Starch
Starch, a vital carbohydrate, serves as a primary source of energy for various living organisms. It is composed of glucose units linked together through alpha-1,4 and alpha-1,6 glycosidic bonds. This macromolecule forms two distinct fractions: amylose, a linear chain, and amylopectin, a branched structure. These arrangements and the number of glucose units contribute to the characteristic properties of starch, impacting its functionality in food applications.
Starch is a multifaceted ingredient with diverse applications in the confectionery industry. Understanding its chemical structure, extraction process, functions, and physical properties is crucial for food scientists and manufacturers seeking to optimize its use in the formulation of delightful treats.
Starch properties can undergo alterations through suitable treatments to yield starch varieties tailored for specific purposes. Modifications may encompass acid treatment, enzyme treatment, cross-linking, substitution, oxidation, and heat application.
Source and Processing
Starch finds its origins in diverse plant sources, with cereals (corn, wheat, rice) and tubers (potatoes, cassava) being major contributors. Extraction involves grinding, washing, and separating the starch granules from the plant matrix. The subsequent refining process yields a purified starch product. This extraction method ensures the starch maintains its natural properties, critical for its various applications.
Starch Ingredients and Processing
Main function in Confections
In confections, starch plays a pivotal role as a thickening and gelling agent. It imparts texture, structure, and mouthfeel to a wide array of sweets. Starch's ability to form a gel under specific conditions is exploited in the production of fruit jellies, gummy candies, and various desserts. This functional versatility makes it an indispensable ingredient in confectionery formulations.
It is also widely used as molding medium where a male mold is pressed into a tray with smooth conditioned starch, then filled with a hot syrup that will jellify into a confection such as gummies or marshmallows.
Another popular use is as an anti-sticking agent, for example, in marshmallow surface.
Molecular Structure
The molecular formula of starch is (C6H10O5)n.
It is composed of n number of glucose monomers joined by ɑ (1,4) linkage in chains and ɑ(1,6) linkages at branching point.
Starch molecules exist in two forms – a simple linear polymer called amylose and a more complex branched form called amylopectin.
Amylose is a linear polysaccharide chain that is made up of glucose monomers joined by ɑ (1,4) glycosidic linkage. Amylose makes upto 30% of the total starch molecule. It has a helical structure and is more resistant to digestion.
Amylopectin is a highly branched polymer made up of glucose subunits. It is made up of linear chains of glucose units that are linked by ɑ (1,4) glycosidic linkage along with a number of side chains that branch the structure by ɑ(1,6) glycosidic linkages.
Properties
Hygroscopicity: Starch exhibits hygroscopic tendencies, absorbing moisture from the environment. This property influences the texture and shelf life of confections, impacting their sensory attributes over time.
Crystalline arrangement: Starch granules possess a semi-crystalline structure, influencing their gelatinization properties. This crystalline arrangement dictates the thickening ability of starch in confections during the cooking process.
Solubility: While native starch is generally insoluble in cold water, modification processes such as heat treatment or chemical alteration enhance its solubility. This solubility is crucial for achieving desirable textures in confections.
Shelf stability: Starch contributes to the shelf stability of confections by controlling water activity. This property prevents undesirable textural changes and extends the product's overall quality during storage
Gelling properties: Because of the many hydroxyl groups, starches have great capacity to hydrogen bond. Water in dry starch is held between chains of starch molecules through hydrogen bonds. To start gelatinization of starch, energy (heat) must be supplied to break the hydrogen bonds, and thus allow for water to enter and form new hydrogen bonds. Starches vary in the percentage of amylose and amylopectin, this content/ratio will determine the temperature required to achieve the gelatinization as they are 2 very different molecules. Amylopectin are very ramified molecules and amylose is a more linear chain. The higher the amount of amylose, the higher the temperature needed.
When starch swells and absorbs water causes the granules to increase in volume and eventually burst, releasing the starch molecules into the surrounding liquid, leading to the gel formation. This process can be monitorized through microscopic techniques. The link provided below is a guide on how to prepare samples and observe starch gelatinization using a microscope
Starch Identification by Microscopy
In this document, you'll find instructions on sample preparation, slide preparation, and techniques for observing starch granules as they undergo the gelatinization process. Microscopy can reveal the structural changes in starch granules as they absorb water, swell, and ultimately break down to form a gel. This visual examination helps researchers and food scientists understand the properties of starch and its behavior in various food applications.
Regulatory
In the United States, the Food and Drug Administration (FDA) regulates starch as a food ingredient. Starches used in confections must comply with the Code of Federal Regulations (CFR) Title 21, which sets standards for food safety and quality. Manufacturers must adhere to Good Manufacturing Practices (GMP) to ensure the consistent production of safe and high-quality starch-based ingredients for confectionery applications.
