C.V. Hanson1, E.A. Oelke2, D.H. Putnam2, and E.S. Oplinger3
1Center for Alternative Plant and Animal Products, University of Minnesota, St. Paul, MN 55108.
Psyllium is the common name used for several members of the plant genus Plantago whose seeds are used commercially for the production of mucilage. The genus Plantago contains over 200 species. P. ovata and P. psyllium are produced commercially in several European countries, the former Soviet Union, Pakistan, and India. Plantago seed known commercially as black, French or Spanish psyllium is obtained from P. psyllium and P. arenaria. Seed produced from P. ovata is known in trading circles as white or blonde psyllium, Indian Plantago or Isabgol. Isabgol, the common name in India for P. ovata, comes from the Persian words "isap" and "ghol" that mean horse ear, which is descriptive of the shape of the seed. India dominates the world market in the production and export of psyllium. Psyllium research and field trials in the U.S. have been conducted mainly in Arizona and also in Washington.
Recent interest in psyllium has arisen primarily due to its use in high fiber breakfast cereals and from claims that these high fiber cereals containing psyllium are effective in reducing cholesterol. Several studies point to a cholesterol reduction attributed to a diet that includes dietary fiber such as psyllium. Research reported in The American Journal of Clinical Nutrition concludes that the use of soluble-fiber cereals is an effective and well tolerated part of a prudent diet for the treatment of mild to moderate hypercholesterolemia. Research also indicates that psyllium incorporated into food products is more effective at reducing blood glucose response than use of a soluble fiber supplement that is separate from the food. Although the cholesterol reducing properties and glycemic response properties of psyllium containing foods are fairly well documented, the effect of long term inclusion of psyllium in the diet has not been determined. Cases of allergic reaction to psyllium containing cereal have been documented.
Psyllium is produced mainly for its mucilage content, which is highest in P. ovata. Mucilage describes a group of clear, colorless, gelling agents derived from plants. The mucilage
obtained from psyllium comes from the seed coat. Mucilage is obtained by mechanical milling/grinding of the outer layer of the seed. Mucilage yield amounts to approximately 25% or more (by weight) of the total seed yield. Plantago seed mucilage is often referred to as husk or psyllium husk. The milled seed mucilage is a white fibrous material that is hydrophilic (water-loving). Upon absorbing water the clear colorless mucilaginous gel that forms increases in volume by ten-fold or more. Psyllium is mainly used as a dietary fiber, which is not digested by action in the small intestine. The purely mechanical action of psyllium mucilage absorbs excess water while stimulating normal bowel elimination. Although its main use has been as a laxative, it is more appropriately termed a true dietary fiber.
The United States is the world's largest importer of psyllium "husk" with over 60% of total imports going to pharmaceutical firms for use in products such as "Metamucil", "Effersyllium" and "Fiberall". Psyllium mucilage is also used as a natural dietary fiber for animals. The dehusked seed that remains after the seed coat is milled off is rich in starch and fatty acids and is used in India as chicken feed and as cattle feed.
Psyllium mucilage possesses several other desirable properties. As a thickener, it has been used in ice cream and frozen deserts. A 1.5% weight/volume ratio of psyllium mucilage exhibits binding properties that are superior to a 10% weight/volume ratio of starch mucilage. The viscosity of psyllium mucilage dispersions are relatively unaffected between temperatures of 68 to 122°F, by pH from 2 to 10 and by salt (sodium chloride) concentrations up to 0.15 M. These properties in combination with psyllium's natural fiber characteristic may lead to increased use by the food processing industry. Technical grade psyllium has been used as a hydrocolloidal agent to improve water retention for newly seeded grass areas and to improve transplanting success with woody plants.
Plantago ovata is an annual herb that grows to a height of 12 to 18 in. Leaves are opposite, linear or linear lanceolate (0.4 × 7.5 in.) The root system has a well developed tap root with few fibrous secondary roots. A large number of flowering shoots arise from the base of the plant. Flowers are numerous, small, and white. Plants flower about 60 days after planting. The seeds are enclosed in capsules that open at maturity.
