Elma posası ve bu posadan elde edilen pektinlerinin mikrodalga fırında kurutulması ile oluşan değişimlerin incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 55828
- Danışmanlar: PROF.DR. NURSEN İPEKOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 57
Özet
ÖZET Pektin, stabilizör ve jel yapıcı bir madde olarak kullanılan değerli bir polisakkarittir. Yenilebilir bitkilerin hücre duvarlarından ekstrakte edilerek el de edilir. Bu amaçla, genellikle, elma posası ve narenciye kabuklan kullanılır. Üretimi toz ve sıvı olmak üzere iki şekilde gerçekleştirilir. Pektinin kullanım alanı esterleşme derecesine göre farklılık gösterir. Yüksek esterli pektinler özellikle meyvaya dayalı ürünlerde homojenliğin sağlanması ve ü- rünün uzun süre dayanıklılığının korunmasında, düşük esterli pektinler ise daha çok diyabetik ürünlerin hazırlanmasında kullanılır. Bu çalışmada, posa ve pektin üzerinde mikrodalga kurutmanın etkisi incelenmiştir. Sonuç değerlere göre; posanın ve pektinin mikrodalga kuru tulmalarının pektin kalitesi üzerinde etkili olduğu saptanmıştır. Kuru halde bulunan ticari pektin çöktürülerek mikrodalgada kurutulmuş ve elde edilen değerler karşılaştırılmıştır.
Özet (Çeviri)
SUMMARY EXAMINATION OF DRYING VARIATIONS OF APPLE POMACE AND PECTINS THIS POMACE BY MICROWAVE Pectin is the designation for a group of valuable polysaccharides extracted from edible plant material and used extensively as gelling agents and stabilizers by the food industry. The discovery of the chemical compound was made by Vauquelin in 1790. But Braconnot was the first to characterize it as the active fruit component responsible for gel formation and suggest the name“pectin”. The isolation of commercial pectins from suitable plant material commenced early in this century. Like starch and cellulose, pectin is a structural carbohydrate product present in all plants. Pectic substances are integral components of the cell structures and play an important role as cementing material in the middle lamellae of primary cell walls. Pectic substances are abundant in fruits and vegetables. Pectin and pectic substances are heteropolysaccharides mainly consisting of galacturonic acid and galacturonic acid methyl ester residues. In 1944, the American Chemical Society adapted a“Revised Nomenclature of the pectic substances”. These uniform definitions are as follows; -Protopectin is the water-insoluble parent pectic substance, the part of the pectic material which is strongly bound to the cell walls, probably plays a major role in the connections between cell wall polymers. -Pectinic acids are the colloidal polygalacturonic acids containing more than a neglible proportion of ethyl ester groups. Under suitable conditions, pectinic acids, are capable of forming gels in water with sugar and acid. The salts of pectinic acids are either normal or acid pectinates. - Pectin are those water-soluble pectinic acids of varying methyl ester content and degree of neutralization. Pectin are capable of forming gels with sugar and acid under suitable conditions. - Pectic acid is a term applied to pectic substances composed mostly of colloidal polygalacturonic acids and essentially free from methyl ester groups. The salts of pectic acids are either normal or acid pectates. The pectic substances are found in the intercellular regions and the cell walls of all higher plants. In most plant tissue and certainly in immature fruit, the major portion of the pectic material is present in a water insoluble form commonly designated as protopectin. During fruit ripening theinsoluble protopectin is gradually transformed into a more water soluble form. This change in pectic solubility has an influence on the textural changes accompanying ripening. Due to increasing commercialization of pectinic acids with a low methyl ester content and partly amidated pectinic acids for use in various food products. Pectin is a complex high molecular weight polysaccharide mainly consisting of the partial methyl esters of polygalacturonic acid and their sodium, potassium and ammonium salts. The product is otained by aqueous extraction of appropriate edible plant material usually citrus fruits and apples. The structural aspects of the mixture of acidic and neutral polysaccharides, which together constitute pectic substances, have been the subject of recent reviews. The major structural feature of the pectic substances is the presence of acid polysaccharides composed largely of D- galacturonic acid units linked through ot-1,4 glycosidic bonds. Normally some of the carboxyl groups are esterified with methyl alcohol. Formation of methyl ester groups seems to happen after polymerization of the galacturonan chain has begun. The presence of free carboxyl groups causes pectin solutions to display an acidic pH. A 1 % solution of a nonbuffered pectin may give a pH ranging from 2.7-3.0. Before standardization most commercial pectins are buffered by partial neutralization so that the pH of a 1% solution will fall between pH 3-4. When subjected to acidic conditions, the glycosidic bonds and the methyl ester linkages of pectin are prone to hydrolysis leading eventually to galacturonic acid. The solubility, viscosity and gel-forming ability of a pectin depend on the chemical characteristic of the pectin, degree of esterification, molecular weight, plus the presence and level of chemical entities that may be part of the pectin molecule. Water is the best solvent for pectin; aqueous solutions containing up to 4% pectin are commonly prepared. Ultimately, viscosity acts to limit the level of pectin that can be conveniently dissolved. Upon contact with water, the outer portion of the pectin particles softens; the partially hydrated particles tend to stick to each other. Pectin is generally insoluble in organic solvents; it can be precipitated from aqueous solutions by addition of polyvalent cations has been used for many years. Pectin is soluble to some degree in formamide,dimethylsulfoxide, dimethylformamide and hot glycerol, but this behavior has no present industrial application. Commercial pectin is generally obtained by dilute-acid extraction of citrus albedo or apple pomace followed by various purification and isolation processes. The product usually occurs as a practically odorless. For practical purposes, the pectin molecule can be considered as an unbranched chain containing 200 to 1000 