Evaluation of protein content, lysine and sulfur-containing amino acids content and electrophoretic patterns of soluble proteins for gamma-irradiated semolina before and after milling of durum wheat

Influenced of gamma irradiation (0, 0.25, 1, 2.5, 5 and 10 kGy) on total nitrogen, lysine and sulfur-containing amino acids content and electrophoretic patterns of soluble proteins of semolina was studied. The effect of irradiation before and after milling on previous parameters was also investigated. Protein content of semolina was not affected with gamma irradiation before and after milling. Up to 10 kGy dose, cystine and methionine were not significantly changed, although they increased slightly with increasing irradiation dose. Lysine content decreased significantly (P≤0.05) at irradiation dose higher than 5 kGy. At 10 kGy dose, lysine decreased 5% and 14% for irradiated semolina and that obtained from irradiated wheat grains, respectively. The bands number and intensity of soluble proteins decreased with increasing irradiation dose higher than 5 kGy, as shown on SDS-PAGE electrophoresis. Irradiated semolina and semolina obtained from irradiated wheat grains at 10 kGy showed 13 and 15 bands, respectively. Unirradiated sample showed 19 bands.     

Change in the enzymatic dual function of the peroxiredoxin protein by gamma irradiation

PP1084 protein was exposed to gamma irradiation ranging from 5 to 500 kGy. Native PAGE showed minor structural changes in PP1084 at 5 kGy, and major structural changes at >15 kGy. Size-exclusion chromatography (SEC) showed the formation of a new shoulder peak when the protein was irradiated with 15 and 30 kGy, and a double peak appeared at 100 kGy. The results of PAGE and SEC imply that PP1084 protein is degraded by gamma irradiation, with simultaneous oligomerization. PP1084 chaperone activity reached the highest level at 30 kGy of gamma irradiation, and then, decreased in a dose-dependent manner with increasing gamma irradiation. However, the peroxidase activity significantly decreased following exposure to all intensities of gamma irradiation. The improvement of chaperone activity using gamma irradiation might be promoted by the oligomeric structures containing covalently cross-linked amino acids. Consequently, PP1084 modification using gamma irradiation could elevate chaperone activity by about 3–4 folds compared to the non-irradiated protein.     

Nutritional,physiological, physicochemical and sensory stability of gamma irradiated Kimchi (Korean fermented vegetables)

Effects of gamma irradiation on nutritional, physiological, physicochemical and sensory properties of the Korean lactic acid fermented vegetable, Kimchi, were investigated. The composition of amino acids and organic acids in Kimchi were not influenced by gamma irradiation less than 10 kGy. Angiotensine converting enzyme inhibitory, xanthin oxidase inhibitory, electron donating and antimicrobial activity of Kimchi extract were stable up to 10 kGy. There were no significant changes in pH and texture at less than 10 kGy. Color values were influenced at 10 kGy of gamma irradiation, and resulted in the increase of L*- and reduction of a*-value. About 90% of panelists identified a sensory difference between non-irradiated and 10 kGy-irradiated sample, and Kimchi irradiated at 10 kGy had lower scores in acceptability than those of the control or irradiated at 2.5 and 5 kGy.     

Color,flavor, and sensory characteristics of gamma-irradiated salted and fermented anchovy sauce

Color, flavor, and sensory characteristics of irradiated salted and fermented anchovy sauce were investigated. The filtrate of salted and fermented anchovy was irradiated at 0, 2.5, 5, 7.5, and 10 kGy. After irradiation, Hunter’s color values were increased, however, the color values were gradually decreased in all samples during storage. Amount of the aldehydes, esters, ketones, S-containing compounds, and the other groups were increased up to 7.5 kGy irradiation, then decreased at 10 kGy (P<0.05), while the alcohols and furan groups were increased by irradiation. Different odor patterns were observed among samples using electronic nose system analysis. Gamma-irradiated samples showed better sensory score and the quality was sustained during storage. In conclusion, gamma irradiation of salted and fermented anchovy sauce could improve its sensory quality by reducing typical fishy smell.     

The changes of fatty acid and amino acid compositions in sea bream (Sparus aurata) during irradiation process

Aqua cultured fish (sea bream) were irradiated by Cobalt-60 at commercial irradiation facility at dose of 2.5 and 5 kGy at 2–4 °C. The proximate composition, fatty acid and amino acid composition changes of irradiated aqua cultured sea bream (Sparus aurata) of Aegean Sea were investigated. Total saturated (28.01%) and total monounsaturated (28.42%) fatty acid contents of non-irradiated decreased content of 27.69–27.97% for 2.5 kGy irradiated groups and increased content of 28.33–28.56% for 5 kGy irradiated groups after irradiation process. Total polyunsaturated fatty acid content for irradiated samples was lower than that of non-irradiated samples. Aspartic acid, glutamic acid, serine, glycine, arginine, alanine, tyrosine, cystine, tryptophan, lysine and proline contents for 2.5 and 5 kGy irradiated sea bream are significantly different (p<0.05).     

