Growing consumer demand for the food without chemical preservatives focused significant extent of research in the direction of finding natural compounds that can be used in food preservation. In this context, natural substances with strong antimicrobial and antioxidant properties, like essential oils, as well as natural biopolymers, particularly draw attention. Natural biopolymers can serve as carriers of the active components, such as essential oils in order of their sustained release to the food during storage, and may themselves exhibit activity in protecting foods from oxidation and/or microbial spoilage. Chitosan has been extensively studied as semi-natural polymer with expressed bioactive properties. While antimicrobial activity of chitosan solution in different acids has been confirmed towards different bacteria, yeasts and moulds, reports concerning intensity, underlying machanism and different factors afecting antioxidant activity of chitosan vary through the available literature. This paper presents a review in the field of antioxidative activity of chitosan with different properties, as well as chitosan based biopolymer films in order to clarify this aspect of chitosan bioactivity and confront different reports found in the literature.

In this work, the possibility of obtaining biopolymer films from Camelina sativa oilseed cake (CSoC) at different parameters of the synthesis process was investigated. The pH (values 8, 10, and 12), the temperature (60, 80, and 100 °C), and the concentration of the cake in the film-forming suspension (3, 4, and 5%) were varied. The films obtained were characterized by studying the mechanical, barrier, physico-chemical, structural, and biological properties (antioxidant and antimicrobial). The results showed moderate mechanical properties, indicating the application of these biopolymer materials as coatings. Low values of water vapor permeability (5.1–12.26 g/m²h) and very low transmission in the UV range (less than 2%) indicate good barrier properties. FTIR analysis confirmed the films’ composite structures: peaks related to proteins, polysaccharides, lipids, and cellulose were detected. The biological activity of the obtained CSoC films was pronounced so that they could be used for active packaging. All films have high antioxidant activity, which is more pronounced in samples synthesized at pH 8. The films possess antibacterial properties against S. aureus, while some had an inhibitory effect on S. typhimurium. Standard score analysis showed that the film sample synthetized at pH = 10, temperature = 100 °C, and concentration = 5% had optimal investigated properties.

In this work, caraway or oregano essential oils were added to the cast chitosan film in an attempt to design a natural, biodegradable, bioactive (antioxidant and antimicrobial) packaging film. When the structure of the tested films was analyzed with Fourier transform infrared spectroscopy, no significant differences were found between the chitosan film with and without essential oils of caraway or oregano. The lowest antioxidant activity, based on the scavenging of the stable DPPH? free radical, was detected for the chitosan film without oil addition, going from 11.64%, after 2.5 h to 28.96%, after 24 h. When the caraway essential oil was added to the chitosan film, the antioxidant activity was increased (p<0.05) to 33.47?4.77%, after 2.5 h and to 81.08?0.64%, after 24 h. This increase in the antioxidant activity was even higher in the film with oregano essential oil (p<0.05). After 2.5 h, the value for the antioxidant activity of the chitosan-oregano film was 87.58?1.71%, and after 4 h and 24 h it was above 90%. The obtained results for the antimicrobial activity showed that the chitosan film is an effective antimicrobial agent against Escherichia coli and Staphylococcus aureus. When caraway essential oil was added in 1% volume concentration to the film, no increase in the antimicrobial action of chitosan film was detected. On the other hand, the addition of oregano essential oil promoted chitosan film antimicrobial activity, which was particularly evident with Escherichia coli. The results showed that the chitosan film can be successfully applied as a matrix carrier for essential oils in the active film system.

Chitosan, the second most abundant polysaccharide in nature, after cellulose, has been tested for numerous applications, among which for edible film and coating. Chitosan-based coating showed positive results for shelf life prolongation of meet products. In this paper, dry fermented sausage (Petrovsk? klob?sa) was coated with chitosan-caraway film. The effect of coating on the moisture content, color and lipid oxidation was investigated during a fivemonth period of storage. The moisture content decreased rapidly during the storage and the coating did not slow down the loss of moisture. The Lightness (L*) of the sausage surface increased by the coating application, while the redness (a*) and yellowness (b*) did not change. The coated sausages showed a better color stability of the sausage core through the storage time. Also, coated sausage showed a better oxidative stability till the 60th day of storage, while this difference was not detected at the end of the storage period. Apart from slowing down sausage drying during the storage, chitosan-caraway coating was effective in preserving the sausage quality.