Comparison between essential oils and supercritical extracts into chitosan-based edible coatings on strawberry quality during cold storage

Global Research Network Analysis of Edible Coatings and Films for Preserving Perishable Fruit Crops: Current Status and Future Directions

Edible coatings and films have gained substantial attention as a promising and sustainable technology for fruit preservation. This study employed a bibliometric analysis to identify core research areas, research gaps, and emerging trends, thus providing a comprehensive roadmap for future research on the use of edible coatings and films for fruit quality preservation. The study involved 428 research articles related to edible coatings and films for fruit preservation published in the Scopus database before 06 October 2023. Utilizing Vosviewer and R for network analysis, we generated network visualization maps, research performance statistics, and identified key contributors and their collaborations. The results show the evolution of this field into three distinct phases: Initial Exploration (1998-2007), Growing Interest (2008-2015), and Rapid Expansion (2016-2023). The study revealed contributions from 1713 authors, with the first article appearing in 1998. Brazil and China emerged as the most productive countries in this domain. The core research areas focus on biomaterials, functional properties, and natural substances. Identified research gaps include pilot and industrial-scale applications, the lack of a regulatory framework and safety guidelines, and the application of artificial intelligence (AI), particularly deep learning and machine learning, in this field of edible coatings and films for fruit preservation. Overall, this study offers a scientific understanding of past achievements and ongoing research needs, thus aiming to boost a broader adoption of edible coatings and films by consumers and the food industry to preserve fruit quality, thereby enhancing their societal and environmental impact.

Effects of Litsea cubeba Essential Oil-Chitosan/Corn Starch Composite Films on the Quality and Shelf-Life of Strawberry (Fragaria × ananassa)

In this work, we have developed a composite chitosan film incorporating the Litsea cubeba essential oil (LCEO) and starch with good physical properties, and investigated the effect of coating strawberries with this composite film. The best formula of the LCEO/chitosan/corn starch/glycerol (LCEO/CH/CS/gly) composite films is 0.25% LCEO, 2.75% CH, 0.40% corn starch, and 0.75% glycerol. Coating strawberries with CH/CS/gly film or LCEO/CH/CS/gly films resulted in significantly lower respiration intensity and a slower decay rate, much slower decreases in the firmness, and reductions in the sugar and ascorbic acid content of the fruit during storage (p < 0.05). The coatings also led to a much slower accumulation of malondialdehyde and anthocyanins (p < 0.05). The LCEO/CH/CS/gly film was generally more effective than the CH/CS/gly film; however, the effect was more obvious in the later stages of storage. Thus, coating strawberries with CH/CS/gly film or LCEO/CH/CS/gly film can be a viable method for extending the shelf-life of the fruit.

Rosemary: Unrevealing an old aromatic crop as a new source of promising functional food additive-A review

Rosemary (Rosmarinus officinalis L.) is one of the most famous spice plants belonging to the Lamiaceae family as a remarkably beautiful horticultural plant and economically agricultural crop. The essential oil of rosemary has been enthusiastically welcome in the whole world for hundreds of years. Now, it is wildly prevailing as a promising functional food additive for human health. More importantly, due to its significant aroma, food, and nutritional value, rosemary also plays an essential role in the food/feed additive and food packaging industries. Modern industrial development and fundamental scientific research have extensively revealed its unique phytochemical constituents with biologically meaningful activities, which closely related to diverse human health functions. In this review, we provide a comprehensively systematic perspective on rosemary by summarizing the structures of various pharmacological and nutritional components, biologically functional activities and their molecular regulatory networks required in food developments, and the recent advances in their applications in the food industry. Finally, the temporary limitations and future research trends regarding the development of rosemary components are also discussed and prospected. Hence, the review covering the fundamental research advances and developing prospects of rosemary is a desirable demand to facilitate their better understanding, and it will also serve as a reference to provide many insights for the future promotion of the research and development of functional foods related to rosemary.

