Starch Slurry Research Articles

Hurdle Approach to Simulate Corn Wet Milling Inactivation of Undesirable Microorganisms: A Pilot Scale Microbial Challenge Study Using Salmonella Surrogate Enterococcus faecium.

Corn wet milling (CWM) and corn starch flash drying processing conditions reduce undesirable microorganisms, such as Salmonella.Finished products are historically safe, with intrinsic properties such as low water activity inhibiting microbial growth. Corn processors could use quantified levels of reduction in this study of Salmonella surrogate Enterococcus faecium (E. faecium) to update their food safety plans. Industry-relevant conditions for CWM processes were recreated at pilot or lab scale for 3 unit operations: (1) steeping treatment in sulfur dioxide (SO2) with low (750 ppm SO2, 20 hours, 43.3°C), medium (1,500 ppm SO2, 30 hours, 48.9°C), and high (2,200 ppm SO2, 40 hours, 53.3°C) treatment conditions; (2) hydrogen peroxide (H2O2) treatment tested on bench scale with a factorial design (pH 3.5, 4.0, and 4.5), H2O2 concentrations (0.05%, 0.10%, 0.15% (w/w)), and temperatures (32, 38, and 46°C) for 3 and 6 hours; (3) flash drying treatment at 4 different temperatures (149, 177, 204, and 232°C) with 2 different inoculation methods. E. faecium was reduced during each of these unit operations. By the end of each steeping treatment E. faecium was consistently below the limit of quantitation (LOQ), meaning > 6.5 log CFU/mL reduction in steep water, and > 3.7 log CFU/g reduction in ground corn. The peroxide step had a reduction range from 0.03 log CFU/mL in the control group (0% H2O2 added) to >6 log CFU/mL observed in the high-intensity treatment of corn starch slurry. Flash drying had a reduction range from 1.7 to 2.7 log CFU/g. There was also no biologically meaningful change (<1 log CFU/g reduction) of E. faecium counts during an 8-week survival study of the dried final product. This hurdle approach study shows that existing CWM conditions are effective for Salmonella surrogate reduction through processing into finished starch and provides quantified E. faecium reductions for use in of food safety plans.

Regulating the structure and gelling properties of maize starch by non-thermal effect of low intensity radio frequency wave

To verify whether there is a non-thermal effect in the radio frequency (RF) treatment process, it's very important for effectively excluding the thermal effect. Native maize starch (MS) slurry was treated under a specific electric field intensity while maintaining the sample temperature at 25 ± 2 °C for different times (1, 2, 4 and 8 h), which would effectively eliminate the influence of thermal effect on starch. A corresponding low electric field intensity of 3.3–3.4 kV/m was established after adjusting the electrode gap to be 220 mm of the 27.12 MHz RF system. Samples treated without RF-wave for the same time (1, 2, 4 and 8 h) were used as controls. The differences between the effect of these two treatments on the multi-scale structural and gelling properties of starch samples were investigated. Results showed that the low intensity RF-wave treatment enhanced the short-range structural order. A higher degree of order value and the double helical structure were observed from Fourier transform infrared (FTIR) spectra and solid state 13C nuclear magnetic resonance (13C NMR). Moreover, compared to control MS, the crystallinity of low intensity RF-treated starch significantly increased though the crystal pattern remained unchanged. Low intensity RF-wave treated starch had no significant difference in loss modulus, energy and distance of inter-double helices hydrogen bond, and pasting properties (i.e. TV, SB and BD) when compared with control sample. The effect of low intensity RF wave on starch without heating was insufficient to cause macroscopic property changes. These results provide valuable insights into the structural changes of starch treated by low intensity RF-wave and verify that the non-thermal effect of RF waves may be primarily achieved through the dipole polarization mechanism.

Microbial Community Dynamics and Metabolite Changes during Wheat Starch Slurry Fermentation.

