Effects of radiation dose and dose rate on alginate and the use of radiation degraded alginate for peanut.

Aqueous solutions of alginate (4 %) with or without hydrogen peroxide (0-2 % H2O2) were irradiated under a gamma Co-60 source. The effect of dose rate on the radiation scission yield (Gs) of resulting irradiated alginate was determined. At the dose of 20 kGy, the G(s) value of irradiated alginate decreased with the increase dose rate, suggesting that the irradiation at a suitable dose rate could further improve the radiation chemical yield of degradation. For the alginate irradiated at the same dose rate, G(s) value increased with the increase of H2O2 concentration. Average molecular weight (Mw) and polydispersity index (PI) of irradiated alginate rapidly decreased with the increase in dose and further decreased by addition of H2O2. The oligoalginate with Mw ~ 9800 g/mol was obtained by radiation degradation of 4 % alginate solution containing 2 % H2O2 at dose of 20 kGy. Radiation scission of glycoside bonds and formation of carbonyl groups (C=O) were indicated in UV and FTIR spectra of irradiated alginate. Peanut seedlings were fertilized with alginate and oligoalginate solutions, and the results showed that all growth parameters of the treated plants were better than those of the control. Furthermore, the oligoalginate prepared by gamma irradiation can be applied as a plant growth promoter for agriculture production.

ScRNA-seq reveals dark- and light-induced differentially expressed gene atlases of seedling leaves in Arachis hypogaea L.

Although the regulatory mechanisms of dark and light-induced plant morphogenesis have been broadly investigated, the biological process in peanuts has not been systematically explored on single-cell resolution. Herein, 10 cell clusters were characterized using scRNA-seq-identified marker genes, based on 13 409 and 11 296 single cells from 1-week-old peanut seedling leaves grown under dark and light conditions. 6104 genes and 50 transcription factors (TFs) displayed significant expression patterns in distinct cell clusters, which provided gene resources for profiling dark/light-induced candidate genes. Further pseudo-time trajectory and cell cycle evidence supported that dark repressed the cell division and perturbed normal cell cycle, especially the PORA abundances correlated with 11 TFs highly enriched in mesophyll to restrict the chlorophyllide synthesis. Additionally, light repressed the epidermis cell developmental trajectory extending by inhibiting the growth hormone pathway, and 21 TFs probably contributed to the different genes transcriptional dynamic. Eventually, peanut AHL17 was identified from the profile of differentially expressed TFs, which encoded protein located in the nucleus promoted leaf epidermal cell enlargement when ectopically overexpressed in Arabidopsis through the regulatory phytohormone pathway. Overall, our study presents the different gene atlases in peanut etiolated and green seedlings, providing novel biological insights to elucidate light-induced leaf cell development at the single-cell level.

Effect of light and mechanical stress in combination with chemical elicitors on the production of stilbene compounds and defensive responses in peanut hairy root culture.

Plants encounter diverse stressors simultaneously with changing environmental factors. The combined effect of different types of stresses can have a wide range of effects on plants. The present study demonstrated that various stress factors such as the combination of chemical elicitors, namely paraquat (PQ), methyl jasmonate (MeJA) and methyl-ß-cyclodextrin (CD), light exposure versus darkness, and mechanical shearing stress affected the defence response in peanut hairy root culture. The antioxidant activities were dramatically increased at all time points after hairy roots were subjected to elicitation with PQ + MeJA + CD under root cutting in both light and dark conditions. The stilbene compounds were highly increased in the culture medium after elicitor treatment of uncut hairy roots under dark conditions. In contrast to the high stilbene contents detected in culture medium under dark conditions, the transcription of the stilbene biosynthesis genes PAL, RS and RS3 was enhanced by the effect of light in uncut hairy root tissues. The antioxidant enzyme genes APX, GPX and CuZn-SOD of uncut and cut hairy roots were more highly expressed in light conditions than in dark conditions. The pathogenesis-related protein (PR)-encoding genes chitinase, PR4A, PR5 and PR10 of uncut hairy roots were highly expressed in response to light conditions compared to dark conditions at all time points. Recent evidence of the production of antioxidant stilbene compounds and defence response genes has implicated plant protective functions through defence responses under different stress challenges. Plant responses might therefore be regulated by the coordination of different signal responses through dynamic pathways.

Effects of White LED Light and UV-C Radiation on Stilbene Biosynthesis and Phytochemicals Accumulation Identified by UHPLC-MS/MS during Peanut (Arachis hypogaea L.) Germination.