Photoantimicrobial chitosan-gelatin-pomegranate peel extract films for strawberries preservation: From microbiological analysis to in vivo safety assessment

This study aimed to investigate the application of biopolymeric materials (chitosan, gelatin, and pomegranate peel extract as photosensitizer) and antimicrobial photodynamic therapy (aPDT) on the physicochemical and microbial safety of strawberries. The photosensitizer potential of the materials was confirmed by a light-dose-dependent photobleaching profile. The application of light (525 nm; 50 J cm-2) decreased by >2 log CFU mL-1 the survival of Staphylococcus aureus on the surface of the photoactive-biopolymeric films. Moreover, the materials did not present in vivo cytotoxicity using Danio rerio (Zebrafish) as well as cytophytotoxic, genotoxic, or mutagenic potentials against Allium cepa plant model, which points out their safety to be used as films without posing a risk to the humans and the environment. The photoactive-polymeric coatings were able to maintain the strawberries weight, and the association with green light was 100 % effective in delaying fungal contamination. These coated-strawberries presented a significant reduction in S. aureus survival after light application (5.47-4.34 log CFU mL-1). The molecular level analysis of the photoactive compound cyanidin-3-glucoside indicates absorption on UV-Vis consistent with aPDT action. Therefore, this study showed that the antimicrobial effects of aPDT combined with photoactive-biopolymeric coatings were enhanced, while the quality of the strawberries was maintained.

Development, characterization and use of rosemary essential oil loaded water-chestnut starch based nanoemulsion coatings for enhancing post-harvest quality of apples var. Golden delicious

The study aimed at evaluating the influence of water-chestnut starch-based coatings loaded with rosemary essential oil (REO) at concentrations of 0.10%, 0.25% and 0.50% (w/v) on postharvest cold storage stability of apple var. Golden delicious for 120 days. Average droplet diameter of nanoemulsions was in range of 315-450 nm and it increased with increase in the REO concentration. Minimum weight loss was observed in fruits treated with coating material containing 0.50% REO. Samples coated with starch+0.50% REO exhibited highest firmness value of 68.22 ± 1.02 N under controlled atmosphere storage (CAS). Anthocyanins, ascorbic acid, total phenolic content and antioxidant activity were retained in all samples coated with formulated emulsion. Antifungal assay against Pencillium expansum indicated that 0.50% REO had maximum antifungal activity. Increase in REO concentration from 0.10 to 0.50% in starch coating formulations resulted in reduced lesion diameter in coated samples under both the storage conditions. Lesion diameter (LD) was found highest in control (39.40 ± 0.20 mm) under ambient conditions. Coated fruit samples showed a significant (p≤0.05) reduction in LD under both the ambient and CAS conditions however, more pronounced effect was reported under CAS. Fruits coated with edible coatings enriched with different REO concentrations under CAS exhibited significantly (p≤0.05) lower chilling injury index (ST+0.50%REO < ST+0.25%REO<0.10%REO) compared to control.

The Effects of Poly-γ-Glutamic Acid on the Postharvest Physiology and Quality of Strawberry cv. Hongyan during Cold Storage

This study investigated the effects of poly-γ-glutamic acid (γ-PGA) on the postharvest physiology and quality of the strawberry cv. Hongyan during cold storage. The results showed that all concentrations of γ-PGA improved decay control and strawberry preservation by enhancing antioxidant capacity, delaying the softening process, and maintaining fruit quality, especially for 100 mg·L-1 γ-PGA. After 14 days of treatment, compared with control, 100 mg·L-1 γ-PGA decreased weight loss, decay rate, and index by 21.9%, 75.0%, and 66.7% and increased the total antioxidant capacity by 43.5% through antioxidant enzymes. In addition, 100 mg·L-1 γ-PGA increased fruit firmness by 53.6% by decreasing the activities of polygalacturonase, pectin lyase, cellulase, and β-galactosidase. In terms of color quality, 100 mg·L-1 γ-PGA improved the values of lightness and yellowness by 30.9% and 52.8%. As regards nutritional quality, 100 mg·L-1 γ-PGA increased the contents of protein, soluble sugars, vitamin C, and total phenols by 106.6%, 80.6%, 51.2%, and 78.4%. In terms of sensory quality, 100 mg·L-1 γ-PGA increased the soluble solids' content by 19.0% and decreased the titrated acids' content by 21.1%, which increased the sugar-acid ratio by 50.9%. Our findings suggest that 100 mg·L-1 γ-PGA can be used to improve the decay control and preservation of strawberry cv. Hongyan under cold storage.

