An Extensive Review of Natural Polymers Used as Coatings for Postharvest Shelf-Life Extension: Trends and Challenges

Application of bacteriophages in biopolymer-based functional food packaging films

Recently, food spoilage caused by pathogens has been increasing. Therefore, applying control strategies is essential. Bacteriophages can potentially reduce this problem due to their host specificity, ability to inhibit bacterial growth, and extend the shelf life of food. When bacteriophages are applied directly to food, their antibacterial activity is lost. In this regard, bacteriophage-loaded biopolymers offer an excellent option to improve food safety by extending their shelf life. Applying bacteriophages in food preservation requires comprehensive and structured information on their isolation, culturing, storage, and encapsulation in biopolymers for active food packaging applications. This review focuses on using bacteriophages in food packaging and preservation. It discusses the methods for phage application on food, their use for polymer formulation and functionalization, and their effect in enhancing food matrix properties to obtain maximum antibacterial activity in food model systems.

Fabrication and Characterization of Taro (Colocasia esculenta)-Mucilage-Based Nanohydrogel for Shelf-Life Extension of Fresh-Cut Apples

Taro mucilage is a cost-effective, eco-friendly, and water-soluble edible viscous polysaccharide, which possesses diverse techno-functional properties including gelling and anti-microbial. Therefore, the objective of this study was to formulate and evaluate the efficacy of taro mucilage nanohydrogel for the shelf-life enhancement of fresh-cut apples. Taro mucilage was extracted using cold water extraction, and the yield of mucilage was found to be 2.95 ± 0.35% on a dry basis. Different concentrations of mucilage (1, 2, 3, 4, and 5%) were used to formulate the nanohydrogel. A smaller droplet size of 175.61 ± 0.92 nm was observed at 3% mucilage, with a zeta potential of -30.25 ± 0.94 mV. Moreover, FTIR data of nanohydrogel revealed the functional groups of various sugars, uronic acids, and proteins. Thermal analysis of nanohydrogel exhibited weight loss in three phases, and maximum weight loss occurred from 110.25 °C to 324.27 °C (65.16%). Nanohydrogel showed shear-thinning fluid or pseudo-plastic behavior. Coating treatment of nanohydrogel significantly reduced the weight loss of fresh-cut apples (8.72 ± 0.46%) as compared to the control sample (12.25 ± 0.78%) on the 10th day. In addition, minor changes were observed in the pH for both samples during the 10 days of storage. Titrable acidity of control fresh-cut apples measured 0.22 ± 0.05% on day 0, rising to 0.42 ± 0.03% on the 10th day, and for coated fresh-cut apples, it was observed to be 0.24 ± 0.07% on the 0th day and 0.36 ± 0.06% on 10th day, respectively. Furthermore, the total soluble solids (TSS) content of both control and coated fresh-cut apples measured on the 0th day was 11.85 ± 0.65% and 12.33 ± 0.92%, respectively. On the 10th day, these values were significantly increased (p < 0.05) to 16.38 ± 0.42% for the control and 14.26 ± 0.39% for the coated sliced apples, respectively. Nanohydrogel-coated fresh-cut apples retained antioxidant activity and vitamin C content as compared to the control sample. Taro mucilage nanohydrogel-based edible coating showed distinct anti-microbial activity against psychrotrophic, aerobic, and yeast molds. In summary, taro mucilage nanohydrogel can be used as a cost-effective natural coating material for the shelf-life enhancement or freshness maintenance of fresh-cut apples.