Wheat starch fermentation slurry is the main substrate for producing Ganmianpi, a traditional Chinese fermented wheat starch-based noodle. In the present work, the microbial population dynamics and metabolite changes in wheat starch fermentation slurry at different fermentation times (0, 1, 2, 3, and 4 days) were measured by using high-throughput sequencing analysis and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) methods. The texture and sensory properties of Ganmianpi made from fermented starch slurry are also evaluated. The results showed that Latilactobacillus curvatus and Leuconostoc citreum were the dominant bacteria in wheat starch fermentation slurry, while Saccharomyces cerevisiae and Kazachstania wufongensis were identified as the main species of fungi. With the extension of fermentation time, the reducing sugar content first increased and then decreased, when the titratable acidity content showed an increasing trend, and the nonvolatile acid was significantly higher than the volatile acid. A total of 62 volatile flavor compounds were identified, and the highest content is alcohols, followed by acids. Fermentation significantly reduced the hardness and chewiness of Ganmianpi, and increased its resilience and cohesiveness. Ganmianpi made from fermented starch slurry for two and three days showed a higher sensory score than other samples. The present study is expected to provide a theoretical basis for exploiting the strains with potential for commercial application as starter cultures and quality improvement of Ganmianpi.

Evaluation of the physico-chemical properties of cassava, cocoyam, sweet potato starches and glucose syrups produced from the hydrolysis of the starches with sorghum malt enzyme extract

Some physicochemical properties of starches from cocoyam, cassava and sweet potato were compared for suitability in glucose syrup production. Glucose syrups were produced from the starch slurry using 30 g of sorghum malt per 250 g starch weight. Malts were produced from Nigerian sorghum varieties; SFF- Sorghum ‘Farafara’ and SFD-Sorghum ‘Farindawa’ (Sorghumbicolor L. Moench). The grains were steeped for 24 h with 8 h air rest and germinated for 96 h. Results showed that malted SFD and SFF-sorghum grains recorded diastatic powers (61.45 and 52.32 DU.g-1), α-amylase (38.19 and 43.3 DU.g-1) and β-amylase (14.13 and 18.15 DU.g-1) activities, respectively. Cocoyam starch contained highest amylose (28.20%) when compared with sweet potato starch (22.50%) and cassava starch (20.40%). Solubility and swelling power of cassava, sweet potato and cocoyam starches were 17.2, 16.5 and 15.3 g.g-1 and 9.6, 6.2 and 7.6% at 90℃, respectively. Cocoyam starch showed the highest transition temperatures (69.5, 73.6, 82.3℃) and gelatinization enthalpy (17.3 J.g-1) than sweet potato (67.4, 71.3, 78.4℃, 12.3 J.g-1) and cassava (61.3, 65.5, 75.6℃, 13.4 J.g-1) starches. Dextrose equivalent for cassava, sweet potato and cocoyam glucose syrups were 40, 36, 30. Cassava starch glucose syrup obtained from SFD-malt hydrolysis met most of the Standard Organization of Nigeria set specifications.

Modification of starch digestibility and phenolic bioaccessibility in phenolic-rich flours by physical treatments with ferulic acid followed by vacuum oven and freeze-drying

Consumer demand for healthy snack products has led to increased efforts to modify glycemic responses of these products. The formation of starch-ferulic acid (FA) complexes through acidified water steeping leads to an increase in RS content and reduction of glycemic responses in animal models. However, the application of these methodologies to commercially relevant phenolic-rich flours (black rice, BR; purple maize, PM) and their impacts on starch digestibility and phenolic bioaccessbility remain unclear. Using an acidified water steeping method previously reported in pure starch, potato starch (PS), BR and PM flour slurries were prepared with FA at a 20:1 and 8:1 ratio in HCl-acidified water (pH 2). The steeping process reduced phenolic content (∼75%) and increased starch digestibility. Ferulic acid loading capacity on PS (22–124 mg/g starch) was greater than for PM and BR flours (8–40 mg/g starch). Ferulic acid bioaccessibility decreased with an increase in its amount in PS and flours. Steeping enhances cyanidin 3-O-glucoside bioaccessibility, while addition of FA decreases its bioaccessibility. The increase in starch digestibility of phenolic-rich flours after steeping with and without FA can be attributed to the limited loading capacity of FA and loss of native phenolics during the steeping process.