The role of gamma irradiation on the extraction of phenolic compounds in onion (Allium cepa L.)

The effect of gamma irradiation on the content of total phenolic compounds, especially quercetin (Q), in onion (Allium cepa L.) skin was investigated. Onion skin extracts contained two predominant flavonoid compounds, Q and quercetin-4′-glucoside (Q4′G). After 10 kGy gamma irradiation, the yield of Q in the extracts increased significantly from 36.8 to 153.9 μg/ml of the extract, and the Q4′G content decreased slightly from 165.0 to 134.1 μg/ml. In addition, the total phenolic compound content also increased after irradiation at 10 kGy, from 228.0 μg/g of fresh weight to 346.6 μg/g; negligible changes (237.1–256.7 μg/g) occurred at doses of up to 5 kGy. As we expected, radical-scavenging activity was enhanced remarkably (by 88.8%) in the 10 kGy irradiated sample. A dose-dependent increase in the peak intensity of the electron paramagnetic resonance (EPR) spectra was observed in all irradiated samples, with a maximum increase at 10 kGy. The intensity relative to that of the control was 0.15, and it increased to 1.10 in 10 kGy irradiated samples. The optimum gamma irradiation dose, which is sufficient to break the chemical or physical bonds and release soluble phenols of low molecular weight in onion skin, is about 10 kGy.     

Gamma irradiation improves the antioxidant activity of Aloe vera (Aloe barbadensis miller) extracts

Aloe has been widely used in food products, pharmaceuticals, and cosmetics because of its aromatic and therapeutic properties. In the present study, the ethanolic extracts of aloe gel were gamma-irradiated from 10 to 100 kGy. After gamma irradiation, the color of the ethanolic extracts of aloe gel changed to red; this color persisted up to 40 kGy but disappeared above 50 kGy. Liquid chromatography/mass spectrometry analysis demonstrated the production of a new, unknown compound (m/z=132) after gamma irradiation of the ethanolic extracts of aloe gel. The amount of this unknown compound increased with increasing irradiation up to 80 kGy, and it was degraded at 100 kGy. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by the 1,1-diphenyl-2-picrylhydrazyl-radical scavenging capacity. The antioxidant activity of aloe extract was dramatically increased from 53.9% in the non-irradiated sample to 92.8% in the sample irradiated at 40 kGy. This strong antioxidant activity was retained even at 100 kGy. These results indicate that gamma irradiation of aloe extract can enhance its antioxidant activity through the formation of a new compound. Based on these results, increased antioxidant activity of aloe extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.     

Oxidation of Dimethyl Sulfide in Air Using Electron-Beam Irradiation,and Enhancement of its Oxidation Via an MnO<Subscript>2</Subscript> Catalyst

The decomposition of dimethyl sulfide (DMS) at initial concentrations of 4.5–18.0 ppmv in air was studied under electron-beam (EB) irradiation. Doses to decompose 90% of input DMS were 2.5 kGy for 4.5 ppmv, 3.4 kGy for 10.6 ppmv, and 3.9 kGy for 18.0 ppmv. HCOOH, (CH₃)₂SO, and trace CH₃OH and (CH₃)₂SO₂ were produced as irradiation products in addition to CO₂ and CO. Application of an O₃ decomposition catalyst to an irradiated sample gas led to an enhancement in the oxidation of DMS and its products into CO₂ and the decomposition of O₃. For 10.6 ppmv DMS/air, the mineralization ratio increased from 41% via only EB irradiation to 100% via the combination treatment at 6.3 kGy. The yield of CO₂ to CO_x increased from 5.3 to 87.6% by combination with catalytic oxidation. This combination treatment enables the irradiation energy used to deodorize gas streams containing DMS to be reduced.     

