At present, discards from the world’s fisheries exceed 20 million tons. Traditionally, fisheries
wastes are used in the production of fertilizers, fish silage or pet foods; nowadays with advances in
bioprocess engineering technologies and novel enzymatic and microbial hydrolysis methods, processing
wastes may serve as cheap raw materials for the generation of high-value bioactive compounds and novel
environmental and ecological material derived from marine wastes. In particular, shellfish waste is the main
source of biomass for chitin (and its derivatives) production. In this contest chitosan, thanks to its versatility,
has found numerous applications as antimicrobial agents, antioxidants, additives, enzyme immobilization and
use in the encapsulation of nutraceuticals. In addition, chitosan possesses a film-forming properties for use as
edible films or coating. Several researchers studied chitosan, its chemical and physical characteristics and its
applications. This chapter is an attempt to summarize these works focused on the following questions: what is
chitosan? How does it act against microorganisms and what is its impact on food properties?
Keywords: What is chitosan, How it acts against microorganisms to enhance shelf life of foods, What is its impact on
food properties.
