Chitosan is a biopolymer with high added value, and its properties are related to its molecular weight. Thus, high molecular weight values provide low solubility of chitosan, presenting limitations in its use. Based on this, several studies have developed different hydrolysis methods to reduce the molecular weight of chitosan. Acid hydrolysis is still the most used method to obtain low molecular weight chitosan and chitooligosaccharides. However, the use of acids can generate environmental impacts. When different methods are combined, gamma radiation and microwave power intensity are the variables that most influence acid hydrolysis. Otherwise, in oxidative hydrolysis with hydrogen peroxide, a long time is the limiting factor. Thus, it was observed that the most efficient method is the association between the different hydrolysis methods mentioned. However, this alternative can increase the cost of the process. Enzymatic hydrolysis is the most studied method due to its environmental advantages and high specificity. However, hydrolysis time and process cost are factors that still limit industrial application. In addition, the enzymatic method has a limited association with other hydrolysis methods due to the sensitivity of the enzymes. Therefore, this article seeks to extensively review the variables that influence the main methods of hydrolysis: acid concentration, radiation intensity, potency, time, temperature, pH, and enzyme/substrate ratio, observing their influence on molecular weight, yield, and characteristic of the product.

The goal of the present study was to determine, through full 2³ factorial design, the optimum process conditions to develop a biodegradable film, made from gelatin with buriti oil (BO) as additive, characterizing their physical, mechanical, and antioxidant aspects. The conditions for the optimization were 2.3% of fish gelatin, 30% of BO, and 13.18% of plasticizer. The films produced under this condition presented high antioxidant activity (24.77 µmol de TE/g), mechanical resistance (8.04 MPa), and satisfactory water vapor permeability (WVP; 0.38 × 10⁻¹⁰ g.m. m⁻². s⁻¹. Pa⁻¹). The film presented low solubility in water, low humidity, and low water activity, contributing to its integrity, without identifiable flaws. The increase in the concentration of BO provided higher antioxidant properties to the films and the reduction in gelatin and glycerol concentrations provided lower WVP, increasing the traction resistance.

Fish industry residues are used due to their easy transformation into several products and because they have nutrients with high biological value, being rich in proteins and fatty acids. The gelatin extraction process from the skin of kumakuma (Brachyplatystoma filamentosum) using sodium hydroxide was optimized and the product was characterized. The optimized conditions established in the process were 6 h extraction at 58°C, with yield and gel strength at 19.7% and 244.3 g, respectively, which is considered acceptable for foods. The maximum desirability condition was 0.998. When the technological properties of the gelatin extracted from fish skin was compared with commercial gelatin, a difference (p < 0.05) was observed for all parameters analyzed, but within the appropriate range for gelatin. The gelatin obtained from kumakuma skin may be a new alternative to replace gelatin from mammals, besides contributing to less fish residue released into the environment.