In this study, the effects of white light-emitting diode (LED) and UV-C radiation (with the same intensity) on stilbene biosynthesis and phytochemicals accumulation of peanut sprouts were investigated. Results showed that white light radiation promoted the growth of peanut sprouts while UV-C radiation had the opposite effect. Contents of total phenolics, total flavonoids, and phytochemicals significantly increased in peanut sprouts treated by white light or UV-C radiation. Besides, light radiation significantly induced stilbene accumulation by upregulating the expression of genes and enzymes in stilbene biosynthesis-related pathway, and UV-C was more effective to promote stilbene accumulation. Compared with piceid and piceatannol, resveratrol showed the highest accumulation in peanut sprouts treated by light radiation. In summary, white light or UV-C radiation could be used as a method to promote stilbene biosynthesis and phytochemicals accumulation in peanut sprouts and UV-C was more effective.

Blanchability and sensory quality of large runner peanuts blanched in a radiant wall oven using infrared radiation.

BACKGROUND: The main factors behind the growing popularity of infrared radiation heating in food processing include its energy efficiency, food quality retention and process speed, as well as the simplicity of equipment. Infrared radiation was employed as an alternative heat treatment to the conventional hot air method used in peanut blanching. The present study aimed to investigate the application of infrared heating for blanching peanuts and determine their blanchability and sensory quality under various processing conditions. RESULTS: The total blanchabilities (expressed as a percentage of total blanched) of the infrared radiation trials (radiant wall oven) at 343 °C for 1.5 min, 316 °C for 1.5 min, 288 °C for 1.5 min and 343 °C for 1 min did not differ significantly compared to the hot air control trials (impingement oven) at 100 °C for 30 and 20 min. All infrared trials had significantly lower (P < 0.05) numbers of split kernels compared to those of the conventional trials and all blanched peanuts in the experiment remained raw. A descriptive sensory shelf-life study with one control and three infrared samples demonstrated the possible initiation of oxidation for the conventionally blanched sample at 18 weeks of storage at 24 °C (room temperature), with no indication of oxidation in the infrared samples stored at the same temperature. CONCLUSION: Infrared radiation peanut blanching is a viable alternative to conventional hot air blanching because of the shorter process time and longer shelf-life, as evident from the sensory storage study. © 2017 Society of Chemical Industry.

Electron beam irradiation revealed genetic differences in radio-sensitivity and generated mutants in groundnut (Arachis hypogaea L.).

Electron beam accelerators are being used for many industrial applications including food and agriculture. A 10MeV linear accelerator facility was standardized for low dose application 0.1-1 kGy) in pulse mode using unscanned scattered beam for irradiation of groundnut seeds for mutation breeding. Using this facility, 50% growth reduction (GR50) dose was standardized in five groundnut genotypes. There were significant differences for radio-sensitivity among these genotypes. Seed mutagenesis of two groundnut genotypes, TG 26 and TG 68 with electron beam has generated one large seeded and four high yielding mutants in preliminary field trials.

Comparative transcriptome analysis of basal and zygote-located tip regions of peanut ovaries provides insight into the mechanism of light regulation in peanut embryo and pod development.

BACKGROUND: Peanut zygotes typically divide a few times to form a pre-embryo before further embryonic development halts under normal day/night photoperiods. Ovary elongation, however, continuesforming a downward growing peg-like structure. When the peg is buried in the soil, embryo development resumes in the darkness. The embryo-located region (ER) of the peg begins to enlarge and form a pod, while the basal region (BR) of the peg has a distinct fate. The molecular mechanisms governing these unique embryo development processes are unknown. RESULTS: In this study, histological analysis demonstrated that from 4 days after pollination to 3 days after soil penetration, the peanut pre-embryo remained morphologically similar. By 9 days after soil penetration, the embryo had changed to a globular embryo. Transcriptome analysis revealed differentially expressed genes in the ER and BR before and after peg soil penetration. In addition to light signaling and plant hormone metabolism genes, we identified differentially expressed genes in the ER that contribute to embryo development and pod formation processes, including MADS-box transcription factors, xyloglucan endotransglucosylase/hydrolase protein, cellulose synthase, homeobox-leucine zipper (HD-Zip) protein family genes, amino acid permease, and seed growth and embryo morphogenesis regulators (DA1, TCP3, and YABBY). CONCLUSIONS: A large number of genes were found to be differentially expressed in the ER and BR across three developmental peg stages. Exact changes in gene expression were also identified in the ER during early embryo and pod development. This information provides an expanded knowledgebase for understanding the mechanisms of early peanut pod formation.

