Ayva pektinin ekstraksiyonu
Extraction of quince pection
- Tez No: 75380
- Danışmanlar: PROF. DR. ÖZGÜL EVRANUZ
- Tez Türü: Yüksek Lisans
- Konular: Gıda Mühendisliği, Food Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Gıda Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 54
Özet
ÖZET Pektin saflaştırılmış bir karbonhidrat bileşiği olup esas olarak, değişen oranlarda metoksil grubu bulunduran poligalakturonik asit zincirinden oluşur. Ticari pektinler genellikle, turunçgil kabuklan ve elma posalarından ekstrakte edilen pektinlerin şeker ile standardize edilmesi yoluyla elde edilir. Gıda endüstrisinde pektinler genellikle kıvam verici, stabilizör veya jelleştirici olarak kullanılmaktadır. Bütün yeşil bitkiler, yapısal özelliklerini belirleyen pektik maddeleri ve selülozları karışım halinde içermektedir. Ham meyvede daha çok suda çözünmeyen formda bulunan pektin (protopektin), olgunlaşma sırasında enzimlerin etkisi ile metil alkol ve pektik asite dönüşmekte ve suda çözünür hale gelmektedir. Endüstriyel ölçekte pektin üretimi 3 şekilde yapılmaktadır. Bunlar: 1) Sıcak asit ekstraksiyonu, 2) Alkali ekstraksiyonu, 3) Enzim ekstraksiyonudur. Pektinler, molekülde bulunan galakturonik asit ünitelerindeki karboksil gruplarının, metil grupları ile esterleşme derecesine göre sınıflandırılırlar. Ticari pektinler yüksek metoksilli pektinler (>%50) ve düşük metoksilli pektinler ( 1 o. cd «T "n o M CO si c3 3 *5 p co CO C e». e- (3D S120-i 1. dakika 2.dakika 3.dakika 4.dakika S.dakika 6.dakika 7.dakika Süre Şekil 1. Sitrik asit kullanılarak mikrodalga ısıtma ile yapılan ekstraksiyonlarda sıcaklık artışının asitlik değerine göre değişimi. 120 100 80 o * 60 S5 40 20 1. dakika 2.dakika S.dakika 4.dakika 5.dakik2 6.dakika 7.dakika Sûre Şekil 2. HC1 kullanılarak mikrodalga ısıtma ile yapılan ekstraksiyonlarda sıcaklık artışının asitlik değerine göre değişimi.
Özet (Çeviri)
EXTRACTION OF QUINCE PECTIN SUMMARY Pectin is a purified carbonhydrate product obtained by aqueous extraction of appropriate edible plant material. It is composed mainly of partially methoxylated polygalacturonic acids. Commercially pectins are standardized pectin which is usually extracted from citrus peels or apple pomace. Pectin is usually used in food industry as thickening agent, stabilizer or jelling agent. Fruits and vegetables contain pectic substances as a complex which is responsible from their structural properties. Pectin is present as protopectin in green fruits or vegetables. Protopectin is a water-insoluble parent pectic substance. During subsequent ripening it is hydrolized by enzyme action to pectin, and during rotting or overripening much of the pectin may further decompose to from methyl alcohol and pectic acid. In industrial production there are three ways to produce pectin. These are; 1) Hot acid extraction, 2) Alkaline extraction, 3) Enzyme extraction (with pectin esterase). Pectins are classified according to the degree of esterification of the carboxyl groups of the galacturonic acid chains. 50% degree of esterification divides pectins into two groups: High methoxyl pectins and low methoxyl pectins. High methoxyl pectins have over 50% esterified carboxyl groups. High methoxyl pectins will form gel in the presence of relatively high sugar concentrations (%55-85) at a pH of about 2.5- 3.8. The degree of esterification strongly influences the time and temperature relationships required for gelation. High methoxyl pectins are classified according to the setting time of gel as rapid-set, medium-rapid-set or slow set. High degree of esterification increases setting temperature and decreases setting time. Low methoxyl pectins have below 50% esterification degree. It can gel in the presence of polyvalent cations such as Ca+2, Mg+2. It is not sensitive to pH values unlike to high methoxyl pectins. Low methoxyl pectins are produced from high methoxyl pectins by suitable de-esterifications. In this study, quince pectin was extracted in acidic conditions. The effects of pH value, acid type and heat source on pectin quality were evaluated. Extract viscosities, pectin yield(g pectin/100 mis extract) and degree of esterification were determined for each extraction. In this study, frozen quince pulp was used (78.5% moisture) as a pectin source. Before extraction, samples were heated in microwave oven for 4 minutes to thaw. In each extraction 100 g thawed quince pulp was used. Before extraction samples were washed using hot water(750C) for 25 minutes to remove some of the sugars, pigments and minerals which can prevent pectin precipitation after extraction. In washing step 500 ml deionized water was used for 100 g quince pulp. »After filtration, washed pulp was mixed with 400 ml acidified water. For acidification HC1 or citric acid were used. Extractions were made with acidified water with the pH values of 1.5, 2.0 and 2.5. Two kinds of healing methods were used to extract pectin. 