Effect of heating cast kafirin films on their functional properties

Abstract

Edible films can be produced from kafirin but the diverse food product requirements necessitate modification of the films. To modify their functional properties, kafirin films were cast, with and without plasticizer, from glacial acetic acid (GAA) and aqueous ethanol (AE), then heated using microwave energy. A power of 80 W for 2 min caused an approximately two-and fourfold increase in the tensile strength of nonplasticized and plasticized films, respectively. Film glass transition temperature increased by about 15%. Film biodegradability was slowed. However, only the digestibility of the non-plasticized films cast from AE heated for the longest time (4 min) was decreased, by about 25%; while that of the other films was not affected. GAA cast films had higher digestibility than AE cast ones, possibly as a result of acid-mediated deamidation of kafirin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated heat-induced kafirin oligomers. Scanning electron microscopy of heated plasticized films showed more wrinkled structures compared to non-heated films, whereas the non-plasticized films appeared more brittle with heating. The results indicate that heat-induced intermolecular disulfide cross-linking was involved in modifying the properties of kafirin films.

The Impact of Anthocyanin‐Rich Red Raspberry Extract (ARRE) on the Properties of Edible Soy Protein Isolate (SPI) Films

“…Consequently, a water layer may create larger spaces between soy protein molecules, which presumably increase the free volume between the soy protein molecules, making them more susceptible to enzyme attack. LC has been reported to be capable of forming a lubrication layer in kafirin films and increased the PD of kafirin films containing LC (Byaruhanga and others 2007). EA may also work in a similar fashion to LC by lubricating the layers of protein.…”

Making Kafirin, the Sorghum Prolamin, into a Viable Alternative Protein Source

“…Although heat‐induced cross‐linking of kafirin has negative implications with regard to the protein quality of sorghum foods, it improves the kafirin functionality as a bioplastic material. This has been demonstrated when heat treatments were applied to kafirin films (Byaruhanga et al, , , ), kafirin microparticles (Anyango et al, ), and kafirin microparticle films (Anyango et al, ).…”

“…These improvements were associated with increased levels of β‐sheet structure both in the kafirin and in the films (Byaruhanga et al, ; Gao et al, ). Microwave heating after film formation was found to be more effective in increasing the tensile strength of kafirin films (Byaruhanga et al, ). Although this treatment had no effect on film WVP, film biodegradation was slowed.…”

Developments in the Science of Zein, Kafirin, and Gluten Protein Bioplastic Materials

“…For example, work by on kafirin cast films showed that microwave heating wet kafirin before film making increased film tensile strength but decreased both the film extensibility and film water vapour permeability (WVP). Crosslinking using microwave heating reduced the rate of kafirin film degradation under composting conditions (Byaruhanga et al 2007). These effects of disulfide bond mediated polymerization of the kafirin polypeptides (Byaruhanga et al ( , 2006(Byaruhanga et al ( , 2007 were associated with increase in β-sheet structure in the kafirin (Byaruhanga et al 2006).…”

“…Crosslinking using microwave heating reduced the rate of kafirin film degradation under composting conditions (Byaruhanga et al 2007). These effects of disulfide bond mediated polymerization of the kafirin polypeptides (Byaruhanga et al ( , 2006(Byaruhanga et al ( , 2007 were associated with increase in β-sheet structure in the kafirin (Byaruhanga et al 2006). The acylation reaction through treatment with lauryl chloride has been found to result in a reduction in zein film T g with increase in content of the lauryl chloride, probably due to plasticization by the lauryl moiety (Shi et al 2011).…”