Starch - Occurrence, Variants, Characteristics, and Usage

It has long been established that starch is an indispensable component of a balanced and healthy human diet, as it should make up 80 to 90% of all carbohydrates we consume. However, it is crucial to remember that raw starch is not absorbed by our digestive system. Therefore, for its digestion to be feasible, it must be subjected to heat treatment prior to consumption. Utilizing the properties of starch thus necessitates cooking or baking products that contain it.

Starch is a plant-based polysaccharide. It is made up entirely of D-glucose molecules, joined together by α-glycosidic bonds. However, starch is made up of two fractions that differ in structure. The first of these, amylose, is a fraction with a low molecular weight. Its structure resembles a simple, long, twisted chain made up of up to 1000 glucose particles. The glucose-amylose bonds are connected to it exclusively by α-1,4-glycolic bonds. Amylose makes up about 10-35% of the total composition of the starch, depending on its type. It dissolves exclusively in hot water, not reacting with cold water. The second fraction, amylopectin, has a significantly higher molecular weight and can consist of several million D-glucose molecules. The weight of the amylopectin is due to its branched structure. In amylopectin, side chains are connected by α-1,6-glycolic bonds. This fraction is largely responsible for the physicochemical properties of the starch, such as swelling and the formation of viscous solutions. Amylopectin makes up about 65-90% of the total mass of the starch. The ratio of amylopectin to amylose varies depending on the botanical origin of the plants in which they occur. The chemical structure of amylose can be found at: http://www.edupedia.pl/words/index/show/542465_slownik_chemiczny-amyloza.html (26.02.2018). The chemical structure of amylopectin can be found at: http://www.edupedia.pl/words/index/show/542464_slownik_chemiczny-amylopektyna.html (26.02.2018). Pure starch is a white, crystalline substance without a distinct taste or smell. It does not react with cold water, does not dissolve, and does not change its form. However, when hot or boiling water is used, starch changes its physical properties, forming solutions and a so-called starch paste, also known as starch.

Starch, as previously noted, is a polysaccharide of plant origin. It is primarily found in cereal grains such as wheat, rye, oats, barley, rice, millet, sorghum, and corn, as well as in potatoes and various root vegetables and legumes. The grain of cereals is predominantly composed of endosperm, which is mainly made up of starch, serving as the primary source of nourishment for the plant embryo. The size of the starch granules varies depending on the plant species, with the largest starch granules evident in wheat and rye (3050 µm) and the smallest (2–10 µm) in rice and oats. Cereal grains also contain a minor proportion of protein, ranging from 7 to 18% depending on the variety, as well as an average of 2–4% fat in dry matter. Starch derived from cereal grains is a highly valued raw material for food with a wide range of physicochemical properties. Presently, the most significant demand in the market is for cornstarch, closely followed by potato starch and wheat starch. The list concludes with tapioca, wax, and rice starch.

Corn starch is also known as mazeina. It is a solid with a yellow color and a consistency similar to that of starch powder. It is a particularly popular product among people who follow a gluten-free diet. Corn starch is suitable for baking and thickening sauces. Its disadvantage, however, is its low mineral and dietary fiber content. Recently, it has become known that there is a so-called wax starch (corn wax). It is a specific variety of corn starch that is characterized by a very high level of amylopectin. This fraction, due to its branched structure, is more easily digestible than amylose. Therefore, wax starch is digested faster than regular corn starch. This substance is becoming increasingly popular among bodybuilders and strength athletes, as it quickly replenishes the glucose level that drops after intense physical exertion. Additionally, it stays in the stomach for a short time, which aids digestion. Wax starch is often an ingredient in dietary supplements, and like most supplements, its effects are not fully scientifically proven. The tolerance of wax starch and its utilization by the body can be very individual, so it is not recommended to use it as the only source of carbohydrates. Wax starch can also be obtained from other grains such as rice, barley, sorghum, millet, and amaranth. However, due to the high production costs, they are not used on an industrial scale.

A substantial portion of the starch in the Polish diet originates from potatoes, which are the most favored vegetables in our country. It is projected that the current average consumption level of these vegetables stands at around 100 kg/person/year. The primary constituent of potatoes is starch, the content of which in the bulb fluctuates between 8 and 29%, contingent on the specific variety. Due to the high polysaccharide content, potatoes have emerged as an exceptionally valuable commodity for the food industry, being indispensable in the manufacture of foodstuffs for humans and animals. Furthermore, potatoes have proven to be a valuable raw material source for the spirits and starch industries. Based on the starch content, potatoes can be categorized as follows: varieties with low starch content 20%.

Starch subjected to modification is a type of starch whose characteristics have been altered to enhance its properties or to impart new ones. Used in the food industry, modified substances may involve changing one or more chemical or physical properties. However, it is important to note that such intervention should not be confused with genetic modification, as they are two completely different matters. Intentional changes in the properties of starch can be divided into physical, chemical and enzymatic modifications. Starch subjected to modification is used in the food industry, where it increases production efficiency and stabilizes and emulsifies processed foods. The most commonly used modified starches in industry include: dextrin, acetylated starch, bleached starch, and acetylated polyphosphate starch. Regarding the safety of using modified starch, we can be sure that its addition to food is safe for our health. Modified starch has been included in the official list of safe food additives. According to the regulation of the Minister of Health from April 2011, the amount of modified starch added to food should be as low as possible. To check if modified starch is present in a particular food, one should carefully read the label. This substance is hidden behind the symbols: E 1404, E 1410-E 1414, E 1422, E 1440, E 1442, E 1450-E 1452.

The most significant technological and utilitarian traits of our starch are influenced by the rheological properties of the various types of starch solutions. The starch solutions are characterized by varying temperatures of thickening and varying degrees of viscosity. These two factors have the greatest impact on the usability of starch in different sectors of the food industry and beyond. The rheological properties of the aqueous solutions of various types of starch are presented below.