The Effect of Glucose Syrup on Rheological Properties of Sago Starch

The effect of glucose syrup on the rheological properties of sago starch was examined. The glucose syrup (30 - 75 g) was mixed with sago starch 100 g and baked at 60 °C for 16 h. The sago starch formulas 1 - 10 were analyzed rheological properties using a strain sweep test for evaluated Linear Viscoelastic Range (LVR) used for studied temperature test and frequency test. The result showed that the G’ values of the sago starch formulas 1 - 10 decreased respectively which indicated an increase in the amount of glucose syrup resulting in the storage modulus within the starch structure decreasing causing agglomeration. In addition, in the temperature range of 70 - 95 °C, the sago starch formula 1 - 10 began to gelatinize and then stabilize. It indicated that the sago starch slurry was more similar to the solid. When the temperature was lowered from 95 to 30 °C, the G’ and G” values of the sago starch formulas 1 - 10 gradually increased and then decreased because the starch solution during heating is agglomerated into large particles. The flexibility of solids within the powdery structure is very high and very viscous, so that during the initial decrease in temperature, the G’ and G” values increase. After a while, when the temperature inside the structure begins to decrease, which causes the value of G’ and G” to decrease. In the analysis of texture characteristics of the sago starch formulas 1 - 10, it was found that Hardness, Gumminess and Chewiness decreased significantly as the ratio of glucose syrup was increased in the formulations of the sago starch. The lower hardness value of the sago starch formulation with more added content of glucose syrup. Adhesiveness, cohesiveness and springiness values were not different between all the sago starch formulations. HIGHLIGHTS Rheological properties of the sago starch formulas showed that more glucose syrup mixed with sago starch, increased viscoelastic behavior because when increasing the frequency, there will be a value G' &gt; G'' The different textures of the sago starch formulations indicated the basic action of glucose syrup on the microstructure of the sago starch The differences in rheological properties and texture of the sago starch formulas are the reasons for choosing different filling ratios of sago starch and glucose syrup for cooking GRAPHICAL ABSTRACT

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.

Designing a Specific Pretreatment on Corn Starch to Facilitate Enzymatic Rearrangement of Glycosidic Bonds for Efficiently Reducing Starch Digestibility.

Bacterial 1,4-α-glucan branching enzymes (GBEs) provide a viable strategy for glycosidic bond rearrangement in starch and regulation of its digestion rate. However, the exponential increase in paste viscosity during starch gelatinization has a detrimental effect on the catalytic action of GBEs, thereby limiting productivity and product performance. Here, we designed an enzymatic treatment on corn starch granules by the GBE from Rhodothermus obamensis STB05 (Ro-GBE) prior to the glycosidic bond rearrangement of gelatinized starch catalyzed using the GBE from Geobacillus thermoglucosidans STB02 (Gt-GBE). Specifically, a moderate amount of Ro-GBE was required for the pretreatment stage. The dual GBE modification process enabled the treatment of more concentrated starch slurry (up to 20%, w/w) and effectively reduced starch digestibility. The resulting product contained a rapidly digestible starch fraction of 66.0%, which was 11.4% lower than that observed in the single Gt-GBE-modified product. The mechanistic investigation showed that the Ro-GBE treatment promoted swelling and gelatinization of starch granules, reduced starch paste viscosity, and increased the mobility of water molecules in the starch paste. It also created a preferable substrate for Gt-GBE. These changes improved the transglycosylation efficiency of Gt-GBE. These findings provide useful guidance for designing an efficient process to regulate starch digestibility.

Non-thermal effect of radio frequency treatments verified by the multi-scale structure and in-vitro digestibility of sweet potato starch

To verify whether there is a non-thermal effect in the radio frequency (RF) heating process, a heat block (HB) system was used to simulate the RF process for excluding the influence of thermal effect. Sweet potato starch (SNS) slurry was treated to 60 °C by RF and HB systems with different heating rate, while the heat uniformity was determined to ensure the feasibility and reliability of the method and results. The long- and/or short - range structural, molecular, and digestive characteristics of samples were investigated to elucidate the difference of the RF and HB treatments. The X-ray diffraction patterns (XRD) analysis demonstrated that crystal pattern remained A-type, but the crystallinity of treated samples was significantly reduced. Compared with HB treatment, the RF- treated starch had a more compact, or ordered structure, higher z-average radius of gyration (Rz), peak viscosity (PV) and setback (SB) based on small angle X-ray scatter (SAXS), Fourier-transform infrared spectra (FTIR), size-exclusion chromatography (SEC) and pasting properties observations, respectively. Especially, RF- treated starches with higher heating rate had lower weight-average molar mass (Mw), rapidly and slowly digestive starch content, resulting in the highest resistant starch content and polydispersity index (PDI) in comparison with other samples. The structural characteristics and digestibility of starch were significantly different between RF and HB treatments under the same conditions. This study may provide valuable insights into the thermal and non-thermal effects of RF treatment on starch structure to broaden the application of RF heating in the food processing filed.

