Effect of irradiation on the microbiological status and flavouring materials of selected spices

Spices from Egyptian local markets were irradiated with different recommended doses (0, 5, 10, 20 and 30 kGy). The spices tested included dried leaves of marjoram (Majorana hortensis Moench), rhizomes of ginger (Zingiber officinale Roscoe) and powdered hot pepper (Capsicum annum L.). The study included the isolation and identification of micro-organisms in spices following their irradiation, as well as gas Chromatographic (GLC) chemical analysis for the presence and structure of volatile oils, pungent and pigment materials. The results showed that hot pepper was contaminated more (9.2 x 10⁵/g) than marjoram (4.2 x 10³/g) and ginger (14.3 x 10³/g) with respect to total aerobic bacterial content. The total contents of moulds were 4.8 x 10³/g, 5.7 x 10³/g and 19 x 10³/g in the same spices, respectively, but the pathogenic moulds and bacterial strains differed according to the type of spice. Irradiation at 10, 20 and 30 kGy caused complete elimination of micro-organisms, whereas 5 kGy was less effective. With the GLC method chosen 18 and 50 compounds could be detected in the extracts of marjoram and ginger, respectively; -terpinen and zingiberen being the major compounds in marjoram and ginger, respectively. A noticeable reduction was observed in the amount of terpenes present in irradiated marjoram; they were converted to monoterpe-nesalcohols. Ginger was more sensitive to irradiation, especially at high doses, but moderate changes were detected at low doses (5 and 10 kGy). A slight, but significant effect on the capsaicin (pungent compound) in hot pepper was observed following irradiation, whereas no changes in total pigments resulted at any dose. These results prove that 10 kGy is a sufficiently high dose to eliminate the microorganisms in spices, causing only slight changes in the flavouring materials.     

Degradation of the natural mutagenic compound safrole in spices by cooking and irradiation

Safrole was determined using gas-liquid chromatography in some common spices as star anise, cumin, black pepper and ginger. Safrole concentration in these spices was 9325, 3432, 955 and 500 mg · kg^?1, respectively. Black pepper was chosen to use in the following experiments. Using Ames-test with Salmonella TA 98 and TA 100 proved high cytotoxic effects due to pure safrole and black pepper volatile oil in both of them. The degradation of safrole was obvious after drying of the washed seeds of black pepper especially at 70 °C for 30 min or with sun-drying. Also, high irradiation doses (20 and 30 kGy) caused high degradation of more than 90% of the initial toxic concentration in black pepper. Whereas, microwave caused same effects at 75 s, but unfortunately, the powder was burned due to moisture absence. Boiling whole seeds or powder of black pepper during cooking for few minutes (1-5 min) were more efficient in decreasing safrole content. Finally, these results proved that the mutagenicity of some spices due to presence of safrole can be destructed during drying of the washed seeds or during cooking either with or without any additional treatment as irradiation. But irradiation of these spices became more necessary for using in some food industries as milk products to get more safe for human consumption.     

Effect of γ-irradiation on antioxidant activity of black pepper (Piper nigrum L.)

Antioxidant activity and EPR investigations of irradiated ground black pepper (Piper nigrum L.) were evaluated. The black pepper was exposed to γ-irradiation at doses from 5 to 30 kGy. The effect of irradiation on antioxidant properties of black pepper extracts was investigated by radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, by determination of reducing power and content of thiobarbituric acid-reactive substances. Some significant changes were observed in creation of thiobarbituric acid-reactive substances (TBARS). Difference between non-irradiated and irradiated samples at the legal European limit dose of 10 kGy reached, on average, 23% and, at the Food and Drug Administration (FDA) 30 kGy limit, 33%. Irradiation affected significantly the DPPH radical-scavenging activity and reducing power of ground black pepper extracts. The γ-radiation treatment of ground black pepper samples observed by EPR, resulted in the production of three paramagnetic species (GI–GIII) characterized by different origin, thermal behaviour and stability. The axially symmetric EPR resonances, GI and GII, were assigned to the carbohydrate radical structures. The spin Hamiltonian parameters of GIII possessed the characteristic features of “cellulosic” radical species. The EPR measurements, performed 20 weeks after the radiation process, confirmed that temperature increase from 298 to 353 K, caused significant decrease of integral EPR signal intensity for γ-irradiated samples (∼40%), compared to the reference (non-irradiated) ground black pepper, where only 13% drop was found. Significant correlation between EPR and thiobarbituric acid methods was assessed by study of antioxidant activity changes in relation to irradiation doses and also in the case of spice storage, between EPR and reducing power methods.     