Emerging Food Packaging Applications of Cellulose Nanocomposites: A Review

Cellulose is the most abundant biopolymer on Earth, which is synthesized by plants, bacteria, and animals, with source-dependent properties. Cellulose containing β-1,4-linked D-glucoses further assembles into hierarchical structures in microfibrils, which can be processed to nanocellulose with length or width in the nanoscale after a variety of pretreatments including enzymatic hydrolysis, TEMPO-oxidation, and carboxymethylation. Nanocellulose can be mainly categorized into cellulose nanocrystal (CNC) produced by acid hydrolysis, cellulose nanofibrils (CNF) prepared by refining, homogenization, microfluidization, sonification, ball milling, and the aqueous counter collision (ACC) method, and bacterial cellulose (BC) biosynthesized by the Acetobacter species. Due to nontoxicity, good biodegradability and biocompatibility, high aspect ratio, low thermal expansion coefficient, excellent mechanical strength, and unique optical properties, nanocellulose is utilized to develop various cellulose nanocomposites through solution casting, Layer-by-Layer (LBL) assembly, extrusion, coating, gel-forming, spray drying, electrostatic spinning, adsorption, nanoemulsion, and other techniques, and has been widely used as food packaging material with excellent barrier and mechanical properties, antibacterial activity, and stimuli-responsive performance to improve the food quality and shelf life. Under the driving force of the increasing green food packaging market, nanocellulose production has gradually developed from lab-scale to pilot- or even industrial-scale, mainly in Europe, Africa, and Asia, though developing cost-effective preparation techniques and precisely tuning the physicochemical properties are key to the commercialization. We expect this review to summarise the recent literature in the nanocellulose-based food packaging field and provide the readers with the state-of-the-art of this research area.

Bio-nanocomposite edible coatings based on arrowroot starch/cellulose nanocrystals/carnauba wax nanoemulsion containing essential oils to preserve quality and improve shelf life of strawberry

This study investigated the effects of bio-nanocomposite coatings developed using arrowroot starch (AA), cellulose nanocrystals (CNC), carnauba wax nanoemulsion (CWN), and Cymbopogon martinii and Mentha spicata essential oils (CEO and MEO, respectively) on the physicochemical, microbiological, bioactive, antioxidant, and aromatic characteristics of strawberries cv. 'Oso Grande' in refrigerated storage for 12 days. The coatings improved the shelf life and stability of strawberries, minimizing their weight loss (2.6-3.9 %), as well as changes in color and texture (except for those coated with CEO), titratable acidity, pH, soluble solids, anthocyanins, phenolic compounds, ascorbic acid content, and antioxidant activity compared with uncoated control strawberries. The bio-nanocomposite coatings containing MEO and CEO also exhibited antimicrobial activity, reduced visible fungal deterioration (40-60 %), and reduced microbial load (3.59-4.03 log CFU g^-1 for mesophilic aerobic bacteria and 4.45-5.22 log CFU g^-1 for fungi and yeast) during storage. They also significantly reduced the severity of decay caused by inoculation with Botrytis cinerea or Rhizopus stolonifer. The coatings altered the volatile profile of the fruits during storage, decreasing aldehyde and alcohol concentrations and increasing ester concentrations. Thus, these bio-nanocomposite coatings, especially those containing MEO, can be used as antimicrobial coating materials to preserve the post-harvest quality of fresh strawberries.