P. ovata is a 119 to 130 day crop that responds well to cool, dry weather. In India, P. ovata is cultivated mainly in North Gujarat as a "Rabi" or post rainy season crop (October to March). During this season, which follows the monsoons, average temperatures range between 60 to 85°F and moisture is deficient. Isabgol (P. ovata) which has a moderate water requirement, is given 5 to 6 light irrigations. A very important environmental requirement of this crop is clear, sunny and dry weather preceding harvest. High night temperature and cloudy wet weather close to harvest have a large negative impact on yield. Rainfall on the mature crop may result in shattering and therefore major field losses. The growing season in Wisconsin and Minnesota is not likely to be suitable for production of psyllium.
Isabgol grows best on light, well drained, sandy loams. The nutrient requirements of the crop are low. In North Gujarat, the soil tends to be low in nitrogen and phosphorus and high in potash with a pH between 7.2 and 7.9. Nitrogen trials under these conditions have shown a maximum seed yield response with the addition of 20 lb/acre of nitrogen.
P. ovata has small seeds, 1000 seeds weigh less than 2 grams. Under ideal conditions of adequate moisture and low temperature (50 to 68°F) 30% of the seed germinates in 5 to 8 days. The seed shows some innate dormancy (3 months) following harvest. Various treatments including wet and dry heat, cold, scarification, ethylene and CO2 do not eliminate this dormancy period. Post-dormancy seeds show reliable germination in excess of 90% at 84°F and lower rates of germination as temperature is increased.
The fields are generally irrigated prior to seeding to achieve ideal soil moisture, to enhance seed soil contact, and to avoid burying the seed too deeply as a result of later irrigations or rainfall. Maximum germination occurs at a seeding depth of 1/4 in. Emerging seedlings are frost sensitive, therefore planting should be delayed until conditions are expected to remain frost free. Seed is broadcast at 5 to 7.5 lb/acre in India. In Arizona trials, seeding rates of 20 to 25 lb/acre resulted in stands of 1 plant/in. in 6 in. rows produced excellent yields. Weed control is normally achieved by one or two hand weedings early in the growing season. Control of weeds by pre-plant irrigation that germinates weed seeds followed by shallow tillage may be effective on fields with minimal weed pressure. Psyllium is a poor competitor with most weed species.
Plantago wilt Fusarium oxyspirum and downy mildew are the major diseases of Isabgol. White grubs and aphids are the major insect pests.
The flower spikes turn reddish brown at ripening, the lower leaves dry and the upper leaves yellow. The crop is harvested in the morning after the dew is gone to minimize shattering and field losses. In India, mature plants are cut 6 in. above the ground and then bound, left for a few days to dry, thrashed, and winnowed.
Harvested seed must be dried below 12% moisture to allow for cleaning, milling, and storage. Seed stored for future crops has shown a significant loss in viability after 2 years in storage.
The contract price for 95% purity psyllium husk set by the Indian Basic Chemical, Pharmaceutical and Cosmetic Export Promotion Council for April of 1988 was $1.65/lb F.O.B. This price is up from $1.14/lb set in 1985. The average seed yield of P. ovata in India often exceeds 1000 lb/acre. Net yield of 95% purity husk after milling would be 250 lb/acre. Average gross revenue from milled product at 1988 prices would be $412/acre. The costs of production and milling in the U.S. are unknown but would certainly need to be determined in order to analyze the potential profitability of a commercial psyllium venture.
The U.S. currently imports and consumes approximately 8,000 metric tons of psyllium annually. A continued expansion of this market seems likely due to the high level of interest in natural dietary fibers. No variety has been tested in the Upper Midwest but it would seem that the varieties that are grown in India would not be suited to production in this area. A major cultural problem limiting psyllium production in this area is the shattering characteristic of the mature crop. Some success has been achieved by cross-breeding high yielding Indian varieties with varieties that are more shatter resistant. Until shatter resistant varieties are available, production of Isabgol is likely to be restricted to environments that consistently provide a cool dry harvest season.