Assessment of Microbiological Quality of Some Gamma Irradiated Indian Spices

Irradiated (10 kGy) and unirradiated pre-packed whole and ground spices including black pepper, red chilli, and turmeric were examined by six different laboratories for microbiological quality. No colony forming units (CFU) were reported in the largest quantity of irradiated spices used in the study by three out of six laboratories. The other three laboratories reported counts ranging between 0–90 CFU/g in irradiated samples. None of the six laboratories reported the presence of E. coli or B. cereus in the spices exposed to gamma irradiation. These data suggest that a standard plate count of 0–100 CFU/g and a count of zero CFU/g for E. coli and B. cereus be fixed for spices exposed to a 10 kGy dose of gamma rays.     

RADIATION STERILIZATION OF RED CHILI PEPPER (CAPSICUM FRUTESCENS)

The effect of radapertization using ⁶⁰Co gamma radiation on the chemical and organoleptic properties of ground and whole dry pungent red pepper has been investigated. The fungal population was eliminated with a dose of 7.5 kGy and a dose of 10 kGy was required to radapertize the samples. Irradiation up to 10 kGy did not produce any significant (P > 0.05) changes in the contents of capsaicin and carbohydrate. Oleoresin content was significantly (P < 0.05) increased from 24.45 to 31.61% and lipid from 16.80 to 19.30%. The observed effect on apparent oleoresin and lipid contents was due to enhanced extractability. Storage time had no effect on the sensory properties of the spice but rather enhanced microbial load reduction in the medium dose (5.0 and 7.5 kGy) treated samples. A dose of 10 kGy has been certified to pose no health hazard to humans; hence decontamination of red pepper with up to 10 kGy gamma radiation does not require any further toxicological study and is therefore recommended.     

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.     

Effects of gamma irradiation on aflatoxins

Summary The effects of gamma irradiation on a mixture of aflatoxins B₁, B₂, G₁, G₂ were studied. Standard solutions of A and B were irradiated at 5, 10, and 20 kGy in a solution of water/DMSO (9+1, v/ v) by using a¹³⁷Cs source. The control (0 kGy) and irradiated samples were subjected to RP-HPLC analyses with methanol/water (4+5, v/v) as the mobile phase. Aflatoxin B₁ (AFB₁) was the most radio-sensitive of the four compounds. The radiosensitivity of the other aflatoxins, was in increasing order: G₂, B₂, G₁. Only about 5% of AFB₁ remained after irradiation of solution A at 5 kGy. When the concentration of solution B was increased two-fold, trace amounts of AFB₁ remained after irradiation doses of 10 and 20 kGy. Irradiation was found to be suitable for the destruction of aflatoxins in solution.

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Einfluß von Gammastrahlung auf die Aflatoxine

Zusammenfassung Der EinfluB von -Strahlen auf die Aflatoxinmischung B₁, B₂, G₁ und G₂ wurde untersucht. Standardlösungen A und B wurden mit -Strahlung von 5; 10; bzw. 20 kGy in der Lösung von Wasser/DMSO (9+1, v/v) unter Verwendung einer¹³⁷Cs-Quelle bestrahlt. Kontroll(0 kGy)-und bestrahlte Proben wurden der RP-HPLC Analyse unter Verwendung von Methanol/Wasser (4+5, v/v) als mobile Phase unterworfen. Aflatoxin B₁ (AFB₁) war die strahlenempfindlichste von den vier, die Strahlenempfindlichkeit der anderen Aflatoxine nahm bei 5 kGy in der Reihenfolge: G₂, B₂, G₁ zu. Nur ca. 5% von AFB₁ ist nach der Bestrahlung üibriggeblie-ben. Wenn sich die Konzentration zweifach erhöht (Lösung B), ist von AFB₁ nur eine Spur nach der 10 kGy- und 20 kGy-Bestrahlung übriggeblieben. Es wurde gefunden, daß die Bestrahlung zur Zerstörung der Aflatoxine in der Lösung geeignet ist.

