Modifications of structure and physicochemical properties of maize starch by γ-irradiation treatments

Maize starch powder was exposed to a ⁶⁰Co source (0, 1, 2, 5, 10, 20, 50, 100, 200, or 500 kGy) and the effects of γ-irradiation treatment on the structure and physicochemical properties of the starch granules were studied. The results showed that peak, trough, final, and setback viscosities were significantly reduced, whereas the solubility was increased following irradiation. Gelatinization temperature and enthalpy decreased significantly when the dose is higher than 50 kGy. On the surface, the starch granules did not display any visible physical change up to a 500 kGy dose was. X-ray diffraction (XRD) analysis showed that the relative crystallinity of starch decreased slightly, and the starch exhibited an A-pattern without any change. Fourier transform infrared (FTIR) spectral intensity at 1018 cm^?1 increased with the irradiation dose up to 200 kGy. Irradiation dose was positively correlated with solubility and negatively correlated with relative crystallinity. There were high positive correlations between thermal properties and pasting properties.     

Effect of γ-irradiation on granule structure and physicochemical properties of starch extracted from two types of potatoes grown in Jammu & Kashmir,India

In this study red and white potato starches were treated with γ-irradiation of 0, 5, 10 and 20 kGy. Physicochemical, pasting and morphological properties of the irradiated starches were investigated. Apparent amylose content, pH, moisture, swelling power and syneresis decreased; whereas carboxyl content, water absorption capacity and solubility increased with increasing irradiation dose. Pasting properties also decreased significantly (p ≤ 0.05) upon increasing the irradiation dose. Observation under scanning electron microscope (SEM) showed surface cracking of the starch granules by γ-irradiation which increased with increase in irradiation dose. X-ray diffraction pattern remained the same upon irradiation but a decrease in relative crystallinity was observed with increasing irradiation dose.     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) flours and pastes: Effects on functional,thermal and molecular properties of isolated proteins

In a previous study irradiation of cowpea flours and pastes at medium (10 kGy) and high (50 kGy) doses resulted in significant changes in protein-related functional properties. To understand some of the effects of gamma irradiation on cowpea proteins in particular, we isolated proteins from cowpea flours (FPC) and pastes (PPC) treated with gamma irradiation at 2, 10, and 50 kGy and analyzed their functional, thermal and molecular properties. Nitrogen solubility index of both FPC and PPC decreased, whereas oil absorption and emulsion capacities increased significantly with increasing irradiation dose. Differential scanning calorimetry showed decreases in transition temperatures (T_d) and enthalpies (ΔH), indicating a progressive denaturation of cowpea proteins with increasing irradiation. Size exclusion HPLC revealed increases in protein molecular weights, probably due to protein–protein cross-linking with irradiation in a dose-dependent manner. Reducing SDS-PAGE of FPC and PPC samples seems to suggest that the contribution of disulphide bonds to irradiation-induced cowpea protein–protein cross-linking is small.     

Effects of low dose gamma irradiation on microbial inactivation and physicochemical properties of fried shrimp (Penaeus vannamei)

Changes in microbiological, physicochemical and sensory properties of shrimp gamma irradiated with ⁶⁰Co at doses of 0, 1, 3, 6, 9 kGy were investigated. Irradiation at 6 kGy eliminated most of the spoilage microorganisms and did not affect sensory quality. The L* value increased as irradiation dose increased, while a* value decreased as irradiation dose increased. Irradiation had no significant effect on the texture of shrimp samples; however, increasing the dose up to 9 kGy significantly increased the amount of volatile compounds, such as, alcohols, ketones, aldehydes, furans, and oxides. According to the total sensory points, the appearance and flavour of the shrimp product was considered as acceptable by sensory evaluation when irradiated at doses of 0–6 kGy. These results showed that gamma irradiation processing (<6 kGy) had the potential to extend the shelf life of fried shrimp.     

