Sulu deterjan fraksinasyon prosesinin hayvansal iç yağlarına uygulanması

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Fen Bilimleri Enstitüsü
Et endüstisinin yan ürünü alan iç yağları eritilmek suretiyle yağdan başka dokulardan ve yabancı maddelerden ayrılır. iç yağının özel koku ve lezzetinin tam alarak giderilmesi ve asidiklerinin nötralleşmesi için fiziksel vs kimyasal işlemlere tabi tutulmak suretiyle rafine edilir. Ayrıca fraksinasyon işlemi uygulanarak erime noktaları farklı ürünler elde edilir. Bu çalışma, iç yağının deterjan fraksinasyanunu kapsamaktadır. Bu proseste temel prensip basittir. Yağ kont rollü şartlar altında soğutularak kristalize edilir. Kıs men kristalize yağa surfaktant ve elektrolit içeren sulu çözelti ilave edilir ve yüksek erime noktasına sahip stnarin ve düşük erime noktasına sahip olein santrifüj edilerek ayrılır. Deneysel çalışmalarda, öncelikle sulu solüsyonun içerdiği surfaktant ve elektrolit konsantrasyonlarının olein verimine etkisi incelenmiştir. Ayrıca solüsyonun yağa oranı ile olein ürünü arasındaki miktarsal ilişkiler saptanmıştır. Elde edilen yağ ürünleri üzerinde analizler yapılarak tanınmalarına çalışılmıştır. Kristalize yağa ilave edilen solüsyonun içerdiği surfaktant ve elektrolit konsantrasyonlarının fraksinasyonun yürütülmesinde önemli olduğu bulunmuştur.
In recent years the worlds production of fats and oils has increased at an avarage annual rate of ca. k%. The S million tons of tallow produced in the world consti tute only ca. 11% of the total supply at fats and oils, since tallow is the largest single source of the industrial fatty acids. The use of animal fats are feed stock for oleochemi- cals appears to have a history of more than 5DDD years. Markley quates sources that report the finding of earthen vases in Egyption tombs believed to predate the First Dynasty (ca. 3200 B.C.). One of these vases contained a solid that was high in stearic acid and was believed to have been beef or mutton tallow. Soap was made by the Phonecians as early as 600 B.C, and candles made of bees wax and tallow were known to the Romans. Animal fats (sometimes called meat fats) are by pro ducts of the meat-packing industry. The principal animal fats are butter, tallow and lard. Edible tallow is usually derived from beef fat. Inedible tallow also known to industrial or technical tallow. The districtions between edible and inedible tallow are based on hygienic and rugulatory considerations rather than on chemicial differen ces. In contrast to edible tallow the inedible material is classified and traded in varius grades in which minimum melting point (titer) and maximum color, free fatty acid cantent, and MIU (moisture, insoluble, unsaponnif rabies) are specified rather than origin. Several past studies indicate that the composition of animal fats varies as function of georaphic location, breed, age and feed of the animal. Some evidence exists IX that bady fat af cattle is relatively little, especially with respect to sturated acids, by the feed af the animal The environment of the animal appears to influence the com position of the fat with warmer temperatures tending to reduce the unsaturation. Impurities may introduced during the collection and handling of the fat and tallow. Among the impurties that are of importance to the producer of fatty acidsare poly meric materials, such as polyethylene. These polymers stem from the packaging materials used for retail meat cuts. Animal tissue containing fat is converted to tallow and grease by a process called rendering. Basically, rndering is a procedure by which lipid material is sepera- ted from meat t,issue and water under the ifluence of heat. The rendering process is primarily little refining is carried out on technical inedible fats. Natural oils, and fats have different characteristics, since they are composed of a great number of different triglycerides. Chemically a triglyceride is a combination of three fatty acid molecules and one Qly çerin molekül. Fatty acids consists of carbon chains of varying lengths and with different degress of unsaturation. Triglycerides with a high degree of unsaturation, as indicated by a high iodine value, have a lower melting point them those containing more saturated fatty acids. If an oil is cooled to a certain temperature, the high melting paint trigly cerides (stearin) will crystallize, while the low melting paint ones will remain in liquid form. The stearin can then be separated from the oil (olein) by different methods and the fat or oil is thus divided into two fractions: strearin with a high melting point and olein with a low melting point. This method is konwn fractionation process. In this method, three successive stages can be dis tinguished: 1- Cooling of the liquid oil to super saturation, resulding in the formation of nuclei for crystal lization. 