Hydroxypropylated Corn Starches Research Articles

Mechanistic study on the effect of hydroxypropyl corn starch, guar gum and compound phosphates on the freeze-thaw quality of quick-frozen kuey teow

Kuey teow is one of the delicacies of Guangdong, China and is a gluten-free noodle dish made from rice. It has a short storage period and extending the shelf life by quick freezing induces quality deterioration due to temperature fluctuations. To improve its freeze-thaw frozen storage quality, this paper examined the effects of hydroxypropyl corn starch (HCS), guar gum (GG), and compound phosphates (CP) on the quality of quick-frozen kuey teow during freeze-thaw cycles. The mechanism was investigated by identifying changes in the moisture status, aging degree of the starch, and textural and cooking characteristics. The results showed that all three additions improved the toughness, chewiness and steaming characteristics of the kuey teow, with CP significantly enhancing chewiness. XRD and FTIR results revealed that GG more significantly inhibited the decrease of starch crystallinity, while HCS inhibited starch aging. GG, HCS and CP all improved the hydration characteristics and water holding capacity of rice starch. GG enhances the ability of starch to bind more tightly with water, resulting in a more uniform water distribution and a more continuous and tight structure of the kuey teow. This study will provide a theoretical basis for compounding and optimizing the quick-freezing of kuey teow.

Developing Edible Starch Film Used for Packaging Seasonings in Instant Noodles.

Edible starch-based film was developed for packaging seasoning applied in instant noodles. The edible film can quickly dissolve into hot water so that the seasoning bag can mix in the soup of instant noodles during preparation. To meet the specific requirements of the packaging, such as reasonable high tensile properties, ductility under arid conditions, and low gas permeability, hydroxypropyl cornstarch with various edible additives from food-grade ingredients were applied to enhance the functionality of starch film. In this work, xylose was used as a plasticizer, cellulose crystals were used as a reinforcing agent, and laver was used to decrease gas permeability. The microstructures, interface, and compatibility of various components and film performance were investigated using an optical microscope under polarized light, scanning electron microscope, gas permeability, and tensile testing. The relationship was established between processing methodologies, microstructures, and performances. The results showed that the developed starch-based film have a modulus of 960 MPa, tensile strength of 36 Mpa with 14% elongation, and water vapor permeability less than 5.8 g/m2.h under 20% RH condition at room temperature (25 °C), which meets the general requirements of the flavor bag packaging used in instant noodles.

Antistaling effects of hydrocolloids and modified starch on bread during cold storage

Antistaling effects of some hydrocolloids (guar gum, xanthan, and sodium alginate; 0.3 g/100 g flour) and modified starches (acetylated, oxidized and hydroxypropylated corn starches; 10 g replacing flour) on bread during cold storage (4 °C for 10 d) were investigated. Loaf volume, moisture content, texture, and the degree of starch recrystallization of the bread crumb were examined. The minor addition of hydrocolloids increased the loaf volume of fresh bread and retarded textural changes of crumb induced by cold storage. The partial replacement (10%) of flour with modified starches induced antistaling effects similar to those obtained by hydrocolloid addition. In particular, acetylated or hydroxypropylated starches were more effective than oxidized starch. Crystallinity analysis of bread crumb using X-ray diffraction pattern revealed that the effects of hydrocolloids and modified starches on the starch recrystallization were not substantial. Amorphous rearrangements in starch were responsible for changes in crumb texture during storage, and the minor addition of hydrocolloids and the partial replacement of flour with modified starches retarded the rearrangement induced by the storage.

