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Antimicrobial cellulose nanofiber coatings can control mold on fresh fruit.

Cellulose nanofibers form highly water-resistant coatings. When incorporated with antimicrobial agents, such as potassium sorbate (PtSb) and other functional substances, these coatings can be applied to fresh fruits in order to control mold growth and improve the quality of the product.

Cellulose nanofibers are made of nanosized cellulose fibrils with a high aspect ratio--length to width ratio.

In general, nanocellulose can be a low-calorie replacement for carbohydrate additives used as thickeners, flavor carriers and suspension stabilizers in many products.

Scientists at Oregon State University were able to develop cellulose nanofiber PtSb-based antifungal coatings which offer good wettability, flexibility, barrier and mechanical properties.

The researchers evaluated their use on fresh grapes. The coatings are promising for controlling mold growth while simultaneously providing improved wettability, flexibility, barrier and mechanical properties.

The researchers used cellulose nanofibers at 0.5% levels and PtSb, also at 0.5% levels, as the base coating formulation. They optimized surfactant concentrations, the coating solution, the type of plasticizer used and plasticizer concentrations in the cellulose nanofiber coating formulations to improve wettability, flexibility, barrier and mechanical properties.

The scientists evaluated the contact angle (CA) and spreadability of the coating solution, as well as tensile strength (TS), elongation at break (EL), and the water solubility (WS), water adsorption (WA), and water vapor permeability (WVP) of cellulose nanofiber films, as well as the film surface characteristics.

A Taguchi experimental design was applied to optimize the coating formulations. All experiments were performed in triplicate. The coatings were applied to fresh grapes to evaluate their control of mold growth during ambient storage. Data were analyzed using one-way analysis of variance (ANOVA) statistical models.

The scientists found that the coating solution significantly affected the CA, WA, TS and EL. The type and concentration of plasticizer only impacted TS and EL. EL was an important coating performance attribute in pre-harvest coating applications.

Glycerol provided the coatings with better homogeneity than sorbitol and polyethylene glycol 400. Grapes coated with one of the optimal cellulose nanofiber coating formulations had more than a five-fold lower decay rate than uncoated grapes after two weeks of storage.

Further information. John Simonsen, Department of Wood Science and Engineering, College of Forestry, Oregon State University, Corvallis, OR 97331; phone: 541-737-4217; email: john.simonsen@oregonstate.edu.

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Publication:Emerging Food R&D Report
Date:Oct 1, 2016
Words:373
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