The hydrolyzed products of chitosan are called as chitosan oligosaccharides (COSs) due to its shorter chain length and presence of amino groups in D-glucosamine, which is readily soluble in water. The low viscosity and greater solubility of COS at neutral pH serves application in versatile areas. COS produced by acid or enzymatic hydrolysis method, in which enzymatic hydrolysis is preferred due to its safe and ease of control. Due to its cationic character, chitosan presents a wide variety of physicochemical and biological properties, including antimicrobial, antioxidant and antihypertensive properties. Its cationic character, chitosan presents a wide variety of physicochemical and biological properties, including antimicrobial, antioxidant and antihypertensive properties.

With an excellent absorption due to its high solubility, it has been found as high functional bioactive material with a wide range of immune enhancement, antitumor effect, antibacterial function, and calcium absorption acceleration effect. Chitosan oligosaccharide is a saccharine which is combined with glucosamine hexaose from two to ten with a structure of Chitosan. COS in food and nutrition arenas have emphasized their ability to improve food quality and human health progression.The health benefits of COS including lowering of blood cholesterol, lowering of high blood pressure, protective effects against infections , controlling arthritis and enhancing antitumor properties.

Different chitosan derivatives and enzymatic products have different structures and physicochemical properties, which may result in novel bioactivities or novel findings in known bioactive compounds. The lack of toxicity, allerginicity with its biocompatibility, biodrgradablity and bioactivity attracted in medicine, biotechnology. The cationic character, chitosan presents a wide variety of physicochemical and biological properties, including antimicrobial, antioxidant and antihypertensive properties. These properties make it suitable for numerous applications in different fields, for instance, medicine (pharmacology, cosmetics), biotechnology, agriculture, the food industry (nutritional enhancement and food processing), the environment

Water soluble chitosan

(waste and water treatment) and the textile industry. Generally, molecular weight of COS can be considered up to 10 kDa or less, and during preparation of different molecular weight chitosans, viscosity is used as a parameter to determine the molecular weight.