Evaluation the effect of gamma irradiation on microbial, chemical and sensorial properties of peanut (Arachis hypogaea l.) seeds.

BACKGROUND: The aim of the present study was to evaluate the possibility to apply gamma radiation treatment for decontaminating and assuring the quality of peanut seeds. METHODS: The radiation processing was carried out at dose levels of 3, 6 and 9 kGy. The irradiated and non-irradiated (control) samples were stored at room temperature for 12 months, and analyzed for microbial load, proximate composition, sensorial acceptance and chemical properties. RESULTS: The results indicated that gamma irradiation treatment significantly (p < 0.05) reduced microbial load and enhanced the safety of the irradiated samples. The irradiated samples were also acceptable sensorically. The total acidity and total volatile nitrogen (TVBN) contents increased with the increase of radiation dose. Furthermore, in general, no substantial change in proximate constituents was observed amongst the samples. No significant (p > 0.05) differences in the taste, flavor, color and texture score were observed among treatments (0, 3, 6 and 9 kGy). CONCLUSIONS: Irradiation protected again bacterial and fungal growth and retained the nutritional components of samples during long-term storage.

Performance of peanut mutants and their offspring generated from mixed high-energy particle field radiation and tissue culture.

To develop new ways to breed peanut, we irradiated seeds of the Luhua 11 cultivar with a mixed high-energy particle field at different doses. The embryonic leaflets were extracted as explants and incubated on somatic embryo induction medium and then on somatic embryo germination and regeneration medium. After being grafted, the M1-generation plants were transplanted, and seeds from each M1-generation plant were harvested. In the following year, the M2-generation seeds were planted separately. Some M2-generation plants showed distinct character segregation relative to the mutagenic parent in terms of vigor, fertility, plant height, branch number, and pod size and shape. M2-generation plants that had a high pod weight per plant tended to produce M3-generation offspring that also had a high pod weight per plant, much higher than that of the mutagenic parent, Luhua 11. M4-generation seeds varied greatly in quality, and 35 individuals with an increased fat content (>55%) were obtained. Overall, the results indicate that the combination of mutagenesis via mixed high-energy particle field exposure and tissue culture is promising for peanut breeding.

Generation of peanut mutants by fast neutron irradiation combined with in vitro culture.

Induced mutations have played an important role in the development of new plant varieties. In this study, we investigated the effects of fast neutron irradiation on somatic embryogenesis combined with plant regeneration in embryonic leaflet culture to develop new peanut (Arachis hypogaea L.) germplasm for breeding. The dry seeds of the elite cultivar Luhua 11 were irradiated with fast neutrons at dosages of 9.7, 14.0 and 18.0 Gy. The embryonic leaflets were separated and incubated in a medium with 10.0-mg/l 2,4-D to induce somatic embryogenesis. Next, they were incubated in a medium with 4.0-mg/l BAP for plant regeneration. As the irradiation dosage increased, the frequency of both somatic embryo formation and plantlet regeneration decreased. The regenerated plantlets were grafted onto rootstocks and were transplanted into the field. Later, the mature seeds of the regenerated plants were harvested. The M2 generation plants from most of the regenerated cultivars exhibited variations and segregation in vigor, plant height, branch and pod number, pod size, and pod shape. To determine whether the phenotypes were associated with genomic modification, we compared the DNA polymorphisms between the wild-type plants and 19 M3-generation individuals from different regenerated plants. We used 20 pairs of simple sequence repeat (SSR) primers and detected polymorphisms between most of the mutants and the wild-type plants (Luhua 11). Our results indicate that using a combination of fast neutron irradiation and tissue culture is an effective approach for creating new peanut germplasm.

Calcium contributes to photoprotection and repair of photosystem II in peanut leaves during heat and high irradiance.