Freeze-thaw stability, glass transition, and retrogradation of high hydrostatic pressure-assisted hydroxypropylated corn starch

Effects of high hydrostatic pressure (HHP) and the propylene oxide (PO) concentration on the freeze-thaw stability, glass transition temperature (Tg′), and retrogradation degree of HHP-assisted hydroxypropylated corn starch were investigated. HHP-assisted hydroxypropylated corn starches were prepared using propylene oxide (4, 8, and 12%, v/w) at 25°C for 15 min under HHP (100, 200, 300, and 400 MPa). The freeze-thaw stability, Tg′, ice melting enthalpy (H i ), and retrogradation degree of HHP-assisted hydroxypropylated corn starches showed patterns different from native corn starch. In general, higher pressures and PO levels lowered Tg′ and H i values, and the retrogradation degree. The highest freeze-thaw stability was observed in HHP-assisted hydroxypropylated corn starch prepared using 12% PO at 400 MPa for 15 min. Retrogradation kinetics of hydroxypropylated corn starch gels observed from the glass transition temperature, ice melting enthalpy, and retrogradation degree revealed that recrystallization occurred with instantaneous nucleation, followed by rod-like growth of crystals.

Gelatinization and Retrogradation of Hydroxypropylated Cornstarch

Gelatinization and retrogradation of a high amylose cornstarch modified by hydroxypropylation were studied by DSC. It was found that the gelatinization temperature of the starch was decreased and a narrow gelatinization range was measured by DSC after hydroxypropylation. The decreasing of the gelatinization temperature is explained by disrupting inter- and intra-molecular hydrogen bonds, while the narrowing of the gelatinization endotherm is explained by destroying the amylose-lipid complex. Morphologies of the starch granules with and without iodine treatment were studied under microscopy with normal and polarized lights. Brightness and birefringence decreased with increasing molar substitution since crystal structure in starch granular was partly destroyed. Weaker retrogradation was observed for the hydroxpropylated starch, ascribed not only to steric effects imposed by the bulky hydroxypropyl groups in amylopectin, but also to the removing of amylose-lipid complexes during alkaline treatment.

Preparation of hydroxypropyl corn and amaranth starch hydrolyzate and its evaluation as wall material in microencapsulation

Hydroxypropylation of starches lends it useful physicochemical and functional properties that are industrially important. The literature on hydroxypropylation using organic solvents for obtaining higher molar substitution (MS) is scantily available. The present work reports on hydroxypropylation of corn and a waxy amaranth starch to different MS with propylene oxide in an alkaline-organic medium (isopropanol). The synthesis was followed in terms of MS. The parameters optimized were starch:isopropanol ratio (w/w), reaction temperature, reaction time and the quantity of alkali required in the process. A maximal MS of 0.180 and 0.162 were obtained for hydroxypropyl corn starch (HPSC) and hydroxypropyl amaranth starch (HPSA), respectively. Enzymatic hydrolysis of the HPSC and HPSA of the above MS was carried out on a 30% (w/v) solution at a pH of 6.5 and 95°C for varying time periods using 0.1% (w/w based on starch) bacterial α-amylase, termamyl. The hydrolysis was terminated by adjusting the pH to 3.5 using 0.1N HCl. The hydrolyzates were characterized in terms of dextrose equivalent and viscosity. The hydrolyzate obtained after 3h of hydrolysis was spray dried and compared to gum arabic with respect to encapsulation of model flavourings, orange oil and lemon oil.

Extrusion of Cross‐Linked Hydroxypropylated Corn Starches II. Morphological and Molecular Characterization