Usage of biological chitosan against the contamination of post-harvest treatment of strawberries by Aspergillus niger

Developing bioactive food packaging, capable of extending the shelf life of fruits, has received increasing attention in recent years. The present study highlights the interest in post-harvest treatment for strawberries with chitosan as a preservation solution. Chitosan extraction was carried out from shrimp shells (Parapenaeus longirostris), composed of chitin, using citric acid during the demineralization step. Extracted chitosan was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The presence of amino group (-NH2) in the obtained chitosan was confirmed by infrared (IR) spectral data. Deacetylation degree (DD), which has a value of 80.86%, was determined by FTIR spectra. X-ray diffraction pattern (XRD) showed two peaks of crystalline character, characteristic of extracted chitosan, approximately at 20° and 30° (2θ). Extracted chitosan morphology was studied by scanning electron microscopy (SEM) and showed a relatively smooth top surface and fibrous structures. Chitosan, acetic acid, and their interaction effects were evaluated on Aspergillus niger mycelial growth strain isolated from spoiled strawberries. Chitosan revealed a strong anti-fungal activity, dose-dependent (from 0 to 3%), on Aspergillus niger mycelial growth, while acetic acid showed moderate anti-fungal activity against the Aspergillus niger strain. Agri-food application was carried out using chitosan solubilized in acetic acid as a post-harvest treatment tool for the prolongation of shelf life of strawberries (by using an experimental design). Coating, with the developed preservative solution, significantly reduced microbial spoilage in strawberries. Treated strawberries retained their initial pigmentation for a longer period when compared to untreated strawberries. The treatment carried out maintained the cellular structures of treated strawberries during the storage period and thus extended the shelf life of strawberries which is considered very susceptible to reduce post-harvest losses.

Emerging chitosan-essential oil films and coatings for food preservation - A review of advances and applications

With the rising demand for fresh and ready-to-eat foods, antimicrobial packaging has been developed to control or prevent microbial growth as well as maintain food quality and safety. Chitosan is an advanced biomaterial for antimicrobial packaging to meet the growing needs of safe and biodegradable packaging. The application of natural essential oils as antimicrobial agents effectively controls the growth of spoilage and pathogenic microbes. Thus, chitosan edible coatings and films incorporated with essential oils have expanded the general applications of antimicrobial packaging in food products. This review summarized the effect of essential oils on modifying the physicochemical characteristics of chitosan-based films. Notably, the antimicrobial efficacy of the developed composite films or coatings was highlighted. The advances in the preparation methods and application of chitosan films were also discussed. Broadly, this review will promote the potential applications of chitosan-essential oils composite films or coatings in antimicrobial packaging for food preservation.

Effect of chia seed mucilage/bacterial cellulose edible coating on bioactive compounds and antioxidant activity of strawberries during cold storage

This study aimed to investigate the effect of chia seed mucilage (CSM) - bacterial cellulose nano-fiber (CNF) edible coating on bioactive compounds and antioxidant enzyme activity of strawberries. Strawberries were coated with CSM containing 0.6 and 8.0% (w/w) of CNF. The content of total phenol, flavonoids, anthocyanin, ascorbic acid, protein content, antioxidant activity and the activity of polyphenol oxidase, peroxidase, superoxide dismutase and phenylalanine ammonia-lyase enzymes were evaluated. The use of CSM - CNF edible coatings further preserved the phenolic, flavonoid, ascorbic acid and antioxidant activity of strawberries, and this effect was more evident in the CSM-coated sample containing CNF; However, the accumulation of anthocyanins in the coated samples was lower than the control sample. The activity of polyphenol oxidase and peroxidase enzymes, which lead to the degradation of phenolic compounds and brown color in the product, was also effectively controlled by the edible coating.

