Galacturonic content Pectin Characterization

19 methoxyl content is less than 7, the pectin is categorized as low methoxyl pectin LMP Goycoolea and Adriana 2003. Methoxyl content of extracted pectin ranged from 4.07-6.43. Based on the value of methoxyl content, the resulted pectin in this study was relatively low in methoxyl. Graph showing the relationship of microwave power and time of extraction treatment on methoxyl level of pectin can be seen in Figure 13. The graph showed that the methoxyl content will become higher with increasing microwave power and the length of extraction time. Figure 13. The relationship between microwave power and extraction time to methoxyl content. Results of analysis of variance showed that the microwave power and extraction time significantly affected the methoxyl content of pectin, but interaction between microwave power and extraction time was not significantly affect the methoxyl content of pectin Appendix 5b. The highest methoxyl content was pectin with treatment microwave power of 800 W for 7 minutes, while the lowest methoxyl content was obtained from pectin with treatment microwave power of 600 W for 3 minutes. The range of methoxyl content from this pectin was 4.07-6.43 which was under 7. Because of the methoxyl pectin was under 7, so the pectin extracted from sugar palm seed was belongs to Low Methoxyl Pectin LMP category. Methoxyl content of pectin has an important role in determining functional properties of pectin solution and can affect the structure and texture of pectin gel Constenla and Lozano 2006. High methoxyl pectin forms a gel in the presence of sugar and acid. Conditions required for gel formation is 58- 75 sugar content with a pH 2.8-3.5. Low methoxyl pectin does not have the ability to form gel in the presence of sugars and acids, but it can forms a gel with presence of polyvalent cations Cruess 1958. LMP on industry can be used as a thickener in manufacturing of low calories beverage, jelly for diabetic, and others healthy food. The pectin industry normally produces high methoxyl pectin though there are some plants that produce low methoxyl pectin. There are four methods of demethylation including the use of acid, alkali, enzyme and ammonia in ethanol. Demethylation using acidis commonly used to produce low methoxyl pectin Kertesz 1951. Extraction of high methoxyl pectin is easier to do with lower cost. In addition, most of the sources of raw materials produce high methoxyl pectin. High methoxyl pectin is more considered to meet the market needs. If the market want slow methoxyl pectin, the high methoxyl pectin can be easily converted into low methoxyl pectin. But low methoxyl pectin is more difficult to be converted to high methoxyl pectin Kertesz 1951.

5. Galacturonic content

Galacturonic content and pectin molecule charge have an important role in determining the functional properties of pectin solution. Galacturonic content can affect the structure and texture of pectin gel Constenla and Lozano 2006. f e d c b a 0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00 600 800 M et ho xy l C on te nt Microwave Power Watt 3 min 5 min 7 min 20 Galacturonic acid content of extracted pectin ranged between 34.64-57.11. The lowest galacturonic content was pectin extracted with microwave power of 600 W for 3 minutes. The highest galacturonic acid content is pectin extracted with microwave power of 800 W for 7 minutes. Figure 14 shows the relationship between microwave power and extraction time to galacturonic content. Figure 14. The relationship between microwave power and extraction time to galacturonic content. Figure 14 showed that the galacturonic content would increase when microwave power and extraction time was increased. This was due to the length of the protopectin hydrolysis reaction so that the galacturonic levels produced were also increasing. Results of analysis of variance showed that the microwave power and extraction time significantly affected the galacturonic content of pectin, but interaction between microwave power and extraction time was not significantly affect the galacturonic content of pectin Appendix 6b. FDA of Thailand 1986 determined that minimum anhidrouronic acid content in commercial pectin minimum is 35. Pectin that extracted longer with higher microwave power will contain higher galacturonic content. The resulted pectin extracted from sugar palm seed contain galacturonic acid above 35 and meet the standard from FDA of Thailand. One of factor that determines the quality levels of pectin is galacturonic content. The higher the value of galacturonic contents, the quality of pectin will be higher. According to Nelson et al. 1977, beside of galacturonic acid, pectin also contains other substances like neutral sugar D-galactose, L-arabinose, and L-rhamnose. Non-uronic substances can be washed during precipitation process of pectin with ethanol. These substances will affect the composition of pectin. The difference of pectin composition also affected by extraction method that been used Towle and Christensen 1973. Some of non-uronic substances may be eliminated by re-dissolved in water or precipitation with ethanol, but it is impossible to eliminate all non-uronic substances.

6. Degree of esterification