Measurement of starch gelatinization using a spectrophotometer

Starch gelatinization behaviors significantly affect functionalities of starch-based foods and materials. Various analytical techniques have been used to measure starch gelatinization behaviors, but these instruments are not commonly found in laboratory and industrial settings. This study aimed to investigate whether spectrophotometer, a more ubiquitous instrument, could be used for measuring starch gelatinization. The relative crystallinity and enthalpy of starch granules remained unchanged during heating at 54–56 °C, but decreased at higher temperatures. The transmittance of starch slurry at 620 nm also remained unchanged at 54–56 °C, but significantly increased at higher temperatures. Furthermore, the changes in transmittance were negatively and significantly correlated with both the changes in relative crystallinity and enthalpy. This suggested that changes in transmittance of starch slurry during heating could be used to evaluate the temperature at which starch gelatinization occurred. However, further research is needed to determine if the changes in transmittance of starch slurry can be used to evaluate the thermostability of starch granules during heating. These findings offer a simple and feasible pathway for measuring starch gelatinization properties using ubiquitous spectrophotometer.

Development of value-added sustainable products from paper mill sludge: An experimental approach

The disposal of paper mill sludge waste generated by the paper industry is a tough and challenging task. In this work, an attempt is made to develop various value-added products namely bricks, briquettes, ground chakra base, and eco-friendly composites from the secondary paper mill sludge (PMS). The secondary PMS was initially dewatered to remove the moisture content, ground to powder, and mixed with cement, MSand. quarry dust, and fly ash to produce bricks. The brick specimens were tested for compressive strength, water absorption, and efflorescence as per the standards and found to be 5.29 ± 0.11 N/mm2, 3.84 ± 0.13% respectively, and have NIL efflorescence. The PMS is mixed with paraffin wax and compressed in a squeeze moulding to form briquettes and observed that the percentage of ash content in the briquette is 66.6% which is less than that of the PMS. Further, a ground chakra base is produced using a slurry of starch and dried in a heater at 60° exhibiting better properties. An eco-friendly composite pottery product was developed by mixing PMS, clay, and starch and tested for breakage.

Nanohybrid emulsions stabilized with calcium phosphate oligomers prepared by self‐emulsification technology for ultra‐high abrasion resistance coating

AbstractPolyethylene waxes are low molecular weight polyolefin synthetic waxes with outstanding mechanical properties, lubricating performance, and chemical stability, which are widely used in various industrial fields. The nonpolar nature of polyethylene waxes leads to low surface energy and poor compatibility with polar materials, which limits their development applications. Therefore, developing composites with better mechanical properties is essential to overcome this drawback. In this work, calcium phosphate oligomers (CPO) are employed to stabilize nano‐emulsions of polyethylene wax modified with maleic anhydride. The emulsification of emulsions was investigated under different NaOH dosages, temperatures, emulsification times, and rotational speeds. The prepared emulsions are used as additives in polyurethane coatings and starch slurries. The CPO can reduce the particle size of the nanohybrid emulsions and greatly improve the abrasion resistance of some polymer films as additive agents. The organic and inorganic units were homogeneously combined with properties of a complete and continuous organic–inorganic network. The emulsions exhibit ultra‐high abrasion resistance when applied to polyurethane coatings and starch pastes, broadening their range of applications.

The microstructure and thermal properties of pulsed electric field pretreated oxidized starch

The structure and thermal properties of pulsed electric field (PEF) assisted sodium hypochlorite oxidized starch were investigated. The carboxyl content of the oxidized starch was increased by 25 % when compared with the traditional oxidation method. Dents and cracks were evident on the surface of the PEF-pretreated starch. Compared with native starch, the peak gelatinization temperature (Tp) of PEF-assisted oxidized starch (POS) was reduced by 10.3 °C, while that of the oxidized starch without PEF treatment (NOS) was only reduced by 7.4 °C. In addition, PEF treatment further reduces the viscosity and improve the thermal stability of the starch slurry. Therefore, PEF treatment combined with hypochlorite oxidation is an effective method to prepare oxidized starch. PEF showed great potential in expanding starch modification, to promote a wider application of oxidized starch in the paper, the textile and the food industry.

