Irradiation and storage effects on some properties of potato starch and use of thermoluminescence for identification of irradiated tubers

The effect on properties of starch isolated from Ajax and Diamant potatoes freshly harvested and irradiated immediately after harvest and after two weeks with 0.05, 0.10, 0.15, and 0.20 kGy were reported. Changes due to postirradiation storage up to six months at two different conditions (5 C, 90±2% RH and 20 C, 79±5% RH) were also studied. Swelling power (SP) slightly decreased or remained unchanged with different irradiation dose, but the effect of timing of irradiation after harvest was significant. Doses of 0.2 and 0.15 kGy significantly (p≤0.05) increased solubility, particularly at 90 C solubility temperature compared to lower doses. Decrease in viscosity with increasing dose immediately after irradiation was observed in both varieties but was more pronounced in Diamant. However, changes were dependent on variety, irradiation dose, timing of irradiation, and postirradiation storage conditions. Viscoamylograph test showed that 0.2 kGy significantly (p≤0.05) increased transmission temperature (TT) and temperature at maximum viscosity (TMV), but decreased the maximum viscosity immidiately after irradiation. The same trend was established during the post-irradiation storage time, particularly in Ajax starch, regardless of timing of irradiation or storage conditions. Thermoluminescence (TL) glow curves exhibited qualitative differences between irradiated and unirradiated tubers during the entire storage period, but dose estimation could not be determined.     

In vitro starch digestibility and pasting properties of germinated brown rice after hydrothermal treatments

Germinated brown rice (GBR) recently has received renewed attention due to its enhanced nutritional value. Pasting properties and in vitro starch digestibility of GBR were examined before and after hydrothermal treatments. Steeping in water (30 °C, 24 h) raised the moisture content and germination percentage of brown rice. Pasting viscosity was substantially decreased but gelatinization temperatures and enthalpy were decreased only marginally by germination (30 °C, 48 h). However, annealing (50 °C, 24 h) and heat-moisture treatment (100 °C, 1 h at 30% moisture) after germination resulted in increased pasting viscosity and gelatinization temperatures. The hydrothermal treatments, however, induced browning reactions to darken the flour of GBR. The digestibility of starch in brown rice was increased by germination. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in the cooked brown rice were 47.3%, 40.8%, and 11.9%, respectively, but changed to 57.7%, 39.1%, and 3.2%, respectively upon germination. The hydrothermal treatments, however, decreased the digestibility of starch in GBR. The heat-moisture treatment decreased the RDS content in GBR near to that of native brown rice. The digestibility and physical properties of brown rice can be controlled by germination and hydrothermal treatments.     

In vitro starch digestibility,degree of gelatinization and functional properties of twin screw prepared cereal-legume pasta

The investigation explores the possibility of utilizing legume flour (pigeon pea:10–30%) and brown rice flour (35–45%) for production of pasta using twin screw extruder. RSM was used to analyse the effect of feed moisture (28–36%), barrel temperature (70–110 °C) and legume:brown rice ratio on quality responses (in vitro starch and protein digestibility, degree of starch gelatinization, cooking quality, pasting properties, color and textural properties) of pasta. Extrusion processing significantly enhanced in vitro starch and protein digestibility of prepared pasta. The in vitro starch and protein digestibility of pasta ranged between 15.00 and 26.77 g/100 g and 50.34–84.82 g/100 g respectively. Addition of brown rice flour and pigeon pea flour exhibited dominating positive effect on cooking quality of the pasta. Degree of gelatinization of prepared pasta was found in range of 52.13–90.10 per cent. Color characteristics viz. luminosity, redness and yellowness of pasta enhanced with feed moisture. Pasting properties revealed lower peak and final viscosity at higher processing conditions. Firmness of cooked pasta elevated with an increase in the barrel temperature. Acceptability score of health based pasta on the basis of sensory attributes was 8 as inferred from 9 point hedonic scale.     

