Mechanical and Barrier Properties of Films from Millet Protein Pennisetin

Abstract

Plastics are one of the most commonly used materials today in an immense range of applications. Since plastics originate from petroleum, which is not a renewable resource, we need to find alternatives to achieve environmentally sustainable goals. One of our most abundant renewable resources is cereals; wheat gluten is recognized as a replacement for synthetic plastics. Another cereal protein is pennisetin from pearl millet, which can grow in more arid areas and is therefore an important crop in times of climate change. In contrast to gluten, the material properties of pennisetin have as yet been relatively unexplored. This work evaluated the mechanical and barrier properties of pennisetin films, including three different plasticizers (glycerol only, glycerol/citric acid mixture, and glycerol/ lactic acid/polyethylene glycol mixture). The films were cast from ethanol solutions. It was found that all of the three plasticizers resulted in approximately equal thermomechanical properties in the pennisetin films. However, the glycerol/citric acid mixture seemed to give more beneficial tensile and barrier properties. The advantage of this plasticizer mixture was believed to be due to the altered microstructure of the films. The material properties of pennisetin were found to be fully comparable to those of other cereal protein materials.

Properties of triticale protein films and their relation to plasticizing–antiplasticizing effects of glycerol and sorbitol

“…The three-dimensional networks are dependent of the intra and intermolecular interactions among proteins, but also from interactions between proteins and the constituents of films like plasticizers. To date, numerous protein sources have been proposed for the preparation of films (Aguirre et al, 2011;Bamdad et al, 2006;Bodnár et al, 2007;Gillgren et al, 2011;Valenzuela et al, 2013). A particular interest has been focused on the use of triticale protein to prepare films.…”

Rye secalin characterisation and use to improve zein‐based film performance

“…essential oil (Ghadetaj et al ., 2018). The higher solubility of SCL‐containing films in water was probably induced by the presence of glycerol and by its ability interacting with water to exfoliate SCL molecules which expose additional domains able, in turn, to bind with water and to increase film solubility (Gillgren et al ., 2011). It is worthy to note that both moisture content and swelling values of the SCL/zein blend, as well as its solubility, were halfway between the values detected for SCL‐ and zein‐based films, respectively, due to the different amino acid composition and structure of the two proteins.…”

“…The results of WVP properties did not demonstrate any significant difference among the various films. However, the WVP values of SCL‐ and zein‐based films, reported in Table 2, were lower than those previously reported for other prolamins, such as pennisetin, avenin, kafirin and even zein films (Gillgren & Stading, 2008; Gillgren et al ., 2011), as well as for further protein‐based films, such as soy protein films (dos Santos Paglione et al ., 2019), fish skin gelatin films (Menezes et al ., 2019) and whey protein films containing or not bergamot oil (Sogut, 2020).…”

“…Hence, since prolamins are generally soluble in 70% ethanol, their films are particularly promising exhibiting moderate permeability to both gas and water vapour (Gao et al ., 2005). Most researches on prolamin‐based films have been focused on the use of gliadin, zein, kafirin, pennisetin and hordein as biopolymer sources (Gillgren & Stading, 2008; Li et al ., 2010; Gillgren et al ., 2011), and no information has been published, to our knowledge, on the film‐forming ability of SCL. The objective of this study was, thus, the extraction and characterisation of SCL and the evaluation of its potential to serve as biopolymer of the film matrix alone or in combination with zein, the most investigated cereal protein in obtaining biodegradable/edible films for food and pharmaceutical applications (Pena Serna & Lopes Filho, 2015).…”