Title：Preserving fruit freshness with amyloid-like protein coatings

Journal:  Nature Communications

IF: 15.7

Original link：https://doi.org/10.1038/s41467-025-60382-4

Reporter：Qian Wang-25-master

Addressing critical challenges in perishable fruit preservation, including hydrophobic surface treatment, protective layer adhesion on complex cuticles, and synergistic integration of preservation components, here we present an eco-friendly amyloid-like protein coating strategy developed through computer-aided molecular simulation. This system employs phase-transitioned lysozyme as an adhesive layer bonded to fruit epicuticular wax, synergized with sodium alginate and cellulose nanocrystals to form a proteinaceous barrier. Validated across 17 fruit varieties, the coating extends shelf-life by 2-5-fold through microbial inhibition, moisture loss reduction, and rot delay, while maintaining 60–98% nutrient retention, surpassing chemical preservation efficacy without toxicity risks. With edible properties, easy washability, and low cost, the coating demonstrates universal applicability for post-harvest and fresh-cut fruits. Notably, it reduces carbon dioxide emissions by 90% versus refrigeration while achieving 2.5-fold longer shelf-life. These positions the amyloid-like protein coating as a practical and sustainable approach to mitigating global food waste issues.

The global food system confronts a critical challenge posed by postharvest losses of perishable fruits, a major contributor to food waste wherein an estimated 50% of field-grown fruits are discarded annually. While possessing a natural cuticular wax layer as a physico-chemical barrier, fruits remain highly susceptible to rapid spoilage and quality deterioration driven by a complex interplay of postharvest biological processes, including microbial infestation, oxidative stress, moisture loss, and physiological senescence. Current preservation paradigms, such as chemical preservatives with potential toxicological risks and energy-intensive cold chains with significant carbon footprints, are misaligned with sustainability goals. Furthermore, edible coating technologies based on biopolymers, despite their promise, are fundamentally constrained by poor interfacial wettability and adhesion universality on hydrophobic and heterogeneous fruit surfaces, alongside the difficulty in achieving synergistic efficacy among multi-functional components. Consequently, the development of a novel coating system capable of robust interfacial anchoring, integrated multi-protective functionality, and environmental benignancy is urgently required to address the dual challenges of mitigating food waste and advancing sustainable agriculture.

1.  Design and preparation of the adhesive fresh-keeping ALP coating

Molecular dynamics simulations and experimental validations demonstrated that phase-transformed amyloid-like lysozyme exhibits superior and robust interfacial binding to fruit cuticular wax compared to its native counterpart. The simulations revealed a 31% increase in binding energy and a 26% expansion in contact area. Experimentally, the adhesive coating (ALP), formulated with this amyloid-like protein, sodium alginate, and cellulose nanocrystals, achieved a 5-fold stronger adhesion than native lysozyme and spread rapidly to form a uniform film on various hydrophobic fruit peels. This enhanced performance is attributed to the protein's conformational shift to β-sheet structures and the exposure of diverse functional groups during phase transition, which collectively fortify both the coating's internal cohesion and its multifunctional bonding with the fruit wax.

2. Versatile fresh-keeping features of the ALP coating

The study confirms that the ALP coating exhibits excellent comprehensive properties, fully meeting the requirements of an ideal preservation material. Demonstrating shear-thinning behavior suitable for spray coating, it forms uniform films with mechanical strength (2.82 MPa tensile strength, 39% strain) comparable to common edible and synthetic packaging films, while maintaining high transparency. Notably, the coating shows outstanding barrier properties, with water vapor transmission rate (~4 g mm m⁻² d⁻¹) and oxygen permeability (22 cm³ μm m⁻² day⁻¹ kPa⁻¹) significantly lower than most biopolymers. Functionally, it possesses strong antioxidant activity (71% DPPH and nearly 100% ABTS radical scavenging) and remarkable antibacterial capability. These attributes collectively delay the fruit respiration peak, effectively inhibit browning and softening, thereby providing multi-faceted preservation to extend shelf life.

3. Universal fruit’s fresh-keeping traits of the ALP coating

The ALP coating demonstrated remarkable preservation efficacy across 17 fruit varieties. Experiments on both non-climacteric (e.g., strawberry, loquat) and climacteric fruits (e.g., cherry tomato, mango, banana) showed a 2-5 fold shelf-life extension, maintained even at elevated temperatures (37-42°C). The preservation mechanism involves multiple effects: effective inhibition of various spoilage microorganisms (>90% inhibition against Mucor, Fusarium, etc.), significant reduction in weight loss (33-69%), maintained fruit firmness (9-91% reduction in stiffness loss), and notable nutrient retention (14-92% less VC loss, 21-65% less TA loss). E-nose/tongue analyses confirmed that coated fruits retained aroma, flavor, and texture similar to fresh produce throughout storage, achieving a 30-90% higher edible ratio.

4. The suitability to employ the ALP coating for the preservation of fresh-cut fruits

The ALP coating demonstrates exceptional efficacy in preserving fresh-cut fruits. Experiments show it significantly delays enzymatic browning in fresh-cut apples, reduces weight loss by up to 88%, and improves nutrient retention to 57%-86% (versus 8%-39% in untreated groups). Antimicrobial tests reveal the coating delays bacterial and fungal appearance by 6 and 8 days, respectively. For various fresh-cut fruits including apples, strawberries, and blueberries, the coating extends shelf life by 4-fold, maintaining significant effects even at 42°C. E-nose/tongue analyses confirm treated fruits retain aroma and flavor profiles similar to fresh produce, highlighting the technology's substantial potential in fresh-cut fruit preservation.

5. Washable, edible, and sustainable properties of the ALP coatings

Biosafety and sustainability assessments confirm the high application potential of the ALP coating. Safety tests demonstrate easy washability, no toxicity in 28-day rat feeding studies, normal organ pathology, blood parameters, and liver/kidney function, with a hemolysis rate (2.46%) well below international safety standards (5%). Life cycle assessment reveals that compared to 4°C refrigeration, the ALP coating extends cherry tomato shelf life to 10 days at 23°C while reducing carbon emissions by 90%. For non-climacteric fruits like strawberries, the coating achieves preservation efficacy comparable to refrigeration with a significantly lower carbon footprint, highlighting its potential as an eco-friendly alternative to cold chain storage.

This study successfully developed an eco-friendly amyloid-like protein (ALP) coating for fruit preservation. Comprising phase-transformed lysozyme, sodium alginate, and cellulose nanocrystals, the coating forms a dense, stable protective film on fruit surfaces. Molecular dynamics simulations confirmed a 31% increase in binding energy and 5-fold stronger adhesion compared to native lysozyme. Validated across 17 fruit types, the ALP coating extended shelf life by 2-5-fold, effectively inhibited microbial growth (>90% inhibition against various pathogens), reduced weight loss by 33-69%, and preserved 60-98% of nutritional components. It also exhibited excellent antioxidant activity (near 100% ABTS scavenging) and mechanical properties. Safety assessments confirmed its edibility, washability, and biocompatibility. Life cycle analysis demonstrated its potential to replace cold chain storage, reducing carbon emissions by 90% at room temperature with a low cost of $0.09 per kilogram of fruit, offering a sustainable solution to mitigate postharvest loss.