2- Progressive growth of the crystals by gradual cooling 3_ Seperation Df the crystalline and liquid phases, In recent years, three fat fractionation processes have been commercialized: dry, solvent and detergent. The dry fractionation process involves partial crystallization of the oil followed by vacuum filtration Df the partially crystallized oil. The filtration yields clear oil but results in significant olein entrainment in the stearin fraction. Solvent fractionation of fats by hexane and other solvents yields fractions containing residual sol - vent. Process equipment must be explosion proof. Solvent recovery can be a significant portion of total process costs. In detergent fractionation, the liquid-solid sepera tion is accomplished by adding an aqueous solution, conta ining a surfactant and electrolyte; to a partially crys tallized oil which prefentially wets the crystals into the aqueous solution. In this study, the detergent fractionation of tallow have studied. The process consists of a partial crystal lization step followed by the addition of a detergent so lution to form an aqueous dispersion. F yield tant c in ole point phase phases concen f erent solids extra oil-in and ma loweri or g from once in y at w has, an trat iall hav surf wat kes ng t iven the ntra ield hich a de d re ion, y we e be acta er e the he o parti centr tion i with emuls n c i t y duces olein ts the en enc nt app mulsio centri lein y ally ifug s in surf ion betw the yie cry lose ears n. f uga ield crysta ation w creased actant f ormati een tho olein y Id is s stal su d by a to be The emu tion llize ill i from conce on oc se of ield. porod rf ace water avail lsion more d tall ncreas zero, ntrati curs. the w At g ic. S s unti dropl able f phase diffic ow t e as Th on m The ater reat urf a 1 mo et. or f ent ult, he ol the e max arks emul and er su ctant st of At h Qrmin rains ther em surf ac- imum the sion olein rf actant pre- the is point g an olein eby - xi A detergent solution to tallow weight ratio of 0,8 was used for all seperations except those in which the ratio was changed intentionally, The detergent solution to tallow weight ratio was specified for each experiment. The electrolyte (sodium citrate) concentration in the detergent solution was 5.0% for all seperations unless otherwise specified. The surfactant weight fraction re ported used based on the aqueous phase composition. Dis tilled water, the electrolyte and the surfactant were mixed together thoroughly and heated to 49°C prior to mixing with the oil. The detergent solution was added to the partially crystallized tallow by mixing with a stirring rod. Mixing was carried out until a uniform dispersion was obtained. The dispersion was allowed to sit for one hr before it was centrifuged at a force of 4000 times that of gravity. The olein was poured out of the centrifuge tubes af ter the centrif ugation. Little of the olein adhered to the tubes. The yield of olein and stearin was calculated as the weight ratio of the olein collected to the original tallow. The dispersion is centrifuged to yield an olein frac tion and a fraction with solid for entrained in the water phase. The olein fraction recoverable from a specific tallow sample depends primarily on the crystallization temperature. Tests indicated that the olein yield reached a maximum at on SDS concentration of 0.6wt%. At that moment ratio of detergent solution to tallow weight used was O.fl. At concentrations above D.6 wt % SDS olein yield was reduced by emulsion formation. At SDS concentrations below 0.1wt% the olein yield was lowered due to ineffective wetting of the crystals into the aqueous phase. The detergency mechanism suggests that the surfactant should be adsorbed on the crystal surf aces, in cases where too much surfactant was used, the surfactant completely coated emulsified olein. It is possible that the low amount of mixing during the dispersion step in this study reduce the amount of emulsif ication occuring at SDS con centrations greater than those needed to coat all the crystals. xn The role af the electrolyte, sodium citrate, in the seperstion atep was investigated by using various elect rolyte concentrations for the seperation step while hold ing other variables constant. The olein yield increased as a function of the electrolyte concentration until an electrolyte concentration of 5.Q % was reached. The olein yield neither increased nor decreased above the 5.0% electrolyte concentrations. If the electrolyte or surfactant concentration was ton low, the crystals were not wetted into the aqueous phase completely. If the surfactant concentration was too low there were insufficent surfactant molecules to coat the crystals. If the electrolyte concentration was toolow, the surfactant molecules could not be aligned properly. Experiments were alsa performed to determine the ef fects on the olein yield using various rations of deter gent solution to tallow weiht. Another interesting fea ture of the result shown that the amount Df detergent so lution used had a great effect on the olein yield achieved The olein yield was rising at the maximum ratio of deter gent solution to tallow weight used. Typically, ails and fats contain mixtures of trigly ceride of varying melting and solubility characteristics due essentially to differences in triglyceride composition The range of melting and solubility characteristics avai- leble from commerical fats and oils can be significantly increased by combiantions involving blending, hyrogenation or interesterification. On the other hand, fractional crystallization can be used to select desired melting and solubility windows from this wide range of triglycerides present in nonfractionated fat source. Fractional crystal lization is used to obtain fats or oils better suited for applications such as: * varius types of margarine * shortening * edible oils * special products for varius types of food, bakery and confectionery industries * various industrial applications. By dividing up the fat or oil into a olein phase and a stearin phase, the field of application of the raw material can thus be increased. In addition the refining value is high, particularly that of the olein phase.
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1990
Anahtar kelimeler
Kimya Mühendisliği, Fraksinasyon, Hayvansal yağlar, Chemical Engineering, Fractionation, Animal fats