Gamma rays as an effective tool for removing undesirable color without adverse changes in biological activities of red beet extracts

The ethanolic extracts of red beet (Beta vulgaris L.) hairy root were used to investigate the removal of color and improvement of biological activity for enhanced industrial applications. The extracts were exposed to gamma rays ranging from 2.5 to 30 kGy. The red beet hairy root is composed of two major red-colorants, betanin and isobetanin. Gamma ray radiation at 5 kGy remarkably reduced the levels of the major colorants by 94% and the reddish color was eliminated by doses greater than 10 kGy. Color removal was likely due to the gamma ray radiolysis of ethanol. Although details on the mechanism responsible for the decay of the chromophore have not been entirely determined, our results suggest that the free radicals that are produced during this process are capable of destroying the chromophore group in isobetanin, thus bleaching the substrate solution. In spite of the degradation of the major colorants, the biological activities of constituents of the extract such as DPPH radical scavenging and tyrosinase inhibition were negligibly affected by the gamma ray radiation up to 20 kGy. The antioxidant activity was 92.7% in control samples and 90.0–92.0% in irradiated samples (2.5–20 kGy), and a slight decrease to 87.5% was observed for gamma ray radiation at 30 kGy. In addition, tyrosinase inhibition activity has also the same pattern; the activity is slightly increased from 50.7% of control to 49.1–52.8% of irradiated samples (2.5–20 kGy) with a 46.8% at 30 kGy.     

Applicability of the Sunna dosimeter for food irradiation control

The quick development concerning the commercial application of food irradiation in the USA recently resulted in growing marketing of irradiated red meat as well as irradiated fresh and dried fruits. These gamma and electron irradiation technologies require specific dosimetry systems for process control. The new version of the Sunna dosimeter has been characterized in gamma, electron and bremsstrahlung radiation fields by measuring the optically stimulated luminescence (osl) at 530 nm both below and above 1 kGy, i.e. for disinfestation and for meat irradiation purposes. No humidity and no significant dose rate effect on the green osl signal was observed. The temperature coefficient was determined from 0°C up to about 40°C and to stabilize the osl signal after irradiation a heat treatment method was introduced. Based on these investigations the Sunna ‘gamma’ film is a suitable candidate for dose control below and above 1 kGy for food irradiation technologies.     

Gamma irradiation of sun-dried apricots (Prunus armeniaca L.) for quality maintenance and quarantine purposes

The study is aimed at the optimization of gamma irradiation treatment of sun-dried apricots for quality maintenance and quarantine purposes. Sun-dried apricots pre-treated with potassium meta-bisulphite (KMS) at 2.5% w/v were procured from progressive apricot grower of district Kargil, Ladakh region of Jammu and Kashmir state. The sun-dried apricots were packed in 250 gauge polyethylene packs and gamma irradiated in the dose range 1.0–3.0 kGy. The gamma irradiated fruit including control was stored under ambient (15±2–25±2 °C, RH 70–80%) conditions and periodically evaluated for physico-chemical, sensory and microbial quality parameters. Radiation treatment at dose levels of 2.5 and 3.0 kGy proved significantly (p≤0.05) beneficial in retention of higher levels of β-carotene, ascorbic acid, total sugars and color values without impairing the taste as perceived by the sensory panel analysists. The above optimized doses retained the β-carotene content of sun-dried apricots to the extent of 71.2% and 72.6% compared to 63.9% in control samples after 18 months of storage. Irradiation treatment facilitated the release of residual sulfur dioxide in KMS pre-treated sun-dried apricots significantly (p≤0.05) below the prescribed limit for dried products. During storage, two-fold decrease in sulfur dioxide content was recorded in irradiated samples (3.0 kGy) as compared to 16.9% in control. The above optimized doses besides maintaining the higher overall acceptability of sun-dried apricots resulted in 5 log reductions in microbial load just after irradiation and 1.0 and 1.3 log reductions in yeast and mold and bacterial count after 18 months of ambient storage.     

Gamma radiation influence on technological characteristics of wheat flour

This study aimed at determining the influence of gamma radiation on technological characteristics of wheat (Triticum sativum) flour and physical properties of pan breads made with this flour. The bread formulation included wheat flour, water, milk, salt, sugar, yeast and butter. The α-amylase activity of wheat flour irradiated with 1, 3 and 9 kGy in a Gammacell 220 (AECL), one day, five days and one month after irradiation was evaluated. Deformation force, height and weight of breads prepared with the irradiated flour were also determined. The enzymatic activity increased—reduction of falling number time—as radiation dose increased, their values being 397 s (0 kGy), 388 s (1 kGy), 343 s (3 kGy) and 293 s (9 kGy) respectively, remaining almost constant over the period of one month. Pan breads prepared with irradiated wheat flour showed increased weight. Texture analysis showed that bread made of irradiated flour presented an increase in maximum deformation force. The results indicate that wheat flour ionizing radiation processing may confer increased enzymatic activity on bread making and depending on the irradiation dose, an increase in weight, height and deformation force parameters of pan breads made of it.     