Starch Digestibility and Physicochemical and Cooking Properties of Irradiated Rice Grains

This study evaluated the starch digestibility, physicochemical properties and cooking characteristics of polished rice (varieties IRGA417 and IAC202) subjected to the doses of 0 (as the control), 1, 2 and 5 kGy of gamma radiation. The highest dose decreased the apparent amylose content, peak viscosity, water absorption and volume expansion. Irradiation increased the solid loss by 119% and 187% for IAC202 and IRGA417, respectively, when comparing the higher dose with the control. For IAC202, irradiation decreased the rapidly digestible starch and increased the slowly digestible starch (SDS) and resistant starch (RS). IRGA417 showed an elevation of SDS and a reduction in RS. And 1 kGy dose of gamma radiation generated the highest level of RS for both the two varieties and presented the smallest changes in other physicochemical and cooking properties.     

Starch Digestibility and Functional Properties of Rice Starch Subjected to Gamma Radiation

This study investigated the effect of gamma radiation on the digestibility and functional properties of rice starch. Rice cultivars IRGA417 and IAC202 were used for isolation of starch by the alkaline method. Starch samples were irradiated with 1, 2 and 5 kGy doses of ⁶⁰Co at a rate of 0.4 kGy/h. A control sample, which was not irradiated, was used for comparison. Irradiated and control starches were characterized by in vitro starch digestibility, total dietary fiber, color, water absorption index, water solubility index, syneresis, swelling factor, amylose leaching, pasting properties and gel firmness. Irradiations changed starch digestibility differently in either cultivar. Increasing radiation doses promoted increase in the color parameter b* (yellow), elevation in the capacity to absorb water, and solubility in water as well as the amylose leached from granules for both cultivars. Pasting properties showed a decrease that was proportional to the dose applied, caused by the depolymerization of starch molecules. Gel firmness of the starch from IAC202 was inversely proportional to the radiation dose applied, whereas for IRGA417, there was a reduction at 5 kGy dose. Rice starches can be modified by irradiation to exhibit different functional characteristics and they can be used by the food industries in products such as soups, desserts, flans, puddings and others.     

Effect of emulsifiers on complexation and functional properties of oxidized white sorghum (Sorghum bicolor) starch

The effect of addition of three commonly used emulsifiers namely GMS (glycerol monostearate), SSL (sodium stearoyl lactylate) and DATEM (diacetyl tartaric acid esters of monoglycerides) on complexation, thermal, pasting and textural properties of OWSS (oxidized white sorghum starch) was studied. The study is of interest as both oxidized starches and emulsifiers are present as co-ingredients in different food products and thus their complexation could affect the textural characteristics of foods. The complexation index (CI) reduced on oxidation of sorghum starch. The CI for native white sorghum starch (NWSS) was in the order GMS > SSL > DATEM whereas for OWSS, CI was in the order GMS > SSL > DATEM. Presence of emulsifiers significantly reduced gelatinization enthalpies of starches. Types I and II amylose–lipid complexes were observed in NWSS and OWSS on addition of GMS. Pasting temperature of NWSS increased while peak viscosity reduced on addition of SSL and GMS. Cold paste and setback viscosities of OWSS increased significantly (p ≤ 0.05) on addition of emulsifiers. Emulsifiers reduced firmness and rupture strength of NWSS and OWSS gels. Increase in firmness of gels on storage increased in NWSS and decreased in OWSS on addition of emulsifiers. Elasticity of OWSS on cold storage was higher in the presence of SSL and GMS.     

Effect of process conditions and amylose/amylopectin ratio on the pasting behavior of maize starch: A modeling approach

The effects of different process conditions on the pasting behavior of the 14%, w/w suspensions of high amylose, waxy and normal maize starches at mixing speeds of 50, 160 and 250 rpm with the heating rates of 2.5, 5 and 10 °C/min were investigated. In addition, the impact of the starch mixture with an amylose-amylopectin ratio of 0–70% at 160 rpm and a heating rate of 5 °C/min on the pasting parameters was studied. According to the results, when stirring speed decreased from 250 rpm to 50 rpm, the peak viscosity dramatically increased. Furthermore, both heating and stirring rates significantly affected the pasting properties (p < 0.05). The amylose content of maize starch had a negative correlation with peak viscosity, trough viscosity, breakdown viscosity, final viscosity, and setback viscosity. Besides, syneresis values decreased as amylose content decreased from 70% to 0%. According to the kinetic modelling of pasting curves, starch coefficients were found to be higher than 1 for all starches, indicating that the penetration of water into starch granules increased granule swelling rate. The findings of the present study confirmed that both process conditions and amylose/amylopectin ratio can be optimized without necessity of starch modification to obtain the products with the desired quality.     

