Gamma irradiation of chestnuts: dosimetric study and its influence in drying

Food irradiation is a process that has been regaining an increasing interest for different food products to increase shelf life, for disinfestation or sterilization. In industry the drying of chestnuts is used to produce other sub-products, such as flour. So far as we know this is the first time that the influence of gamma irradiation in drying behaviour of an european chestnuts variety was performed. First the dose rate distribution was measured in one of the four levels of a Cobalt-60 irradiation experimental chamber to evaluate the uniformity dose during the irradiation process. The corners of a rectangle with the sample dimensions were chosen, being used the chemical Fricke standard dosimeter for dose rate estimation and routine Amber Perspex during irradiations. The average dose rate for the irradited positions was 2.1 ± 0.8 kGy h–1 , and the ratio Dmax/Dmin was 2.5. Afterwards the chestnuts were subjected to different doses (0, 1, 3 and 6 kGy), and then dried in a forced convective oven at 50 oC. The moisture ratios for each irradiation dose, as well as the drying rates, were determined. The Page model was used to modelize the drying behaviour, obtaining adjusted R squares higher than 0.98. Only the falling rate period was detected. At begininng the drying rates were high, decreasing very fast till 2 h of drying, after that the rates practically did not change till the end of the process. For the irradiation doses up to 6 kGy, it was observed a slight difference between non-irradiated and irradiated fruits drying behaviour

Electron beam irradiator for post-harvest processing of chestnut fruits: technical parameters and feasibility

In a recent worldwide estimation, food irradiation processing represents about 400 000 ton, from which almost half (186 000 ton) were to eliminate insects. In EU Mediterranean countries chestnut fruits production represents a market of more than 100 000 ton, being Portugal the third producer with an amount of 20 000 ton, exporting 25% of the production, representing an income of about 15 million Euros. In March 2010, a European Union commission decision prohibited the use of methyl bromide (MeBr), a wide spectrum fumigant used for different agricultural purposes, namely for post-harvest disinfestation of chestnut fruits. The banning of MeBr could represent an opportunity to implement ionizing radiation treatment, as a well tested technology in other food commodities for post-harvest preservation. Electron beam irradiators are more hardware sophisticated than gamma irradiators, however due to several factors they are becoming more popular and being the first choice, whenever the product can be treated by low penetration radiation. Since the current focus for food irradiation is in e-beam versatility and advantages, it is presented in this paper a detailed analysis and discussion about technical characteristics and feasibility for post-harvest irradiation of chestnut fruits, taking in account the physical dimensions and fruits seasonality, beam energy, throughput and total costs of operation, to estimate the impact on the final price of the irradiated product

Antioxidant properties of three different Castanea sativa Portuguese varieties submitted to gamma irradiation

The Northeast of Portugal is responsible for 82% of the nation's total production of chestnuts. Since 2010, European legislation has banned the use of Methyl Bromide in chestnut disinfestation due to environment concerns and health related issues. This fumigant was widely applied over chestnuts and other fruits to kill insects and other contaminating agents, and, although dangerous, it was the most efficient treatment available, since other heat treatments still pose relevant drawbacks. Food irradiation has stepped in as an alternative treatment for food commodities, and our research group has investigated its potential to treat chestnuts [1]. Antioxidants have long been regarded as having beneficial effects in human health by neutralizing free radicals that arise from various metabolic processes. Recent discoveries have proven that the consumption of fruits and vegetables rich in antioxidants is healthier than consuming antioxidant supplements [2]. In this work, we have tested the effects of gamma irradiation at 1 kGy on the antioxidant potential of three different chestnut varieties from Portugal (Judia, Longal and Cota), as a continuing research of previous results with a single variety [1 ,3]. The antioxidant potential was determined through the DPPH (2,2-diphenyl-1-pycrilhyd razyl) scavenging activity, reducing power, lipid peroxidation inhibition by ~-carotene bleaching and Thiobarbituric Reactive Species (TBARS) assays and total phenolics by Folin-ciocalteu assay. The variety with the highest quantity of total phenolics was Judia, followed by Longal. The phenolics in Longal and Cota varieties were preserved by radiation. The biggest difference in DPPH radical scavenging was recorded for Judia, since the other two didn't vary significantly. The reducing power didn't seem to be affected by radiation in all the varieties. In terms of β-carotene bleaching inhibition, the irradiated samples displayed lower EC50 values in Longal and Judia, while in Cota the values were very similar. The TBARS assay showed inverse results, with higher EC50 values for the non-irradiated samples. These results showed that chestnuts are a valuable fruit in terms of antioxidants, and that radiation does not induce significant alterations in their antioxidant potential.FCT and COMPETE/QREN/EU (ON.2/QREN/EU Project no.13198/201 0; CIMO strategic project PEst-OE/AGR/UI0690/2011 andA.L. Antonio grant- SFRH/PROTEC/67398/2010)

Effects of gamma radiation on the biological, physico-chemical, nutritional and antioxidant parameters of chestnuts - a review

Gamma radiation has been used as a post-harvest food preservation process for many years. Chestnuts are a seasonal product consumed fresh or processed, and gamma irradiation emerged recently as a possible alternative technology for their post-harvest processing, to fulfil the requirements of international phytosanitary trade laws. After harvest and storage, several problems may occur, such as the presence of infestations and development of microorganisms, namely rotting and fungi. These diminish the quality and safety of the product, decreasing the yield along the production chain. In fruits, gamma irradiation treatment is for two main purposes: conservation (ripening delay) and insect disinfestation (phytosanitary treatment). In this review, the application of gamma irradiation to chestnuts is discussed, including production data, the irradiated species and the effects on biological (sprouting, rotting, respiration rate, insects, worms and fungi), physico-chemical (colour, texture, drying rate), nutritional (energetic value, proteins, sugars and fatty acids) and antioxidant (tocopherols, ascorbic acid, phenolics, flavonoids and antioxidant activity) parameters. These changes are the basis for detecting if the food product has been irradiated or not. The validation of standards used for detection of food irradiation, as applied to chestnuts, is also discussed

