Features and performance of edible films, obtained from whey protein isolate formulated with antimicrobial compounds

• Published in: Food research international Vol. 45; no. 1; pp. 351 - 361
• Main Authors: Ramos, Óscar L., Silva, Sara I., Soares, José C., Fernandes, João C., Poças, M. Fátima, Pintado, Manuela E., Malcata, F. Xavier
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2012; Elsevier
• Subjects: Active packaging; agar; Antimicrobial agents; Antimicrobial packaging; antimicrobial properties; Biological and medical sciences; cheeses; chitooligosaccharides; edible films; Food industries; Food microbiology; Food safety; Fundamental and applied biological sciences. Psychology; General aspects; glycerol; Gram-negative bacteria; Hygiene and safety; lactic acid; modulus of elasticity; natamycin; optical properties; permeability; Physical properties; propionic acid; solubility; spoilage; tensile strength; water activity; water content; water vapor; Whey protein isolate; yeasts; Antimicrobial packaging; Antimicrobial agents; Food safety; Whey protein isolate; Active packaging; Physical properties; Protein isolate; Antimicrobial agent; Milk protein; Edible film; Conditioning; Performance; Whey protein; Edible packaging
• DOI: 10.1016/j.foodres.2011.09.016
• ISSN: 0963-9969

The goal of this research effort was to assess the efficacy of edible films produced from whey protein isolate (WPI) and glycerol, including incorporation of lactic acid (LA) and propionic acid (PRO), chitooligosaccharides with nominal MW of 3kDa (COS) and natamycin (NA) as antimicrobial agents. Their features were evaluated in vitro via agar diffusion and viable cell counting, against spoilage microflora often found contaminating cheese surfaces. The effect of incorporating the aforementioned compounds upon thickness, moisture content (MC), solubility (S), density (ρs), water activity (aw) and water vapor permeability (WVP), as well as upon tensile and optical properties of those films were also evaluated. Films formulated with LA, PRO or COS exhibited antimicrobial activity against all microorganisms tested, yet the viable cell count assay was more sensitive and reproducible. COS was the most active against Gram-negative bacteria, whereas LA was the most active against Gram-positive ones. NA was not active against bacteria, but displayed the strongest effect against yeasts. Incorporation of said antimicrobial compounds did not significantly (p>0.05) affect film thickness, yet it significantly (p<0.05) reduced tensile strength (TS). Incorporation of LA and NA in particular did not significantly (p<0.05) affect MC, S, ρs, WVP, elongation at break (EB) and Young's modulus (YM) values; however, a statistically significant increase (p<0.05) of MC, S and WVP, together with a statistically significant decrease (p<0.05) of ρs were attained upon incorporation of PRO or COS. Moreover, PRO produced the highest variation (p<0.05) in EB, TS and YM, whereas COS produced the highest change (p<0.05) in optical properties. ► Antimicrobial efficacy of additives to whey-protein based edible films was tested. ► Effects of said additives upon mechanical and optical properties were assessed. ► Chitooligosaccharide (COS) was strongest against Gram-negative bacteria. ► Lactic acid was strongest against Gram-positive bacteria. ► COS produced the highest change in optical properties.