Nonlinear rheological properties of Chinese cold skin noodle (liangpi) and wheat starch gels by large amplitude oscillatory shear (LAOS)

The recipe secret of making Chinese cuisine cold skin noodles (liangpi) with wheat flour was revealed by linear and nonlinear rheological characterization of wheat starch gel systems, which were made from different concentrations of liangpi slurry (LPS) and wheat starch slurry (WSS). The peak viscosity of LPS was suppressed at low concentrations and significantly higher than that of WSS at high concentrations. The G′ and G″ of LPS gels were higher than that of WSS gels under the same concentration, while the tanδ values were low in LPS gels and exhibited relatively greater mobility. This difference in LPS may be related to the non-starch components in it. The two starch gel systems were further characterized by the large amplitude oscillatory shear (LAOS) test. Lissajous curves showed that LPS gels follow a highly different elastic and viscous evolution than WSS gels during large deformation cycles. This was also evidenced by more pronounced strain stiffening and shear thickening trends of LPS gels and the larger I3/I1 values. The introduction of non-starch components was responsible for the significant changes in the properties of starch gels, and the LAOS method helped us to better understand these differences.

Promoting starch interaction with caffeic acid during hydrothermal treatment for slowing starch digestion

The control of the formation of starch-guest inclusion complex is significant for slowing starch enzymatic digestion. This work opened a pathway to promote the formation of starch-caffeci acid inclusion complex via simply heating and cooling of starch slurry with caffeic acid. Caffeic acid was hardly but freely dissolvable in cold and hot water, respectively, which enabled caffeic acid in hot solution potentially interacted with starch to form starch-caffeic acid inclusion complex during the cooling. Molecular dynamic simulation and starch structures verified that starch-caffeic acid inclusion complex formed via two steps: (i) heating the cold slurry containing starch and supersaturated caffeic acid; (ii) reasonably cooling the hot solution. The formation of the inclusion complex was promoted via increasing the cooling rate and shear speed during the cooling, which increased the resistant starch content by ca. 5%–18% compared with native cooked starch complexation without caffeic acid.

Effect of fluorescence dyes on wet gluten structure studied with fluorescence and FT-Raman spectroscopies

Fluorescence spectroscopy coupled with FT-Raman spectroscopy were used to determine effect of two fluorescent dyes (fluorescein and rhodamine B) on the structure of wet gluten (hydrated gluten). Additionally, PCA analysis was applied to find correlations between fluorescence and Raman parameters. The fluorescent dyes, regarded as model representatives of phenolic compounds, were added to model dough in six concentrations (0.05%–0.5%). Wet gluten samples and starch slurries (as a residue after washing out gluten) were excited by two wavelengths – one assigned to tryptophan, and the second to the particular dye. Fluorescence and UV-VIS analysis of starch slurries show that the dyes can be completely bound to gluten proteins because of their absence in the slurries. Analysis of the spectroscopic results indicate that fluorescein and rhodamine B interact with gluten proteins in different ways depending on the type of functional groups present in the dye structure. The fluorescein molecules, due to the presence of hydroxyl and carboxyl groups may incorporate into gluten network by forming hydrogen and/or covalent bonds, whereas rhodamine B with four methyl groups may be enclosed in hydrophobic pockets formed by gluten polypeptide chains. These differences can be related to the type of functional groups present in the dye structure (fluorescein has one hydroxyl group, rhodamine B has four methyl groups). PCA analysis showed correlations between dye fluorescent parameters (maximum wavelength and band intensity) and some structural parameters (presence or absence of bands assigned to α-helices, β-turns and S S bonds conformations). The PCA results also suggest that mechanism of interactions gluten – dye depends on type of functional groups present in the dye molecule. • Interactions between gluten and dyes depend on functional groups present in dye. • Fluorescein with hydroxyl and carboxyl groups can incorporate into gluten network. • Rhodamine B with four methyl groups may be enclosed in hydrophobic pockets. • Structural changes observed in gluten network depend on the dye concentration. • Fluorescence spectra of TRP may indicate type of gluten-polyphenols interactions.

Modulating Functionality of Starch-Based Patchy Particles by Manipulating Architecture and Environmental Factors.