Gamma-irradiation as a method of microbiological control,and its impact on the oxidative labile lipid component of <Emphasis Type="Italic">Cannabis sativa</Emphasis> and <Emphasis Type="Italic">Helianthus annus</Emphasis>

The effect of irradiation (0–20 kGy) on hemp and sunflower seeds was assessed, with specific reference to the oxidatively labile lipid component (unsaturated fatty acids and tocochromanols). Total protein, lipid, and solids content of the seeds did not vary with irradiation dose. Lipid hydroperoxide concentration increased significantly in the sunflower seeds (48 mmol kg⁻¹ lipid) and a significant increase in volatile secondary oxidation products was measured in both seeds (e.g. hexanal, heptanal, 1-penten-3-ol) with increasing irradiation dose. Irradiation at 5 kGy sterilised the seeds of all microbial contamination and irradiation doses of 20 kGy prevented germination. A loss of the antioxidant tocopherol was shown with increasing irradiation doses, although this was selective for specific tocopherol isoforms (α-tocopherol, β-tocopherol and γ-tocopherol).     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) seeds: effect on colour,cooking quality and pasting characteristics

Cowpea seeds were treated to various gamma irradiation doses, and their colour, cooking quality and pasting properties studied. Irradiation at 50 kGy resulted in significant browning (indicated by decreases in L colour value) of cowpea seeds. At 2 and 10 (but not at 50) kGy, irradiation led to significant reduction in cooking time of cowpea seeds possibly through irradiation‐induced degradation of starch and pectic substances (indicated by decreases in peak and final viscosities) leading possibly to enhanced heat and mass transfer within the seed cotyledon and cell wall, respectively. At 50 kGy, the cooking time of cowpea seeds was prolonged significantly owing possibly to extensive polymer cross‐linking occurring within the seeds at this high dose. Splitting of cowpea cotyledons during cooking decreased significantly at 50 kGy, but was unaffected at 2 and 10 kGy. Irradiation resulted in significant leaching of nutrients from cowpea seeds during cooking in a dose‐dependent manner.     

Effects of electron‐beam irradiation on physicochemical properties of starches separated from stored wheat

Effects of electron‐beam irradiation (0, 1.0, 2.7, and 4.4 kGy) on physicochemical properties, MW distribution as well as microstructure of starches separated from electron‐beam irradiated and stored wheats were investigated by differential scanning calorimeter (DSC), SEM, and static multi‐angle laser light scattering (MALLS). The profiles of starch viscosity illustrated that peak, hot paste, cold paste, and setback were considerably decreased with increasing irradiation dose. The DSC pattern indicated that the electron‐beam irradiation caused a slight decrease in gelatinization temperature. SEM results showed that on the surfaces of a few starch granules fissures appeared and that they become rough when the irradiation doses reached 4.4 kGy. Damaged starch (DS) contents analysis suggested that the DS increased from 5.33 to 7.38% as the dose increased from 0 (control) to 4.4 kGy. HPSEC measurement showed that the starch molecule were gradually degraded due to the electron‐beam irradiation treatment, and the molar mass of wheat starches decreased by one order of magnitude when the irradiation doses reached 4.4 kGy.     

Improved Extraction and Quality Characterization of Water‐Soluble Polysaccharide from Gamma‐Irradiated Lentinus edodes

Gamma irradiation was applied to the improved extraction of water‐soluble polysaccharides (WSPs) from dried Lentinus edodes. Irradiation provided a dose‐dependent increase in extraction yield (0 kGy, 2.01%; 7.5 kGy, 4.03%; 15 kGy, 7.17%) and purity (0 kGy, 78.8%; 7.5 kGy, 83.1%; 15 kGy, 85.6%) of the WSPs from hot‐water extraction. The effect of irradiation was evident in the degraded microstructures and reduced molecular weights of the WSPs. However, nuclear magnetic resonance, Fourier‐transform infrared, and X‐ray diffraction spectroscopic analyses provided comparable structures of WSPs from nonirradiated and irradiated samples. UV–visible spectra showed a dose‐dependent decline in intensity, but an improvement in thermal properties of the WSPs from the irradiated mushroom samples was observed.     

