But in tropical developing countries, the very success of starch crops as staple foods is limiting their potential contribution to agricultural development and general economic growth. A recent study by AG's Agricultural Industries and Post-harvest Management Service (AGSI) found that, while exhaustive research has been carried out on their agronomic and phenotypic properties, tropical crops have not benefited from the kind of value-added research required for competitiveness on an international scale. As a result, maize, wheat and potato continue to dominate lucrative world markets for starches in food and non-food industries. These modern value-added products are, generally, very application-specific and thus far less susceptible to the market fluctuations that can cause chaos in developing economies built on basic commodities.
Breaking out of this subsistence crop mentality and competing with mainstream starch products will not be easy - because it is not maize, wheat or potato themselves that are the competition, but rather the functional characteristics of their value-added products.
Starch is used in a wide range of non-food products. For example:
Adhesives hot-melt glues, stamps, bookbinding, envelopes, labels
Explosives match-head binder
Paper paper coating, disposable diapers
Construction concrete block binder, plywood adhesive
Metals sintered metal adhesive, foundry core binder
Textiles fabric finishing, printing
Cosmetics make-up, face creams
Pharmaceuticals pill coating, dispersing agents
Mining ore floatation and sedimentation
Others biodegradable plastic film, dry cell batteries
High potential exists for the profitable commercial use of tropical starches. But massive research and product development of a new type is needed to properly exploit these materials. The model for product quality and reliability has already been set by the international starch industry. If locally-produced tropical starches cannot attain an equivalent level of quality, functionality or reliability, they will simply not survive in the competitive market - there is only so much that a more equitable trade environment can offer.
Far more work must be carried out on those characteristics that make products more convenient to distribute and easier to process, and that enhance the physical, chemical and organic properties required by target markets. For those starches that do not have the native functional characteristics desired, additional efforts must be made to value-add or modify them so that they can compete internationally.
The AGSI study says the single most important guide for practical research is undoubtedly the marketplace. Large markets require a consistent supply, and reliable price and quality. They are reluctant to be pioneers and it is extremely difficult to interest markets in new products unless these criteria can be assured. Large markets also need time to test and re-test new products until they are absolutely certain that they are suitable (imagine, for example, the problems of a large paper company if 5,000 tonnes of white paper turned yellow after one year on the shelf because a new starch additive proved unstable).
Starch basics: granule size, amylose and amylopectin. Once these basic factors are accounted for, the next most critical consideration is product performance, which depends on functional characteristics. In fact, that is how starch should be viewed: as a set of functional characteristics suited to a particular application.
These characteristics follow on from the physico-chemical properties of starch granules. The size and distribution of starch granules is important for specific applications. For instance, the small granule size of rice starch makes it highly suitable for laundry sizing of fine fabrics and for skin cosmetics. Arrowroot was once the product of choice in carbonless paper, which requires starch of a particular size and uniformity. A starch such as wheat could not be used - at least not without modification - because of the bimodal distribution of its starch granules, whose average size ranges from 6.5 to 19.5 microns.
Other simple physical characteristics important to functionality are starch granule shape and surface, critical factors when starch is used as a surface carrier of colours, flavours and seasonings. These qualities are functions of starch's amylose/amylopectin ratio. The two polymers are very different structurally - amylose being linear and amylopectin highly branched - and each plays a critical role in the ultimate functionality of the native starch and its derivatives: viscosity, shear resistance, gelatinization, textures, solubility, tackiness, gel stability, cold swelling and retrogradation all depend on the amylose/amylopectin ratio.
Adding value to native starches. When aiming at functional properties in starch, most commercial companies examine the characteristics of competitive starches in particular applications. This sets the target to shoot for. When those characteristics are unattainable with native starches, the only alternative is some form of value-addition. This can be as simple as sterilizing products required for the pharmaceutical industry or highly complex chemical modification to confer properties totally different from the native starch.
The extent of specific functional properties of starches required by the food industry is almost unlimited. No other ingredient provides texture to as many foods as starch does. Whether it is a soup, stew, gravy, pie filling, sauce or custard, starch provides a consistent shelf-stable product that consumers rely on. A growing proportion of these characteristics is being sourced from genetically-modified native starches as a result of the growing demand for natural foods.
There is also a great variety of value-added applications for starch in non-food industries, and each application requires very particular functional characteristics. Even in the most basic non-food applications of starch, a great deal of value-addition is employed: adhesive starches are acid- or alkali-treated, and modified with oxidizing agents, salts and alcohols. Textile starches are esterified, oxidized and subject to various cross-linking agents.
The use of sophisticated, value-added starches is especially notable in paper products. Starches are used to give greater strength to tissues and paper towels, and they allow a greater use of recycled paper in liner board and cardboard. The growing demand for biodegradability promises to provide additional volumes as starch is used in plastic films and sheets as well as natural fibre formulations that will eventually replace plastic foams.
The volume of starch going into non-food uses is enormous. In fact, non-food uses of starch are a prime indicator of a country's economy. An active economy needs construction materials for buildings, industrial plants and housing, paper for administration, packaging and wrapping various products, and adhesives to stick all this economic activity together. As the economy booms, so does the volume of starches going into non-food uses. As countries develop, so does their demand for high quality, highly functional, value-added starches.
Information gap. The particular physical and chemical properties of individual starches are the keys to their commercial success. A search of Food Science and Technology Abstracts and the Foods Intelligence databases found a huge gap between information available on the physical properties of the Big Three of starch - wheat, maize and potato - and information on tropical starches.
Publications on yam, millet, sorghum and cassava account for less than 12% of the total. A similar profile emerges in research on chemical properties and on the modification of starches.
The AGSI study concludes that much work remains to be done on the functional characteristics of native as well as modified tropical starches if they are ever to become competitive. It urges a shift in agricultural research in tropical countries - where no strong tradition of value-added research and development has been established - toward those product characteristics that make processing easier or more efficient, such as uniform-shaped roots or thin, easy-to-peel skins. Slight changes in amylose/amylopectin ratios can have tremendous effects on a wide range of functional characteristics.
These are properties that the end-user requires and is willing to pay for. Without this new orientation in research - at national and international levels - there is little hope of establishing a significant presence of value-added starches from developing countries on world markets.
Published September 1998