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SÃO PAULO, Brazil — Anyone who’s experienced the disappointment of finding moldy strawberries in their refrigerator just days after purchase will appreciate this innovation. New research from Brazil could revolutionize how we store and enjoy one of America’s favorite fruits with a natural coating that keeps strawberries fresh for up to eight days longer than normal.
According to a study published in Food Chemistry, this novel coating minimizes weight loss in strawberries and substantially delays the onset of mold. This could be a major advance in natural food preservation.
The coating is completely natural, edible, and estimated to cost just three cents per strawberry. This could make throwing away expensive produce a less frequent problem.
How the Natural Coating Works
The coating works by forming a protective barrier on the strawberry’s surface that restricts moisture loss and prevents microorganisms from taking hold. Beyond just extending shelf life, the coated strawberries also retained more of their nutritional value, including vitamin C, anthocyanins (the compounds responsible for strawberries’ red color), and other beneficial antioxidants.
The coating also doesn’t affect the taste of the strawberries. In a blind taste test, participants couldn’t tell the difference between coated and uncoated berries. There was no significant difference between the fruits, suggesting consumers would readily accept this preservation method.
Brazil, where the study was conducted, is the largest strawberry producer in South America, yielding about 165,000 tons annually. However, strawberries are among the most wasted items in Brazilian markets due to their short shelf life, which is typically just seven days under refrigeration.
The innovative coating combines three main ingredients. Chitosan, a polysaccharide derived from the shells of crustaceans, has natural antimicrobial properties. Gelatin adds structure to the coating, while pomegranate peel extract—normally discarded as waste—provides powerful antioxidants that further extend shelf life.
Fresher Berries for Nearly Twice as Long
To test their creation, researchers compared three groups of strawberries: uncoated ones, those coated with just chitosan and gelatin, and those with the complete formulation including pomegranate peel extract. All were stored at refrigerator temperature (around 45°F) for 12 days.
By the sixth day of storage, more than 70% of uncoated strawberries showed visible signs of fungal growth, while only 20% of coated berries were affected. At the end of the study, the coated strawberries had 30% less fungal contamination than uncoated ones.
Weight loss, a major factor in berry deterioration, was also substantially reduced. Uncoated strawberries lost over 43% of their weight during the study period, compared to just under 32% for the fully coated berries.
The coating also preserved the fruits’ firmness, color, and respiratory rate, all indicators of freshness. While uncoated strawberries became soft and lost their bright color, the coated ones maintained their appealing appearance and texture.
Perhaps most importantly for consumers, the coating preserved the strawberries’ volatile compounds, the chemicals responsible for their distinctive aroma and flavor. Uncoated strawberries showed a nearly 40% reduction in these compounds, approximately six times greater than coated fruits.
Sustainability and Savings
Beyond simply extending shelf life, this innovation could have significant environmental and economic benefits. Food waste is a major contributor to greenhouse gas emissions, and reducing it is crucial for sustainability efforts. Additionally, extending the viable selling period for strawberries could help farmers and retailers reduce losses and potentially lower consumer prices.
This natural coating is a step forward in the fight against food waste. It is a simple, affordable solution that could transform how we store and enjoy fresh strawberries without relying on synthetic preservatives and packaging.
Paper Summary
Methodology
Researchers created coatings using chitosan (derived from squid pens), gelatin, and pomegranate peel extract. They applied these coatings to freshly sanitized strawberries by dipping them in the solutions for two minutes, then letting them dry at room temperature. The strawberries were split into three groups: uncoated control, coated with chitosan/gelatin (CG), and coated with chitosan/gelatin/pomegranate peel extract (CGPPE). All strawberries were stored at 45°F with 60-70% relative humidity for 12 days. Throughout the storage period, researchers measured various quality attributes including weight loss, fungal decay, firmness, respiration rate, color, soluble solids content, acidity, pH, bioactive compounds, volatile profile, and conducted a sensory analysis with 19 trained evaluators.
Results
The CGPPE coating showed the most promising results, reducing weight loss to 31.89% (compared to 43.09% in uncoated strawberries) and delaying fungal contamination by 6-8 days. The coatings preserved fruit firmness, respiratory quotient, color properties, and bioactive compounds (phenolics, anthocyanins, vitamin C). The volatile compound profile was better maintained in coated strawberries, with uncoated fruits showing a 39.4% reduction in total volatile compounds compared to just 6.9% in CGPPE-coated strawberries. Sensory tests revealed no significant difference in taste between coated and uncoated strawberries, indicating the coating didn’t negatively impact flavor. The cost of coating was estimated at approximately $0.03 per strawberry.
Limitations
The study was conducted in laboratory conditions rather than in commercial storage or retail environments, which might affect real-world application. The researchers didn’t investigate whether the coating could be applied at industrial scale, which would be crucial for commercial adoption. Additionally, the sensory analysis was conducted immediately after coating application rather than throughout the storage period, potentially missing flavor changes that might develop over time. The research was also conducted with a single strawberry cultivar (Camino Real), and results might vary with different varieties.
Funding/Disclosures
This work was supported by grants 2019/18748-8, 2018/24612-9, and 2022/03229-8 from the São Paulo Research Foundation (FAPESP). The researchers declared no known competing financial interests or personal relationships that could have appeared to influence the work reported in the paper.
Publication Information
The paper titled “Improvement of the physical-chemical, microbiological, volatiles and sensory quality of strawberries covered with chitosan/gelatin/pomegranate peel extract-based coatings” was published in Food Chemistry (volume 471) in January 2025. The research was conducted by Mirella Romanelli Vicente Bertolo and colleagues from the University of São Paulo (USP), Brazilian Agricultural Research Corporation (Embrapa Instrumentação), and the Federal University of São Carlos in Brazil.
