The common industrial starches are typically derived from cereals (corn, wheat, rice, and sorghum) tubers (potato, sweet potato) roots (cassava) and legumes (mung, bean, green pea). The sago is a starch extracted from the pith of sago palm stems, Metroxylon Sagu and is the only starch derived from another source. It is often cultivated and grown well in freshwater swamps. The sago palm tolerates a wide variety of soils and may reach up to 30 meter in height. There are several species of Metroxylon but the less important sources are M.Solaomonense and Mamicarum.
The palms reproduce once before dying and are harvested just before flowering, usually when they attain the age of seven to 15 years. The stems will be full of starch for use in reproduction during the harvest. The trunk is cut into sections that are split lengthwise and the soft material in the centre is scooped out (Fig-1). The starch is extracted from the soft material by washing and straining. The product is dried to yield sago meal or granulated to make "Pearl" sago (Fig-2). A single sago palm may yield about 150-300 kg of sago. A normal fresh water swamp can produce 50 palms suitable for felling per hector. The sago palm cultivation yield seven tonnes of starch per hector land. The palm will mature and be ready for harvest in six to eight years during which it attains 24-26 feet high and 17-27 inch thickness.
The sago cultivation is the most appropriate method of land utilization. At present, it is estimated that there are about two million hector of natural sago palm forest and about 0.14 million hector of planted sago palm out of a total swamp area of about 20 million hector in Asia and Pacific region. The cultivation of sago starch in a suitable environment with organized farming practice could yield up to 25 tons of starch per hector per year. The nutritional value of 100 grams of dry sago yields 355 calories, including an average of 94 grams of carbohydrate, 0.2 grams of protein, 0.5 grams of dietary fibre, 10 mg of calcium, 1.2 mg of iron, and negligible amounts of fat, carotene, thiamine, and ascorbic acid. The sago can be stored for weeks or months, although it is generally eaten soon after it is processed.
The sago is traditionally cooked and eaten in various forms such as rolled into balls, mixed with boiling water to form paste or as pancake, steamed puddings called sago plum and as ground powder as thickener for other dishes. In India pearl sago is called javvarisi, sabudana (Hindi) and saggubeeyan (Telugu) used in a variety of dishes. The sago is a main staple of many traditional communities in New Guinea, Borneo, Maluka, Sumatra, Indonesia and Malaysia. The popular local cuisine in Brunei called "ambuyat" and "sawakandd" in Srilanka are made from sago. The sago is commercially used in making noodles and white bread. Principally the sago is used in a variety of dishes such as desserts boiled with sweetened milk on occasion of religious fest.
In the ayurvedic system of medicines, the sago porridge can be an effective and simple food to cool and balance one's body heat, while taking strong medicine or antibiotics. Sago-C-500 is a powerful mixture featuring corn-free, Sago palm vitamin C teaming up with rich bioflavonoid and glandular support to help maintain a solid immune barrier. The sago starch has been given less attention compared to the other common industrial starches. This article highlights some pertinent information related to sago palm and sago starch application.
There is an increased demand of sago starch in the market due to the increased utilization of sago starch in the production of food, polymer, in pharma and in textile industry. The sago starch (sabu medium) has been extensively used as gelling agent for the isolation of starch degrading micro organism. Sago starch represents an alternative carbon source for the fermentation of micro organism, and is widely available throughout the year.
The sago medium is 10 times cheaper than its counterpart and provides a cost effective alternative. The Cyclodextrin (CD) is an important polysaccharide due to its unique hydrophobic interior cavity and hydrophilic surface can encapsulate other hydrophobic organic substances, aiding solubilization in water. This is useful in food, pharma, cosmetic and agricultural applications. The cyclodextrin can be produced by Bacillus Circulans CGTase from sago starch. The starch and their derivatives and the blends are used in single-use disposable short life packaging materials. The advantage of these packaging materials is that, the starting materials used for preparing it are completely biodegradable making it environmentally friendly.
The microbial production of bio-fuel from organic by-products has acquired significance in recent years. Among the bio-fuel ethanol has been trusted as an alternative fuel for the future. The microbes used for the bio conversion includes Clostridium species, Saccharomyces Cerevisiae and facultative bacteria Zymomonas Mobilis. The Zymomonas species have additional advantage over Saccharomyces Cerevisiae, that ethanol productivity and tolerance are more. The production of bioethanol utilizes sago "hampas", a solid residue produced as waste by the increased utilization of sago starch which otherwise can cause environmental pollution. The bioconversion of the sago "hampas" can also be utilized for the production of fermentable sugar, industrially important enzymes, feed, compost etc. The studies are on for the production of bioethanol from sago "hampas" and are an economical process, when compared with production of the same from petroleum resources. For the effective conversion of sago "hampas" into fermentable sugar, depends on the improvement of "hampas" hydrolysis condition. The R&D wing is focusing on this factor, which can pave the way for the increased yield in the production of bioethanol. The Penicillium brunneum from sago palm tree was discovered and is used as a source of starch digesting amylase.
The sago starch can be chemically modified by esterification and etherification, which improves the physicochemical properties. The process loosens the structure of starch and requires less temperature for gelatinization. The chemical modification can be done by treating the sago starch with hydrochloric acid in the presence of methanol, ethanol and 2-propanol at 450C for one hour improves the solubility property of native sago starch. The novel composite containing sago starch filled with linear low density polyethylene was prepared and has modified the mechanical properties such as increased proportion of starch and good uptake of water. The composite can be studied for the application in drug delivery technology.
The study of the disintegrating properties of papaya and sago starch revealed that both has disintegrating property, but in comparison, sago starch possess higher disintegrating property than papaya starch. The starch is widely used as a pharma excipient in various pharmaceutical dosage forms. The unmodified starch has poor flow property and compressibility, which otherwise showed defects if used in high concentration. The modification of sago starch through pregelitinization techniques can improve the flowability, compressibility and swelling properties. The swelling property can be used as a valuable guideline to determine the disintegration efficiency of the excipient. The higher the swelling the better will be the disintegrating power.
The starch based transparent hydrogel membrane is studied for its application as wound dressing and showed promising results. The combination of sago starch and polyvinyl alcohol (PVA) give tremendous improvement on strength and elasticity of the gel, adding additives like carboxy methyl cellulose enhance the swelling property and can be applied as wound dressing. The study of starch from sago palm as a binder in parecetamol tablets showed significant binding property and can be used as tablet binder. The grafting of methacrylic acid monomer onto sago starch showed a decrease in the gelatinization temperature (temperature at which the disruption of the molecular orders in the starch granules occurs).
The grafting of sago starch on to mathacrylic acid monomer has immense biomedical application as drug delivery system. The sago blends (sago starch-polyvinyl alcohol and sago-polyvinyl pyrrolidone) can be used as an alternative biodegradable packaging material. The suitability of sago starch in the preparation of capsules was studied. The moisture content, strength and water vapour permeability of sago starch capsules were comparable to that of capsules made of gelatin. The sago starch capsules only swelled and failed to disintegrate within 30 minutes. The sago starch capsule shell does not comply with pharmacopoeial standards in disintegration test for capsules.
(This article was compiled from the B.Pharm project carried out by Mohammed Mehrooful Huck.N.V).
The author is assistant professor, National College of Pharmacy, Manassery, Calicut
Processing of Sago starch from Sago palm (Fig-1)
Pearl Sago (Fig-2)