Starch fine structure and physicochemical properties of specialty rice for canning

Multi-scale structural insights on starch digestibility of instant rice

Multi-scale structures were investigated to understand starch digestibility of instant rice. A wide range of maximum starch digested ratio, up to about 20%, was observed among instant rice prepared from different rice varieties. Instant rice with a smooth and densely packed cross-section showed slower starch digestibility than those with a porous and loosely packed structure. All samples displayed B + V type crystallinity, with V-type crystallinity negatively correlating with maximum starch digested percentage. After digestion, starch chain-length distributions were significantly altered: rapidly digested starch comprised long amylose and short amylopectin chains, while slowly digested starch comprised chains with a peak degree of polymerization (DP) around 130. These results indicate that instant rice with a compact microstructure, high V-type crystallinity, and DP 130 fractions during digestion can reduce starch digestibility. This study provides insights for food industry to develop instant rice products with slow starch digestibility, potentially improving human health.

Dry-milled flour rice 'Seolgaeng' harbors a mutated fructose-6-phosphate 2-kinase/fructose-2,6-bisphosphatase2

'Seolgaeng', an opaque-endosperm rice (Oryza sativa) mutant, is used to prepare high-quality dry-milled rice flour. The mutation causing its opaque-endosperm phenotype was unknown. Map-based cloning identified a missense mutation in the gene FRUCTOSE-6-PHOSPHATE 2-KINASE/FRUCTOSE-2,6-BISPHOSPHATASE 2 (OsF2KP2) in Seolgaeng. Transfer DNA insertion and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-induced f2kp2 mutants exhibited opaque endosperm. Rice harbors another F2KP gene, OsF2KP1. CRISPR/Cas9-induced double mutants of OsF2KP1 and OsF2KP2 (f2kp-d) possessed more opaque endosperm compared to f2kp2 single mutants, whereas the endosperm of the f2kp1 single mutant was normal. Grain hardness and damaged starch content were significantly reduced in f2kp2 mutants compared to the wild type and f2kp1. Amylose content was lower than normal in f2kp2 mutants but not f2kp1. Grain hardness and amylose content were much lower in f2kp-d than in f2kp2. Starch polymerization analysis revealed altered amylopectin structure in f2kp2 and f2kp-d mutants. F2KP activity was lower in f2kp2 and much lower in the double mutants when compared to the wild types, but f2kp1 showed no significant difference. In coleoptiles, hypoxia induced OsF2KP2 expression but downregulated OsF2KP1. These results suggest that OsF2KP2 functions as the main F2KP isoform in endosperm experiencing hypoxia, but OsF2KP1 may partially compensate for the absence of OsF2KP2. We propose that F2KP has a crucial role in inorganic pyrophosphate-utilizing energy metabolism for starch biosynthesis in rice endosperm.

Development and characterization of novel packaging films from composite mixtures of rice-starch, tara gum and pectin

Biodegradable films intend to replace polymers derived from petroleum. The effect of pectin and Tara gum on the properties of films prepared with rice starch and glycerol was studied in this context. FTIR analysis determined the presence of complex interactions between the components. SEM showed regular film surface with minor roughness. The evaluation of mechanical properties of the films proved the importance of pectin, Tara gum and glycerol concentration. When the proportion of pectin to Tara gum was 1:1, the tension at break, the elongation and the solubility reached the highest values while the water vapor permeability dropped to a minimum. Statistical analysis demonstrated non-linear behavior between composition and properties of the films and stated the importance of interactions between the components. Films produced from rice starch and glycerol in combination with pectin and Tara gum present competitive properties in terms of elongation, tensile stress, permeability to water vapor and solubility, displaying a uniform structure suitable for the packaging of food materials.

Variation of resistant starch content in different processing types and their starch granules properties in rice

Ninety-nine lines from recombinant inbred lines were selected to investigate the effects of starch synthesis-related genes on resistant starch (RS) content in different proceeding types. RS in raw milled rice (RSm), hot cooked rice (RSc), and retrogradation rice (RSr) showed a wide variation among the lines, especially RSm arrived at 10.61%. Divergent variability of RSm, RSc and RSr indicated that there were different regulation mechanisms for them. Waxy wildtype allele (Wx^a) could elevate RSm, RSc and RSr, but Soluble starch synthase IIa (SSIIa) only played a vital role in regulating RSm. Wx^a-indica SSIIa could increase RSm, and Wx^a-japonica SSIIa (SSIIaj) could elevate RSc and RSr. The mean diameter of Wx^a-SSIIaj was significantly bigger than others. The bigger starch granules, the higher RSc and RSr. Starch granules morphology with high-RSm would have a higher percentage in polyhedral and angular shape. The results provide new information for rice breeding with high-RS content.