In this study, we investigated the effects of exogenous calcium nitrate on photoinhibition and thylakoid protein level in peanut plants under heat (40°C) and high irradiance (HI) (1,200 µmol/m(2) per s) stress. Compared with control seedlings (cultivated in 0 mmol/L Ca(NO3 )2 medium), the maximal photochemical efficiency of photosystem II (PSII) in Ca(2+) -treated plants showed a slight decrease after 5 h stress, accompanied by lower degree of PSII closure (1-qP), higher non-photochemical quenching, and lower level of membrane damage. Ca(2+) inhibitors were used to analyze the varieties of antioxidant enzymes activity and PSII proteins. These results indicated that Ca(2+) could protect the subunits of PSII reaction centers from photoinhibition by reducing the generation of reactive oxygen species. In the presence of both ethyleneglycol-bis(2-aminoethylether)-tetraacetic acid and ascorbic acid (AsA), the net degradation of the damaged D1 protein was faster than that only treated with AsA. Our previous study showed that either the transcriptional or the translational level of calmodulin was obviously higher in Ca(2+) -treated plants. These results suggested that, under heat and HI stress, the Ca(2+) signal transduction pathway can alleviate the photoinhibition through regulating the protein repair process besides an enhanced capacity for scavenging reactive oxygen species.

Physicochemical properties of peanut protein isolate-glucomannan conjugates prepared by ultrasonic treatment.

Peanut protein isolate (PPI) was glycated with glucomannan through classical heating or ultrasound treatment in this work. The physicochemical properties of PPI-glucomannan conjugates prepared by ultrasound treatment were compared to those prepared by classical heating. Compared with classical heating, ultrasound treatment could accelerate the graft reaction between PPI and glucomannan and improve the concentration of available free amino groups of PPI. Solubility and emulsifying properties of the conjugates obtained by ultrasound treatment were both improved as compared to those obtained by classical heating and native PPI. Decreases of lysine and arginine contents during the graft reaction indicated that these two amino acid residues attended the covalent linkage between PPI and glucomannan. Structural feature analyses suggested that conjugates obtained by ultrasound treatment had less α-helix, more ß-structures and random coil, higher surface hydrophobicity and less compact tertiary structure as compared to those obtained by classical heating and native PPI.

Very low dose gamma irradiation stimulates gaseous exchange and carboxylation efficiency, but inhibits vascular sap flow in groundnut (Arachis hypogaea L.).

PURPOSE: An experiment was carried out to determine the effect of low dose gamma radiation on germination, plant growth, nitrogen and carbon fixation and carbon flow and release characteristics of groundnut. MATERIALS AND METHODS: Dry seeds of groundnut variety Trombay groundnut 37A (TG 37A), a radio mutant type developed by Bhabha Atomic Research Centre (BARC), Mumbai, India, were subjected to the pre-sowing treatment of gamma radiation within low to high dose physiological range, i.e., 0.0, 0.0082, 0.0164. 0.0328, 0.0656, 0.1312, 5, 25, 100, 500 Gray (Gy) from a cobalt source ((60)Co). Observations were recorded for the radiation effect on percentage germination, vigour, gas exchange attributes such as photosynthetic rate, stomatal conductance and transpiration rate, chlorophyll content, root exudation in terms of (14)C release, vascular sap flow rate and activities of rate defining carbon and nitrogen assimilating enzymes such as ribulose-1,5-bisphosphate carboxylase (rubisco) and nitrate reductase (NR). RESULTS: Seed germination was increased by 10-25% at the lower doses up to 5 Gy while the improvement in plant vigour in the same dose range was much higher (22-84%) than the unirradiated control. For radiation exposure above 5 Gy, a dose-dependent decline in germination and plant vigour was measured. No significant effect was observed on the photosynthesis at radiation exposure below 5 Gy but above 5 Gy dose there was a decline in the photosynthetic rate. Stomatal conductance and transpiration rate, however, were only inhibited at a high dose of 500 Gy. Leaf rubisco activity and NR activities remained unaffected at all the investigated doses of gamma irradiation. Mean root exudation and sap flow rate of the irradiated plants, irrespective of the dose, was reduced over the unirradiated control more so in a dose-dependent manner. CONCLUSIONS: Results indicated that a very low dose of gamma radiation, in centigray to gray range, did not pose any threat and in fact stimulated metabolic functions in such a way to aid growth and development of groundnut plants. It further showed that the radiation threshold for the gas exchange traits and rubisco activity, which ultimately determine the plant health and yield, were higher than compared to the other metabolic attributes and were well beyond 500 Gy and that the dose range above 500 Gy should be targeted to measure lethal effects of radiation on carbon assimilation attributes in leguminous crops, in general, and groundnut in particular.

Trans-thylakoid ∆pH dependent oscillation of F(PSI)/F(PSII) under continuous irradiance in isolated thylakoids.

