STUDY ON THE USING OF SOME METALLIC NANOPARTICLES AS PRESERVATIVES OF VEGETABLE OILS

Abstract

Vegetable oils are one of the major components of human diets, comprising as much as 25% of average caloric intake. These oils becomes more susceptible to oxidation, resulting in several oxidation products, and many of them results in quality reduction, improving undesirable flavour compounds, generating many toxic effects such as cell injuries, cell membrane cytotoxity and coronary heart disease. Microorganisms were important factors in oil deterioration (acid value and peroxide value), and the deteriorated degree is proportional to the number of microorganisms. The numbers of microorganisms, storage period and temperature of the oil all affect the lipolysis process of microorganisms and thus determine the deterioration degree of oil. Nanotechnology is the industry and use of materials and structures at the nanometer scale (a nanometre is one millionth of a millimetre). It offers a wide range of chances for the development of innovative products and applications in food system. Recent technological developments lead the way for the manufacture of nanoparticles to be added to food. These could be divided forms of existing ingredients, or completely novel chemical structures. Nanotechnology is quickly moving from the laboratory into supermarket shelves and our kitchen tables and has the potential to revolutionize food systems. The worldwide commercial foods and food supplements consisting of added nanoparticles are becoming available. Silver nanoparticles is inorganic antibacterial agent used for centuries and is capable of killing about 650 types of diseases caused by microorganism. It has a significant possibility for a wide range of biological applications such as antifungal agent, antibacterial agents for antibiotic resistant bacteria, preventing infections, healing wounds and anti-inflammatory.On the other hand, Nano-gold possess not only the antibacterial function, but also has good safe guarantee in human edible and touchable field, its anti-bacteria, safety and nontoxic, odorless and safe having passed the FDA attestation in U.S. In the present study, the use of gold and silver nanoparticles to improve the quality of three edible oils namely corn oil (CO), flaxseed oil (FO) and sunflower oil (SO) were studied. Corn oil (CO), Flaxseed oil (FO) and Sunflower oil (SO) were collected randomly from local market. Then prepared gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) were carried out by citrate reduction method in oleic acid as stabilizing agent. The size and shape of the AuNPs were measured by TEM imaging. The particles show mostly spherical or triangle shapes with uniform in size and shape, it shows that an average size of the prepared AuNPs is ranged 40-50 nm. It was clear from TEM image that the shape of the prepared AgNPs was mainly spherical with average diameter from 8-15 nm. Oils samples without NPs (0NP) and with NPs using three different concentrations (17X10-3, 3.4 X10-3 and 0.34 X10-3ppm). Samples were divided into two groups, one group exposed to light and the other group stored at dark. The samples were stored in transparent plastic bottles in the summer and for total period of 4 months and chemical and microbiological analysis for them were performed after at starting time, after 2 and 4 months. The most important results of the chemical and microbiological analysis of the samples were as follows. -Peroxide value (PV), Thiobarbituric acid (TBA), acid value (AV) and p-anisidine value (P-anV) of oils samples that exposed to light were higher than that of their parallels at dark. -Iodine value (IV) of all samples decreased slightly during the storage period but at dark, the amount of decrease was with lower rate than that at light. The PV, TBA, AV, P-anV and number of microorganisms of samples with NPs were lower than that of their counterparts without NPs The IV of samples with NPs decreased with lower rate than that of their counterparts without NPs. On the other hand, PV, TBA, AV and P-anV and microorganisms number during storage period for all oils reduced in the presence of AuNPs and AgNPs compared with the absence of it (0NP). This indicated that without addition of AuNPs and AgNPs to CO, FO and SO there might be more rapid deterioration during storage period. After storage, the AV, PV, TBA and P-anV of all the tested oil samples increased in varying degrees even that which have not microorganisms increased too. For AuNPs at dark the most effective concentration was the lowest concentration 0.34X10-3 ppm while at light, the most effective concentration of AuNPs was the higher concentration 17X10-3ppm. On the other hand, for AgNPs the lowest concentration 0.34X10-3 ppm was the most efficient concentration in the samples stored in the dark or in the light. At dark AgNPs was more effective than AuNPs. Whereas at light AuNPs was more effective than AgNPs Corn oil has the highest oxidative stability (i.e. has lowest PV, P-anV, TBA, AV and has lowest rate of decrease in IV) followed by sunflower oil and then flaxseed oil.