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.     

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).     

Analysis of volatile organic compounds of ‘Fuji’ apples following electron beam irradiation and storage

The volatile organic compounds of non-irradiated and electron-beam irradiated ‘Fuji’ apples (Malus domestica Borkh.) at 0, 0.5, and 1 kGy were isolated through simultaneous distillation extractions and analyzed using gas chromatograph–mass spectrometry. A total of 53 volatile organic compounds were characterized in 0 and 1 kGy irradiated samples, whereas two more compounds related to ketone and terpenoid group were identified in 0.5 kGy irradiated samples. The contents of volatile compounds were 24.33, 36.49, and 35.28 mg/kg in 0, 0.5, and 1 kGy irradiated samples, respectively. The major compounds identified were butanol, hexanal, [E]-2-hexenal, and hexanol in all samples. The relative content of alcohol increased after 30 days of storage in all samples, whereas that of aldehyde decreased. Although the contents of some volatile compounds were changed by electron-beam irradiation, the total yield and major flavor compounds of irradiated ‘Fuji’ apples were similar to, or even greater than, those of the control. Therefore, the application of e-beam irradiation if required for microbial decontamination of ‘Fuji’ apples is an acceptable method as it does not bring about any major quantitative changes of volatile organic compounds.     

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.     

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.     

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.     

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.     

Gas chromatographic/mass spectrometric and microbiological analyses on irradiated chicken

Ionizing radiation is widely used as treatment technique for food preservation. It involves among others reduction of microbial contamination, disinfestations, sprout inhibition and extension of shelf life of food. However, the commercialization of irradiated food requires the availability of reliable methods to identify irradiated foodstuffs. In this paper, we present results on the application to irradiated chicken of this method, based on the detection, in muscle and skin samples, of the peaks of ions 98 Da and 112 Da, in a ratio approximately 4:1, typical of radiation induced 2-dodecylcyclobutanones (2-DCB). Aim of the work was also to study the time stability of the measured parameters in samples irradiated at 3 and 5 kGy, and to verify the efficacy of the treatment from a microbiological point of view. Our results show that, one month after irradiation at 3 kGy, the method is suitable using the skin but not the muscle, while the measured parameters are detectable in both samples irradiated at 5 kGy. The microbial population was substantially reduced even at 3 kGy.     

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.     

Shelf-life extension of convenience meat products sold in Indian supermarkets by radiation processing

A variety of ready-to-cook meat products available in Indian supermarkets (mutton mince, chicken mince, chicken chunks, and chicken legs) were studied. The samples were irradiated (2.5 kGy), or left untreated as control, and stored at 0–3 °C for up to 21 days. The effect of irradiation on the microbiological, chemical, and sensory properties was evaluated at intervals during the storage period. Irradiated samples had a longer shelf-life at 0–3 °C compared with the corresponding non-irradiated samples. Fecal coliforms were eliminated by irradiation treatment. Radiation processed samples had lower counts of Staphylococcus spp. There were no significant organoleptic changes in irradiated samples stored at chilled temperatures.     

Application of gamma irradiation for inactivation of three pathogenic bacteria inoculated into meatballs

In this research, the effect of gamma irradiation on the inactivation of Escherichia coli O157:H7 (ATCC 33150), Staphylococcus aureus (ATCC 2392) and Salmonella typhimurium (NRRL 4463) inoculated into Tekirdag meatballs was investigated. The meatball samples were inoculated with pathogens and irradiated at the absorbed doses of 1, 2.2, 3.2, 4.5 and 5.2 kGy. E. coli O157:H7 count in 1 kGy irradiated meatballs stored in the refrigerator for 7 days was detected to be 4 log cfu/g lower than the count in nonirradiated samples (p<0.05). S. aureus counts were decreased to 4 log cfu/g after being exposed to irradiation at a dose of 1 kGy. Although it was ineffective on elimination of S. typhimurium, irradiation at a dose of 3.2 kGy reduced E. coli O157:H7 and S. aureus counts under detectable values in the meatballs. However, none of the test organisms were detected in the samples after irradiation with 4.5 kGy doses.     

Sensory evaluation by gamma radiation effect on protein allergen of laying hen eggs

Although considered the most complete food and nutritionally shown to be part of a healthy diet, the egg is the source of many eating disorders, especially for infants. Irradiation has been used in studies not only as a means of microbiological control, but also on its structural action in the substances molecules and has been used to reduce the allergenic effects. The aim of this study was to evaluate the sensory effects of Co⁶⁰ gamma radiation on proteins, enabling the acceptability of allergy food for genetically intolerant people. Eggs commercial fresh and freeze-dried and subjected to gamma irradiation by Co⁶⁰ source at doses 0 (control), 10 kGy; 20 kGy and 30 kGy and rates of doses of 19.4 kGy/h and 31.8 kGy/h. Acceptability test was used by the hedonic scale, since it is necessary to know the “affective status” of consumers for the product, implying a preference, i.e. the most preferred samples are the most accepted and vice versa. The samples were presented as the habit of consumption (cooked) to a group of 41 adults panelists of both gender, aged from 21 to 40 years, and served under complete block design balanced with respect to the order of presentation. The evaluated attributes was flavor, appearance and overall acceptability. In general, for boiled eggs and freeze-dried, it was observed that the control sample was the most acceptable, followed by the sample irradiated with 10 kGy in both dose rates. In addition, panelists presented in testimony that they found interesting changes due to irradiation; also said they would not buy the product because of the marked change in appearance and smell, which at one point he ended up in disgust and detract from sales of the product, but they would buy irradiated with 10 kGy in both dose rate and dose of 20 kGy at a dose rate of 19.4 kGy/h.     

