A combined recrystallization and acetylation strategy for resistant starch with enhanced thermal stability and excellent short-chain fatty acid production

Effects of debranched starch on physicochemical properties and in vitro digestibility of flat rice noodles

Aiming to develop flat rice noodles with both desirable textural quality and lower starch digestibility, we investigated the effect of adding indica rice debranched starch (RDBS) on the quality of flat rice noodles. In this study, adding RDBS to flat rice noodles enhanced their mechanical properties. Cooking characteristic analysis showed that incorporating RDBS into dried flat rice noodles increased the rehydration ratio by 16.1 % and reduced rehydration time by 26.5 %. Scanning electron microscopy (SEM) revealed the presence of microparticles formed through the self-assembly of RDBS within the network of flat rice noodles. X-ray diffraction (XRD) analysis demonstrated that the addition of RDBS elevated the crystallinity of the flat rice noodles, rising from 9.59 % to 22.57 %. In addition, the in vitro simulated digestion test suggested the addition of RDBS led to a threefold increase in the content of slowly digestible starch (SDS) and a ninefold increase in resistant starch (RS) content in flat rice noodles. This study found that adding RDBS into flat rice noodles can effectively reduce their digestion rate and improve their eating quality. It could be a promising approach for creating functional rice noodles aimed at alleviating public health concerns such as diabetes and obesity.

Improvement of resistant starch content and thermal-stability of starch-linoleic acid complex: An attempt application in extruded recombinant rice

The utilization of resistant starch in food industry is restricted due to its susceptibility to thermal degradation. This work aimed to address this issue by preparing a starch-linoleic acid complex (RS5) via extrusion method combined with heat moisture treatment, obtaining VII-type crystal (melting temperature ∼110 °C). The complex obtained through an 8-hour heat moisture treatment exhibited a high RS content of 46.7 %. The glycemic index (pGI) values predicted by two different methods for this complex were 54.5 and 64.2. The complex was further processed into recombinant rice, which exhibited similar textural properties to commercial rice products after cooking. Notably, the recombinant rice maintained an anti-enzyme structure (VII-type complex) as evidenced by its significant resistant starch content of 38.1 %, the lowest pGI values of 59.6 and 72.5. These findings could serve as a useful reference to aid in developing low glycemic index foods based on starch.

Enzymatic modification lowers syneresis in corn starch gels during freeze-thaw cycles through 1,4-α-glucan branching enzyme

The current research in the food industry regarding enzymatic modification to enhance the freeze-thaw (FT) stability of starch is limited. The present study aimed to investigate the FT stability of normal corn starch (NCS) modified using 1,4-α-glucan branching enzyme (GBE) derived from Geobacillus thermoglucosidans STB02. Comprehensive analyses, including syneresis, scanning electron microscopy, and low-field nuclear magnetic resonance, collectively demonstrated the enhanced FT stability of GBE-modified corn starch (GT-NCS-30) in comparison to its native form. Its syneresis was 66.4 % lower than that of NCS after three FT cycles. Notably, GBE treatment induced changes in the pasting properties and thermal resistance of corn starch, while simultaneously enhancing the mechanical strength of the starch gel. Moreover, X-ray diffractograms and microstructural assessments of freeze-thawed gels indicated that GBE treatment effectively hindered the association of corn starch molecules, particularly amylose retrogradation. The enhanced FT stability of GBE-modified starch can be attributed to alterations in the starch structure induced by GBE. This investigation establishes a foundation for further exploration into the influence of GBE treatment on the FT stability of starch and provides a theoretical basis for further research in this area.

Recrystallized resistant starch by encapsulation with konjac glucomannan: Structural changes, digestibility, and its effect on glucose response and short-term satiety in mice

The effects of the structure and digestibility of konjac glucomannan (KGM)-recrystallized resistant starch complex (KRS3) on the glycemic response and short-term satiety in mice were investigated. KRS3 samples were prepared by recrystallized debranched starch (RS3) at 50 °C, and then combined with KGM. The RS3 and KRS3 samples displayed an A-type pattern and maintained peak temperature values above 110 °C. With an increase in KGM, the swelling power and apparent viscosity of KRS3 increased. The results of in vitro and in vivo digestion revealed that KRS3 with a resistant starch content ranging from 69.4 % to 78.8 % could effectively maintain postprandial blood glucose levels. KRS3, particularly with 0.5 % KGM, slowed gastric emptying of mice from 82.7 % to 36.6 % and intestinal propulsion rate from 60.9 % to 35.3 %, resulting in strong satiety. RS3 combined with KGM could serve as a new approach to develop RS3 based foods with low glycemic responses and high-satiety.