Aroma, Quality, and Consumer Mindsets for Shelf-Stable Rice Thermally Processed by Reciprocal Agitation

Food engineering, food chemistry, and consumer segmentation were used to evaluate ready-to-eat rice. The aromatic Louisiana Clearfield Jazzman (CJ) and Thai Jasmine (TJ), and a non-aromatic parboiled (PB) rice were hydrated during the first 10 min of processing with reciprocal agitation followed by static retort processing. The aroma compound, 2-Acetyl-1-pyrroline (2-AP) was more heat-stable in CJ than TJ rice but decreased 15-fold compared to the rice cooker method. Pareto analysis indicated that rice type and agitation had the main effect on amylose and total starch and chroma and hue. Color differences of rice agitated during hydration and between rice cooker or static retort processed rice, indicated only slight differences for each rice variety. Hydration of dry rice during retort cooking and similar starch, color, and aroma quality were achieved with reciprocal compared to static or rice cooker methods. Survey responses categorized consumers into three, mindsets driven by rice consumption, convenience, or packaging.

Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest

The objective of this study was to determine if the pre-harvest glyphosate application time affects the chemistry of wheat starch. Glyphosate was sprayed at the ripe stage (recommended) and the soft dough stage (early application) of hard red spring wheat. Wheat kernel samples were collected before application and every 3 days until harvest, after which different starch characteristics were analyzed. The results indicate that glyphosate timing does not impact the spatial distribution or morphology of starch granules, as well as the percentage or molecular weight of amylose and amylopectin. However, thermal characteristics of wheat starch, especially when glyphosate was applied at the soft dough stage, showed significant differences. A decrease in the average amylopectin chain length and differences in the proportion of short-, medium-, and long-chain amylopectin was also observed. Overall, this study shows that the pre-harvest application of glyphosate can affect wheat starch chemistry, especially if applied earlier than recommended. PRACTICAL APPLICATIONS: Glyphosate is the most commonly used herbicide in the world, and it is sometimes used pre-harvest during wheat cultivation. The recommended time of application is 7 days prior to harvest when the crops are in the ripe stage of physiological maturity. However, some crops may not be at this stage during application due to non-uniform maturation in the field. The goal of this work was to determine the effect of glyphosate application time (recommended/ripe stage vs. early/soft dough stage) on wheat starch chemistry. The results show that the starch chain length characteristics and thermal behavior are impacted, especially if applied early. Thus, this study shows the importance of timely application to avoid effects on starch chemical properties, which in return could impact starch functionality in food systems. This information is critical in the field of agriculture and to our knowledge this study is one of the first in this area.

Structural, pasting and thermal properties of common buckwheat (Fagopyrum esculentum Moench) starches affected by molecular structure

Common buckwheat starch (CBS) has extensive using value in the human diet. In this study, the molecular structure and physicochemical properties of CBS isolated from five cultivars collected from three regions of China were studied. Variations in molecular structure, crystalline structure, complexity, water solubility (WS), swelling power (SP), pasting properties, and thermal characteristics were recorded among the starches. The CBS had both similarities and differences in its properties by comparison with maize starch (MS) and potato starch (PS). The average molecular weight (M_W) and amylopectin average chain length (ACL) of CBS ranged from 3.86 × 10⁷ g/mol to 4.68 × 10⁷ g/mol and from 21.29% to 22.68%, respectively. CBS and MS were divided into one subgroup and showed typical A diffraction patterns, while PS was divided into two subgroups and exhibited a typical B polymorphic pattern. The WS and SP of all the starches significantly increased with increasing temperature and had great variation at 70 °C and 90 °C. Pearson's correlation analysis showed that the molecular structure of starches greatly affected the physicochemical properties. This study revealed that the physicochemical properties of CBS could be affected by the molecular structures.

