Antimicrobial, Optical and Mechanical Properties of Chitosan–Starch Films with Natural Extracts

Abstract

Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan–starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV–VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications.

Starch Modified With Chitosan and Reinforced With Feather Keratin Materials Produced by Extrusion Process: An Alternative to Starch Polymers

“…Thus, they are difficult to compare with other starch‐chitosan materials. For instance, values of maximum Tan δ have been obtained from starch‐chitosan materials (50 wt.% of each polysaccharide and approximately 6.2 wt% of plasticizer) at around 185 °C and also at around 89 °C (66 wt% of starch and 33 wt% of chitosan, considering 10 wt% of plasticizer). Thus, the polymer starch‐chitosan (5–95 wt% and 1 wt% of plasticizer) in this research presented a Tg around 104 °C, and as mentioned earlier, this value tended to decrease in the samples with keratin.…”

Fabrication and Testing of PVA/Chitosan Bilayer Films for Strawberry Packaging

“…CH is a linear polysaccharide that consists of a low acetyl substituted form of chitin and a natural carbohydrate copolymer. CH offers several advantages such as biodegradability, broad availability, and non-toxicity [8]. CH also has good anti-fungal activity against several postharvest pathogens, particularly the grey mold that is one of the main causes of strawberry deterioration and postharvest decay [9].…”

Chitosan–Starch Films Modified with Natural Extracts to Remove Heavy Oil from Water

“…Each film blend was stirred for 5-10 min, and later, the resulting blend was verted in a polystyrene tray. Finally, the films were dried at 25 • C for 15 days [13]. For the films with natural extracts, two fixed quantities (0.4 and 1.6 mL) of each extract were added into the polymer solution (corresponding to 0.5% and 2% of the total blend weight).…”

“…This is confirmed by the research of Rongsayamanont et al (2017), who indicated the stability of biosorbents (composed by lipopeptides, glycerol, and palm oil) at a pH media range of 4-10 (using substances such as deionized water, alkaline water at pH 9, methanol, ethanol, dimethyl sulfoxide, acetone, chloroform, and hexane, it pointed the sorption capacity of biomaterials in acidic and alkaline media) without losing the film stability [23]. It is important to remark that the addition of higher quantities of extract gives the materials a lower pH value [13]. This fact allows the films to have a higher affinity and effectivity in acid media.…”