Bionanocomposite films developed from corn starch and natural and modified nano-clays with or without added blueberry extract

Abstract

Edible and bionanocomposite films were developed by extrusion followed by thermo molding. Corn starch (Zea mays), glycerol, and several nano-clays were used as the carbohydrate polymer, plasticizer and nano-fillers, respectively. Pure blueberry (Vaccinium corymbosum) extract (BE, 100% anthocyanin), as well as natural and modified montmorillonites (Mnt) with or without BE nano-packaged within their layers were incorporated into the thermoplastic starch (TPS) matrix. Previous studies by our research group have shown that BE, and BE nano-packaged within natural and modified Mnt, are pH-sensitive. With this in mind, we set out to develop edible and intelligent (pH-sensitive) bionanocomposite films with improved properties. Unfortunately however, none of the films formulated were pH-sensitive. All the films showed X-ray diffractograms typical of semicrystalline, albeit largely amorphous, materials coinciding with the morphological observations made under scanning electron microscopy. The results confirmed that total starch gelatinization occurred under the selected extrusion conditions. Films prepared from corn starch containing BE showed a plasticizing effect, giving materials with lower thermal resistance and surface moisture values, which were also more opaque, denser, and rougher. All the nanofillers tested were completely exfoliated within the TPS matrix, except for the natural Mnt that was partly exfoliated and partly intercalated in the matrix. In general, materials containing nano-fillers with a greater degree of interlayer spacing (more exfoliated) showed higher thermal resistance and Young's modulus, but lower strain at break values.

The Influence of Kaolin Clay on the Mechanical Properties and Structure of Thermoplastic Starch Films

“…The lowest S a value was recorded for k0, and was 114.8 nm, and the highest for k15 was 187.7 nm. Gutierrez et al [15] showed a similar increase in the roughness of the starch film S q from 25 nm for pure TPS up to 80 nm for TPS with 4% MMT.…”

Development of active and intelligent films based on cassava starch and Chinese bayberry (Myrica rubra Sieb. et Zucc.) anthocyanins

“…49 In addition, the UV-vis light barrier ability of starch-BBE lms was positively correlated with BBE content in the lms. Luchese et al 19 and Gutiérrez et al 50 also found the UV-vis light barrier property of anthocyanin-rich starch lms was elevated with the increase of the content of anthocyanins. Notably, a signicant reduction in the light transmittance at about 550 nm was observed for starch-BBE lms, which corresponded to the visible absorption peak of anthocyanins.…”

Influence of Green Tea and Basil Extracts on Cassava Starch Based Films as Assessed by Thermal Degradation, Crystalline Structure, and Mechanical Properties

“…For the systems with the different extracts, 5 wt% of the distillated water used in the matrix was replaced by the same concentration of green tea or basil extracts (they will be referred to as TPS‐T and TPS‐B, respectively). The amount of the additives has been selected considering the literature, which showed that the use of 5 wt% of different extracts in starch films led to materials with antioxidant activity and significant changes in mechanical and thermal properties . Each solution was heated with constant stirring at 96 °C for 40 min to ensure starch gelatinization .…”

“…The amount of the additives has been selected considering the literature, which showed that the use of 5 wt% of different extracts in starch films led to materials with antioxidant activity and significant changes in mechanical and thermal properties. [17,30] Each solution was heated with constant stirring at 96°C for 40 min to ensure starch gelatinization. [31] The gel was then degassed by applying vacuum for 7 min and casted on acrylic Petri dishes, which were subsequently dried at 50°C for 48 h at ambient relative humidity (RH).…”

“…In this way, films with better flexibility and processability can be obtained. [15,16] In the past years, some researchers evaluated the antioxidant activity of starch films containing natural extracts; [3,14,17] however, only a few works have evaluated the plasticizing effect of the extracts in terms of the starch film properties. In particular, the plasticizing effect of yerba mate extract at different concentrations was revealed from the decrease of the relaxation of glycerol-rich phase of starch films [18] and the increase of strain at break, leading to more flexible materials.…”