The addition of corn fiber gum improves the long-term stability and retrogradation properties of corn starch

This study was designed to test the hypothesis that the stability and physical properties of starch gels could be improved by adding small amounts of corn fiber gum (CFG). In the differential scanning calorimeter measurement, the enthalpy of retrogradation was 7.30 J/g for starch without CFG and 4.30 J/g for starch composite gel with 1.0% CFG. The addition of 1.0% CFG to starch significantly (p < 0.05) decreased the degree of retrogradation during the long-term storage from 61.6% to 36.5%. The addition of CFG retarded the syneresis of the starch system from 17.97% and 34.93%–6.15% and 26.57% after storage for 7 and 14 days respectively. The crystallization peak of starch containing 0.5–1.0% CFG was quite diminished. When compared with the starch gel alone, the addition of CFG significantly lowered the hardness of the composite starch gel from 60.92 to 45.81 N after 14 days storage. The starch gel without CFG showed the lowest rapidly digestible starch content and the highest resistant starch content in comparison to starch/CFG composite gels after 7 and 14 days storage. Over all, the addition of CFG considerably inhibits the retrogradation of corn starch gels during long-term storage.     

Effects of gamma-irradiation of wheat on gluten proteins

The effects of ⁶⁰Co gamma-irradiation treatments (2·5, 5·0, 10·0 and 20·0 kGy) on the gluten proteins of two bread wheats and one durum wheat cultivar were investigated. Dough rheological properties of the flour processed from the irradiated wheat were also determined using a computerised micromixograph. Irradiation caused a significant deteriorating effect on all mixogram parameters. There was no observable effect of irradiation on gliadin proteins analysed by polyacrylamide gel electrophoresis. The 50% 1-propanol-insoluble (50 PI) glutenin fraction was highly affected by irradiation. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, reduced 50 PI glutenin showed a noticeable reduction in band intensities of both high (HMW) and low molecular weight (LMW) glutenin subunits (GS) with increasing irradiation dosage greater than 5 kGy. The irradiation effect on 50 PI glutenin was further studied and quantified by reversed-phase high-performance liquid chromatography of glutenin subunits; there was a progressive decrease in the quantity of subunits with increasing irradiation dose level. Compared to non-irradiated wheat, the relative decline in total insoluble glutenin at the 20 kGy dosage level ranged from 34–49% depending on cultivar. Increasing levels of irradiation also progressively reduced the ratio of HMW:LMW-GS up to 13–15% at 20 kGy indicating that irradiation had a greater effect on the largest polymers of glutenin. The observed weakening of dough mixing properties and concomitant decline in the quantity of 50 PI glutenin with increasing levels of gamma-irradiation are consistent with a degradation of glutenin to a lower average molecular size by depolymerisation and/or disaggregation.     

Pasting characteristics and in vitro digestibility of γ-irradiated RS4 waxy maize starches

The effect of γ-irradiation on the physicochemical properties of cross-linked waxy maize resistant starches was examined. The cross-linked waxy maize starches contained resistant starch (RS) of 56.1 and 63.5%, respectively for 5 and 10% sodium trimetaphosphate (STMP)/sodium tripolyphosphate (STPP) cross-linking, and the RS contents slightly decreased as the irradiation dose increased whereas the RS content in unmodified waxy maize starch increased with an increase in irradiation dose. For both native and cross-linked starches, the rapidly digestible starch (RDS) content increased and the slowly digestible starch (SDS) content decreased by the irradiation. The solubility of the native and cross-linked starches increased as the irradiation dose increased. The cross-linked starches did not swell in boiling water without showing pasting viscosity. However, the starches became swellable, forming pastes by irradiation, and the pasting viscosity gradually increased with an increase in irradiation dose. The crystallinity as determined by an X-ray diffraction analysis remained unchanged upon cross-linking and γ-irradiation. However, the gelatinization enthalpy of the cross-linked starches decreased in proportion with irradiation dose. The melting temperatures of cross-linked starches gradually decreased and the temperature range for melting increased with an increase in irradiation dose.     