     

The effects of gamma-irradiation on some pure aroma compounds of spices

Summary Chemical changes due to gamma-irradiation were investigated in 11 pure aroma compounds typically found in spices. Samples were irradiated with doses of 0, 10, and 50 kGy. The irradiation source was⁶⁰Co. Irradiated samples and unirradiated controls were analyzed by gas chromatography alone and coupled with mass spectrometry. Significant changes due to the irradiation occurred only in (±)-linalool and-terpineol, which are typical components of, for example, coriander and bay leaf. Their total amounts decreased by about 4–13% and some minor peaks increased as a result of irradiation. However, different results may be obtained when the spices themselves are irradiated.

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Auswirkungen der -Strahlung auf einige Gewürz-Aromastoffe

Zusammenfassung An elf gewürztypischen Aromastoffen wurden die von der-Strahlung verursachten Veränderungen untersucht. Die Proben wurden unter Verwendung von⁶⁰Co als Strahlungsquelle mit Dosen von 0, 10 und 50 kGy bestrahlt. Die bestrahlten und unbestrahlten Proben wurden gaschromatographisch (GC) und GC-massenspektrometrisch untersucht. Erhebliche Veränderungen zeigten sich nur beim (±)-Linalool und beim-Terpineol, die zum Beispiel für die ätherischen Öle von Koriander und Lorbeerblatt typisch sind. Die Peaks dieser Aromastoffe reduzierten sich um 4–13%, und dem entsprechend waren einige kleinere Peaks zu beobachten. Es kann dennoch zu unterschiedlichen Resultaten kommen, wenn Gewürze bestrahlt werden.

     

Alteration of apparent viscosity of irradiated pepper — a tool for semi-quantitative estimation of irradiation dose

The feasibility of using apparent viscosity (_a) as a method for detecting the occurrence of previous irradiation of pepper was studied. Apparent viscosity of heat-treated suspensions of white and black pepper, nonirradiated or irradiated with different doses of ionising radiation (), was measured under different shear rates. Results of previous research were therefore expanded and their usefulness examined; low shear rate conditions were found to be preferable for the detection and semi-quantitative evaluation of irradiation doses. The experimental methodology for semi-quantitative estimation was developed and its scope and limitations are presented.     

Effect of gamma irradiation and sodium hydroxide treatment on the debittering of olive (Olea europaea) fruits

The effect of gamma irradiation and sodium hydroxide (NaOH) treatment on the debittering of olive (Olea europaea, var Surrany) fruits was investigated. Fruits were treated with 1, 2 or 3 kGy of gamma irradiation at a dose rate of 669 Gy h^?1. Irradiated and unirradiated fruits were processed with NaOH solution (11 g l^?1) for 3 or 6 h and washed once per day for 3 days. The fruits were then immersed in brine (56 g l^?1 sodium chloride) and stored for 12 months at room temperature. Dissolved organic and inorganic solids, Na⁺, K⁺ and Ca²⁺ contents, pH and electrical conductivity values were determined in the debittering solutions (lye, rinse and washing waters) and brines. Gamma irradiation significantly (p < 0.05) increased the dissolved organic and inorganic solids and the Na⁺ and K⁺ concentrations in the debittering solutions when the fruits were treated with NaOH for 3 h. On the other hand, gamma irradiation had no significant effect on these parameters, except for an increase in K⁺ concentration, when using NaOH solution for 6 h. Gamma irradiation with NaOH treatment for 3 h decreased the concentration of Ca²⁺ in the debittering solutions, whereas irradiation and treatment with NaOH solution for 6 h increased its concentration. © 2003 Society of Chemical Industry     

Effects of <Superscript>60</Superscript>Co-γ and Electron Beam Irradiation on Storage Quality of <Emphasis Type="Italic">Panax ginseng</Emphasis>

