The role of indica starch in the mechanism of formation of fresh rice noodles

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 peanut oligopeptides on the pasting properties of potato starch and digestive characteristics of dry, flat potato starch noodles

In this study, we developed dry, flat potato starch noodles with an ideal taste and low digestibility. Peanut oligopeptide and potato starch were combined to form dry, flat potato starch noodles containing different peanut oligopeptide contents using a steam-slice method. Adding 5 % and 10 % peanut oligopeptides maintained the dry, flat starch noodles' quality. Scanning electron microscopy (SEM) analysis showed that dry, flat starch noodles containing peanut oligopeptides had more pores with pore sizes ranging from 0.30 μm to 2.00 μm. X-ray diffraction (XRD) results showed that peanut oligopeptide promoted the recrystallization of amylopectin during the retrogradation process after gelatinization, and the crystallinity of noodles ranged from 4.31 % (control noodles) to 18.24 % (noodles containing 10 % peanut oligopeptides). An in vitro simulated digestion test showed that the slowly digestible starch and resistant starch contents of noodles containing 10 % peanut oligopeptides were 18.24 % and 22.03 %-significantly higher than control starch noodles (14.88 % and 9.9 %, respectively). Therefore, when peanut oligopeptides were added to dry, flat starch noodles, it was a promising material for lowering blood sugar levels after meals.

Effects of high-speed shear and double-enzymatic hydrolysis on the structural and physicochemical properties of rice porous starch

This study aimed to investigate the physicochemical properties of the rice porous starch (HSS-ES) prepared by high-speed shear combined with double-enzymatic (α-amylase and glucoamylase) hydrolysis, and to reveal their mechanism. The analyses of ¹H NMR and amylose content showed that high-speed shear changed the molecular structure of starch and increased the amylose content (up to 20.42 ± 0.04 %). FTIR, XRD and SAXS spectra indicated that high-speed shear did not change the starch crystal configuration but caused a decrease in short-range molecular order and relative crystallinity (24.42 ± 0.06 %), and a loose semi-crystalline lamellar, which were beneficial to the followed double-enzymatic hydrolysis. Therefore, the HSS-ES displayed a superior porous structure and larger specific surface area (2.962 ± 0.002 m²/g) compared with double-enzymatic hydrolyzed porous starch (ES), resulting in the increase of water and oil absorption from 130.79 ± 0.50 % and 109.63 ± 0.71 % to 154.79 ± 1.14 % and 138.40 ± 1.18 %, respectively. In vitro digestion analysis showed that the HSS-ES had good digestive resistance derived from the higher content of slowly digestible and resistant starch. The present study suggested that high-speed shear as an enzymatic hydrolysis pretreatment significantly enhanced the pore formation of rice starch.

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.

Starch-based noodles: Current technologies, properties, and challenges

Starch noodles are gaining interest due to the massive popularity of gluten-free foods. Modified starch is generally used for noodle production due to the functional limitations of native starches. Raw materials, methods, key processing steps, additives, cooking, and textural properties determine the quality of starch noodles. The introduction of traditional, novel, and natural chemical additives used in starch noodles and their potential effects also impacts noodle quality. This review summarizes the current knowledge of the native and modified starch as raw materials and key processing steps for the production of starch noodles. Further, this article aimed to comprehensively collate some of the vital information published on the thermal, pasting, cooking, and textural properties of starch noodles. Technological, nutritional, and sensory challenges during the development of starch noodles are well discussed. Due to the increasing demands of consumers for safe food items with a long shelf life, the development of starch noodles and other convenience food products has increased. Also, the incorporation of modified starches overcomes the shortcomings of native starches, such as lack of viscosity and thickening power, retrogradation characteristics, or hydrophobicity. Starch can improve the stability of the dough structure but reduces the strength and resistance to deformation of the dough. Some technological, sensory, and nutritional challenges also impact the production process.