Microbiological Assessment of White Button Mushrooms with an Edible Film Coating

The development of edible coatings incorporating bioextracts from mushrooms native to Portuguese forests aims to enhance the value of the endogenous forest and mycological resources by harnessing their potential as a source of antimicrobial and antioxidant compounds. Edible coatings represent an important pathway to decreasing food waste and contributing to implementing a circular bioeconomy. The coating should result in product valorization through improved preservation/conservation, increased shelf life, as well as enhancement of its antioxidant and enzymatic properties. To evaluate the effectiveness of an edible coating on fungal food matrices, a 14-day shelf-life study was conducted, wherein both coated and untreated mushrooms were examined under controlled storage temperatures of 4 °C and 9.3 °C. Agaricus bisporus was chosen as the food matrix for its bioeconomy significance, and Pleurotus eryngii was selected for the preparation of the food-based coating due to its profile of bioactive compounds. Microbiological analysis and physicochemical monitoring were conducted on the food matrices and the coating. Coated mushrooms had less mass loss and color change, and had better texture after 14 days. Microbiological analysis revealed that the coating had no antimicrobial activity. Overall, the coating improved the shelf life of the coated mushrooms but had less effect on the microbial community.

Applications of date pits in foods to enhance their functionality and quality: A review

Summary of the abstract

Physicochemical, Morphological, and Functional Characterization of Edible Anthocyanin-Enriched Aloevera Coatings on Fresh Figs (Ficus carica L.)

In the present investigation, Aloe vera gel (AVG)-based edible coatings enriched with anthocyanin were prepared. We investigated the effect of different formulations of aloe-vera-based edible coatings, such as neat AVG (T1), AVG with glycerol (T2), Aloe vera with 0.2% anthocyanin + glycerol (T3), and AVG with 0.5% anthocyanin + glycerol (T4), on the postharvest quality of fig (Ficus carica L.) fruits under refrigerated conditions (4 °C) for up to 12 days of storage with 2-day examination intervals. The results of the present study revealed that the T4 treatment was the most effective for reducing the weight loss in fig fruits throughout the storage period (~4%), followed by T3, T2, and T1. The minimum weight loss after 12 days of storage (3.76%) was recorded for the T4 treatment, followed by T3 (4.34%), which was significantly higher than that of uncoated fruit (~11%). The best quality attributes, such as the total soluble solids (TSS), titratable acidity (TA), and pH, were also demonstrated by the T3 and T4 treatments. The T4 coating caused a marginal change of 0.16 in the fruit titratable acidity, compared to the change of 0.33 in the untreated fruit control after 12 days of storage at 4 °C. Similarly, the total soluble solids in the T4-coated fruits increased marginally (0.43 °Brix) compared to the uncoated control fruits (>2 °Brix) after 12 days of storage at 4 °C. The results revealed that the incorporation of anthocyanin content into AVG is a promising technology for the development of active edible coatings to extend the shelf life of fig fruits.

Edible Xanthan/Propolis Coating and Its Effect on Physicochemical, Microbial, and Sensory Quality Indices in Mackerel Tuna (Euthynnus affinis) Fillets during Chilled Storage

Worldwide aquaculture production is increasing, but with this increase comes quality and safety related problems. Hence, there is an urgent need to develop potent technologies to extend the shelf life of fish. Xanthan gum is commonly used in the food industry because of its high-water solubility, stability of its aqueous solutions in a wide pH range, and high viscosity. One of its modern food applications is its use as a gelling agent in edible coatings building. Therefore, in this study, the effect of xanthan coating containing various concentrations (0, 1, 2%; w/v) of ethanolic extract of propolis (EEP) on physicochemical, microbial, and sensory quality indices in mackerel fillets stored at 2 °C for 20 days was evaluated. The pH, peroxide value, K-value, TVB-N, TBARS, microbiological and sensory characteristics were determined every 5 days over the storage period (20 days). Samples treated with xanthan (XAN) coatings containing 1 and 2% of EEP were shown to have the highest level of physicochemical protection and maximum level of microbial inhibition (p < 0.05) compared to uncoated samples (control) over the storage period. Furthermore, the addition of EEP to XAN was more effective in notably preserving (p < 0.05) the taste and odor of coated samples compared to control.