Energy distribution between photosystems (PSI & PSII) under prolonged and continuous white light irradiance was assessed by monitoring the progress of their fluorescence emission (FPSI/FPSII) at 77 K. Our observations indicate FPSI/FPSII to oscillate with the progress of irradiance treatments at all intensities tested (100, 200, 500, and 800 µE m(-2) S(-1)). The amplitude of the oscillation increased with the progress, whereas the periodicity of the oscillation increased with the intensity of the incident irradiance. Spectral analysis indicated fluctuation of FPSI to be the major determinant of the observed oscillation. The first rise and fall of FPSI/FPSII overlapped with phosphorylation and dephosphorylation of LHCII, but oscillation of FPSI/FPSII continued for several cycles without any further phosphorylation of LHCII. Moreover, in presence of DCMU where linear electron flow (LEF) is suppressed and LHCII phosphorylation is completely abolished, the oscillation of FPSI/FPSII was not abolished. These data indicated that LHCII phosphorylation was not essential for the observed oscillation of energy distribution between the photosystems. In contrast, in the presence of inhibitors of cyclic electron flow (CEF) like Antimycin A (AA) and rotenone, the oscillation of FPSI/FPSII was either abolished or severely dampened. Additionally, the oscillation was also abolished in presence of uncouplers like NH4Cl and nigericin that cancels the trans-thylakoid ∆pH. Thus, trans-thylakoid ∆pH, generated through CEF, appear to be an important determinant of oscillation of FPSI/FPSII in isolated thylakoids. The phenomenon of oscillation could be associated with a CEF mediated chromatic adaptation of PSI in presence of excess irradiance.

Exogenous calcium alleviates photoinhibition of PSII by improving the xanthophyll cycle in peanut (Arachis hypogaea) leaves during heat stress under high irradiance.

Peanut is one of the calciphilous plants. Calcium (Ca) serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO3)2] (6 mM) on the dissipation of excess excitation energy in the photosystem II (PSII) antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C) and high irradiance (HI) (1 200 µmol m(-2) s(-1)) stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO3)2 medium], the maximal photochemical efficiency of PSII (Fv/Fm) in Ca(2+)-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ), higher expression of antioxidative genes and less reactive oxygen species (ROS) accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z)/(V+A+Z) were also detected in Ca(2+)-treated plants under such stress. These results showed that Ca(2+) could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion), LaCl3 (a blocker of Ca(2+) channel in cytoplasmic membrane), and CPZ [a calmodulin (CaM) antagonist] were used to analyze the effects of Ca(2+)/CaM on the variation of (A+Z)/(V+A+Z) (%) and the expression of violaxanthin de-epoxidase (VDE). The results indicated that CaM, an important component of the Ca(2+) signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle.

Inactivation of Salmonella enterica serovar Typhimurium and Escherichia coli O157:H7 in peanut butter cracker sandwiches by radio-frequency heating.

A multistate outbreak of Salmonella enterica serovar Typhimurium recently occurred in the USA, which was traced back to various food products made with contaminated peanut butter. This study was conducted to investigate the efficacy of radio-frequency (RF) heating to inactivate S. Typhimurium and Escherichia coli O157:H7 in peanut butter cracker sandwiches using creamy and chunky commercial peanut butter and to determine the effect on quality by measuring color changes and sensory evaluation. Samples were treated for a maximum time of 90 s in a 27.12 MHz RF heating system. Samples were prepared in the form of peanut butter cracker sandwiches and placed in the middle of two parallel-plate electrodes. After 90 s of RF treatment, the log reductions of S. Typhimurium and E. coli O157:H7 were 4.29 and 4.39 log CFU/g, respectively, in creamy peanut butter. RF treatment of chunky peanut butter for 90 s also significantly (P < 0.05) reduced levels of S. Typhimurium and E. coli O157:H7 by 4.55 log CFU/g and 5.32 log CFU/g. Color values and sensory characteristics of the RF treated peanut butter and crackers were not significantly (P > 0.05) different from the control. These results suggest that RF heating can be applied to control pathogens in peanut butter products without affecting quality.

A potential practical approach to reduce Ara h 6 allergenicity by gamma irradiation.