Insights into formation and stability mechanism of V7-type short amylose-resveratrol complex using molecular dynamics simulation and molecular docking

Pre-formed V-type amylose as a kind of wall material has been reported to carry polyphenols, while the interaction mechanism between V-type amylose and polyphenol is still elusive. In this work, the formation and stability mechanism of a V7-type short amylose-resveratrol complex was investigated via isothermal titration calorimetry, molecular dynamics, and molecular docking. The results presented that two stoichiometric ratios of resveratrol to short amylose were calculated to 0.120 and 0.800, and the corresponding main driving force was hydrogen bonding and hydrophobic interaction, respectively. The folding and unfolding conformation of V7-type short amylose chains appeared alternately during the simulation. Resveratrol tended to be bound in the short amylose helix between 40 ns and 80 ns to form a more stable complex. Hydrogen bonds between resveratrol molecule and O6 at the 22nd glucose molecule/O2 at the 24th glucose molecules and hydrophobic interaction between resveratrol molecule and glucose molecules (19th, 20th, 21st and 23rd) could be found.

Structure and in vitro digestibility of amylose-lipid complexes formed by an extrusion-debranching-complexing strategy

The formation of amylose-lipid complexes, known as resistant starch type Ⅴ (RS5), is limited by the low content of amylose in natural starch, increasing the amylose content is an effective approach to improve the yield of RS5. In this paper, an extrusion-debranching-complexing strategy with two extrusions was proposed to increase the formation of amylose-lipid complexes. A combination of corn starch (CS), pullulanase (60 U/g, w/w), and lauric acid (LA) with different contents of 4 %, 6 % and 8 % (w/w) generated enzymatically debranched extruded corn starch-lauric acid (EECS-LA) complexes after the second extrusion. The EECS-LA complexes were ordered form II complexes, with a significantly improved short-range molecular order. The melting temperature was in the range of 105-145℃. The enthalpy change increased with the increase of LA content and the value was 9.42 J/g for EECS-8 %LA complexes; these complexes could reform after dissociation. Scanning electron microscopy examination of the EECS-LA complexes revealed an irregular lamellar structure. The RS content of EECS-LA complexes increased significantly, achieving a value of 38.34 % for EECS-8 %LA complexes. This extrusion-debranching-complexing strategy is effective for preparing RS5 and could be useful in industry for the continuous production of RS5.

Enzymatic Modification of Starch Using Recombinant Genes from Sorghum in Escherichia coli: Insights and Potential Applications

SBEIIb (Sobic.004G163700), SSSIIa (Sobic.010G093400), and GBSSI (Sobic.010G022600) genes that regulate starch synthesis in sorghum endosperm were transferred into Escherichia coli by transgenic technology. SBEIIb, SSSIIa, and GBSSI enzymes were separated and purified through a Ni column and analyzed by electrophoresis with molecular weights and activities of 91.57 84.57, and 66.89 kDa and 551 and 700 and 587 U/μL, respectively. Furthermore, they were applied to starch modification, yielding interesting findings: the A chain content increased from 25.79 to 89.55% for SBEIIb-treated waxy starch, while SSSIIa extended the A chain to form DPs of the B chain, with A chain content decreasing from 89.55 to 37.01%, whereas GBSSI was explicitly involved in the synthesis of B1 chain, with its content increasing from 9.59 to 48.45%. Modified starch was obtained, which could be accurately applied in various industries. For instance, we prepared a sample (containing 89.6% A chain content) with excellent antiaging and antidigestion properties through SBEIIb modification. Moreover, higher RS3 (34.25%) and SDS contents (15.75%) of starch were obtained through the joint modification of SBEIIb and SSSIIa. These findings provide valuable insights for developing sorghum starch synthesis-related enzymes and offer opportunities for improving starch properties through enzymatic approaches.