Physicochemical, Mechanical, and Structural Properties of Bio-Active Films Based on Biological-Chemical Chitosan, a Novel Ramon (Brosimum alicastrum) Starch, and Quercetin

The properties of biological-chemical chitosan (BCh) films from marine-industrial waste and a non-conventional Ramon starch (RS) (Brosimum alicastrum) were investigated. Blended films of BCh/RS were prepared to a volume ratio of 4:1 and 1:4, named (BChRS-80+q, biological-chemical chitosan 80% v/v and Ramon starch, BChRS-20+q, biological-chemical chitosan 20% v/v and Ramon starch, both with quercetin), Films from commercial chitosan (CCh) and corn starch (CS), alone or blended (CChCS-80+q, commercial chitosan 80% v/v and corn starch, CChCS-20+q commercial chitosan 20% v/v and corn starch, both with quercetin) were also prepared for comparison purposes. Films were investigated for their physicochemical characteristics such as thickness, moisture, swelling, water-vapor permeability, and water solubility. In addition, their mechanical and structural properties were studied using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Scanning Electron Microscopy (SEM) techniques. Antioxidant activity was evaluated as radical scavenging, and antimicrobial effect was also determined. The BCh and RS films presented similar tensile strength values compared with commercial biopolymers. Only films with chitosan presented antioxidant and antimicrobial activity. The FTIR spectra confirmed the interactions between functional groups of the biopolymers. Although, BChRS-80+q and BChRS-20+q films exhibited poor mechanical performance compared to their commercial counterparts, they showed good thermal stability, and improved antioxidant and antimicrobial activity in the presence of quercetin. BChRS-80+q and BChRS-20+q films have promising applications due to their biological activity and mechanical properties, based on a novel material that has been underutilized (Ramon starch) that does not compete with materials for human feeding and may be used as a coating for food products.

Recent Advancements of Polysaccharides to Enhance Quality and Delay Ripening of Fresh Produce: A Review

The freshness of fruits and vegetables plays a significant role in consumers' decision to purchase a product at the supermarket. Fresh-cut products are the latest trend in fulfilling society's restless needs, and the food industry is faced with the challenge of maintaining the quality of fresh produce. The food industry is concerned with the natural maturation and degradation of fruits and vegetables, primarily due to enzymatic reactions. It has been demonstrated that polysaccharide coatings effectively preserve the freshness of these products, extending their shelf life depending on the preservation method used. This review informs readers about the different types of polysaccharides and their novel applications as natural food preservatives in the past five years (2018-2022). The key findings summarized the properties of the antimicrobial agent, the molecular mechanism of action, coating methods, and formulation for the preservation approach. Additionally, we discuss the scientific factors influencing polysaccharide processing and preservation efficacy, allowing it to be used in post-harvest management.

Polysaccharide-Based Active Coatings Incorporated with Bioactive Compounds for Reducing Postharvest Losses of Fresh Fruits

This review reports recently published research related to the application of polysaccharide-based biodegradable and edible coatings (BECs) fortified with bioactive compounds obtained from plant essential oils (EOs) and phenolic compounds of plant extracts. Combinations of polysaccharides such as starches, pectin, alginate, cellulose derivatives, and chitosan with active compounds obtained from clove, lemon, cinnamon, lavender, oregano, and peppermint have been documented as potential candidates for biologically active coating materials for retardation of quality changes in fresh fruits. Additionally, polysaccharide-based active coatings supplemented with plant extracts such as cashew leaves, pomegranate peel, red roselle, apple fiber, and green tea extracts rich in phenolic compounds and their derivatives have been reported to be excellent substituents to replace chemically formulated wax coatings. Moreover, EOs and plant polyphenolics including alcohols, aldehydes, ketones phenols, organic acids, terpenes, and esters contain hydroxyl functional groups that contribute bioactivity to BECs against oxidation and reduction of microbial load in fresh fruits. Therefore, BECs enriched with active compounds from EOs and plant extracts minimize physiological and microbial deterioration by reducing moisture loss, softening of flesh, ripening, and decay caused by pathogenic bacterial strains, mold, or yeast rots, respectively. As a result, shelf life of fresh fruits can be extended by employing active polysaccharide coatings supplemented with EOs and plant extracts prior to postharvest storage.