is able to differentiate the sequential and parallel digestion patterns for different starch digestible fractions existing in food systems. Understanding these assumptions enables a better selection of an appropriate mathematical model for improving the understanding of in vitro starch digestion characteristics. This review meets the growing interest of the food industry in terms of developing a new generation of foods with slower starch digestibility.

Leached starch content and molecular size during sorghum steaming for baijiu production is not determined by starch fine molecular structures

Sorghum steaming properties are important for both flavor and brewing efficiency of baijiu (Chinese alcohol liquor). However, it is currently unclear with respects to structural factors that affect sorghum steaming properties during baijiu production. In this study, starch fine molecular structures were characterized by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis for 8 sorghum varieties used in baijiu production. Starch crystalline structures and ordering of double helices were characterized by the X-ray diffraction and differential scanning calorimetry. Results showed that only small differences were observed for starch molecular size distributions and chain-length distributions in the raw sorghum flour. Of significance, the leached starch content and molecular size during steaming was very different among these sorghum varieties. Furthermore, Spearman correlation analysis showed that there was no significant correlation between starch fine structural parameters with the leached starch content. On the other hand, the correlation analysis showed that leached starch molecular size was negatively correlated with starch crystallinity, while positively correlated with the onset and peak gelatinization temperatures. It is concluded that the sorghum steaming property is controlled by the starch crystalline structures instead of starch fine molecular structures. These results could help the baijiu industry to produce baijiu with more desirable properties.

Chemical components and chain-length distributions affecting quinoa starch digestibility and gel viscoelasticity after germination treatment

A germination treatment was explored in this study as a green strategy to reduce the in vitro starch digestibility of cooked quinoa. The alterations of chemical compositions, starch chain-length distributions (CLDs) and rheological characteristics of quinoa flours after the germination treatment were characterized. Results showed that a significant alteration of amylose CLDs and the starch digestibility was observed for cooked quinoa flours after different germination times. By fitting starch digestograms to the logarithm of slop (LOS) plot and the combination of parallel and sequential kinetics model (CPS), two starch digestible fractions with distinct rate constants were identified. Pearson correlation analysis further found that the observed starch digestive characteristics could be largely explained by the alterations of amylose CLDs caused by the germination treatment. More specifically, the rapidly digestible starch fraction mainly consisted of amorphous amylopectin molecules and amylose intermolecular crystallites. On the other hand, the slowly digestible starch fraction was largely formed by intramolecular interactions among amylose short chains (degree of polymerization (DP) < 500). These results suggest that germination may be a promising way to develop cereal products with slower starch digestibility.