Effect of irradiation on properties and storage stability of Som-fug produced from bigeye snapper

Effects of irradiation at different doses (0, 2 and 6 kilogray (kGy)) on the microbiological, chemical and physical properties of Som-fug, a Thai fermented fish mince, were investigated. Lactic acid bacteria (LAB), yeast and mould counts in samples irradiated at 6 kGy were not detectable throughout the storage of 30 days at 4 °C, whereas no growth was found in the sample irradiated at 2 kGy within the first 10 days. Generally, greater carbonyl contents of lipid and protein, as well as thiobarbituric acid-reactive substances (TBARS), were noticeable in the irradiated samples, than in the non-irradiated sample (p < 0.05). The carbonyl contents and TBARS increased with increasing storage time and the rate of increase was more pronounced in samples irradiated at higher dose (p < 0.05). With increasing storage time, Som-fug irradiated at 6 kGy showed greater decreases in hardness, adhesiveness, springiness and cohesiveness, than did non-irradiated samples and those irradiated at 2 kGy (p < 0.05). L^∗ value of all samples decreased, whereas a^∗ and b^∗ values increased throughout storage (p < 0.05). Lower acceptance in all attributes was observed in the samples irradiated at 6 kGy, than in other samples, particularly when storage time increased (p < 0.05). However, samples irradiated at 2 kGy showed no changes in acceptability within 20 days. The results revealed that irradiation at high dose (6 kGy) might induce lipid and protein oxidation, though the growth of microorganisms was inhibited. Therefore, the irradiation at low dose (2 kGy) could be used to control the overfermentation of Som-fug up to 20 days at 4 °C without adverse effects on quality and acceptability.     

Reduction of Carcinogenic N-Nitrosamines and Residual Nitrite in Model System Sausage by Irradiation

Gamma irradiation was used to reduce the N‐nitrosamines and residual nitrite in model system sausage during storage. Aerobic or vacuum packaged sausage was irradiated at 0, 5,10, 20, and 30 kGy. The residual nitrite levels were significantly reduced by gamma irradiation, and, in vacuum packaging, the reduction was dose dependent. The N‐nitrosodimethylamine of the sausage irradiated at 10 kGy or above reduced in aerobic packaging, while a dose of 20 kGy was needed in vacuum packaging. The N‐nitrosopyrrolidine reduction was found at 20 and 30 kGy‐irradiation. Results indicated that high dose irradiation (> 10 kGy) was needed to reduce the carcinogenic N‐nitrosamine and nitrite levels in pork sausage during storage.     

E‐Beam Irradiation for Improving the Microbiological Quality of Smoked Duck Meat with Minimum Effects on Physicochemical Properties During Storage

This study was performed to evaluate the effect of different doses (0, 1.5, 3, and 4.5 kGy) of e‐beam irradiation on the quality parameters (pH, Hunter's parameter, and heme pigment) and stability qualifiers (peroxide value [POV], thiobarbituric acid reactive substances [ TBARSs], and total volatile basic nitrogen [TVBN]) of smoked duck meat during 40 d of storage under vacuum packaging at 4 °C. The initial populations of total bacteria (7.81 log CFU/g) and coliforms (5.68 log CFU/g) were reduced by approximately 2 to 5 log cycles with respect to irradiation doses. The results showed that pH, myoglobin, met‐myoglobin, L^*, a^*, and b^* showed significant differences with respect to different doses and storage intervals; a^* and b^* did not vary significantly because of storage. Higher pH was found in samples treated with 4.5 kGy at 40 d, while the minimum was observed in nonirradiated samples at day 0 of storage. Higher POV (2.31 ± 0.03 meq peroxide/kg) and TBARS (5.24 ± 0.03 mg MDA/kg) values were found in 4.5 kGy‐treated smoked meat at 40 d and the lowest was reported in 0 kGy‐treated meat at initiation of storage (0 d). However, irradiation suppressed TVBN during storage and higher TVBN (7.09 ± 0.32 mg/100 mL) was found in duck meat treated with 0 kGy at 40 d. The electronic nose (e‐nose) effectively distinguished flavor profiles during the different storage intervals. The results showed that different sensory attributes did not vary significantly with respect to the dose of irradiation. We conclude that low dose of e‐beam irradiation and vacuum packaging is beneficial for safety and shelf life extension without affecting the sensory characteristics of smoked duck meat.     