Fresh ginseng was irradiated with ⁶⁰Co-γ or an electron beam at the dose of 2 and 4 kGy and stored at 2 °C. The quality of ginseng was evaluated after 60 and 120 days. Results suggest that when the storage time was 120 days, 2 kGy EI-treated ginseng had the lowest decay rate. During the 2 storage periods, the amounts of most of 9 ginsenosides decreased with an increase in the irradiation dose. The total saponin content of both ⁶⁰Co-γ-irradiated and EI-treated samples decreased with an increase in the irradiation dose. Significant (P <?0.05) upregulation of total polysaccharide content was observed in the 4 kGy EI samples after storage. Samples irradiated at 2 or 4 kGy by electron beam irradiation had the highest concentration of total saponin and ginseng polysaccharides, respectively. Levels of most of 17 amino acids decreased with the increasing irradiation dose. Exposure to irradiation doses up to 4 kGy affected the amino acid content of fresh ginseng. Ginseng irradiated at 4 kGy by ⁶⁰Co-γ irradiation and stored for 120 days had a significantly higher activity of superoxide dismutase (P <?0.05). A significant difference was observed in the total concentration of nucleosides and nucleobases between irradiated and un-irradiated ginseng samples (P <?0.05). These data suggest that the combination of a lower irradiation dose and low temperature is an optimal condition for extending the shelf-life of fresh ginseng without detriment to its ingredients.     

Comparing effects of washing,thermal treatments and gamma irradiation on quality of spieces

Selected five spices were treated with simple natural methods as washing with pure tap water then drying at room temperature, thermal treatment at 70 °C/15 minutes besides irradiation with 5.0 and 10 kGy. The evaluation of the used treatments efficiency depends on microbiological and chemical studies. The results show that untreated samples were highly contaminated with pathogenic and toxigenic microbes. Gamma irradiation was effective in decontamination especially 10 kGy but caused losses in major components of flavour as anethol, mechavicul, anise-aldehyde in anise, β-pinen and cineol in black pepper. Also, irradiation induced the changes of monoterpene hydrocarbons to alcohol terpens in essential oils of black pepper. Thermal treatment reduced the microbial count and pathogenic microbes to the same safe range as an irradiation dose of 5 kGy. Thermal techniques improved the flavour, as anisealdehyde in fennel, anethol in anise and B-pinen in black pepper. Washing of the spices removed slightly the microbes but revealed no changes in flavour except the anise flavour which increased markedly. Finally, thermal and washing treatments could be recommended as simple natural techniques to produce spices with good flavour and in safe range for hygienic quality comparing with sterilized dose 10 kGy.     

Effects of irradiation and drying on volatile components of fresh shiitake (Lentinus edodesSing)

Fresh shiitake (Lentinus edodes Sing) was irradiated with doses of 0·5, 1 and 2 kGy using ⁶⁰Co. Effects of γ-irradiation and drying on the volatile composition of shiitake were studied by gas chromatography (GC) and GC–mass spectrometry. Irradiation above 1·0 kGy could inhibit the growth and mould decay of fresh shiitakes after harvesting. Irradiation with 2 kGy increased the eight-carbon volatile components of fresh shiitake. Treatment at 1 kGy irradiation of fresh shiitake produced some new volatile compounds in the dry product, such as methylethyl disulphide, sulphinylbis methane, methyl(methylthio)ethyl disulphide and N-(3-methylbutyl) acetamide. The eight-carbon compounds mostly disappeared after drying. The amount of sulphur-containing volatile compounds in dried shiitake became lower during irradiation. Irradiation with doses of 1 or 2 kGy of fresh shiitake did not increase the volatile content of shiitake after drying. © 1998 SCI.     

Detection of 5-hydroxymethyl-2-methyl-3(2H)-furanone and of α-dicarbonyl compounds in reaction mixtures of hexoses and pentoses with different amines

Summary In reaction mixtures of hexoses with primary amines, heated at pH 5 and 7, distinctly higher amounts of fragmentation products are formed in the upper pH range. To estimate the amount of fragmentation, all-dicarbonyl compounds which react witho-phenylenediamine to quinoxaline derivatives were recorded. For the first time the-dicarbonyl intermediates in a pentose amine reaction mixture were determined and the formation of 2,3,4-pentantrione was detected. The 1,4-dideoxyosone was formed from hexoses and pentoses in higher yields in the presence of-amino acids, i.e. when Strecker degradation could take place. 5-Hydroxymethyl-2-methyl-3(2H)-furanone was identified as a new hexose product of Strecker degradation, and its structure established unequivocally by independent synthesis as well as by¹H and¹³C NMR.

