Produção de filmes poliméricos biodegradáveis e comestíveis a partir de pólen apícola para aplicação na indústria de alimentos

Abstract

The development of new packaging concepts for the food industry – such as packaging made of biopolymers to replace conventional synthetic materials – is currently growing to meet the demand for food conservation with reduced environmental impact and with mechanical and barrier properties similar to the usual ones. Given this scenario, our work aimed to develop and characterize polymer films spiked with bee pollen for use in food packaging. In our research, we realized a study of the Tubi bee pollen. Due to the lack of information regarding the subject, we performed the characterization of this product, which presented an acceptable physicochemical and nutritional quality, with an average energy value of 388.62 kcal/100g. The Fourier-transform Infrared Spectroscopy (FTIR) exhibited molecular vibrations related to the key major constituents such as carbohydrates (sugars), lipids, and proteins. In our work, we used an experimental design of mixtures with fourteen tests. In these tests, we analyzed the independent variables (alginate, pectin, and starch concentrations) based on subjective aspects, and the characteristics of moisture (ω), thickness (δ), water solubility (S), and water vapor permeability (WVP). Concentrations of 10g of pollen, 3 ml of glycerol, and 30 ml of 1m calcium chloride were established for all tests. We selected the optimized films based on the best results for homogeneity, continuity, transparency, and flexibility, along with the lowest value of ω, δ, S and WVP. After this assessment, we selected five tests: G4 (1/3g alginate + 2/3g pectin), G6 (1/3g pectin + 2/3g starch), G7 (2/3g alginate + 1/3g pectin), G8 (2/3g alginate + 1/3g starch) e G10 (1/3g alginate + 1/3g pectin + 1/3g starch), which were characterized in terms of mechanical properties, FTIR, scanning electron microscopy (SEM), and optical microscopy. The results show that the G6 film presented the best tensile strength (2.83 MPa) but also the lowest elongation at break value (4.05%), showing itself to be more rigid, while the G8 film achieved a better elongation (9.60%). Young’s modulus of elasticity ranged from 35.05 to 137.06 MPa. By analyzing the SEM of the cross-section of the films, it was possible to visualize the presence of pollen granules that interfered with the homogeneity of the films, forming disordered matrices. In the optical microscopies, the presence of pollen granules is evident, corroborating what was obtained in the SEM. Based on the FTIR results, we could see that the combination of polymers and pollen to form the films did not result in significant changes in the spectrum bands. With the X-ray diffractogram, we could observe that the selected films have an amorphous characteristic and a crystallinity index ranging from 6.74% to 14.09%. As for the thermogravimetric analysis, three events of mass loss were identified. In the event I, all the films presented a loss of mass – due to the evaporation of the absorbed water. In films with starch in their composition (G6, G8, and G10), two peaks of maximum temperature of mass loss took place. Therefore, the characteristics observed in the selected films are promising for their use as food packaging, but more tests need to be performed to evaluate the antioxidant potential and microbiological activity.