Evaluation of γ-radiation on oolong tea odor volatiles

The aim of this study was to evaluate the gamma radiation effects on odor volatiles in oolong tea at doses of 0, 5, 10, 15 and 20 kGy. The volatile organic compounds were extracted by hydrodistillation and analyzed by GC/MS. The irradiation has a large influence on oolong tea odor profile, once it was identified 40% of new compounds after this process, the 5 kGy and 20 kGy were the doses that degraded more volatiles found naturally in this kind of tea and the dose of 10 kGy was the dose that formed more new compounds. Statistical difference was found between the 5 kGy and 15 kGy volatile profiles, however the sensorial analysis showed that the irradiation at dose up 20 kGy did not interfere on consumer perception.     

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.     

Effects of gamma irradiation on chemical,microbial quality and shelf life of shrimp

In the present study the combined effect of gamma irradiation (1, 3 and 5 kGy) and storage at two temperatures: refrigeration (+4 °C) and frozen (?18 °C), on the shelf-life extension of fresh shrimp meat was investigated. The study was based on microbiological and physicochemical changes occuring in the shrimp samples. Total volatile base nitrogen values and trimethylamine values for irradiated shrimp samples were significantly lower than non-irradiated samples at both storage temperatures, and the rate of decrease was more pronounced in samples irradiated at the higher dose (p<0.05). Thiobarbituric acid values for irradiated shrimp samples were significantly higher than non-irradiated samples at both storage temperatures (p<0.05). pH values of shrimp samples were affected significantly by both irradiating dose and storage temperatures (p<0.05). Microbial counts for non-irradiated shrimp samples were higher than the respective irradiated samples at both storage temperatures (p<0.05). The results revealed that irradiation at high dose (5 kGy) might enhance lipid oxidation, although the growth of microorganisms and protein oxidation was inhibited.     

The effects of ionizing irradiation on Salmonella inoculated on almonds and changes in sensory properties

The goal of this study was to test the efficacy of irradiation on destroying Salmonella on raw almonds and evaluating the resultant sensory changes in the almonds. Raw almonds inoculated with various strains of Salmonella were irradiated at 5 dose levels up to 3 kGy and the D value was determined. The strain SEPT30 was the most resistant strain with a D value of 1.25 kGy indicating that a 4 log CFU/g reduction would require a dose of 5.0 kGy. Irradiation at 2.98 and 5.25 kGy induced significant sensory changes in almond nuts as manifested by intensity of chemical/metallic/rancid flavor ranked by a trained panel. A consumer panel found that samples treated with 5.25 kGy irradiation rendered the almonds unacceptable. Thus, irradiation by itself is unlikely to be a feasible method to eliminate Salmonella from raw almonds.     

Analysis and identification of irradiated Spirulina powder by a three-step infrared macro-fingerprint spectroscopy

A three-step infrared (IR) macro-fingerprint method combining conventional IR spectra, and the secondary derivative spectra with two-dimensional infrared correlation spectroscopy (2D-IR), was developed to analyze Spirulina powder before and after gamma irradiation. In the IR spectra, most of the absorption peaks of samples irradiated at 1, 2.7, 6, and 10.4 kGy had lower intensities than the non-irradiated ones, whereas peaks at 1152, 1078, and 1051 cm⁻¹ were slightly enhanced with irradiation at 2.7, 6, and 10.4 kGy. Their second derivative spectra amplified the differences and revealed that irradiation affected the C=O band of carboxylic acid and esters, and the N–H band of proteins. The peaks at 1746 and 1741 cm⁻¹, and those at 1730 and 1725  cm⁻¹ became two broad peaks. Meanwhile, the three sharp peaks at 1548 cm⁻¹, 1544 cm⁻¹ and 1536 cm⁻¹ changed to two broad peaks at around 1547 and 1534 cm⁻¹ after irradiation at doses higher than 1 kGy. The characteristic IR bands from 1700 cm⁻¹ to 1600 cm⁻¹, which represent the C=O band in proteins, also have different shapes and intensities after irradiation. The finding indicated that irradiation affected the secondary structures of protein which was confirmed by curve fitting results. During the process of increasing the temperature from 50 to 210 °C, the ratio of amide I to II in absorption intensities in the 2D-IR spectra of the irradiated samples varied with different response for different samples. Saccharides in Spirulina powder had a higher thermostability than proteins, but the autopeaks of irradiated samples did show differences from the non-irradiated sample. The intensity of autopeaks at 1012 cm⁻¹ increased dramatically in the irradiated samples while that of peaks at 1053, 1071, and 1083 cm⁻¹ decreased after irradiation. Based on the three-step IR macro-fingerprint method, irradiated Spirulina powder samples were successfully and fast identified and discriminated.     

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 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.