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Nachweis von 5-Hydroxymethyl-2-methyl-3(2H)-furanon und von -Dicarbonylverbindungen in Reaktionsgemischen von Hexosen und Pentosen mit verschiedenen Aminen

Zusammenfassung In Reaktionsgemischen von Hexosen mit priären Aminen, die bei pH 5 und pH 7 erhitzt wurden, findet man im höheren pH-Bereich wesentlich größere Mengen an Fragmentierungsprodukten. Zur Abschätzung des Fragmentierungsanteils werden alle-Di-carbonylverbindungen herangezogen, die mito-Pheny-lendiamin im Umsetzungsgemisch zu Chinoxalinen reagieren. Erstmals werden die-Dicarbonyl-Zwischenstu-fen in Pentose-Amin-Reaktionsans ätzen untersucht und die Bildung des 2,3,4-Pentantrions nachgewiesen. Interessant ist, daß bei Hexosen und Pentosen das 1,4-Didesoxyoson in wesentlich größeren Mengen entsteht, wenn -Aminosäuren an der Umsetzung beteiligt sind, d.h. wenn ein Strecker-Abbau stattfinden kann. 5-Hydroxymethyl-2-methyl-3(2H)-furanon wird als neues Hexoseprodukt des Strecker-Abbaus identifiziert. Die Absicherung der Struktur erfolgt durch Synthese und NMR-Un-tersuchungen.

     

Efficacy of Integrated Treatment of UV light and Low‐Dose Gamma Irradiation on Inactivation of Escherichia coli O157:H7 and Salmonella enterica on Grape Tomatoes

The study evaluated the efficacy of integrated ultraviolet‐C light (UVC) and low‐dose gamma irradiation treatments to inactivate mixed strains of Escherichia coli O157:H7 and Salmonella enterica on inoculated whole grape tomatoes. A mixed bacterial cocktail composed of a 3 strain mixture of E. coli O157:H7 (C9490, E02128, and F00475) and a 3 serotype mixture of S. enterica (S. Montevideo G4639, S. Newport H1275, and S. Stanley H0558) was used based on their association with produce‐related outbreaks. Spot inoculation (50 to 100 μmL) on tomato surfaces was performed to achieve a population of appropriately 10^7–8 CFU/tomato. Inoculated tomatoes were subjected to UVC (253.7 nm) dose of 0.6 kJ/m² followed by 4 different low doses of gamma irradiations (0.1 kGy, 0.25 kGy, 0.5 kGy, 0.75 kGy). The fate of background microflora (mesophilic aerobic) including mold and yeast counts were also determined during storage at 5 °C over 21 d. Integrated treatment significantly (P < 0.05) reduced the population of target pathogens. Results indicate about 3.4 ± 0.3 and 3.0 ± 0.1 log CFU reduction of E. coli O157:H7 and S. enterica, respectively, per tomato with UVC (0.6 kJ/m²) and 0.25 kGy irradiation. More than a 4 log and higher reduction (>5 log) per fruit was accomplished by combined UVC treatment with 0.5 kGy and 0.75 kGy irradiation, respectively, for all tested pathogens. Furthermore, the combined treatment significantly (P < 0.05) reduced the native microflora compared to the control during storage. The data suggest efficacious treatment strategy for produce indicating 5 or higher log reduction which is consistent with the recommendations of the Natl. Advisory Committee on Microbiological Criteria for Foods.     

Synthesis and Characterization of Nano‐Encapsulated Black Pepper Oleoresin using Hydroxypropyl Beta‐Cyclodextrin for Antioxidant and Antimicrobial Applications

