GRASAS Y ACEITES 70 (2) April–June 2019, e308 ISSN-L: 0017-3495 https://doi.org/10.3989/gya.0933182 Controlling fungal growth in sesame (Sesamum indicum L.) seeds with f-irradiation: impacts on some properties of sesame oil A.B. Hassana, I.A. Mohamed Ahmedb, *, K.A. Sir Elkhatima, R.A.A. Elagiba, N.S. Mahmouda, M.M. Mohamedc, A.M. Salihc and G.J. Fadimub aEnvironment and Natural Resource and Desertification Research Institute (ENDRI), National Center for Research, P.O. Box 6096, Khartoum, Sudan bDepartment of Food Science and Nutrition, Faculty of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Kingdom of Saudi Arabia. cInstitute of chemistry and Nuclear Physics, Sudanese Atomic Energy Commission (SAEC), Khartoum, Sudan *Corresponding author: [email protected];[email protected] Submitted: 13 September 2018; Accepted: 08 November 2018. Published online: 19 February 2019 SUMMARY: This study investigated the free fatty acids, fatty acid profile, total phenolics, and antioxidant activity of sesame seed oil extracted from γ-irradiated seeds and the decontamination effects of the treatment on fungal incidence in the seeds. Gamma irradiation reduced (P ≤ 0.05) fungal growth and colony forming units of sesame seeds in a dose-dependent manner. The free fatty acid content of sesame oil decreased (P ≤ 0.05) in irradiated samples compared to non-radiated controls, but there was no difference (P ≥ 0.05) between samples treated at doses ≥ 1.0 kGy. A concomitant (P ≤ 0.05) increase in total phenolic and scavenging activity was observed in the oil extracted from γ-irradiated sesame seeds in comparison with non-radiated samples, while free fatty acid (FFA) content decreased. The results obtained in the present study demonstrate that γ-irradiation at low doses can be used as an effective post-harvest preservation method for sesame seeds without a major effect on the quality of sesame oil. KEYWORDS: Antioxidant activity; Free fatty acids; Gamma irradiation; Sesame seed oil; Total phenolics RESUMEN: Control del crecimiento de hongos en semillas de sésamo (Sesamum indicum L.) con irradiación γ: impactos en algunas propiedades del aceite de sésamo. Este estudio investigó los ácidos grasos libres, el perfil de los ácidos grasos, los fenoles totales, la actividad antioxidante del aceite de semillas de sésamo extraído de las semillas irradiadas con rayos gamma y los efectos de descontaminación del tratamiento sobre la incidencia de hongos en las semillas. La irradiación gamma redujo (P ≤ 0,05) el crecimiento de hongos y las unidades forma- doras de colonias en las semillas de sésamo de una manera dependiente de la dosis. El contenido de ácidos gra- sos libre del aceite de sésamo disminuyó (P ≤ 0,05) en las muestras irradiadas en comparación con los controles no irradiados, pero no hubo diferencia (P ≥ 0,05) entre las muestras tratadas a dosis ≥ 1,0 kGy. Se observó un aumento concomitante (P ≤ 0,05) en la actividad fenólica total y de eliminación en el aceite extraído de semillas de sésamo irradiadas con rayos gamma en comparación con muestras no irradiadas, mientras que el contenido de ácidos grasos libres (FFA) disminuyó. Los resultados obtenidos en el presente estudio demostraron que la irradiación con rayos γ a dosis bajas se puede usar como un método efectivo de conservación del sésamo después de la cosecha sin un efecto importante en la calidad del aceite de sésamo. PALABRAS CLAVE: Aceite de semilla de sesame; Ácidos grasos libres; Actividad antioxidante; Fenoles totals; Irradiación gamma ORCID ID: Hassan AB https://orcid.org/0000-0002-7385-5259, Mohamed Ahmed IA https://orcid.org/0000-0002- 6578-0795, Sir Elkhatim KA https://orcid.org/0000-0002-1069-8524, Elagib RAA https://orcid.org/0000-0003-0411- 9407, Mahmoud NS https://orcid.org/0000-0002-8401-0788, Mohamed MM https://orcid.org/0000-0002-0720-8774, Salih AM https://orcid.org/0000-0001-6152-4869, Fadimu GJ https://orcid.org/0000-0003-4736-5106 Citation/Cómo citar este artículo: Hassan AB, Mohamed Ahmed IA, Sir Elkhatim KA, Elagib RAA, Mahmoud NS, Mohamed MM, Salih AM, Fadimu GJ. 2019. Controlling fungal growth in sesame (Sesamum indicum L.) seeds with γ-irradiation: impacts on some properties of sesame oil. Grasas Aceites 70 (2), e308. https://doi.org/10.3989/ gya.0933182 Copyright: ©2019 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License. 