Bio-based multilayer films: A review of the principal methods of production and challenges.

The development of biodegradable packaging materials has been drawing attention worldwide to minimize the environmental impact of traditional petroleum-based plastics. Nevertheless, it is challenging to obtain bio-based materials with suitable properties for packaging applications. Films produced from a single biopolymer often lack some important properties. An alternative to overcome this limitation is the multilayer assembly. Under this technology, two or more materials with specific and complementary properties are combined into a single-layered structure, thus improving the performance of bio-polymer plastics. This review presents the main aspects of bio-based multilayer film production technologies, discussing their advantages and disadvantages, which have to be considered to produce the most suitable film for each specific application. Most of the studies reported that such films resulted in increased mechanical performance and decreased water, oxygen, and dioxide carbon permeability. This approach allows the addition of compounds leading to antioxidant or antibacterial activity. Finally, a discussion about the future challenges is also presented.

Extraction of soluble sugars from banana puree to obtain a matrix rich in non-starch polysaccharides.

Banana has non-starch polysaccharides (NSP) in its cell wall similar to dietary fiber from cereals like oats. These NSP could be used as potential functional ingredient due to their prebiotic action and potential food immuno-modulators. However, NSP purification is limited due to high quantities of soluble sugars accumulate during banana ripening. The aim of this study was to extract soluble sugars from ripe banana (Musa cavendishii var. Nanicão) to obtain a purified NSP matrix. Two different extraction methodologies (solid-liquid extraction SLE and ultrasound-assisted extraction UAE) were tested using ethanol (99.5 mL/100 mL) as solvent. Soluble sugars were quantified by high-performance liquid chromatography (HPLC). SLE and UAE showed to be effective in extraction process of soluble sugars. Best results were obtained with SLE at sample/solvent ratio of 1:5, 65 °C and 30 min of extraction time. A solid residue with NSP was obtained, that could be used as a functional ingredient.

Light-triggered and cysteine-mediated nitric oxide release from a biodegradable starch-based film.

A new nitric oxide-releasing material produced with cassava starch is described. The ruthenium nitrosyl complex trans-[Ru(NH3)4(isn)NO](BF4)3 (RuNOisn; isn = isonicotinamide) is able to release NO upon either photolysis or chemical reduction. Impregnating this complex under mild conditions into cassava starch (CS) films produced a NO-delivery platform (CSx-RuNOisn). Spectroscopic analysis of CSx-RuNOisn indicates that the coordination sphere of RuNOisn remains intact during film production. Exposure of CSx-RuNOisn to long wave UV-light (λirr = 355 nm) leads to NO release and formation of the paramagnetic photoproduct trans-[RuIII(NH3)4isn(H2O)]3+ in the CS film. Reaction of this aquaruthenium(iii) complex with aqueous nitrite regenerates RuNOisn in the film. Delivery of NO upon photolysis of CSx-RuNOisn was verified by trapping with oxymyoglobin. Moreover, NO release upon chemical reduction was carried out using l-cysteine as a reductant. Cysteine-mediated NO delivery from CSx-RuNOisn persisted for more than 7 h, during which physiologically relevant NO concentrations were liberated. These results suggest that CSx-RuNOisn is a promising candidate for use in biological applications.

Chemical composition and nutritional value of unripe banana flour (Musa acuminata, var. Nanicão).

Banana flour obtained from unripe banana (Musa acuminata, var. Nanicão) under specific drying conditions was evaluated regarding its chemical composition and nutritional value. Results are expressed in dry weight (dw). The unripe banana flour (UBF) presented a high amount of total dietary fiber (DF) (56.24 g/100 g), which consisted of resistant starch (RS) (48.99 g/100 g), fructans (0.05 g/100 g) and DF without RS or fructans (7.2 g/100 g). The contents of available starch (AS) (27.78 g/100 g) and soluble sugars (1.81 g/100 g) were low. The main phytosterols found were campesterol (4.1 mg/100 g), stigmasterol (2.5 mg/100 g) and ß-sitosterol (6.2 mg/100 g). The total polyphenol content was 50.65 mg GAE/100 g. Antioxidant activity, by the FRAP and ORAC methods, was moderated, being 358.67 and 261.00 µmol of Trolox equivalent/100 g, respectively. The content of Zn, Ca and Fe and mineral dialyzability were low. The procedure used to obtain UBF resulted in the recovery of undamaged starch granules and in a low-energy product (597 kJ/100 g).