Researchers investigate natural compound as packaging antioxidant
The researchers incorporated antioxidant agents into corn zein laminated films and tested the tensile strength, water vapour permeability and colour value of beef patties.
They used the minimum effective concentrations of active compounds (such as thymol, carvacrol, eugenol) and laminated them into linear low-density polyethylene (LLDPE) films to develop corn-zein-laminated films with antioxidant agents.
Zein protein is a by-product of the corn processing industry, wrote the researchers in the Journal of Food Science.
Currently, the most frequently and widely used synthetic antioxidants in active food packaging are butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) but potential health risks are seeing natural compounds becoming more appropriate, said the study.
Positive effects
Hye-Yeon Park et al found that the films effectively inhibited lipid oxidation and had a positive effect on the colour stability of beef patties during storage on fresh ground beef packaging.
Beef patties vacuum-packaged with antioxidant films showed lower changes in hue angle values, said the researchers.
“In these groups, the films acted as an oxygen gas barrier preventing the direct contact of meat with oxygen. Moreover, the strong antioxidant property of eugenol released from the films contributed to protection of the beef patties from lipid oxidation.
“[This] data suggests that diffusion of eugenol from the packaging delays oxidation of beef color pigments.”
The work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government.
Examination of release kinetics in the gas and liquid phases verified that antioxidants were effectively released from the films and inhibited oxidation during testing.
Drawbacks
However, tensile strength and percentage elongation were reduced in the corn-zein-laminated films when compared to typical LLDPE film.
Furthermore, the ability of the corn-zein-laminated films to repel moisture decreased by approximately 12.2%, but was improved by incorporating hydrophobic antioxidant compounds in the corn-zein layer.
The team found the tensile strength (TS) measured in MPa of simple LLDPE film was 31.33 MPa, which was the highest value among all tested films.
“When comparing to the simple LLDPE film, the TS of the corn-zein-laminated film (LLDPE/zein/LLDPE) decreased by 28.6% (22.38 MPa). The lower TS of the LLDPE/zein/LLDPE film was probably due to the physical weakness of the zein film layer.”
Simple LLDPE film had a lower water vapour permeability (WVP) (1.778 g·mm/m2·d·kPa) than any other laminated film, indicating that LLDPE film provides a good barrier for moisture.
“In contrast, LLDPE/zein/LLDPE film had the highest WVP at 2.033 g·mm/m2·d·kPa, and thus performed the most poorly as a moisture barrier among the film samples tested in this study.
“Regardless of the type of antioxidant agent used at 3% concentration (v/v), films containing antioxidants had improved water barrier properties when compared to simple zein-laminated film due to the strong hydrophobicity of the added antioxidant agents, which interrupts the penetration of water molecules.”
The researchers concluded that zein-laminated films containing antioxidants are suitable for packaging applications and food protection.
Source: Journal of Food Science, volume 77, Issue 10, pages E273-E279
Published online ahead of print, doi: 10.1111/j.1750-3841.2012.02906.x
“Development of Antioxidant Packaging Material by Applying Corn-Zein to LLDPE Film in Combination with Phenolic Compounds”
Authors: Hye-Yeon Park, Sung-Jin Kim, Ki Myong Kim, Young-Sun You, So Yeon Kim, Jaejoon Han
