Extraction and Physicochemical Analysis of Mucilage in Pitaya Succulent Stem
Date Issued
2015
Date
2015
Author(s)
Chen, Yu-Wan
Abstract
Pitaya (Hylocereus spp.), belonging to the Cactus family, is an important fruit crop in Taiwan. The succulent stem of Cactus contains mucilage cells which are rich in mucilage. There are reports suggests that cactus mucilage may have potential applications in food, pharmaceutical, and cosmetic industries. Each year, periodical pruning of Pitaya plants resulted in huge amounts of succulent stem left in the field as agricultural waste. Currently, effective ways of utilization of these wastes do not exist. The aim of this research was to study the methods of extraction of mucilage from pitaya succulent stem. To investigate the effects of different extraction conditions on the yield of mucilage, and to analyze the chemical compositions and physical properties of mucilage extracted from pitaya succulent stem. In this study, three forms of Pitaya succulent stems starting material were prepared: fresh stems, vacuum-dried powder and hot-air-dried powder. The general process of mucilage extraction was as follows: Starting material was mixed with water and extracted at high temperature for a given time; after filtration through cheese cloth and centrifuged at 7,500 x g for 20 min, the supernatant was precipitated by adding 3 volumes of 95% ethanol and stored at 4℃.The precipitates was centrifuged at 12,000 x g for 20 min to form pellet, which was freeze-dried to give the final gray-white crude mucilage powder. The final weight (to calculate the yield of extraction) and total sugar content of the powder was used as the efficiency of purification. With the extraction temperature increased to 80℃, the yield of extraction and total sugar contents reached its maximum for all three starting material. Further elevation in the temperature resulted in less yield and lower total sugar content. When the fresh stem to water ratio was 1:1, the extraction was incomplete and when the ratio was 1:2, the best extraction efficiency was obtained. Further increase in the ratio of water to fresh stem would affect the process of mucilage precipitation and lowered the yield. When the hot-air-dried powder to water ratio was 1:10, the extraction was incomplete; when the ratio was 1:20, the best extraction efficiency was obtained. Further increase in the ratio of water to fresh stem would also affect the process of mucilage precipitation and lowered the yield. For vacuum-dried powder, changing the material to water ratio from 1:10 to 1:50 did not affect the yield very much. For fresh stems, extraction for 1 hour was not enough and the best result was obtained by extraction for 2 hours. Increase extraction time to 3 hours or more resulted in degradation of mucilage polysaccharide and hence lower the yield. For fresh stems, when the material to water ratio was 1:3 and extracted at 80℃ for 3 hours, the total yield was 1.31% of fresh weight after 4 cycles of extraction, and the extraction percentage of the first cycle was 97.8%. For hot-air-dried powder, when the material to water ratio was 1:30 and extracted at 80℃ for 1 hours, the total yield was 1.56% of fresh weight after 4 cycles of extraction, and the extraction percentage of the first cycle was 89.7%. For vacuum-dried powder at the same conditions, the total yield was 1.03% of fresh weight after 4 cycles of extraction, and the extraction percentage of the first cycle was 68.5%. The total sugar content of mucilage was highest in mucilage extracted from fresh material, followed by vacuum-dried material, and is lowest in hot-air-dried material, the value were 66.9%, 55.9% and 42.6% respectively. The protein content of mucilage was also highest in mucilage extracted from fresh material, followed by vacuum-dried material, and is lowest in hot-dried material, the value were 1.21%, 1.15% and 0.56% respectively. The ash content of mucilage extracted from hot-air-dried material was 28%, which contain 5.7% calcium and 3.4% potassium. All these value were significantly higher than the mucilage extracted from fresh and vacuum-dried material. The value of mucilage swelling power extracted from hot-air-dried material at 30-90℃ were all higher than other two material extracted mucilage. This phenomenon suggested that there might be a positive correlation between the ash and mineral content and the swelling power of mucilage. Mucilage extracted from hot-air-dried pitaya succulent stem was hydrolyzed for 1 hr. at 120℃ with trifluoroacetic acid (TFA) and analyzed by HPLC-RI system with the following two separation condition: (1) column: Shodex Asahipak NH2P-50 4E, mobile phase: 250 mM phosphoric acid/acetonitrile (20/80), column temperature: 50℃; (2) column: Shodex Sugar SP0810, mobile phase: deionized water, column temperature :80℃. Comparison between the separation results of the two column system and sugar standards showed that the mucilage of hot-air-dried powder was a hetero-polysaccharide and composed of arabinose, galactose, rhamnose and another unknown monosaccharide. The content of arabinose, galactose, rhamnose were 15.2%, 27.2%, and 2.15% d.w. respectively.
Subjects
pitaya
succulent stem
mucialge
extraction
Type
thesis
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