ABSTRACTA series of cross‐linked hydroxypropylated corn starches were extruded with a Leistritz micro‐18 co‐rotating extruder. Extrusion process variables including moisture (30, 35, and 40%), barrel temperature (60, 80, and 100°C), and screw design (low, medium, and high shear) were investigated. Scanning electron microscopy (SEM) of extruded starches showed a gel phase with distorted granules and granule fragments after extrusion at 60°C. After extrusion at 100°C only a gel phase was observed with no granular structures remaining. High performance size exclusion chromatography (HPSEC) equipped with multiangle laser light‐scattering (MALLS) and refractive index (RI) detectors showed extruded starches degraded to different extents, depending on extrusion conditions. The average molecular weight of the amylopectin of unextruded native corn starch was 7.7 × 108. Extrusion at 30% moisture, 100°C, and high shear reduced the molecular weight of amylopectin to 1.0 × 108. Hydroxypropylated normal corn starch extruded at identical conditions showed greater decreases in amylopectin molecular weight. With the addition of cross‐linking, the amylopectin fractions of the extruded starches were less degraded than those of their native and hydroxypropylated corn starch counterparts. Similarly, increasing moisture content during extrusion lowered amylopectin degradation in the extruded starches. Increasing temperature during extrusion of cross‐linked hydroxypropylated starches at high moisture content (e.g., 40%) lowered amylopectin molecular weights of the extruded starches, whereas increasing extrusion temperature at low moisture content (30%) resulted in less degraded molecules. This difference was attributed to the higher glass transition temperatures of the cross‐linked starches.

Extrusion of Cross‐Linked Hydroxypropylated Corn Starches I. Pasting Properties

ABSTRACTA series of cross‐linked (0, 0.014, 0.018, 0.024, and 0.028% POCl3, dry starch basis) hydroxypropylated (8%) corn starches were extruded using a Leistritz micro‐18 co‐rotating extruder. Process variables included moisture, barrel temperature, and screw design. Differential scanning calorimetry and X‐ray diffraction studies showed the level of starch crystallinity decreased with increasing severity of extrusion conditions. Pasting properties of the extruded starches were examined using a Rapid Visco Analyser. Pasting profiles of starches extruded at different conditions displayed different hot paste viscosity and final viscosity. Increasing starch moisture content during extrusion and level of cross‐linking increased starch viscosity (P < 0.0001), whereas increasing extrusion temperature and shear decreased starch viscosity (P < 0.0001). Interactions were found between level of cross‐linking and screw design and between extrusion temperature and starch moisture content (P < 0.0001).

Physical Properties of Extruded Strands of Hydroxypropylated Normal and High‐Amylose Corn Starch

ABSTRACTNormal (25% amylose) and high‐amylose (70% amylose) corn starches (CS and HA) were hydroxypropylated to 0.1 degree of molar substitution (MS) with propylene oxide in an alkaline‐ethanol medium (70% ethanol). CS and hydroxypropylated corn starch (HPCS) were mixed on dry basis with water and glycerol at a weight ratio of 7:2:1, and HA and hydroxypropylated high amylose corn starch (HPHA) were mixed at 7:3:1. Stearic acid, glycerol monostearate, or lecithin (3%, based on starch) was added to each mixture to examine the effects on the physical properties of the extrudate. The starch mixtures were extruded at high shear (100 rpm) to nonexpanded strands using a corotating twin‐screw extruder in a temperature range of 75–90°C. HA, alone and with all additives, showed lower die swelling in extrusion than did CS, whereas HPCS and HPHA showed higher die swelling than the corresponding unmodified starches. Water absorption of all HA extrudates was lower than those of all CS extrudates (22–35% and 68–97%, respectively, at 25°C). Hydroxypropylation increased the absorption for both starches. All extruded starches, regardless of additives, showed low solubility in water (0.1–1.0% for 2 hr at 25°C). Differential scanning calorimetry indicated that during extrusion, the lipid additives formed a helical complex with amylose in CS and HA, but weakly with HPCS and HPHA. The extruded strands of HA, alone and with additives, exhibited higher tensile and bending strengths (37.1–58.4 and 2.16–5.07 MPa, respectively), compared to the CS strands (12.5–59.3 and 1.06–4.10 MPa, respectively) at the same moisture content (7.5–8.5%). Both tensile strength and percent of elongation of the starch strands were reduced by the presence of a lipid additive. Hydroxypropylation increased elongation and flexibility of the extrudates. HPHA exhibited the greatest mechanical strength and flexibility among the tested starches.