Physical properties of cryomilled rice starch

Cryomilling of rice starch was evaluated as a non-chemical way to modify starch structure and properties. Cryomilling in a liquid nitrogen bath (63–77.2 K) was done to Quest (10.80% amylose) and Pelde (20.75% amylose) rice starch at five different time frames (0, 15, 30, 45, and 60 min). The viscosity of the cryomilled rice starch decreased significantly (p < 0.05) with increasing milling duration, including peak viscosity, hot-paste viscosity, cold-paste viscosity, breakdown, and consistency. Increasing milling time significantly increased (p < 0.05) water solubility index and water absorption index. Infra-red spectroscopy and X-ray diffraction crystallography both showed that the crystallinity of the cryomilled starch decreased with increasing milling time. Differential scanning calorimetry (DSC) analyses showed that after 60 min cryomilling there was partial loss of crystallinity (86% for Quest and 91% for Pelde) of both cryomilled starches. The cryomilling process modified the rice starch by causing a loss of crystallinity, that reduced its pasting temperature and increased water absorption, and by fragmentation of starch (probably the amylopectin fraction) that reduced the viscosity and increased solubility.     

Irradiation and germination effects on phytate,protein and amino acids of soybean

Influence of irradiation (0.05–0.20 kGy) and germination (24–120 hours) in distilled and tap water on phytate, protein and amino acids of soybean, was studied. Phytate values significantly decreased with increasing germination period and irradiation dose (P<0.01). Irradiation independently decreased the original phytate (212.0 mg/100 g) to a range value of 205.0–190.0 mg/100 g depending upon dose level. Germination of unirradiated seeds for 120 hours in distilled and tap water lowered the phytate to 55.0 and 94.9 mg/100 g (74.1 and 55.2% reduction) respectively. Maximum destruction of phytate to levels of 20.5 and 50.9 mg/100 g (90.3 and 76.0% reduction) occurred during germination of 0.20 kGy samples for 120 hours in distilled and tap water respectively. Total protein content significantly increased during germination (P<0.05) and the increase was more in tap than distilled water. Germination for 120 hours of untreated seeds in tap water increased the essential and decreased non-essential amino acids while in the 0.10 kGy sample, increases in both cases were observed.     

Effects of electron-beam irradiation crosslinking on PA6 fibers

Irradiation crosslinking of PA6 fibers with and without the presence of triallyl cyanurate (TAC) was investigated. The dose for incipient gel formation was 500 kGy for pristine PA6 fibers and it decreased to 12 kGy when 5 % TAC was incorporated. Changes in structure and properties of irradiated PA6 fibers were analyzed by X-ray diffraction, infrared spectroscopy and thermal gravimetric analysis. Irradiation crosslinking improved the anti-dripping properties of PA6 fibers effectively. Irradiated samples showed an increase of the breaking strength and then a decrease at further doses due to radiolysis effect, the elongation at break decreased during the irradiation process. Irradiation crosslinking had not changed the crystal form and crystallinity decreased first and then increased to some extent. DSC measurement reported that the melting temperature decreased with increasing the dose. The thermal stability decreased after irradiation whereas the amount of nonvolatile residue at 600 °C increased as the irradiation dosage increased. The infrared spectra of irradiated samples were identical with the unirradiated, no new bands were observed.XPS analysis showed that the number of C-C band increased after irradiation which proves that branching and crosslinking has occurred.     