Morphology and Characteristics of Starch Nanoparticles Self-Assembled via a Rapid Ultrasonication Method for Peppermint Oil Encapsulation

Starch nanoparticles (SNPs) and peppermint oil (PO)-loaded SNPs were fabricated via an ultrasonic bottom-up approach using short linear glucan debranched from waxy maize starch. The effects of the glucan concentration, ultrasonic irradiation time, and chain length on the SNPs' characteristics were investigated. Under the optimal conditions, i.e., short linear glucan concentration of 5% and ultrasonication time of 8-10 min, SNPs were successfully prepared. The as-prepared SNPs showed good uniformity and an almost perfect spherical shape, with diameters of 150-200 nm. The PO-loaded SNPs also exhibited regular shapes, with sizes of approximately 200 nm. The loading capacity, encapsulation efficiency, and yield of PO-loaded SNPs were ∼25.5%, ∼87.7%, and ∼93.2%, respectively. After encapsulation, PO possessed enhanced stability against thermal treatment (80 °C). The pseudo-first-order kinetics model accurately described the slow-release properties of PO from SNPs. This new approach of fabricating SNPs is rapid, high yield, and nontoxic, showing great potential in the encapsulation and sustained release of labile essential oils or other lipids.

Morphological and starch characteristics of the Japonica rice mutant variety Seolgaeng for dry-milled flour

Producing good-quality, fine rice flour is more difficult than wheat flour because the rice grain is harder. The non-glutinous Japonica-type variety Seolgaeng, derived from N-methyl-N-nitrosourea (MNU) mutagenesis, and four other varieties, representing a range of amylose contents, were evaluated in this study. Dry-milled Seolgaeng rice flour exhibited an average particle size that is <70 μm, a more uniform particle-size proportion than other varieties. Moreover, we noted significant differences in the damaged starch content in flour from Seolgaeng compared to the other varieties (p<0.05). Seolgaeng flour showed a round starch structure, which would lead to better friability, finer particle size, and less damage to the endosperm during dry milling. Indeed, among all varieties evaluated in this study, dry-milled Seolgaeng flour had the finest particle size (averaging <70 μm) and exhibited less damaged starch. With its round starch granules, Seolgaeng is a suitable candidate for drymilled rice flour.

Effects of ripening temperature on starch structure and gelatinization, pasting, and cooking properties in rice (Oryza sativa)

The effect of ripening temperature on rice (Oryza sativa) grain quality was evaluated by assessing starch structure and gelatinization, pasting, and cooking properties. As the ripening temperature increased, the amylose content and number of short amylopectin chains decreased, whereas intermediate amylopectin chains increased, resulting in higher gelatinization temperatures and enthalpy in the starch. These results suggested that an increase in cooking temperature and time would be required for rice grown at higher temperatures. A high ripening temperature increased the peak, trough, and final viscosities and decreased the setback due to the reduction in amylose and the increase in long amylopectin chains. With regard to starch crystallinity and amylopectin molecular structure, the highest branches and compactness were observed at 28/20 °C. Rice that was grown at temperatures above 28/20 °C showed a deterioration of cooking quality and a tendency toward decreased palatability in sensory tests.

Physicochemical, digestibility and structural characteristics of starch isolated from banana cultivars

Banana starches from diverse varieties (Macho, Morado, Valery and Enano Gigante) were studied in their physicochemical, structural and digestibility features. X-ray diffraction indicated that the banana starches present a B-type crystallinity pattern, with slight difference in the crystallinity level. Macho and Enano Gigante starches showed the highest pasting temperatures (79 and 78°C, respectively), whilst Valery and Morado varieties presented a slight breakdown and higher setback than the formers. Morado starch presented the highest solubility value and Valery starch the lowest one. The swelling pattern of the banana starches was in agreement with their pasting profile. All banana starches showed a shear-thinning profile. The resistant starch (RS) fraction was the main fraction in the uncooked banana starches. Morado variety showed the highest amount of slowly digestible starch (SDS) and the lowest RS content reported until now in banana starches. Banana starch cooked samples presented an important amount of SDS and RS. Molecular weight and gyration radius of the four banana starches ranged between 2.88-3.14×10(8)g/mol and 286-302nm, respectively. The chain-length distributions of banana amylopectin showed that B1 chains (DP 13-24) is the main fraction, and an important amount of long chains (DP≥37) are present. The information generated from this study can be useful to determine banana varieties for starch isolation with specific functionality.