Surface and Structural Modifications Induced by Dielectric Barrier Discharge Cold Plasma and Pulsed Light Radiation in Bean Starch Films: Implications for Bread Shelf-Life Extension

In this study, bean starch films were developed and treated with dielectric barrier discharge (DBD) cold plasma (5 min (DBD5), 10 min (DBD10), and 15 min (DBD15)) and pulsed light (PL) radiation (4 J cm−2 (PL4), 8 J cm−2 (PL8), and 12 J cm−2 (PL12)), and the effects of these treatments on the physical, barrier, mechanical, morphological, and structural properties were evaluated, as well as the practical application of the films in bread storage for 7 days. Both treatments significantly modified the film properties (p < 0.05). Film thickness decreased from 95 µm (control) to 87 µm (PL12), while solubility was reduced from 39.40% (control) to 25.32% (PL12), indicating improved water resistance. Reductions in water vapor permeability (WVP) were also observed, with a more pronounced effect for PL12 (approximately 55% reduction compared to the control). The contact angle increased from 58.30° (control) to 67.76° (PL12), indicating a moderate increase in surface hydrophobicity. The DBD cold plasma treatment increased tensile strength (up to 16.05 MPa in DBD15) and reduced elongation (44.72%), whereas PL, especially at PL8, increased flexibility (60.36%). Morphological analyses indicated increased surface roughness for DBD-treated films, while structural analyses suggested subtle changes in molecular organization rather than the formation of well-defined crystalline domains. During bread storage, the treated films, particularly PL12, were significantly more effective than the control in delaying bread staling (final firmness of 6.67 N vs. 11.82 N), reducing mass loss (5.66% vs. 12.66%), and maintaining higher water activity, thereby better preserving product quality. Overall, both treatments showed potential for tailoring film properties: DBD was more effective in enhancing mechanical strength, while PL promoted improvements in barrier properties and practical performance. Therefore, physical treatments, particularly PL, represent promising strategies to overcome intrinsic limitations of starch-based films and to develop packaging materials with potential applications in bakery product preservation.