galacturonic acid units linked together by a-1, 4-gulucosidic bonds. Some of the galacturonic acid units in the molecule are esterified and present as galacturonic acid methyl ester. The degree of esterification is defined as the ratio of esterified galacturonic acid units to total galacturonic acid units in te molecule. High- ester pectins called high methoxyl pectins. High methoxyl pectins are pectins with a degree of esterification above 50%. High-ester pectins require a minimum content of sugar and acid in order to form gels. Once formed, the high-ester pectin gel cannot be remelted by heating. Pectins with a degree of esterification in the range 70 to 75% are offen referred to as rapid set high-ester pectins while the designations low set is used for pectins with a degree of esterification in the range 55 to 65%. Low-ester pectins are pectins with a degree of esterification below 50%. Commercial low-ester pectins are generally produced from plant material containing high-ester pectins. The transformation of high-ester pectin accordingly takes place at controlled conditions during the manufacturing process by treatment at either mildly acidic or alkaline conditions. If ammonia is used for the alkaline de-esterification process, amidated low-ester pectin will result. Apart from galacturonic acids and contain galacturonamide units in the molecular chain. The gelling mechanism of low-ester pectins differs essentially from that of high-ester pectins. To obtain gel formation in a sytem containing low- ester pectin, the presence of calcium ions ancial. Unlike high-ester pectin, low-ester pectin gels may further melt when heated. Pectins as extracted vary in respect of functional proporties and commercial products are therefore most often diluted with sucrose or dextrose for standardization purposes to produce. For example“150 USA- SAG jelly grade”high-ester pectin for use in jams and jellies. A jelly grade designation of 150° USA-SAG implies that 1 part pectin is able to transform 150 parts of sucrose into a jelly prepared under standardized conditions. In addition to sugars, suitable food grade buffer salts may be added for pH control and to achieve desirables in characteristics. Apple pomace and especially citrus peel are the only raw materials of any significance for commercial pectin production. Apple pomace is normally dried immediatelly after the juice pressing. Dried apple pomace generally yields 10 to 15% pectin. XITo solubilize and liberate the pectin, the raw material is added to acidified water. pH is usually 1.5 to 3.0. The acid used is most often hydrochloric acid, nitric acid and sulfuric acid. At the extraction conditions, a certain de-esterification of the pectin will take place. To arrive at the desired degree of esterification at the end of the extraction process. pH, temperature and time must be controlled carefully. Rapid set high-ester pectins are generally extracted at temperatures close to the boiling point. The raw extract is a viscous liquid containing 0.3 to 1.5% dissolved pectin and the peel or pomace residue in a more or less swolen and disintegrated state. More separation processes, filtrations with various types of filter aid and centrifugations, are necessary to obtain a clear extract. The gelatinous precipitate obtained is washed with alkol and pressed to remove soluble impurities and finally dried and milled to yield powdered pectin. In the manufacturing process, pectins are normally dried to a water content below 10%. As the equilibrium moisture content is 12% in 70% relative humidity, pectin tends to take up moisture in most climates. Molecular weight of pectins can be expected to vary with raw material, extraction conditions and isolation procedure. When added to water, powdered pectin tends to form lumps consisting of pockets of semidry powder enrobed by a shell of hydrated material. These lumps dissolve very slowly. Pectin is generally soluble in water and insoluble in most organic solvents. The formation of gels from pectic materials is a complex phenomenon and that the exact mechanism of gel formation is not fully understood. If a gel can be described as an organized state of matter that is intermediate between liquid and solid, then a pectin jelly is an organized matrix of pectin and solution lying between a pectin solution and presipitation of the pectin. Pectins with a degree of esterification of 70% or higher will form satisfactory gels with sugar at pH levels of 3.0-3.4 and relatively high temperatures. At ester levels of 50-70%, pectins will form good gels with sugar at a pH of 2.8-3.2 and somewhat lower temperatures. Low-ester pectins have the abilitiy to form gels upon the addition of multivalent cations, usually calcium. Various viewpoints concerning the mechanism of gel formation with LM pectin and the resulting gel structure have been expressed. Pectin consequently has llimited use as a thickener. It is used to import jams, jellies and preserves, bakery fillings and glazings, dairy product, fruit beverages and sauces, fruit preparations and medicine industries. Uses of pectin is different as degree of esterification. High-ester pectins are principially used in the manufacture of jams, jellies, marmelades and jellied candies of high quality and industrial fruit preparetions are mainly used for combination with yogurt and other dairy products. High-ester pectin is used Xtlin fruit drink concentrates to stabilize oil emulsion and fruit particle suspention. Low-ester pectins, alone or in combination with other food hydrocolloids, are used in fruit or tomato sauces, topping, table syrups. A considerable amount of pectin is further used outside the food industry primarily for pharmaceutical purposes. Pectin is used to treat diarrhea, it has been used for the treatment of wounds, as a hemostatic agent, as a blood-plasma substitute, as a detoxicant of poisonous heavy metals and for the formation of complexes with insulin, penicillin. In the first part of this study, apple pomace is dried in different efficiency of microwave and examined different of structures in FTIR. Then, pedtin is extracted from these dried pomace and examined pectins in FTIR. Commercial pectins and pectin of producted with 50% efficiency in microwave were analized for esterification, jelly degrees and ash quantities. XIII
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