Antimicrobial biopolymer films and coatings are of great interest for many applications. Different chitosan systems were prepared and characterized to evaluate the effect of their composition on the physical and antimicrobial properties. Three types of emulsifiers (Tween 20, 80, and 85) were used as stabilizing agents, combined with thyme essential oil (from two producers) applied as an active substance. A predominant role of the applied stabilizer and its hydrophilic–lipophilic balance value was proven. The incorporation of thyme essential oil and surfactant into the chitosan matrix led to a significant decrease of particle size in film-forming solutions, as well as a thickness increase and the enhancement of the barrier properties in chitosan films. Antimicrobial effects were provided even at the lowest tested concentration of thyme essential oil. Hence, the prepared chitosan films represent promising candidates in antimicrobial packaging applications.

The effect of two essential oils (EOs), from Origanum vulgare and Origanum majorana, their structural properties, and concentration on physical and antimicrobial characteristics of chitosan based solutions as well as films was investigated. Results showed that significantly different behaviour was induced by variation in the compositions of given essential oils. Film-forming solutions (FFS) containing oregano oil comprised considerably greater particles in comparison with the marjoram samples. Similarly, structural changes were confirmed by SEM analysis of chitosan films modified with the EOs; the smaller particles of the marjoram oil demonstrated better compatibility with chitosan matrix. However, chitosan films enriched with the oregano oil showed significantly superior antimicrobial activity compared to the marjoram. The dissimilar effects of the two EOs were also observed by water vapour pressure (WVP) measurement; increasing the amount of oregano oil triggered a drop in the WVP of the prepared films, whereas the marjoram oil had a negligible impact in this respect. These results suggest that the structural features of active substances in the EOs play a crucial role in determining the final properties of FFS and biofilm systems.

Caseinate-stabilized emulsions of black cumin (Nigella sativa) and tamanu (Calophyllum inophyllum) oils were studied in terms of preparation, characterization, and antibacterial properties. The oils were described while using their basic characteristics, including fatty acid composition and scavenging activity. The oil-in-water (o/w) emulsions containing the studied oils were formulated, and the influence of protein stabilizer (sodium caseinate (CAS), 1–12 wt%), oil contents (5–30 wt%), and emulsification methods (high-shear homogenization vs sonication) on the emulsion properties were investigated. It was observed that, under both preparation methods, emulsions of small, initial droplet sizes were predominantly formed with CAS content that was higher than 7.5 wt%. Sonication was a more efficient emulsification procedure and was afforded emulsions with smaller droplet size throughout the entire used concentration ranges of oils and CAS when compared to high-shear homogenization. At native pH of ~ 6.5, all of the emulsions exhibited negative zeta potential that originated from the presence of caseinate. The antibacterial activities of both oils and their emulsions were investigated with respect to the growth suppression of common spoilage bacteria while using the disk diffusion method. The oils and selected emulsions were proven to act against gram positive strains, mainly against Staphylococcus aureus (S. aureus) and Bacillus cereus (B. cereus); regrettably, the gram negative species were fully resistant against their action.

In the present study, commercial cocoa powders with different cocoa fat contents were studied. It was found that the cocoa powders’ flow patterns were of a cohesive to highly cohesive characters. It was demonstrated, that the powders of higher crystalline structure were less flowable compared to the ones with the more amorphous ones. It was observed by SEM that the studied cocoa powders of higher cocoa fat content and the ones with the dietary fibers content (sample 2) exhibited more amorphous structure. The predominantly smooth surface structure of the higher fat content cocoa powder allowed its higher dense packing, triggering the decreased sound absorption typical for non-porous materials as quantified by NRC of 0.289 (sample 1, 100 mm material height) and 0.227 (sample 3) to 0.182 (sample 2). The latter conclusions were also supported by the observed increase of the structural mechanical stiffness of the freely poured powder bed of high cocoa fat amorphous powders, as resulting in the increasing magnitude of the K_l of 12.83 MPa (sample 1, 100 mm material height) and 19.29 MPa (sample 3) to 37.82 MPa (sample 2). Melting temperatures of the samples were determined by DSC. Results were directly corresponded to the cocoa butter content. The highest enthalpy of fusion (ΔH_m) of (23.32 ± 0.21) J/g was obtained for the highest cocoa butter containing sample 2 (of 20–22 wt. %). Obtained values of ΔH_m for samples 1 and 2 were of (12.38 ± 0.20) J/g and (10.27 ± 0.17) J/g. T_{p (melt)} for reversing heat flow was ranging from (30.16 ± 0.10) °C to (32.28 ± 0.10) °C indicating the melting of stable β polymorph. The melting peaks observed at distinct temperatures in the non-reversing heat flow patterns were indicating melting of the unstable α and metastable β’ and stable β cocoa butter polymorphic forms.