2 • A.B. Hassan et al. 1. INTRODUCTION effective in improving the quality and dietary attri- butes of stored agricultural products, while main- Oil seeds are important food stuff all over the taining its shelf-life and hence, irradiation could world, and they are considered as a major source be a better replacement to chemical preservation. of good quality edible proteins and oils due to their In addition, irradiations leave no residue in food availability, great acceptability by religious and materials, unlike other methods such as chemi- health-conscious consumers, and relatively low cost cal treatments. Interestingly, ionizing radiation compared to animal-based foods (Hassan et al., applied at doses below 10 kGy had no effect on 2018). The Sesame seed is one of the oldest seeds micro or macronutrients and it enhanced the shelf- used for oil production and the current world pro- life of food (Brewer, 2009). Recently, it has been duction of this important crop is 6.1 million tons reported that gamma irradiation of sesame seed (FAO, 2018). In recent years, the world produc- flour at doses ≤ 2.0 kGy improved its functional tion of sesame seeds has increased and this can be properties (Hassan et al., 2018). Another report attributed to its wide applications in industries, par- indicated that the total phenolic compounds in ticularly in the production of healthy and nutritious almond skin extract increased following irradiation products. Oil is an important component of seeds at doses below 4 kGy (Harrison and Were, 2007). and its value varies due to the difference in seed type To date, studies on the impact of gamma rays on and the extraction method used. Sesame seeds have the quality of sesame oil are limited (Afify et al., been reported to contain up to 63% oil (Hassan 2013; Al-Bachir, 2017). However, information on et al., 2018) with several health-promoting proper- the effect of gamma irradiation on the FFA, total ties. Nutritionally, sesame oil is a very rich source phenolics, and antioxidant activity of oil extracted of unsaturated fatty acids such as oleic and linoleic from sesame seeds is scarce. Therefore, this study acids, which makes it a perfect raw material for the was conducted to investigate the decontaminating production of margarine and cooking oil. In addi- effect of gamma irradiation on the fungal growth tion, sesame oil contains a substantial amount of and colony formation of sesame seeds and the lignans (sesamin, sesamolin and sesaminol), tocoph- impact of this treatment on the FFA, fatty acid erols and phytosterols (Elleuch et al., 2011). These profile, total phenolics, and antioxidant activity of compounds have been proven to have many health sesame oil extracted from γ-irradiated sesame seeds. benefits including blood pressure reduction, hypo- cholesterolemic effect, antioxidant and anticancer 2. MATERIALS AND METHODS activities (Elleuch et al., 2011). Owing to these nutri- tional and health-promoting effects, sesame oil may 2.1. Sample preparation be useful industrially for the production of func- tional foods and might also find applications in the The sesame seeds used in the present study were pharmaceutical industry. However, in spite of the procured from a sesame farm in Gadairf, Sudan. nutritional and health-promoting effects of sesame The seeds were transported to the laboratory imme- seeds, post-harvest attack by insects, fungi, bacteria diately after harvest, cleaned, sorted and kept in and pests continue to pose a threat to the effective plastic bags at 4 °C before use. utilization of the seeds for various applications. It is therefore essential to apply an appropriate treatment 2.2. Gamma radiation treatments to the seeds to limit post-harvest decomposition in quality without major damages to the nutritional Sesame seeds were sealed in plastic bags prior and health-promoting properties. to and during the irradiation process. The samples Various methods have been developed to con- were irradiated at the Kaila irradiation processing trol food spoilage and improve the safety of foods. unit, Sudanese Atomic Energy Corporation (SAEC) Chemical preservation, freezing, chilling, canning, using an experimental cobalt- 60 gamma source and pasteurization have been successfully used to (Nordion gamma cell 220 - Excell) at the doses of control food spoilage (Agrios, 2005). Irradiation, 0.5, 1.0, 1.5, and 2.0 kGy and with a dose rate of which involves the exposure of food materials to 1.98 kGy/h. To ensure uniform dose delivery and different doses, is an effective method for control- minimize the variations in radiation received by the ling food spoilage due to the effect of its primary samples, both sides of the samples were exposed to and secondary radiolysis on the microorganism; irradiation (double-side irradiation). Three dosim- although it could produce chemical reactions in eters (Gafchromic HD-810 film, International food materials (Hassan et al., 2018). However, the Specialty Products, NJ, USA; FAO/IAEA/USDA effects of these chemical reactions are derived from 2003) were included in each batch of seeds and various factors such as dose rate, quantity of dose read after irradiation with a Radiachromics reader absorbed, availability or unavailability of oxygen, (Far West Technology Inc., CA, USA) to measure and temperature (Brewer, 2009). Mahmoud et al., the dose received by the batch. Triplicate samples (2016) reported that irradiation treatment was of sesame seeds were irradiated, and all treatments Grasas Aceites 70 (2), April–June 2019, e308.