Incorporation of ascorbic acid in chitosan-based edible coating improves postharvest quality and storability of strawberry fruits

Recent postharvest studies have shown that adding an antioxidative agent in a polysaccharide-based edible coating reduces postharvest losses and extends the shelf life of a coated fruit. Therefore, the effect of addition of ascorbic acid (AA, 1%) in chitosan-based coating (CH, 1%) on strawberry fruits under cold storage conditions at 4 ± 1 °C and 85 ± 5% RH was investigated for 15 days. It was observed that addition of AA in CH coating reduced weight loss, decay percentage, malondialdehyde content and hydrogen peroxide compared to CH alone. The combined CH + AA application also suppressed fruit softening by reducing cell wall degrading enzymes (i.e. polygalacturonase, cellulase and pectin methyl esterase) activities. In addition, AA incorporation catalyzed ROS scavenging enzymes (i.e. ascorbate peroxidase, catalase, peroxidase and superoxide dismutase) activities. CH + AA treatment also maintained fruit quality by conserving higher total soluble solids, titratable acidity, ascorbic acid content, total phenolics and antioxidant activity. Sensory quality (color, taste, glossiness and overall acceptability) of fruits coated with CH + AA treatment was also stable during storage. Conclusively, the combined CH + AA application is an effective approach to maintain the postharvest quality of strawberry fruits under cold storage.

Plant Byproducts as Part of Edible Coatings: A Case Study with Parsley, Grape and Blueberry Pomace

Studies dealing with the development of edible/biodegradable packaging have been gaining popularity since these commodities are marked as being ecofriendly, especially when byproducts are incorporated. Consequently, this study aimed at the development of chitosan-based coatings with plant byproducts. Their sensory properties, colour attributes, occurrence of cracks in microstructure and biodegradability were analysed. Coatings containing grape and blueberry pomace had statistically significantly (p < 0.05) higher levels of colour intensity. Coating samples were characterised by lower aroma intensity (3.46–4.77), relatively smooth surface (2.40–5.86), and low stickiness (2.11–3.14). In the overall hedonic evaluation, the samples containing parsley pomace in all concentrations and a sample containing 5% grape pomace achieved a statistically significantly (p < 0.05) better evaluation (5.76–5.93). The lowest values of the parameter ΔE2000 were recorded for the sample containing 5% parsley pomace (3.5); the highest was for the sample with 20% blueberry pomace (39.3). An analysis of the coating surface microstructure showed the presence of surface cracks at an 80 K magnification but the protective function of the edible coating was not disrupted by the added plant pomace. The produced samples can be considered to have a high biodegradability rate. The results of our experimentally produced coatings indicate their possible application on a commercial scale.

Rheological and Microstructural Properties of Xanthan Gum-Based Coating Solutions Enriched with Phenolic Mango (Mangifera indica) Peel Extracts

Mango (Mangifera indica) is a tropical fruit highly desired for its vitamin content and flavor, but its peel is considered a byproduct or waste. However, mango peel contains some bioactive compounds that improve food quality matrix for the development of edible coatings or films. The effect of phenolic mango (Mangifera indica) peel extracts on the physicochemical, rheological, and microstructural properties of xanthan gum-based coating solutions was evaluated. The obtained solutions were stable during the study period and presented a non-Newtonian fluid type shear-thinning behavior described by Ostwald-de Waele. Moreover, viscoelastic properties revealed that the elastic modulus was higher than the viscous modulus, showing a characteristic of weak gels. The addition of extracts did not alter the shear rate and viscoelastic character of the solutions, preserving the pseudoplasticity and weak gel behavior of xanthan gum associated with spreadability and adherence of coatings; it modified the gel structure as a function of temperature. Furthermore, the coating solutions of xanthan gum and phenolic mango peel extracts are an alternative to develop complex food systems such as edible coatings, edible films, or delivery systems.