Retention of antioxidant activity in gamma irradiated argentinian sage and oregano
Introduction
The addition of antioxidants to food as well as to other pharmaceutical and cosmetic products is a strategy used in an effort to prevent their deterioration caused by free radicals (Capecka, Mareczek, & Leja, 2005). Synthetic antioxidants have been used in the food industry for many years; however, at present, they are suspected of promoting deleterious health effects (Kahl & Kappus, 1993). For this reason, consumers are strongly interested in natural antioxidants. Thus, the industrial sector is forced to look for antioxidant natural sources that can replace the synthetic ones or reduce their use as food additives (Kosar, Dorman, & Hiltunen, 2005).
The benefits resulting from the consumption of natural products rich in antioxidant compounds have prompted a renewed interest in their production worldwide. Argentina is an important producer of aromatic and medicinal herbs, reaching an annual average of 8000 tons. Most of these herbs are exported mainly to Germany, Italy, Brazil, Uruguay and Chile (Di Paola, 2006).
Among aromatic herbs, those belonging to the Lamiaceae family should be mentioned. This family includes from 200 to 250 genera (Dorman, Bachmayer, Kosar, & Hiltunen, 2004). Most of these herbs, including oregano and sage, are highly appreciated by consumers and the industry sector both for their cooking properties and their medicinal properties. It is estimated that the use of these herbs, as an antioxidant source, prevents diseases caused by oxidative stress, such as cancer, coronary atherosclerotic heart disease and the ageing process (Capecka et al., 2005).
As other agricultural products, at harvesting and processing, including packaging, sage and oregano are exposed to a wide range of environmental microbiological contamination. Taking into consideration that these herbs are often used raw and that certain pathogen bacteria can survive up to 10 and 12 years in the plant material (Beuchat, 1996), it is necessary to adopt effective decontamination methods to prevent food-transmitted diseases.
Radiation processing with gamma radiation or electron beam is in an exceptional position among the most recent non-thermal methods for post-harvest decontamination of food (Raso & Barbosa-Canovas, 2003). This is the only safe known method to sanitize both herbs and spices (Pezzutti, Marucci, Sica, Matzkin, & Croci, 2005). This fact is evidenced by the increasing number of countries that adopt irradiation technology to ensure the hygienic quality of these products (IAEA, 2006). Kume, Furata, Todoriki, Uenoyama, and Kobayashi (2009) have reported that about 50% of the total amount of irradiated food worldwide is dry herbs and vegetables. The internationally adopted dose to sanitize herbs and species is 10 kGy, while in some countries, including Argentina, this value has increased to 30 kGy (IAEA, 2006). In addition, given that products can be treated in commercial containers, irradiation saves energy and manual work.
In recent years, there has been a growing interest in irradiation-induced modifications on antioxidant activity in aromatic and medicinal herbs, as well as on the compounds responsible for such activity (Brandstetter et al., 2009, Calucci et al., 2003, Horváthová et al., 2007, Suhaj and Rácová, 2005). Literature antecedents on the irradiation processes influence on antioxidant activity of oregano and salvia are limited to works performed with herbs cultivated in some European countries (Brandstetter et al., 2009, Calucci et al., 2003, Horváthová et al., 2007, Suhaj and Rácová, 2005). As there is no such information related to oregano and sage cultivated in Argentina, in this study we have examined in vitro the antioxidant activity of oregano and sage produced in our country and subjected them to a 30 kGy dose of gamma irradiation for sanitization. The reducing power and free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) tests were performed to the methanol and aqueous extracts of dry herbs. In addition, the phenolic compound content was analysed in those extracts to evaluate a possible correlation with their antioxidant activity.
Section snippets
Samples
Fresh sage was dried in an oven at 37 °C until it reached a constant weight. Oregano, already dehydrated, was purchased from a local store. Both dry samples were ground in a grinder until a powder was obtained, which was immediately irradiated.
Irradiation
The dry sage and oregano powder was placed in plastic bags and irradiated at the facilities of the Comisión Nacional de Energía in Ezeiza Atomic Center, Buenos Aires Province, Argentina. The samples were treated under air conditions at 20 °C with a dose of
DPPH radical test
Antioxidants are substances that react and inactivate free radicals, thus preventing and reducing their adverse effects on biological targets. Accordingly, the synthetic DPPH radical, although not biologically relevant, is widely used as an indicator compound to test the radical scavenging ability and therefore the antioxidant activity, both of simple compounds and plant extracts.
The scavenging ability of sage and oregano extracts on the DPPH radical, stated as inhibition percentage, was
Conclusions
The antioxidant activity in vitro and total phenolic content was assessed in methanol and water extracts of non-irradiated and irradiated (30 kGy) dry sage and oregano cultivated in Argentina. The results of this study confirm the significance of sage and oregano as dietary sources of natural antioxidants. The extracts of these herbs have a radical scavenging activity and reducing ability. A good correlation between phenolic content and antioxidant activity was observed. Methanol was more
Acknowledgements
This work was partially financed by the Secretaría General de Ciencia y Tecnología of the UNS.
The authors wish to thank Juan Carlos Suarez and Clara Cousté from the Grupo Profam Cultivos Alternativos for supplying the samples, and Agronomic Engineer Julián Pérez Pizarro (Technician at the Rural Outreach Area of INTA Ascasubi) for his counsel.
References (32)
Pathogenic microorganisms associated with fresh product
Journal of Food Protection
(1996)- et al.
Impact on gamma-irradiation on the antioxidative properties of sage, thyme, and oregano
Food and Chemical Toxicology
(2009) - et al.
Use of free radical method to evaluate antioxidant activity
Lebensmittel-Wissenschaft and Technology
(1995) - et al.
Effects of gamma irradiation on physiological effectiveness of Korean medicinal herbs
Radiation Physics and Chemistry
(1999) - et al.
Antioxidant activity of fresh and dry herbs of some Lamiaceae species
Food Chemistry
(2005) - et al.
Use of an electrochemical method to evaluate the antioxidant activity of herb extracts from the Labiateae family
Food Chemistry
(2006) - et al.
Characterisation of the antioxidant properties of de-odourised aqueous extracts from selected Lamiaceae herbs
Food Chemistry
(2003) - et al.
Effect of an acid treatment on the phytochemical and antioxidant characteristics of extracts from selected Lamiaceae species
Food Chemistry
(2005) - et al.
Effects of irradiation in medicinal and eatable herbs
Radiation Physics and Chemistry
(2002) - et al.
Microbial decontamination of medicinally important herbals using gamma radiation and their biochemical characterisation
Food Chemistry
(2010)
Status of food irradiation in the world
Radiation Physics and Chemistry
Radiation-induced enhancement of antioxidant activity in extracts of rosemary (Rosmarinus officinalis L.)
Food Chemistry
Gamma-ray sanitization of Argentinian dehydrated garlic (Allium sativum L.) and onion (Allium cepa L.) products
Food Research International
Methods for testing antioxidant activity
The Analyst
Effects of γ-irradiation on the free radical and antioxidant contents in nine aromatic herbs and spices
Journal of Agricultural and Food Chemistry
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