Starch Granules
Title: Starch
Aims
1. To identify starch in food. 2. To study the microscopic appearances of raw and heated starch. 3. To compare the viscosity of various gelatinized starch solutions.
Introduction
Starch is one of the most abundant substances on the earth. It can be found in seeds, grains, and roots of many crops where it is synthesized in granular form. Starch granules are packages of starch molecules. The importance of starch is well-known, as is its central role in human diet. Many aspects of starch structure can be measured by chemical, physical, spectroscopic, or microscopic methods (Tina, 2000).
Starch can be separated into two fractions - amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%). Amylose forms a colloidal dispersion in hot water whereas amylopectin is completely insoluble. The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage. Amylose in starch is responsible for the formation of a deep blue colour in the presence of iodine (Frances and Ellie, 2008).
Starch granules are more or less regular spheres which composed of a mass of radiating needle-shaped crystals when the granules are viewed under polarized light (Srilakshmi, 2003). Starch granules do not dissolve easily in cold water but they will form a temporarily suspension with the starch until the mixture is allowed to stand. When heated with water, the intermolecular hydrogen bonding is broken and grains absorb water and swell. The amylose will leach out from the starch granule as heating continues. Besides that, the viscosity increases until a peak thickness is achieved. This process is known as gelatinisation. The changes transform the temporarily suspension into a more permanent one (Srilakshmi, 2003). The thickness of the starch is called “viscosity”. The increase in the viscosity of heated starch solution is caused by the action of the enlarged starch granules bumping
Aims
1. To identify starch in food. 2. To study the microscopic appearances of raw and heated starch. 3. To compare the viscosity of various gelatinized starch solutions.
Introduction
Starch is one of the most abundant substances on the earth. It can be found in seeds, grains, and roots of many crops where it is synthesized in granular form. Starch granules are packages of starch molecules. The importance of starch is well-known, as is its central role in human diet. Many aspects of starch structure can be measured by chemical, physical, spectroscopic, or microscopic methods (Tina, 2000).
Starch can be separated into two fractions - amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%). Amylose forms a colloidal dispersion in hot water whereas amylopectin is completely insoluble. The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage. Amylose in starch is responsible for the formation of a deep blue colour in the presence of iodine (Frances and Ellie, 2008).
Starch granules are more or less regular spheres which composed of a mass of radiating needle-shaped crystals when the granules are viewed under polarized light (Srilakshmi, 2003). Starch granules do not dissolve easily in cold water but they will form a temporarily suspension with the starch until the mixture is allowed to stand. When heated with water, the intermolecular hydrogen bonding is broken and grains absorb water and swell. The amylose will leach out from the starch granule as heating continues. Besides that, the viscosity increases until a peak thickness is achieved. This process is known as gelatinisation. The changes transform the temporarily suspension into a more permanent one (Srilakshmi, 2003). The thickness of the starch is called “viscosity”. The increase in the viscosity of heated starch solution is caused by the action of the enlarged starch granules bumping
References: Brett, F. (2009). The making of wheat industry. In Wheat Science and Trade (pp. 512-515). USA: Wiley Publishers. Frances, S., Ellie, W. (2008). Starch. In Nutrition: Concepts and Controversies (pp. 105-120). USA: Thomson Higher Education. Jeffery, C. (2007). Microbiology of Soil. In Alcamo’s Laboratory Fundamentals of Microbiology (pp. 326-330). UK: Jones and Bartlett Publishers International. Sharma, J. (2000). Carbohydrates. In Science & Technology: Biology (pp. 94-99). USA: Laxmi Publications (P) Ltd. Srilakshmi, B. (2003). Cereals & Cereal Products. In Food Science: Third Edition (pp. 51-59). New Delhi: New Age International (P) Limited. Tina, L., Athene, M., Frazier, P. (2000). Starch. In Starch Advances In Structure And Function (pp. 1-3). UK: The Royal Society of Chemistry. Vickie, A., Elizabeth, W. (2008). Carbohydrates. In Essentials of Food Science: third edition (pp. 52-59). USA: Springer.