Effect of Salts and Plasticizers on Stability of Shellac Film

Abstract

The aim of this study was to increase the stability of shellac because of the polymerization. A few approaches have been applied in this study. Shellac film was prepared in two salt forms, that is, ammonium and 2-methyl-2-amino 1-propanol salts, and a comparison was made with shellac film in free acid form. The other approach was by the application of plasticizers. These plasticizers were diethyl phathalate, triacetin, and polyethylene glycol 400 (PEG 400). Plasticized shellac and unplasticized shellac films in free acid form were then compared. All shellac films were kept in stability chamber at 40 degrees C, 75% RH for a period of 3 months. The studied parameters such as insoluble solid, acid value, mechanical properties, and water vapor permeability were detected every month. Analysis of variance (ANOVA) technique was used to analyze data. The applications of salt forms proved statistically significant (p < 0.01) to reduce the polymerization process whereas certain plasticizers could enhance the stability. PEG 400 was the only plasticizer that could show the increase in stability. The improvement of stability might be a result of the interference of a larger molecule of PEG 400 causing the difficulty in interaction among carboxyl or hydroxyl groups of shellac and the effect of lower loss of plasticizer.

Physicochemical Properties of Various Shellac Types

“…The pK a values of the different shellac types vary between 5.8 and 6.1 (Table 1). These values do not correspond to the higher (about 1 pH unit) values found in the literature (13,15,16), while for Eudragit L and acetic acid, the published values are confirmed. A possible explanation for this discrepancy is the different source of the investigated shellac types.…”

Enhancement of Moisture Protective Properties and Stability of Pectin through Formation of a Composite Film: Effects of Shellac and Plasticizer

“…Upon 90‐d storage, the reduction in WVPC was a result of evaporation of free water in the polymer films, leading to tightness of polymer molecules and creating the hardness in the permeability of moisture. The decreased WVPC of composite film was in accordance with the work of Luangtana‐anan and others (). Therefore, only 50% shellac was the proper concentration that could improve the WVPC of pectin film for a longer period of storage, enabling edible film coating to act as moisture protection for food and pharmaceutical products, that is, fruit, vegetables and hydrophilic drugs.…”

“…Stress and strain were the parameters to indicate the mechanical properties of all films as previously reported by Luangtana‐anan and others (). The samples were cut into a dumbbell shape of 25 mm in length and 6.045 mm in width.…”

“…It can interfere the intermolecular forces and enhance the flexibility of polymer chains, contributing to the stronger mechanical films (Luangtanana‐anan and others , ; Cao and others ; Soradech and others ; Balqis and others ). The physicochemical properties of composite film are types and concentration of plasticizer dependent (Cao and others ; Luangtanana‐anan and others , ; Soradech and others ). Various types of plasticizer, hydrophobic and hydrophilic plasticizers, show different influences on physicochemical properties of composite film.…”

Edible Coating for Fresh Fruit: A Review

“…It is composed of a hard resin and soft resin of polyesters and single esters containing hydroxyl and carboxyl groups (Upadhye et al, 1970). It is an excellent film forming agent with good barrier properties and is soluble in alcohol and alkaline solutions (Luangtana-Anan et al, 2007). It has been widely used in the food and agro industries for water, gas, lipid and microbial spoilage protection and hence prolonging the shelf life of these products (Valencia-Chamorro et al, 2009).…”