Absorbed‐dose estimation and quality attributes of gamma‐irradiated fresh shiitake mushrooms

BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose‐dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low‐dose re‐irradiation (200‐600 Gy), medium‐dose re‐irradiation (1‐3 kGy) and high‐dose re‐irradiation (2‐6 kGy) were performed and compared using an additive dose method. An electronic‐nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One‐kGy‐irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose‐dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1‐3 kGy re‐irradiation technique gave most promising results. An E‐nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy‐irradiated mushrooms. © 2012 Society of Chemical Industry     

Modification of bean starch by γ-irradiation: Effect on functional and morphological properties

Starches isolated from Red, White, Yellow and Black Kidney beans were treated by γ-irradiation doses of 5, 10 and 20 kGy. Physicochemical, morphological and pasting properties of irradiated bean starches were investigated. Microscopic observation under scanning electron microscope (SEM) showed that some of the bean starch granules were destroyed by γ-irradiation and the breakage was greater at a higher dose (20 kGy). Physicochemical properties differed significantly and showed strong dose-dependent relationship. Carboxyl content, solubility, water absorption capacity and transmittance increased, whereas swelling power, apparent amylose content, syneresis and pasting properties decreased upon the irradiation of kidney bean starch. Radiation doses were positively correlated with water absorption capacity and solubility index and negatively correlated with swelling index, peak viscosity, trough viscosity, breakdown and final viscosity. There were high positive correlations between pasting properties. X-ray diffraction pattern remained same upon irradiation but a decrease in crystallinity was observed with increasing irradiation dose.     

Thermo‐rheological and functional properties of gamma‐irradiated wholewheat flour

The effects of different doses (0, 0.5, 1, 2.5, 5 and 10 kGy) of gamma irradiation on the thermal, rheological and functional properties of the wholewheat flour were evaluated. Water and oil absorption capacity of the flour increased from 85.92% to 91.44% and 1.10 to 1.91 g g^?1 of flour, respectively, with increase in irradiation dose. The dough development time decreased with dose from 4.0 to 3.0 min. The transition temperatures (T_o, T_p and T_c) decreased as the dose increased; enthalpy of gelatinisation (?H) decreased from 5.18 to 4.27 J g^?1 with dose. The flow behaviour showed a shear‐thinning behaviour, and the hysteresis area decreased with dose. The structural recovery decreased with dose. FTIR did not show formation of any new chemical groups.     

Changes in the colour and the acidity number of egg yolk upon irradiation

Eggs from laying hens were irradiated using radioactive Co-60 at a dose of 1 kGy, 2.5 kGy, and 5 kGy, with a dose input of 3.21 kGy h^–1. Parameters describing the colour of egg yolk such as L*, a*, and b*, were determined spectrophotometrically using the CIELAB system with the help of the portable spectrophotometer Superchroma S-Spex without gloss. The levels of all three parameters dropped upon ionizing radiation. While at a dose of 1 kGy the difference in the parameters was not statistically conclusive, after irradiation using doses of 2.5 kGy and 5 kGy, the levels of the parameters L*, a*, and b* showed a statistically conclusive decrease which was also accompanied with changes in sensorial properties such as decolouration and decreased colour. The colour of the yolk was evaluated according to the Roche scale, showing that more significant changes occurred upon irradiation at doses of 2.5 and 5 kGy (the value decreased from 6 to 5). The number of acidity estimated in egg yolk (mg KOH/g of fat) increased with the increasing dose, being conclusively higher only for doses of 2.5 kGy and 5 kGy.     

Modification of poovan banana (Musa AAB) starch by γ‐irradiation: effect on in vitro digestibility,molecular structure and physico‐chemical properties

This study focussed at evaluating the effect of gamma irradiation on the in vitro digestibility, molecular structure and physico‐chemical properties of poovan banana (Musa AAB) starch using γ‐rays from a ⁶⁰Co source at different doses with a dose rate of 2 kGy h^?1. Physico‐chemical properties varied significantly and exhibited strong dose‐dependent relationship. Escalating irradiation leads to decrease in amylose content, pH, swelling power of the starch granules and syneresis of the gelatinised starch, while the same led to an increase in carboxyl content, in vitro digestibility, solubility and water absorption capacity of the starch granules. The results revealed that peak, hold, final and setback viscosities were significantly reduced. X‐ray diffraction pattern remained the same upon irradiation but a decrease in relative crystallinity was observed with increasing irradiation dose. Gelatinisation temperature and enthalpy decreased significantly when the increasing the dose of gamma irradiation.     