Previous studies have reported antimicrobial and antioxidant activity of black pepper oleoresin which is associated to its phenolic compounds and piperine. The ability of cyclodextrins to form an inclusion complex with a guest molecule could improve black pepper oleoresin application, bioavailability, and stability in foods. Hydroxypropyl beta‐cyclodextrin (HPBCD) inclusion complex with black pepper olereosin were synthesized using the kneading method and characterized for its physico‐chemical properties and its antioxidant and antimicrobial activities. Inclusion complex size was 103.9 ± 7.6 nm and indicated to be a polydisperse system. The entrapment efficiency was 78.3 ± 3.6%, which suggests that other constituents in black pepper oleoresin have higher affinities for HPBCD than piperine (major compound in black pepper oleoresin). Thermograms showed the disappearance of oxidation peaks of black pepper oleoresin, proving complex formation with HPBCD. Phase solubility results indicated 1:1 stoichiometric inclusion complex formation and an increase of black pepper oleoresin aqueous solubility with HPBCD concentration. Nano‐encapsulation with HPBCD did not affect (P > 0.05) total phenolic content; however, it enhanced (P < 0.05) black pepper oleoresin antioxidant activity. Black pepper oleoresin and its inclusion complex were analyzed for their antimicrobial activity against Escherichia coli K12 and Salmonella enterica serovar Typhimurium LT2. Both free and encapsulated black pepper oleoresin effectively inhibited bacterial growth within the concentration range tested. Black pepper oleoresin encapsulated in HPBCD was able to inhibit Salmonella at lower (P < 0.05) concentrations than its corresponding free extract. Therefore, black pepper oleoresin‐HPBCD nanocapsules could have important applications in the food industry as antimicrobial and antioxidant system.     

Effects of gamma irradiation on physical and chemical properties of chickpeas (Cicer arietinum)

Changes in the physical and chemical properties of chickpeas gamma irradiated with ⁶⁰Co at doses of 0–50 kGy were investigated. Irradiation between 0 and 20 kGy had no significant effect on the hydration capacity of the chickpeas; however, increasing the dose from 20 to 50 kGy significantly decreased the hydration capacity owing to leaching of soluble compounds from the cotyledon to the water. There was an improvement in cooking quality (defined as degree of softness) with increased irradiation. Gelatinisation properties of the starch (measured with a Rapid Visco‐Analyser) exhibited a deterioration with increasing irradiation dose, while reversed phase HPLC identified a sequential decrease in low‐molecular‐weight protein composition with increasing irradiation dose. © 2002 Society of Chemical Industry     

Changes in colour and antioxidant activities of Hizikia fusiformis cooking drips by gamma irradiation

To utilize the cooking drips produced during the seaweed drying process, the effect of gamma irradiation on microbial contamination, colour, and antioxidant activities of Hizikia fusiformis cooking drips (HCD) was investigated. A two log cycles reduction of total aerobic bacteria and yeast and moulds counts was obtained irradiating HCD at 1 kGy. The Hunter L^∗ value of the HCD ethanol extract was increased by the gamma irradiation treatment, but the a^∗ and b^∗ values decreased upon irradiation depending on the absorbed dose. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging and β-carotene bleaching activities of the HCD extracts increased as a result of gamma irradiation, which was rationalized by the observed increase in polyphenolic compounds content. These results suggest that wasted cooking drips can be used as a functional component by the food and cosmetic industries if the irradiation technology were applied.     

Gamma irradiation of air-dried olive leaves: Effective decontamination and impact on the antioxidative properties and on phenolic compounds

Olive leaves are commercialized for their antioxidative value due to their valuable phenolic compounds. The present study aimed to evaluate the effect of gamma irradiation on microbial load, on antioxidative properties and on phenolic compounds of air-dried olive leaves. Irradiation was applied up to 25 kGy (5 kGy intervals) to powdered and intact samples. Total aerobic bacteria, yeast and mold, and lactic acid bacteria were counted after gamma irradiation. Decontamination was obtained at 20 kGy. The radioresistance of microbial population was high with D₁₀ values between 9.74 and 25.12 kGy. Besides, gamma irradiation up to 25 kGy was found to maintain the antioxidant capacity, molecular mass distribution of polyphenolics, total phenolics, ortho-diphenols, flavonoids, oleuropein, verbascoside and rutin contents.     

Effects of γ-irradiation on the flavour of dry shiitake (lentinus edodes sing)

Dry shiitake (Lentinus edodes Sing) was irradiated with doses of 5 and 10 kGy using ⁶⁰Co. The total volatile compounds were decreased by more than 50%. Irradiation increased the concentrations of some minor volatile compounds, such as 3-methyl-2-butanol and I-hexanol. However, the major flavour compounds including eight-carbon and sulphur-containing compounds were significantly reduced. The ratio of the eight-carbon compounds, such as 3-octanone, 3-octanol and 1-octen-3-ol, to total volatiles decreased from 72% in the control to 21% in the 10 kGy irradiated samples. The unidentified compounds which may have been formed by decomposition or polymerization following irradiation of precursors need to be studied in greater depth.