Self assembly of biomolecules (gelatin, coconut oil) combined with surface pH modification (citric/ascorbic acid, baking soda solutions) was used to achieve preservation of easily perishable produce, specifically strawberries. Edible coatings made with oil compounds can increase surface hydrophobicity, preventing spoilage induced by moisture in humid conditions. Intermolecular forces between organic coating molecules allows for arrangement of compact edible layers that can decrease diffusion rate of spoilage-inducing gases, such as oxygen. Oxygen can accelerate growth of harmful microorganisms and cause oxidative spoilage in foods via free radical mechanisms. Physical coatings created by self assembly of organic molecules can create an effective, applicable treatment for fruit preservation. Strawberries were treated with acidic/basic solutions (citric acid, ascorbic acid, baking soda), and gelatin as well as coconut oil spray coatings. Samples were spotted with 2µL (approx. 3.8x106 spores) penicillium mold solution and stored in 80-85% humidity. Spoilage rate was detected via samples’ elasticity by daily weight compression studies and rate of mold growth through area analysis. Thickness of coating was measured through SEM imaging of samples’ cross-section, but proved ineffective due to the coating’s nature to concave when cutting into the sample. Results indicate that citric acid solution was a better preservative than other acidic/basic treatments. Coconut oil coating was a more effective preservative than the gelatin coating, likely due to hydrophobic properties. An interior gelatin and exterior coconut oil coating facilitated the self assembly of multiple, uniform layers on the sample, making it increasingly impermeable to moisture. Future investigations will focus on method development for measuring coating thickness by incorporating fluorescent dye in coating and observing layer thickness under microscope. Additionally, essential oils will be implemented to the coatings to test its antimicrobial factors for preservation. Gas permeability (e.g. oxygen) through coating surface and light sensitivity will be studied to quantify the spoilage inducing factors. Light sensitivity will be tested via UV light exposure to coated and uncoated strawberry samples. Future investigations also include studying chemical and enzyme composition of strawberries during the spoilage process.

Preservation of strawberries via pH modification and biomolecular coatings

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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