Peanut allergen Ara h 6 was isolated and irradiated at 1, 3, 5, or 10 kGy, and a whole peanut protein extract (WPPE) was also treated by irradiation. Alteration in structure of Ara h 6 was characterised by circular dichroism (CD) spectroscopy, ultraviolet (UV) absorption spectroscopy, fluorescence spectroscopy and SDS-PAGE, and antigenicity was evaluated by immunoblotting and indirect ELISA with anti-Ara h 6 polyclonal antibody. Irradiation induced significant changes in the secondary and tertiary structures of Ara h 6, and the antigenicity of both purified Ara h 6 and WPPE were reduced upon increasing the irradiation doses. Moreover, a good correlation between the loss in α-helix and IgG binding to Ara h 6 was observed. This indicated that irradiation might be an efficient approach to reduce or eliminate peanut allergenicity.

Gamma irradiation of in-shell and blanched peanuts protects against mycotoxic fungi and retains their nutraceutical components during long-term storage.

Peanut samples were irradiated (0.0, 5.2, 7.2 or 10.0 kGy), stored for a year (room temperature) and examined every three months. Mycotoxic fungi (MF) were detected in non-irradiated blanched peanuts. A dose of 5.2 kGy was found suitable to prevent MF growth in blanched samples. No MF was detected in in-shell peanuts, with or without irradiation. The colors of the control in-shell and blanched samples were, respectively, 44.72 and 60.21 (L *); 25.20 and 20.38 (Chroma); 53.05 and 86.46 (°Hue). The water activities (Aw) were 0.673 and 0.425. The corresponding fatty acids were 13.33% and 12.14% (C16:0), 44.94% and 44.92% (C18:1, ω9) and 37.10% and 37.63% (C18:2, ω6). The total phenolics (TP) were 4.62 and 2.52 mg GAE/g, with antioxidant activities (AA) of 16.97 and 10.36 µmol TEAC/g. Storage time negatively correlated with Aw (in-shell peanuts) or L *, linoleic acid, TP and AA (in-shell and blanched peanuts) but positively correlated with Aw (blanched peanuts), and with oleic acid (in-shell and blanched peanuts). Irradiation positively correlated with antioxidant activity (blanched peanuts). No correlation was found between irradiation and AA (in-shell samples) or fatty acids and TP (in-shell and blanched peanuts). Irradiation protected against MF and retained both the polyunsaturated fatty acids and polyphenols in the samples.

Gamma radiation induced oxidation and tocopherols decrease in in-shell, peeled and blanched peanuts.

In-shell, peeled and blanched peanut samples were characterized in relation to proximate composition and fatty acid profile. No difference was found in relation to its proximate composition. The three major fatty acids were palmitic acid, oleic acid, and linoleic acid. In order to investigate irradiation and storage effects, peanut samples were submitted to doses of 0.0, 5.0, 7.5 or 10.0 kGy, stored for six months at room temperature and monitored every three months. Peanuts responded differently to irradiation, particularly with regards to tocopherol contents, primary and secondary oxidation products and oil stability index. Induction periods and tocopherol contents were negatively correlated with irradiation doses and decreased moderately during storage. α-Tocopherol was the most gamma radiation sensitive and peeled samples were the most affected. A positive correlation was found among tocopherol contents and the induction period of the oils extracted from irradiated samples. Gamma radiation and storage time increased oxidation compounds production. If gamma radiation is considered an alternative for industrial scale peanut conservation, in-shell samples are the best feedstock. For the best of our knowledge this is the first article with such results; this way it may be helpful as basis for future studies on gamma radiation of in-shell crops.

Gamma radiation effects on peanut skin antioxidants.

Peanut skin, which is removed in the peanut blanching process, is rich in bioactive compounds with antioxidant properties. The aims of this study were to measure bioactive compounds in peanut skins and evaluate the effect of gamma radiation on their antioxidant activity. Peanut skin samples were treated with 0.0, 5.0, 7.5, or 10.0 kGy gamma rays. Total phenolics, condensed tannins, total flavonoids, and antioxidant activity were evaluated. Extracts obtained from the peanut skins were added to refined-bleached-deodorized (RBD) soybean oil. The oxidative stability of the oil samples was determined using the Oil Stability Index method and compared to a control and synthetic antioxidants (100 mg/kg BHT and 200 mg/kg TBHQ). Gamma radiation changed total phenolic content, total condensed tannins, total flavonoid content, and the antioxidant activity. All extracts, gamma irradiated or not, presented increasing induction period (h), measured by the Oil Stability Index method, when compared with the control. Antioxidant activity of the peanut skins was higher than BHT. The present study confirmed that gamma radiation did not affect the peanut skin extracts' antioxidative properties when added to soybean oil.