Microwave irradiation differentially affect the physicochemical properties of waxy and non-waxy hull-less barley starch

Waxy and non-waxy hull-less barley kernels and their isolated starches were irradiated under different microwave conditions (power 640, 720, and 800 W, time 60, 120 and 180 s). Changes in physicochemical properties were studied to investigate the effects of microwave irradiation (MWI) on in-kernel starches and isolated starches. For in-kernel starch, microwave reduced the ratio of 1047/1022 cm⁻¹ wavelengths, gelatinization enthalpy (ΔH_g) and relative crystallinity (RC), indicating that microwave of starch within the cells disrupted the crystalline regions. For isolated starch, microwave decreased the ratio of 1047/1022 cm⁻¹ wavelengths but increased ΔH_g of isolated starch, indicating that microwaving resulted in disruption of amorphous structure and an increase in the amount of remaining double helix structure. Moreover, viscosities of in-kernel starches decreased as microwave power and time increased, but this was not observed in isolated starches. Microwave treatment induced an enhancement of gelatinization temperature for non-waxy starches (NWS) but decreased in waxy starches (WS). Microwave had a greater effect for swelling power and solubility on in-kernel MWI-WS than MWI-WS, whereas the reverse results were found between in-kernel MWI-NWS and MWI-NWS. The results indicated that amylose plays a profound role in the properties of isolated and in-kernel starches during microwaving.     

Effects of gamma irradiation on mycotoxin disappearance and amino acid contents of corn,wheat, and soybeans with different moisture contents

The effects of gamma irradiation on degradation of aflatoxin B₁ in wheat, corn, and soybeans and of T-2 toxin in wheat, deoxynivalenol (DON) in soybeans, and zearalenone in corn at 9, 13, and 17% moisture were studied. Radiation doses of 5, 7.5, 10 or 20 kGy were applied to spiked grain samples, and the residual toxins were measured using an enzyme linked immunosorbent assay (ELISA). Irradiation doses of up to 20 kGy did not significantly affect aflatoxin B₁ in any of the three grains, but significant reductions occurred in T-2 toxin, DON, and zearalenone concentration at doses of 10 or 20 kGy and in T-2 toxin at the 7.5 kGy dose. Two-way analysis of variance with Tukey's Multiple Range Test showed no significant interaction between radiation dose and grain moisture level. Irradiation of the ground grains at doses higher than 5 kGy resulted in small, but significant, losses of lysine in corn (only at 7.5 kGy), wheat, and soybeans, and methionine was reduced in wheat and corn samples. In some cases, phenylalanine decreased in corn and wheat, and histidine levels in wheat were reduced in samples receiving 7.5 kGy of irradiation. Other essential amino acids were not affected significantly by irradiation.Contribution No. 94-114-J of the Kansas Agricultural Experiment Station.     

Partial-degradation and heat-moisture dual modification on the enzymatic resistance and boiling-stable resistant starch content of corn starches

Normal corn, Hylon V and Hylon VII starches were partially degraded by acid-ethanol treatment and applied to heat-moisture treatment (HMT) for improving the enzymatic resistance of starch. The weight-average degree of polymerization (DP_w) of acid-ethanol-treated (AET) corn starches ranged from 6.75 × 10⁵ to 181, 4.48 × 10⁵ to 121, and 1.94 × 10⁵ to 111 anhydrous glucose units for normal corn, Hylon V and Hylon VII starches, respectively. Starch retained its granular structure after AET and HMT, recovery of starch granules after modifications were higher than 92%. Resistant starch (RS) content and boiling-stable RS content of corn starch increased after dual modification, and the increment increased with increasing duration of AET. The boiling-stable RS content of dual-modified starch increased from 1.5 to 9.2, 12.2 to 24.1, and 18.0 to 36.2% for normal corn, Hylon V and Hylon VII starches, respectively. Increments of RS content and boiling-stable RS content of dual-modified starches were significantly correlated (r² > 0.700) with DP_w of starch, revealing that the enzymatic resistance of dual-modified corn starch granules increased with decreasing molecular size of starch. Result also suggested that starch granules partially degraded with AET could improve the molecular mobility and ordering during the consequent HMT.     

