Properties and Microstructure of Zein Sheets Plasticized with Palmitic and Stearic Acids

Abstract

Cereal Chem. 74(1):83-90Interest in biodegradable materials for packaging and agricultural uses has grown in recent years. Plant proteins have been proposed as inexpensive, renewable, and abundant feedstock. Corn zein was investigated based on value-added considerations and on the unique thermoplastic and hydrophobic properties of zein. Films prepared from zein are known to be tough and resistant, but also hard and brittle, thus requiring the addition of plasticizers to improve flexibility. The objectives of this research were to study the tensile properties, water absorption, and microstructure of zein sheets plasticized with palmitic and stearic acids. Both palmitic and stearic acids showed similar effects as plasticizers of zein. Tensile strength of zein sheets increased with the addition of low levels of plasti-cizers. However, beyond a critical point, tensile strength decreased with further addition of fatty acids. Water absorption decreased continuously with increasing fatty acid content. Kinetic parameters indicated fatty acids decreased water absorption by decreasing the saturation level of zein sheets. Coating zein with flax oil decreased the rate of water absorption by sealing off surface pores. Scanning electron micrographs of zein sheets showed the development of layered structures as fatty acid content increased. Zein-fatty acid layers were believed to be responsible for the increased tensile strength of plasticized zein sheets and to have contributed to increased resistance to water absorption.

Properties of Plasticized-Zein Film as Affected by Plasticizer Treatments.

“…Film formed after solvent evaporation is tasteless, but it is glossy, scuff-resistant, and grease-resistant (Pomes, 1971;Gennadios & Weller, 1990). Zein sheets without plasticizer, however, resulted in a very brittle film (Lai et al, 1997), and the addition of plasticizers increases flexibility (Andres, 1984).…”

“…Studies have been made on plasticizers added to zein when it is used as a film for food packaging (Herald et al, 1996;Lai et al, 1997;Di Gioia & Guilbert, 1999;Santosa & Padua, 1999). However, the real mechanism of plasticized action upon the film has not yet been explained.…”

Valorization of Agricultural Wastes for the Production of Protein-Based Biopolymers

“…As a result of its poor nutritional value for human consumption, recent studies in the literature have highlighted its value as an industrial biopolymer with no implications of using food as raw material. In fact, zein is able to form hydrophobic, tough, resistant and fl exible edible coatings with a high barrier to oils and antimicrobial activity [21,22]. As a consequence, zein-based coatings have been used in the packaging industry in medical pills [23], biodegradable plastics [22] and edible fi lms for food packaging [24].…”

“…In fact, zein is able to form hydrophobic, tough, resistant and fl exible edible coatings with a high barrier to oils and antimicrobial activity [21,22]. As a consequence, zein-based coatings have been used in the packaging industry in medical pills [23], biodegradable plastics [22] and edible fi lms for food packaging [24]. Table 1 summarizes the main applications of zein in the formulation of biopolymers with different applications.…”

Pengaruh Penambahan Sorbitol Dan Kalsium Karbonat Terhadap Karakteristik Dan Sifat Biodegradasi Film Dari Pati Kulit Pisang

“…Plasticizer dapat mengurangi ikatan hidrogen internal molekul dan menyebabkan melemahnya gaya tarik intermolekul rantai polimer yang berdekatan sehingga mengurangi daya regang putus. Penambahan plasticizer lebih dari jumlah tertentu akan menghasilkan film dengan kuat tarik yang lebih rendah (Lai et al, 1997). Kalsium karbonat merupakan bahan pengisi pada penelitian ini.…”