Antimicrobial properties and diffusion modeling of preservative-containing whey protein films and coatings on cheddar cheese.

摘要

Because of good oxygen, aroma and oil barrier properties, whey protein isolate (WPI) films are potentially useful in food preservation applications. With the incorporation of preservatives, WPI films and coatings could provide microbiological protection to food products. As surface-applied preservatives migrate away from the surface into cheese, mold spoilage occurs on the cheese surface during ripening and during consumer storage. By incorporating preservatives in WPI film coatings on cheese, preservative migration can be slowed to reduce cheese spoilage.; In the first study, preservative diffusion coefficients were measured at 24°C in WPI films with different WPI:glycerol plasticizer ratios (1:1–15:1), beeswax (BW) content, 0–40% (w/w dry solids), and preservative addition: 0.3% (w/w) natamycin or 1.6% (w/w dry solids) potassium sorbate. Diffusion coefficients for potassium sorbate and natamycin were in the ranges 0.11–1.30 × 10−10m2/s and 6.16–37.8 × 10−14m2/s, respectively, significantly decreasing as the WPI:glycerol ratio increased. No significant difference in sorbate diffusion was seen with the addition of beeswax.; In the second study, the diffusion coefficient of potassium sorbate, a common cheese preservative, was measured in cheddar cheese at 24°C. The diffusion coefficient, D, was determined to be 1.30 × −11m 2/s; and the partition coefficient, K, was determined to be 1.97.; In the third study, by using an analytical solution and experimental data, sorbate diffusion in a coated cheese system was modeled and the partition coefficient for sorbate between the food and film-coating interface, K ₁₂, was determined. The traditional method of independently-determined diffusion coefficients in food and film did not effectively model an actual coated food system.; In the fourth study, potassium-sorbate-containing WPI coatings on cheddar cheese were challenged with a common spoilage mold, Penicillium commune , at 24°C and 94% RH. The samples were analyzed by measuring oxygen and carbon dioxide levels due to mold respiration in the headspace in combination with visual observation. The preservative-containing WPI coating extended the shelf life of cheese by 22 days compared to a control with no coating or preservative and by 18 days when compared with a sample dusted with preservative. These results show the potential for antimicrobial whey protein coatings to significantly extend shelf-life.