Structural,rheological and gelatinization properties of wheat starch granules separated from different noodle-making process

In this study, three typical wheat cultivars (ZM366, AK58, and ZM103) with high, medium, and low gluten strength, respectively, were selected as the raw material. The starch granules separated from different stages of the noodle-making process, including kneading, resting, sheeting, cutting, and drying, were used to explore the structure, dynamic rheology, and quality of the noodles. The D50 (median diameter) of the starch granules decreased during the noodle-making process, and the reduction was enhanced by an increase in the gluten strength of the flour. Between steps 4 and 5 of the noodle-making process, the solubility of ZM103 variety increased from 4.3% to 5.0% at 80 °C, while the peak viscosity decreased from 3626 to 3386 mPa s, which resulted in a decrease in the cooking loss of noodles. Similar trend was observed in the ZM366 and AK58 varieties. The gelatinization enthalpy was reduced, suggesting that the crystalline regions of the starch granules were destroyed during the kneading process. Between steps 4 and 5 of the noodle-making process, the elastic modulus of the starch granules significantly increased, while the temperature at which maximum elastic modulus was decreased, indicating an increase in the crystalline stability of starch during the drying process. Correlation analysis indicated that the changes occurred to the gelatinization property was primarily due to the change in the particle size.     

Water mobility,rheological and textural properties of rice starch gel

Three rice starches from indica (TNuS19), japonica (TNu67) and waxy (TCW70) were used as samples to investigate the water mobility, viscoelasticity and textural properties of starch gels using pulsed nuclear magnetic resonance (PNMR), dynamic rheometer and texture analyzer. The spin–spin relaxation time (T₂), showed water mobility of starch gels was detected with starch concentrations 10–30%. Generally, the TNuS19 and TNu67 at ≥20% showed two components (T_2a and T_2b) in water mobility, where T_2a and T_2b related to solid-like and liquid-like water molecules in starch gels, respectively. However, the TCW70 over the concentrations examined had only T_2b component, higher than those of corresponding TNuS19 and TNu67. The storage (G′) and loss (G″) moduli of starch gels were in the order of TNuS19 > TNu67 > TCW70. Texture analyzer analysis indicated that TNuS19 had higher hardness, stickiness and adhesiveness than did the TNu67 and TCW70, and changed significantly with the starch concentration increase. The value of T_2b was highly correlated with physical properties of starch gels, especially with dynamic rheological parameters. It is suggested that amylose content may play a major role to influence the water mobility of starch gels which affects the specific viscoelasticity and textural properties of starch gels.     

Effect of thermal processing and storage on digestibility of starch in whole wheat grains

Gelatinisation and retrogradation of starch in wheat flour systems and whole wheat grains were studied using DSC and the impact of these events on starch digestibility was investigated. Gelatinisation of starch was possible in wheat flours with more than 60% moisture content (dwb) and gelatinised samples had higher digestibility values. Retrogradation of starch was studied with partially and fully cooked (boiled at 100 °C for 12 min and 32 min, respectively) wheat grains that were subjected to storage at 22 °C for 48 h. Stored samples had lower digestibility values when compared to the freshly cooked counterparts. The effect of moisture on retrogradation was studied with fully cooked wheat grains that were dried to a range of moisture contents (14.6–35.9%, wwb) and stored at 20 °C for 24 h. Retrogradation enthalpy increased with increasing moisture content; however, digestibility values did not reflect the changes in retrogradation enthalpy. The possibility of estimating the degree of retrogradation in fully cooked grains (32 min cooking) was investigated using a wheat flour-water system. The retrogradation enthalpy of fully cooked grains was slightly higher than the wheat flour-water system (at a moisture content of 49%, wwb) during the course of storage at 22 °C.     

Effects of amylose content,cooling rate and aging time on properties and characteristics of rice starch gels and puffed products

This study aimed at investigating the effects of amylose content (AC) of 0.12–19.00% w/w on dry basis, cooling rate (1, 3, 5, and 9 °C/min), and aging time (24, 48, and 72 h) on structure, physical properties and sensory attributes of rice starch-based puffed products. They had an influence upon the crystalline type, and the relative crystallinity (RC). The thermal and physical properties of starch gels were also determined. Amorphism was found for starch gels with 0.12% AC. The polymorphisms (B and V) and differential scanning calorimetric endotherms were found for those with AC ≥4.00%. The RC, retrogradation enthalpy (ΔH_r) and gel hardness increased with AC and aging time. The cooling rate did not affect RC, but increased ΔH_r and gel hardness. The higher AC and aging time resulted in higher hardness, fracturability, crispiness and bulk density, but lower expansion ratio and less oiliness of the puffed products. The hardness, fracturability, crispiness and bulk density of puffed products were well correlated with the RC of starch gel.