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Interest in the development of processes for the production or extraction of bioactive compounds from by-products sources has increased in recent years due to the potential applications of these compounds in food, chemical, and pharmaceutical industries. In the present study walnut leaves and green husks as a potential alternative source of bioactive compounds for vegetable oil stabilization are evaluated (Popovici C. et al., 2008).

Walnut leaves are considered a source of bioactive compounds and have been widely used in traditional medicine. Antiradical and antibacterial activities have also been described for different Juglans regia cultivars. Walnut green husk is a by-product of the walnut production, being formed in large amounts. Probably due to its scarce utilization, this matrix is very little studied. Recently, walnut leaves and green husk were suggested as a low cost alternative natural source of bioactive compounds with antiradical and antimicrobial activities.

Walnut leaves and green husks extracts were analyzed for total polyphenol content (TPC) and antioxidant activity. The TPC was determined using the Folin-Ciocalteu method. The antioxidant activity of the extracts was determined using 2,2 diphenyl-1-picrylhydrazyl radical DPPH (Popovici et al., 2009). The antioxidant activity value was expressed as radical scavenging activity and the antioxidant capacity of the walnut leaves and green husks extracts were analyzed as the kinetics of inhibition of free radicals (the percentage of DPPH remaining at steady state). Experimental results on the antioxidant activity of the bioactive compounds from walnut leaves and green husks allowed to make the assumption about possibility of their incorporation into walnut oil to prevent negative oxidation process.

Being highest in TPC and antioxidant potential, walnut leaves and green husks extracts were added to walnut oil. The efficiency of the studied extracts was evaluated in comparison with synthetic antioxidant butylhydroxytoluene (BHT), which is recommended for oil and fat stabilization. Obtained samples of oils with natural and synthetic antioxidants were heated at different technological temperatures. The oxidation degree of the oil samples was evaluated by means of primary and secondary oxidation products, such as peroxides, conjugated diens and aldehydes. The results of UV/Vis spectroscopy confirm stabilization effect of walnut leaves and green husks extracts on thermal oxidation of the walnut oil samples.

This study demonstrates that natural plants extracts such as walnut leaves and green husks could be used as alternative source of natural antioxidants in food industries, especially for vegetable oil stabilization. The experimental results apparently indicated that walnut leaves and green husks extracts exerts an effective influence on the processes of oil stabilization; i.e., they inhibit the intensity of the primary and secondary oxidation products accumulation during thermal process.

Acknowledgements This work was supported by the Agence Universitaire de la Francophonie (AUF) through the Eugen Ionescu postdoctoral scholarship 2010/2011 and financed by the Romanian Government.

   

Nowadays there is a tendency of improving the food structure, which in most cases is related to creation of functional foods with a balanced content of the major nutrient materials which are, in the same time, daily products. Functional mixtures of vegetable oils provide ample opportunities for preventing deficiency in essential fatty acids, vitamins and other physiologically functional ingredients.

Grape-seed oil has a high bioavailability determined by a complex of biologically active substances, bioflavanoids, a group of vitamins, being the most important of them.

During storage and frying of oils, there is a negative effect happening with the vegetable oils, named oxidation. At the nutritional level, the oxidation of fatty constituents is the major chemical factor in the loss of food wholesomeness by deterioration of flavor and aroma, as well as in decay of nutritional and food safety qualities. In order to retard or prevent the oxidative deterioration and extend the shelf-life of vegetable oils, antioxidants are incorporated into their composition. (Popovici C. et al., 2011). In recent years there is a tendency to use the natural extract of plants as stabilizators for the vegetable oils. This beneficial effect is due to the rich antioxidants content in these herbs (Popovici C. et al., 2010).

The obtained results show that tested extracts of parsley and lovage had strong antioxidant characteristics. The compounds responsible for parsley and lovage antioxidant activity are mainly phenolic acids (caffeic, ferulic, p-coumaric acids) and flavonoids such as flavonol aglycones (quercetin, kaempferol, and their glycosides). The purpose of the current work was to describe the effect of added parsley and lovage extracts in the protection of sunflower and grape seed oils against the thermal oxidation process.

The oils samples stability was analyzed through studying the following indicators:

the acid value determined through potassium hydroxide titration, the refractive index and the conjugated dienes and trienes content was determined through spectrophotometric methods described in AOCS Official Methods and there were also analyzed the UV/Vis spectra of the samples.

Analyzing the results obtained through the experiments there were determined that the incorporation of the natural plant extracts into the composition of the mixture of sunflower and grape seed oils exerts an effective influence on the processes of stabilization of the tested oils; i.e., it inhibits the intensity of the accumulation of the primary and secondary oxidation products during thermal oxidation process. A very important aspect is also the fact that all the oil samples enriched with natural antioxidants, resulted from parsley and lovage extracts, showed an oxidative stability not only at the room temperature, but also after being subjected to high temperature.