The effect of gamma irradiation on the microbial load,mineral concentration and sensory characteristics of liquorice (Glycyrrhiza glabra L)

Ground liquorice roots were exposed to various doses (0, 5, 10, 15 and 20 kGy) of gamma radiation from a ⁶⁰Co source. Irradiated and non‐irradiated samples were stored at room temperature. Microbial population, viscosity, concentrations of some minerals and the sensory properties of the extracts were evaluated after 0 and 12 months of storage. Tests carried out immediately after irradiation showed that the microbial count had been reduced and that the dose required to reduce the count by 1 log cycle (D₁₀) was about 2 kGy. No effect was observed on the total dissolved solids in extracts of liquorice roots. Glycyrrhizinic acid concentration in the extracts and the viscosities of suspensions produced from irradiated roots were lower than those from non‐irradiated ones. Sensory evaluation indicated that there were no significant differences (P < 0.05) in colour, taste or flavour between extracts produced from irradiated and non‐irradiated roots. However, after 12 months of storage, some mineral ion (Na⁺, Ca²⁺ and K⁺) concentrations in extracts produced from irradiated roots were lower than in those from non‐irradiated ones; no significant differences (P < 0.05) in viscosity were found between suspensions of irradiated and non‐irradiated roots. © 2002 Society of Chemical Industry     

The effect of irradiation on technological properties and protein solubility of broiler chicken meat

During investigations on the effects of irradiation of chicken meat it was found that a 5 kGy dose of gamma ⁶⁰Co radiation brings about a statistically significant (P<0.05) increase in free water content, and fall in water holding capacity and water retention capacity, in breast muscles of broiler chickens. The cause of deterioration of hydration properties in meat is a decrease in solubility of the protein fractions after irradiation. The relative protein extractability Y (in 0.1M phosphate buffer+1.1M KI) fell in a linear manner with increase in the radiation dose D according to the equation Y=98.494–0.838 D. The changes in sarcoplasmic fraction extractability Y in 0.03M phosphate buffer are described by the equation Y=101.615–0.515 D, and those of myofibrillar fraction by Y=100.377–1.628 D. Electrophoresis of the protein fraction (soluble in phosphate buffer+1.1M KI) on polyacrylamide gel (with SDS) indicated that the lowest extractability, as compared with untreated samples, was shown by myosin. Other protein solubilities were only slightly altered by the 5 and 10 kGy doses.     

Effect of electron beam irradiation on the functional properties and antioxidant activity of wheat germ protein hydrolysates

In this paper, the effects of electron beam irradiation (EBI) on wheat germ protein hydrolysates (WGPHs) were investigated. The functional properties of WGPHs were enhanced by EBI, with the emulsifying capacity reaching its maximum value at 10 kGy. Moreover, foaming capacity reached its maximum value at 25 kGy. Additionally, EBI can enhance the antioxidant activity of WGPHs, and a dose-dependent effect was observed. Hydrolysates irradiated at 50 kGy had the greatest antioxidant activity; the DPPH and ABTS⁺ radical scavenging activities increased by 45.77% and 52.52%, respectively, compared to the non-irradiated sample. Additionally, surface hydrophobicity reached its minimum value at 10 kGy. After 10 kGy of irradiation, the fraction of hydrolysates with a molecular weight <1 kDa increased from 88.34% to 90.23%. Irradiation caused the surface morphology to become uneven, and it produced smaller peptides.     

GAMMA IRRADIATION IMPROVED THE QUALITY OF ONION FLAKES USED BY ARGENTINE CONSUMERS

A study was carried out on the microbiological status of local and imported packed onion flakes available at retail markets in Argentina. The effectiveness of selected doses of gamma irradiation to decontaminate imported onion flakes and the effects of irradiation on some technological properties were also investigated. Imported onion flakes were contaminated with a high percentage of spore‐forming microorganisms. Imported onion flakes were irradiated at doses of 7, 9, 11, 15, 18 and 23 kGy, and stored at temperatures between 20 and 25C, and relative humidities ranging from 50 to 80%. Irradiation doses between 7 and 11 kGy reduced the aerobic plate count by three log cycles. Doses between 7 and 15 kGy reduced yeast and mold counts by two log cycles. A dose of 7 kGy was sufficient to reduce the sulfite‐reducing Clostridia count to less than detectable levels. We concluded that a dose of at least 7 kGy was necessary to decontaminate imported dry onion marketed in Argentina. No variation in water content or water activity was attributed to selected irradiation doses. Irradiation in the 7–11 kGy range markedly increased the saline extract optical index of imported onion flakes. Gamma irradiation did not significantly affect the flavor intensity as determined by enzymatic production of pyruvic acid.