Influence of gamma irradiation in the antioxidant potential of chestnuts (Castanea sativa Mill.) fruits and skins

As seasonal products chestnuts have to be postharvest treated to increase their shelf-life. The most common preservation method for chestnuts is the chemical fumigation with methyl bromide, a toxic agent that is under strictly use under Montreal Protocol due to its adverse effects on human health and environment. Food irradiation is a possible feasible alternative to substitute the traditional quarantine chemical fumigation treatment. This preliminary study evaluated the influence of gamma irradiation in the antioxidant potential of chestnut fruits and skins, through several chemical and biochemical parameters. The bioactive compounds (phenolics and flavonoids) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, reducing power and inhibition of B-carotene bleaching capacity were determined. The obtained results seem to indicate that the storage favoured chestnuts antioxidant potential. Furthermore, the application of gamma irradiation also seems to be advantageous for antioxidant activity, independently of the dose used (0.27 ± 0.04 kGy or 0.54 ± 0.04 kGy)

Assessing the effects of gamma irradiation and storage time in energetic value and in major individual nutrients of chestnuts.

Chestnut (Castanea sativa Miller) is an important food resource all over the world. In the present study, it is intended to evaluate if the application of gamma irradiation doses < 3 kGy maintain chestnuts chemical and nutritional profiles unaffected. Furthermore, possible interactions among irradiation dose and storage time were accessed using linear discriminate analysis (LDA). The nutritional composition was evaluated through determination of proteins, fat, ash, carbohydrates and energetic value. The chemical composition was focused in the main nutrients found in chestnuts: sugars- sucrose, fatty acids- palmitic, oleic, linoleic and linolenic acids, tocopherols- Y-tocopherol. The obtained results seem to indicate that the irradiation treatment did not affect the nutritional and chemical quality of chestnut fruits. Otherwise, storage time exerted more evident influence in those parameters. The application of gamma irradiation emerges as a promising technology for chestnuts chemical quality, but food safety issues has to be evaluated in order to recommend its application as a useful conservation alternative

Comparative effects of gamma and electron beam irradiation on the antioxidant potential of Portuguese chestnuts (Castanea sativa Mill.)

Chestnuts (Castanea sativa Mill.) are widely consumed all over the world, and have been recently studied for their antioxidant potential. The present study reports the effect of e-beam and gamma radiation (doses of 0, 0.5, 1 and 3 kGy) on the antioxidant potential of Portuguese chestnuts. Irradiation might be an alternative preservation method, since Methyl Bromide, a widely used fumigant, was banished by the European Union in 2010 due to its toxicity. The antioxidant activity was evaluated through 2,2- diphenyl-1-pycrylhydrazyl (DPPH) free radical scavenging activity assay, reducing power by the Ferricyanide/Prussian blue assay, and lipid peroxidation inhibition by β- carotene/linoleate and thiobarbituric acid reactive substances (TBARS) assays. The analysis of total phenolics and flavonoids was performed by spectrophotometric assays. Irradiated samples preserved total phenolics content (but not flavonoids) and revealed higher antioxidant activity (lower EC50 values) than the control samples. The most indicated doses to maintain antioxidants content, and to increase antioxidant activity were 1 kGy and 3 kGy for electron beam and gamma radiation, respectively

Compartment modelling in drying of gamma irradiated chestnut fruits

The main objective of this work was to understand how irradiation processing influences the drying of chestnut fruits. Herein, based on the fruit characteristcs and Computed Tomography (CT) images, we proposed a compartment-model for the kinetic drying curves. The preliminary results seemed to indicate that one-compartment modelling gives good fitting results for the modelization of the drying curves. In this way, this model could be a good approach to the drying process.ON.2-QREN-EU Project nº 13198/2010 for financial support; A.L. Antonio grant SFRH/PROTEC/67398/2010. Dr. Carlos Vaz, General Director of Centro Hospitalar de Trás-os-Montes e Alto Douro, for allowing CT images

Low dose gamma-irradiation as a suitable solution for chestnut (Castanea sativa Miller) conservation: effects on sugars, fatty acids and tocopherols

Along with dehydration, the development of insects and microorganisms is the major drawback in chestnut conservation. Irradiation has been regaining interest as an alternative technology to increase food products shelf-life. In the present work, the effects of low dose gamma irradiation on sugars, fatty acids and tocopherols composition of chestnuts stored at 4 ºC for different storage periods (0, 30 and 60 days) was evaluated. The irradiations were performed in a 60Co experimental equipment, for 1 h (0.27 +/- 0.04 kGy) and 2 h (0.54 +/- 0.04 kGy). Changes in sugars and tocopherols were determined by high performance liquid chromatography (HPLC) coupled to refraction index (RI) and fluorescence detections, respectively, while changes in fatty acids were analysed by gas-chromatography coupled to flame ionization detection (GC-FID). Regarding sugars composition, storage time proved to have higher effect than irradiation treatment. Fructose and glucose increased after storage, with the corresponding decrease of sucrose. Otherwise, tocopherols content was lower in non-irradiated samples, without a significant influence of storage. Saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids levels were not affected neither by storage nor irradiation. Nevertheless, some individual fatty acids concentrations were influenced by one of both factors, such as the increase of palmitic acid in irradiated samples or the decrease of oleic acid after 60 days of storage. Overall, the assayed irradiation doses seem to be a promising alternative treatment to increase chestnuts shelf-life, without affect the profile and composition in important nutrients