Acknowledgements:

The research leading to these results were obtained while preparing the undergraduate thesis in 2010/2011 academic year at the Department of Technology and Organization of Public Catering.

   

The oil-in-water (O/W) food emulsions are the basis of many food products and their properties define food quality to a great extent. As a consequence, interest in the theory and practice of food emulsions has been increasing. Scientific studies are oriented more and more toward different aspects of the characteristics, formation, behavior, and application of these food emulsions. Regarding oils, a wide variety of different types of oils have traditionally been used in food emulsions, including soybean, corn, canola, olive, safflower, and sunflower oils [1].




140 .


The trend has been to replace traditional oils with more health-promoting oils, such as polyunsaturated lipids. Walnut oil is one of these beneficial oils. Walnut oil is high in omega-3 fats, which have been linked to a variety of health benefits [2].

In the present study it was evaluated the possibility to incorporate the walnut oil in food emulsions recipe. It was elaborated obtaining technology of mayonnaise type emulsions based on mixture of sunflower oil and walnut oil. Therefore were obtained emulsions with 50 % fat, containing different concentrations of walnut oil (25, 50, 75, and 100 %).

The microstructure of mayonnaise emulsions were determined using an optical microscope, of digital model Motic DMB 5-5 (China). Photos of mayonnaise samples were obtained by digital camera connected to a microscope. The microstructure of mayonnaise samples is illustrated in figure 1.

The kinetic of lipid oxidation was assessed by measuring peroxide value (PV), acid index (AI), conjugated dienes content (CD), conjugated trienes content (CT), tiobarbituric index (TBA) in studied mayonnaise samples. It was established that with increasing concentrations of walnut oil there had place the increase of the amount of primary and secondary products of lipid oxidation, such as peroxides and aldehides. Sensory profiles were affected only by oil type: at higher walnut oil content correspond more intense colour, bitterness, walnut odour and flavour.

   

Analyzing the results, for production of emulsions with functional properties that would ensure an optimal intake of polyunsaturated fatty acids with special sensory properties, quality indices of which are not inferior than the existing emulsions it is recommended use of ratio sunflower oil: walnut oil 3:1.

   

The elaboration of technologies for obtaining food products with a high biological value is one of the priority directions of development of the food-processing industry. A definite place among fatty foods is occupied by mayonnaises, which vegetable oil is in the dispersed state that increases their comprehensibility and nutritional value and also accelerates the oxidation of emulsified fat fraction.

In order to increase the biological value of food emulsions such as mayonnaise it was offered to replace partially sunflower oil on grape seed oil which is distinguished by a high content of polynonsaturated fat acids (-3 and -6) and such natural antioxidants, as vitamin E (,, ) and polyphenols (proanthocyanidins). Partial substitution of sunflower oil with grape seed oil in the mayonnaise emulsions will enable balancing the levels of fatty acids, increases biological qualities and taste, for producing functional emulsions.

The emulsifying properties of vegetable oils, fatty acid content, and the influence of their mix on structure, rheological properties and the basic physical and chemical indicators of mayonnaise were studied to determine the optimal ratio of vegetable oils. The advisability of the utilization of the grape seed oil was proved by increasing the biological value and improvement the physical-chemical parameters of the emulsions` quality.

To prevent the possible oxidation processes, the development of unfavorable microflora, as well as increase the storage limits and assortment`s variety of fat products it was proposed and proved the advisability of using natural extracts from plant raw materials of local origin such as sweet pepper, parsley and lovage, which exhibit a high antioxidant activity due to the content of polyphenols. The total polyphenol content was determined using the Folin-Ciocalteu method. The antioxidant activity of the extracts was determined using 2,2 diphenyl-1-picrylhydrazyl radical DPPH (Popovici et al., 2009).

Researches of the oxidative stability of mayonnaise emulsions in the process of preserving indicate, that natural extracts have inhibitor effect on the intensity of the accumulation of primary and secondary products of oxidation and is manifested by subtracting of acidity values, content of diene/triene and p-anisidine value for the whole period of sorage (6 months). By IR spectroscopy has demonstrated the stability of the intensity of the vibration strain C-H bonds in the cis-CH = CH-(3,01 10-6 m), characteristic for cis-isomers of unsaturated fatty acid, which shows the stability of the double links.

At studying of a microstructure of compared samples of mayonnaise emulsions it was established, that the samples is characterized by a dense monomodale arrangement of fat droplets with radius of fat globules 5 m (Capcanari et al., 2012).

The technologies of production of vegetable oils and food emulsions with a high biological value, an antioxidant and antiradical potential were developed and proven by patents inventions of the Republic of Moldova (Capcanari et al., 2011).

   

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