Effect of gamma irradiation on microbial load,physicochemical and sensory characteristics of soybeans (Glycine max L. Merrill)

Gamma irradiation is highly effective in inactivating microorganisms in various foods and offers a safe alternative method of food decontamination. In the present study, soybeans (Glycine max L. Merrill) were treated with 0, 1.0, 3.0, 5.0 and 10.0 KGy of gamma irradiation. Microbial populations on soybeans, isoflavone, tocopherol contents, raffinose family oligosaccharides, color and sensory properties were evaluated as a function of irradiation dose. The results indicated that gamma irradiation reduced aerobic bacterial and fungal load. Irradiation at the doses applied did not cause any significant change (p>0.05) in the contents of isoflavone of soybeans, but decreased tocopherol contents. The content of key flatulence-producing raffinose family oligosaccharides in irradiated soybeans (10.0 kGy) decreased by 82.1% compared to the control. Sensory analysis showed that the odor of the soybeans was organoleptically acceptable at doses up to 5.0 kGy and no significant differences were observed between irradiated and nonirradiated samples in flavor, texture and color after irradiation.     

Electron beam irradiations of polypropylene syringe barrels and the resulting physical and chemical property changes

Mechanical, thermal, chemical decomposition and electron spin resonance (ESR) methods were used to study electron beam irradiated polypropylene syringe barrels that were irradiated to a total fractionated dose of 0, 20, 40, 60, and 80 kGy (in steps of 20 kGy). Dose mapping was conducted to determine dose to and through the syringe barrel. Analysis of these data indicated that degradation of the polypropylene syringes increased with an increase in electron beam irradiation.     

Effect of high-dose irradiation on quality characteristics of ready-to-eat chicken breast

High-dose (higher than 30 kGy) irradiation has been used to sterilize specific-purposed foods for safe and long-term storage. The objective of this study was to investigate the effect of high-dose irradiation on the quality characteristics of ready-to-eat chicken breast in comparison with those of the low-dose irradiation. Ready-to-eat chicken breast was manufactured, vacuum-packaged, and irradiated at 0, 5, and 40 kGy. The populations of total aerobic bacteria were 4.75 and 2.26 Log CFU/g in the samples irradiated at 0 and 5 kGy, respectively. However, no viable cells were detected in the samples irradiated at 40 kGy. On day 10, bacteria were not detected in the samples irradiated at 40 kGy but the number of bacteria in the samples irradiated at 5 kGy was increased. The pH at day 0 was higher in the samples irradiated at 40 kGy than those at 0 and 5 kGy. The 2-thiobarbituric acid reactive substance (TBARS) values of the samples were not significantly different on day 0. However, on day 10, the TBARS value was significantly higher in the samples irradiated at 40 kGy than those at 0 and 5 kGy. There was no difference in the sensory scores of the samples, except for off-flavor, which was stronger in samples irradiated at 5 and 40 kGy than control. However, no difference in off-flavor between the irradiated ones was observed. After 10 days of storage, only the samples irradiated at 40 kGy showed higher off-flavor score. SPME-GC–MS analysis revealed that 5 kGy of irradiation produced 2-methylbutanal and 3-methylbutanal, which were not present in the control, whereas 40 kGy of irradiation produced hexane, heptane, pentanal, dimethly disulfide, heptanal, and nonanal, which were not detected in the control or the samples irradiated at 5 kGy. However, the amount of compounds such as allyl sulfide and diallyl disulfide decreased significantly in the samples irradiated at 5 kGy and 40 kGy.     

Quality of fresh-cut Iceberg lettuce and spinach irradiated at doses up to 4 kGy

Fresh-cut Iceberg lettuce packaged in modified atmosphere packages and spinach in perforated film bags were irradiated with gamma rays at doses of 0, 1, 2, 3, and 4 kGy. After irradiation, the samples were stored for 14 days at 4 °C. O₂ levels in the packages of fresh-cut Iceberg lettuce decreased and CO₂ levels increased with increasing radiation dose, suggesting that irradiation increased respiration rates of lettuce. Tissue browning of irradiated cut lettuce was less severe than that of non-irradiated, probably due to the lower O₂ levels in the packages. However, samples irradiated at 3 and 4 kGy had lower maximum force and more severe sogginess than the non-irradiated control. In addition, ascorbic acid content of irradiated lettuce was 22–40% lower than the non-irradiated samples after 14 days of storage. The visual appearance of spinach was not affected by irradiation even at a dose of 4 kGy. Consumer acceptance suggested that more people would dislike and would not buy spinach that was treated at 3 and 4 kGy as compared to the non-irradiated sample. Overall, irradiation at doses of 1 and 2 kGy may be employed to enhance microbial safety of fresh-cut Iceberg lettuce and spinach while maintaining quality.     

