Starch Utilization in Food Industries

The food industries constitute one of the largest consumers of starch and starch products. In addition, large quantities of starch are sold in the form of products sold in small packages for household use. Cassava, sago, and other tropical starches were extensively used for food before the Second World War but use declined owing to the disruption of world trade. Attempts were made to develop waxy maize as a replacement for normal non cereal starches; the production of cassava starch has increased considerably in recent years.
Cassava Utilization
Fufu flour
High quality cassava flour
Glucose syrup
Composite bread
Livestock feed industry
Livestock feed products
Starch in paper, etc.
Starch in food
Starch production
Unmodified starch, modified starch, and glucose are used in the food industry for one or more of the following purposes:
  • Directly as cooked starch food, custard, and other forms.
  • As thickeners, using the paste properties of starch (soups, baby foods, sauces, and gravies, etc.).
  • As fillers, contributing to the solid content of soups, pills, and tablets, and other pharmaceutical products, face cream, etc.
  • As binders, to consolidate the mass and prevent it from drying out during cooking (sausages and processed meats).
  • As stabilizers, owing to the high water holding capacity of starch (e.g., in ice cream).
Functional properties of starch are important for food applications (Table 1)
Table 1. Functional Properties of Starches in Foods
Specific viscosity (hot and cold) Mouthfeel, lubricity, palate-coating
Thin boiling (faster canning heat transfer) Suspension characteristics
Viscosity resistance acid/mechanical sheer Adhesiveness
Freeze-thaw stability (natural/ modified) Crystallinity
Gel texture, body at various temperatures Bland taste
Clarity, opacity Long shelf-life stability
Processing conditions tolerance Hygroscopicity
Oil retention, high or low Color
Resistance to setback (gel formation) Anti-caking
High sheen Cold-water swelling or dispersibility
Flow properties Swelling and resistance to swelling
Emulsion stabilizing capacity Film-forming properties
Postharvest Equipment
Source: Morton Satin (undated). Functional properties of starches Chief, Agro-Industries and post-harvest management service, FAO, Italy.
Examples of the use of starch are given below with various sub-themes of products.

Bakery products
Although starch is the major constituent of flours, the art of' bread baking depends to a large extent on the selection of flour with the proper gluten characteristics. Starch is used in biscuit making to increase volume and crispness. In Malaysia, cassava starch is used in sweetened and unsweetened biscuits and in cream sandwiches at the rate of 5-10% to soften the texture, add taste, and render the biscuit non sticky. The use of dextrose in some kinds of yeast-raised bread and bakery products has certain advantages as it is readily available to the yeast and the resulting fermentation is quick and complete. It also imparts a golden brown color to the crust and permits longer conservation.

Dextrose and glucose syrup are widely used as sweetening agents in confectioneries. In addition to this widespread use, starch and modified starches are also used in the manufacture of many types of candies such as jellybeans, toffee, hard and soft gums, boiled sweets hard candy, fondants, and Turkish delight. The principal use of starch in confectioneries is in the manufacture of gums, pastes, and other types of sweets as an ingredient and in the making of molds or for dusting sweets to prevent them from sticking together. Dextrose prevents crystallization in boiled sweets and reduces hygroscopicity in the finished product.

  Canned fruits, jams, and preserves
Recent advances in these industries include the partial replacement of sucrose by dextrose or sulphur dioxide-free glucose syrup. This helps to maintain the desired percentage of solids in the products without giving excessive sweetness, thereby emphasizing the natural flavor of the fruit. The tendency toward crystallization of sugars is also decreased.

Monosodium glutamate (MSG) and lysine
Monosodium glutamate (MSG) is used extensively in many parts of the world in powder or crystal form as a flavoring agent in foods such as meats, vegetables, soups, sauces, and gravies. Cassava starch and molasses are the major raw materials used in the manufacture of MSG in the Far East and Latin American countries. The starch is usually hydrolyzed into glucose by boiling with hydrochloric or sulphuric acid solutions in closed converters under pressure. The glucose is filtered and converted into glutamic acid by bacterial fermentation.

The resulting glutamic acid is refined, filtered, and treated with caustic soda to produce monosodium glutamate, which is then centrifuged and dried in drum driers. The finished product is usually at least 99% pure. As at 2002, the highest consumption of native cassava starch in Thailand was by the industries making MSG (four factories) and lysine (one factory) in the proportion or 80:20. The production of MSG in Thailand utilizes only two sources of carbohydrates for inoculation; molasses and cassava starch. To produce one tonne of MSG, factories need either about 2.4 t of cassava starch or 7.0 t of molasses.

Citric acid
There are two factories manufacturing citric acid in Thailand though none in Nigeria. One uses cassava pulp from starch factories as the raw material (about 5-6 t/day) for its solid-state (surface) fermentation. The other, recently established, uses cassava chips as the raw material for its submerged fermentation process. About 40 t of chips are needed to produce 6 t/day of citric acid.

Commercial caramel
Caramel as a coloring agent for food, confectionery, and liquor is extensively made of glucose rather than sucrose because of its lower cost. If invert sugar, dextrose, or glucose is heated alone, a material is formed that is used for flavoring purposes; but if heated in the presence of certain catalysts, the coloration is greatly heightened, and the darker brown products formed can be used to color many foodstuffs and beverages. Uniform and controlled heating with uniform agitation is necessary to carry the caramelization to the point where all the sugar has been destroyed without liberating the carbon.

Glucose from starch: starch hydrolysis
Glucose or dextrose sugar is found in nature in sweet fruits such as grapes and in honey. It is less sweet than sucrose (cane or beet sugar) and also less soluble in water; however, when used in combination with sucrose, the resulting sweetness is often greater than expected. The commercial manufacture of glucose sugars from starch began during the Napoleonic Wars with England, when suppliers of sucrose sugar were cut off from France by sea blockade. Rapid progress was made in its production in the United States about the middle of the nineteenth century.

At present, glucose is usually produced as syrup or as a solid. The physical properties of the syrup vary with the dextrose equivalent (DE) and the method of manufacture. Dextrose equivalent is the total of reducing sugars expressed as dextrose and calculated as a percentage of the total dry substance. Glucose is the common name for the syrup and dextrose for the solid sugar. Dextrose, sometimes called grape sugar, is the D-glucose produced by the complete hydrolysis of starch. Today, two methods for starch hydrolysis are used for the commercial production of glucose: acid hydrolysis and partial acid hydrolysis followed by an enzyme conversion.

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