Starch as a food-grade thickener has been commonly used in food products to modulate textural properties. Improving viscosity-enhancing ability, so as to be able to use less starch for the same texture, has been considered as an approach to reduce the dietary consumption of carbohydrates. We have positively charged amaranth starch (∼1 μm) and negatively charged corn starch (>10 μm) and physically fused the particles together to create a starch with a heterogeneous pattern. This starch has a negatively charged main body, due to the larger corn particles, and positively charged patches from the amaranth starch. These patchy particles self-assembled through electrostatic interactions into a shear-reversible thickener. The impact of patchiness and charge density on material functionality was investigated. The degree of patchiness was controlled by manipulating the ratio between the two starches, and results showed that viscosity was reduced when the patchiness was higher. With the same patchy area, a higher charge density did not contribute to higher water-holding capacity. The more charged particles were able to enhance the viscosity, however, due to the stronger interparticle electrostatic interaction. The effects of environmental factors including pH level and ionic strength were also investigated, and the results showed that at extreme pH levels, or in the presence of Na+ or Ca2+, the charges on the starch particles were screened, and this inhibited interaction and reduced viscosity. The present work demonstrates that the texture of starch slurries can be fine-tuned by manipulating the degree of patchiness and the charge density of patchy particles. It also evaluates the application potential in food products with different pH levels and ionic strengths.

3D food printing curing technology based on gellan gum

The fluid state of 3D food printing products greatly limits the customization of the shape. To improve the molding quality, a 3D food printing curing technology based on the temperature-sensitive phase-change characteristics of gellan gum was developed. Corn starch was used as the printing substrate to produce a gel that solidifies during printing. The pre-gelatinized starch slurry containing gellan gum was placed in a barrel with a heating function and extruded onto the printing platform at room temperature. Rheological tests, printing quality evaluations, and low-field nuclear magnetic fields proved that the slurry with gellan gum had good extrusion and printing feasibility. The product supplemented with 4% or 6% gellan gum exhibited significant plastic deformation, which indicated formation of a solid gel. Temperature sweep rheology analyses revealed that gellan gum guided the curing performance by affecting the curing temperature and curing speed of the slurry. Gellan gum improved hardness of the product and destroyed the network structure by self-cooling cross-linking and inhibiting starch gelatinization, which changed product adhesion.

Lipase-polydopamine magnetic hydrogel microspheres for the synthesis of octenyl succinic anhydride starch

Octenyl succinic anhydride (OSA) starch is an important edible additive in the food field, and its synthesis method has attracted much attention. Lipase as a biocatalyst can improve the synthesis efficiency of OSA starch, and significantly inhibit the occurrence of side reactions. However, free lipase has not been widely applied in the synthesis of OSA starch due to the difficulty of separation from starch and poor reusability. In this work, a promising strategy for the synthesis of OSA starch catalyzed by lipase immobilized on polydopamine magnetic hydrogel microspheres (PMHM) is reported. The prepared lipase-polydopamine magnetic hydrogel microspheres (L-PMHM) can be uniformly dispersed in starch slurry, which is conducive to the full contact between lipase and starch. L-PMHM (Km =2.6276 μmol/mL) exhibits better affinity to the substrate than free lipase (Km = 3.4301 μmol/mL). Compared with the OSA starch catalyzed by free lipase (DS = 0.0176), the degree of substitution of OSA starch catalyzed by L-PMHM is up to 0.0277 in a short reaction time. In cyclic catalysis, L-PHMM can remain about 48 % of their original activity after 20 reuses and can be quickly separated from the product. These results suggest that L-PMHM has great potential as a biocatalyst for the efficient synthesis of OSA starch.

Effect of Starch Chain Structure and Non‐Starch Components on the Hydrolysis of Starch by α‐Amylase

AbstractThere are differences in enzymatic hydrolysis of starch slurries determined by the starch‐iodine method, but the reason for this phenomenon is not clear. In this study, corn, cassava, and potato starches that are commonly used in warp sizing as the research object, separating amylose and amylopectin, removing lipids or lipids, and proteins in starch, to explore the effect of starch molecular structure and nonstarch components on the hydrolysis of starch catalyzed by α‐amylase. The results show that about 10% of the corn starch is resistant to hydrolysis, much more than cassava and potato starches. Differences in amylose structure have no significant effect on hydrolysis, but the degree of hydrolysis of corn amylopectin is significantly lower than that of the amylopectins in cassava and potato starch, because of its higher molecular density. Lipid removal has a slight effect on the hydrolysis, but protein removal obviously improves the hydrolysis of corn starch, with only ∼2% of resistant starch remaining. Endogenous protein has the most excellent inhibitory effect on the hydrolysis of starch slurry, followed by lipids and the higher molecular density of amylopectin.