Effects of Multi-Hollow Surface Dielectric Barrier Discharges Atmospheric Pressure Cold Plasma on the Potential Decontamination of Peanut (Arachis Hypoga L) Seeds
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2020-05-25
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Addis Ababa University
Abstract
Peanut (Arachis hypogea L.) is consumed worldwide because of its promoting health and nutritional benefits. However, it is vulnerable to pre and post-harvest aflatoxin contaminations by Aspergillus flavus and Aspergillus parasiticus. Aflatoxin contaminated peanut in raw or processed form increases, the risk of carcinogenic, mutagenic and immunosuppressive agents. Then, developing efficient detoxification methods for aflatoxin degradation and inactivation of Aspergillus flavus and Aspergillus parasiticus becomes very important. Diverse strategic methods have been suggested for suppressing fungal growth and decontamination of aflatoxins. Although these methods can reduce surface fungal and aflatoxins concentration, often require either state-of-the-art equipment and extreme operating conditions and may cause limited detrimental effect to edible food product being treated. Therefore, The food industry faces challenges in improving food safety while maintaining the quality of the biomaterials.
Atmospheric pressure cold plasma is new emerging non-thermal decontamination technology which is chemical-free, environment-friendly, flexible and energy-saving. Due to this potential advantage, it has received a great deal of attention in a large number of fields, especially in the food industry. The plasma is the fourth state of matter which is composed of highly excited atomic, molecular, ionic, radical species and comprises of a large number of reactive species and photons as well as visible light. These species and energy are synergistically used for decontamination. This suggests that this technology may also modify the chemical and physical surface properties of agricultural products. Till date, very little information is available on the effect of plasma operating conditions and optimizations on high lipid and antioxidant-containing foods, degrading of aflatoxin and inactivation of Aspergillus species. Therefore, the aim of this research was to evaluate the effect of multi-hollow surface dielectric barrier discharge on the physicochemical quality of peanut, detoxification of aflatoxins, inactivation of Aspergillus species and oxidation stability of the peanut.
Varying plasma processing conditions showed that plasma power, air flow rate and treatment time had significant (P<0.05) effects on physicochemical properties of peanut. The result revealed that high plasma power, long-duration time caused a reduction in L*, b*, hardness, increased weight loss, and altered the microstructure of the plasma-treated peanut seeds. The fatty acid profile, peroxide value, acid value, moisture content, total polyphenols content, and antioxidant activity were evaluated during cold plasma treatment. The result showed that due to the variation plasma power, treatment time and air flow rate caused a decrease in unsaturated fatty acid and moisture content, increased saturated fatty acids, peroxide value, acid value and total polyphenols comtent of the peanut seeds. The optimal operating conditions of plasma were deduced at plasma power, air flow rate and treating time level of 27 W, 10 L/min and 7 min, respectively, giving predicted weight loss of 0.44%, hardness of 106 N, contact angle of 2.6 °, L* of 34.26, b* of 11, peroxide value of 2.09 mEqO2kg-1, total polyphenols content of 218.97 mgGallic acid/100g and moisture content of 4.91 %. At the optimum condition (27 W, 10 L/min and 7min) of analysis were made to investigate the oxidation stability of the peanut seeds treated by plasma and was compared with the untreated. In this work, the inductive period value calculated using the graphic method for optimum conditions and untreated peanut was 44:40 min and 46.52 min, respectively. These results were closer, and there was no significant difference between the treatment.
Peanut seeds were artificially infected with A. flavus and A. parasiticus and then was treated with 27 W constant plasma power at the various time and air flow rate. For control purpose, 75°C without activated plasma was treated the A. flavus and A. parasiticus. Complete inactivation of A. flavus and reduction in A. parasiticus was achieved after 8 min treatments at an air flow rate of 0.5L/min (27W).The decontamination effect of cold plasma on A. flavus and A. parasiticus spores injected on peanut seeds was decreased with increased air flow rate up to 10L/min but further increased there slight reductions was observed. A 75°C without activated plasma was done an experiment and insignificant (P>0.05) lethal effect on A. flavus and A. parasiticus spores were shown when compared with activated plasma.
The effects of multi-hollow surface dielectric barrier discharges atmospheric pressure cold plasma treatments on the reduction of aflatoxin B1, B2, G1 and G2 in peanut substrate were investigated. A High-performance liquid chromatography with fluorescence detector was used for the quantitative analysis of aflatoxins. To decrease the level of aflatoxins after the plasma treatment, the artificially contaminated aflatoxins (200ppb) peanut samples were used. The reduction rates of total aflatoxins in 5L/min for 8min, 5L/min for15min, 10 L/min for 7min, and 10L/min for 15min, and 15L/min for 8 min were 97.1%, 97.8%, 98.4%, 98.1% and 96.1%, respectively. In the case of cold plasma treatment, the total level of aflatoxin was significantly decreased during treatment process at 10 L/min for 7min, and 10L/min for 15min, compared with the other treatment samples (P<0.05). This study demonstrated that multi-hollow surface dielectric barrier discharges plasma could reduce high rate aflatoxins from peanuts. Therefore, it could be considered as a new technology for the food industry in detoxification of aflatoxins.
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Keywords
Aflatoxin, aspergillus species, multi-hollow surface dielectric barrier discharges, oxidation stability, peanut, physico-chemical properties of peanut