1) Extraction was made by heating at 80°C for 2 hours. 2) Extraction was made using microwave energy at 70% efficiency for 7 minutes. Extracts were filtered immediately after extraction, then cooled to room temperature. Extracts viscosities were determined by Haake RT20 Rotovisco type reometer at 25°C. Precipitation was made using equal volume of 96.6% ethanol and than kept at +4°C for an hour to complete precipitation and to facilitate filtration. After filtration, ^ washing was made using 60% alcohol until the pectin were free from CI“ if the acidified solution is prepared with HC1. If not, washing was made until the acidity was eliminated. Drying of precipitated pectin was made at microwave oven at 50% efficiency for 10 minutes 45 seconds. Pectin yield in extracts were calculated from 100 ml extract. Table 1 shows the results of the experiments. In general, viscosities were decreasing while the pH values were increasing for both HC1 and citric acid extractions. At all conditions, citric acid extracts had higher viscosity than HC1 extracts. At 80°C for 2 hours extractions, HC1 extracts' viscosities were found between 2.84*10”3-6.26*10“3 Pa s and citric acid extracts' viscosities were found between 5.27*10”3-10.6*10“3 Pa s. For microwave energy extractions, HC1 extracts' viscosities were found between 2.11*10”3-6.7*10“3 Pa s and citric acid extracts' viscosities were found between 5.3*10”3-10.9*10“3 Pa s. Viscosity depends on the molecular weight, presence of the electrolhes, pH, temperature and soluble solids of the extracts. Pectin yield in extracts were calculated for 100 ml extract. The highest pectin yield was obtained during microwave extraction by extraction at pH 1.5 using citric asid for acidification. When HC1 was used for acidification the highest pectin yield was obtained at pH 2.0, at 80°C and 2 hours. Beside the raw material, pectin yield and pectin properties are influenced by extraction conditions (pH, temperature, time and acid type). High temperature, long extraction time and high pH decrease the pectin yield. At high temperature, long extraction time prevents pectin precipitation because of the degradation of the pectin molecule. At high temperature, short extraction time influences pectin yield positively. There are many researcher who pointed out that microwave energy can be used in pectin extraction. Figure 1 and Figure 2 show the temperature increases during extractions in microwave oven. For both HC1 and citric acid extractions, at pH 2.5 and 2.0 temperatures higher than pH 1.5. Degree of esterification was influenced from extraction conditions. In general, at the same extraction conditions pectins' degree of esterifications were found close to each other. In this study it was found that for the same pH, microwave energy extractions gave pectins of higher degree of esterification with citric acid than HC1. For extractions using HC1 pectins' degree of esterifications were found between 48.7- 64.0%, for citric acid extractions pectins' degree of esterifications were found between 51.9-82.1%. Degree of esterification, especially for high methoxyl pectins, defines gel strenght and setting time of the pectin together time and temperature. xuO] C O o. -o o> I (M O S3 V 3 > c o *.§ o « ”S -s O a> & v t).o c“o ”>> e 1 ?s 09 O o 09120 100“ 80 O ”i ? 60 H 40 20 İjmmfle 2jmnute 3.minute 4.minute Sminute 6.minule 7.minute Extraction Time Figure 1. Relationship between extraction time-temperature inreases at citric acid extractions in microwave energy extractions. 120 n 1UÜ § 60 {2 40 20 0 1.minute 2jmnute 3.mmute 4.minute Sjninute 6.mmute 7-minute Extraction Time Figure 2. Relationship between extraction time-temperature inreases at HC1 extractions in microwave energy extractions. High methoxyl pectins require high temperature to get gel(>85°C). At low pH values, especially for HC1 extractions, degree of esterifications were found lower than others because of the deesterificatioa XIV
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