Evaluation of instant cup noodle,irradiated for immuno-compromised patients

In the present study, initial microbial load of instant cup noodle (ICN) was investigated and gamma irradiation applied to develop immuno-compromised patients food for their safe consumption. The initial microbial population of dried vegetable and meat, and noodle was below the detection limit (1 log CFU/g); however, that of seasoning powder was just above 4 log CFU/g. Moreover, rehydrated-ICN with water at 100 °C still show above 3 log CFU/g of microbial load, which indicates the need for an additional process to control microbial safety of the seasoning powder. The total aerobic bacteria in seasoning powder and rehydrated-ICN could be controlled with 17 kGy gamma irradiation. This result referred 17 kGy gamma irradiation could reach ‘practical sterility’ of ICN. The overall difference in sensory properties between the non-irradiated and irradiated ICN was insignificant. Thus, gamma irradiation could improve the microbial quality of ICN, and reduce the risk of infection posed by the seasoning powder, without any adverse effects on their sensory quality. These results suggest that gamma-irradiated ICN can be used as a snack food for immuno-compromised patients.     

Determination of the changes of antifungal properties of Satureja hortensis,Thymus vulgaris and Thymbra spicata exposed to gamma irradiation

In this research, changes in the antifungal activity of the extract of Satureja hortensis, Thymus vulgaris and Thymbra spicata exposed to gamma irradiation against two aflatoxigenic moulds Aspergillus parasiticus NRRL 2999 and 465 were investigated. The samples of dry plant leaf powder were irradiated with doses of 1.2, 3.0, 5.1 kGy. While the antifungal activity of S. hortensis with 0 and 1.2 kGy dose irradiation against A. parasiticus NRRL 2999 was found to be similar, it decreased with 3.0 and 5.1 kGy irradiation doses (P<0.05). On the contrary, antifungal activity of T. spicata increased until 3.0 kGy and then it decreased with 5.1 kGy irradiation dose (P<0.05). For T. vulgaris, an increase of irradiation dose resulted in a decrease of antifungal activity against aflatoxigenic moulds. This research shows that antifungal properties of some spices can be changed by gamma irradiation.     

Study of the morphology,thermal and mechanical properties of irradiated isotactic polypropylene films

Thin films of isotactic polypropylene (iPP) are of great economical importance and their production is quite challenging due to the need of very fast uniaxial or biaxial expansion. During the expansion, critical problems usually arise, like structure disruption, shear thinning, causing material, energy and time losses. This work aims to study the surface morphology and compare the thermal, mechanical properties of PP films irradiated by gamma ray in an acetylene atmosphere after uniaxial expansion. PP films were made by compression molding at 190 °C with cooling in water at room temperature and irradiated by gamma ray, at (5, 12.5 and 20 kGy) under acetylene atmosphere. After irradiation the samples were submitted to thermal treatment at 90 °C for 1 h and then stretched out at 170 °C using an Instron machine. The surface of PP films, pristine and modified, (i.e., irradiated), was studied using optical microscopy (OM) and scanning electron microscopy (SEM). The changes in morphology, crystallinity and tensile parameters, like yield stress, rupture stress and elongation strain of the PP with irradiation dose were investigated. The results showed some evidences of gel formation due to crosslinking and/or long chain branching induced by radiation.     

Effect of gamma irradiation on the antimicrobial and free radical scavenging activities of Glycyrrhiza glabra root

The efficacy of gamma irradiation as a method of decontamination for food and herbal materials is well established. In the present study, Glycyrrhiza glabra roots were irradiated at doses 5, 10, 15, 20 and 25 kGy in a cobalt-60 irradiator. The irradiated and un-irradiated control samples were evaluated for phenolic contents, antimicrobial activities and DPPH scavenging properties. The result of the present study showed that radiation treatment up to 20 kGy does not affect the antifungal and antibacterial activity of the plant. While sample irradiated at 25 kGy does showed changes in the antibacterial activity against some selected pathogens. No significant differences in the phenolic contents were observed for control and samples irradiated at 5, 10 and 15 kGy radiation doses. However, phenolic contents increased in samples treated with 20 and 25 kGy doses. The DPPH scavenging activity significantly (p<0.05) increased in all irradiated samples of the plant.