Nanofiber membrane filtration and microwave applications during fruit juice processing

Membranes are barier materials which seperate two or more phases from each other. Basic functions of membranes are caused from a driving force such as pressure or concentration difference. The membrane filtration is a cheap process than other methods and the application have high efficiency. Nanofiber membranes are a good choise for filtration application by the way of their porosity and high surface area per volume. Nanofiber membrane filters can hold some substances and cells by their adsorption and keeping abilities. Therefore, bright and silky fruit juices can be gained by nanofiber membran filtration from liquids. Besides, holding microorganisms through nanofiber memran filters can be provided. Hence, safe foods can be handled with the respect of microorganisms and the composition of treated foods may be similar with non treateed ones. Combination of nanofiber membrane filtration with some other applications such as new technological packaging systems, long shelf life foods can be achieved. Electrospinning is a nanofiber producing method. The process can be performed at room conditions. Besides, the electrospinning technic is cheap, versatile and simple than other nanofiber gaining methods. A spinnable polymer solution is feeded to tip of a capillary tube and applied electrical field. When voltage exceed a critic value, a jet is formed from polymer droplet to the collector. The solvent evaporates during passaging from tip to collector and nanofibers compose from polymer on the collector surface. Polyacrilonitrile is an electrospinnable polymer widely used at ultrafiltration, reverse osmosis and nanofiltration technics. Besides, the polymer have high chemical and heat resistance. Also PAN fibers absorb metal ions quickly. The fibers are reversable and have good mechanic properties. Heat treatment with microwave application is commonly used, cheap and simple process. Comparing with traditional methods, process can be finished quickly and energy saving can be provided. Hence, safe foods can be supplied in terms of microbially by microwave application. Besides, nutrient values can be close to non treated juices. Also, microwave application provide an otocontrol for foodstuff. With increasing the temperature and decreasing water amount of food, the dielectric loss factor decrease along with. Therefore, absorbed electromagnetic energy decreased. The sellective heating was provided through mentioned mechanism. The aim of the thesis was research some differencies between non treated fruit juices and processed fruit juices through nanofiber membrane filtration and microwave application. There may not need a heat treatment owing to nanofiber membrane filtration. Also fruit juices reach targetted temperature value by microwave application quickly. Otocontrol from dielectrical heating can provide microbially safe and silky fruit juices. The nutritient values may similar between non treated ones. At the researches, lemon juices and strawberry juices used. The reasons of choosing lemon juice were the high demand for using soauce and high export amount of lemon fruit. Furthermore, a drinkable lemon juice can be produced. The choosing of strawberry juice is caused from the low consume amounts of strawberry juice than strawberry. By the way of developing new processes for strawberry juice, an increasing of the total quality of the juice can be yielded compared with the traditionally heat treated juices. The nanofiber membrane was produced from PAN-DMF with 10% concentration by electrospinning method. The solution was stirred at 90˚C for at least 3 hours. The feed rate was 3 ml/h, collector distance was about 20 cm and applied voltage was 29-40 kV. Each used nanofiber membrane filter production continued about 1 hour. The membrane thichness was similar like a very thin film. The membrane was waited in a UV cabin for a night before process. Filtering application was carried out sterilized conditions. The filtering equipments were otoclaved at 121˚C for 15 mins. The membrane put on the system with a sterilized pliers and applied 1 bar vacuum. The microwave heat treatment parametres was 90o C temperature and 15 seconds time for lemon juices. The parametres was choosed according to the inactivation of pectinmetilesterase enzyme of limon juices. On the other hand, the heat treatment norms of strawberry juice was 85˚C temperature and 2 mins. Both for lemon juice teratment and strawberry juice, the application power was 300 W. The temperatures of juices were measured with a a microwave termometer. After the processing, the juices were cooled to room temperature. At the end of the research, pH of juices decreaced at microwave application but increased with nanofiber membrane filtration. The surface tension values was founded least at filtrated juices and maximum at microwaved fruit juices. Also zeta potential values of all samples was founded at unstable regions. Zeta potential of lemon juice samples were founded pozitive, on the other hand strawberry juice samples were negative. Filtered lemon juice samples had higher zeta potential values than non treated ones. Total soluble solid content values increased with microwave application, although the brix value decreased with nanofiber membran filtration application. Diameter of particules founded least at filtrated samples and highest at non treated samples. Viscosities decreased by nanofiber membrane filtration application. Although there was a decreasing at viscosity of pasteurized lemon juice sample, the viscosity of microwaved strawberry juice increased. Surface tension rised with microvave application, on the other hand filtrated samples had less surface tension values than others. Dielectrical constants and dielectrical loss factors detected at least microwaved samples and at most filtered samples. Total phenolic content of lemon juices reduced with both nanofiber membrane filtration and microwave application. However, total phenolic content values of strawberry juice were similar between microvawed and non treated samples. There was no microbially growth at microwaved samples. Filtration application did not inactivated the microbial contamination. According to the results, the used PAN nanofiber membrane had not the small pore for elimination of microorganisms or PAN nanofiber membrane harmed when applying the filtration process. The production of each filter took time about 1 hour. By nanofiber membrane filtration, the diameters of particules reduced. The diffusion ability arised with filtration application. Besides, the microwave heat treatment damaged the particules of fruit juices. The based on the total phenolic content analyses, the total phenolic content of the filtered samples decreased. Therefore, microwave application is better choise with respect of phenolics. Nanofiber membrane filtration can be used for concentration of phenolic compounds from fruit juices. The total soluble solids, viscosities and darkness of the colour reduced with nanofiber membrane filtration. Brighter and silkier product handled by filtration on the other hand microwave treatment made darker the colour of fruit juices. According to the zeta potential values, all samples were tend to the collaption. The filtrated lemon juice had the longest collaption time in samples. Dielectric constant and dielectric loss factor were decreased with the reducing water amount and increased with risining amounts.