Investigation of Ultrasonic Treatment on Physicochemical, Structural and Morphological Properties of Sodium Alginate/AgNPs/Apple Polyphenol Films and Its Preservation Effect on Strawberry

Silver Nanocomposites with Enhanced Shelf-Life for Fruit and Vegetable Preservation: Mechanisms, Advances, and Prospects

Reducing fruit and vegetable waste and maintaining quality has become challenging for everyone. Nanotechnology is a new and intriguing technology that is currently being implemented in fruit and vegetable preservation. Silver nanomaterials provide superior antibacterial qualities, biodegradability, and biocompatibility, which expands their potential applications in fruit and vegetable preservation. Silver nanomaterials include silver nanocomposites and Ag-MOF, of which silver nanocomposites are mainly composed of silver nanoparticles. Notably, not all kinds of silver nanoparticles utilized in the preservation of fruits and vegetables are thoroughly described. Therefore, the synthesis, mechanism of action, and advancements in research on silver nanocomposites for fruit and vegetable preservation were discussed in this study.

Chitosan-Based Films Blended with Tannic Acid and Moringa Oleifera for Application in Food Packaging: The Preservation of Strawberries (Fragaria ananassa)

Biobased plastics provide a sustainable alternative to conventional food packaging materials, thereby reducing the environmental impact. The present study investigated the effectiveness of chitosan with varying levels of Moringa oleifera seed powder (MOSP) and tannic acid (TA). Chitosan (CS) biocomposite films with tannic acid acted as a cross-linker, and Moringa oleifera seed powder served as reinforcement. To enhance food packaging and film performance, Moringa oleifera seed powder was introduced at various loadings of 1.0, 3.0, 5.0, and 10.0 wt.%. Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy analyses were performed to study the structure and morphology of the CS/TA/MOSP films. The scanning electron microscopy results confirmed that chitosan/TA with 10.0 wt.% of MOSP produced a lightly miscible droplet/matrix structure. Furthermore, mechanical properties, swelling, water solubility, optical barrier, and water contact angle properties of the film were also calculated. With increasing Moringa oleifera seed powder contents, the biocomposite films' antimicrobial and antifungal activity increased at the 10.0 wt.% MOSP level; all of the observed bacteria [Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Aspergillus niger (A. niger), and Candida albicans (C. albicans)] had a notably increased percentage of growth. The film, with 10.0 wt.% MOSP content, effectively preserves strawberries' freshness, making it an ideal food packaging material.

Nisin and ε-polylysine combined treatment enhances quality of fresh-cut jackfruit at refrigerated storage

This study investigated the effects of nisin combined with ε-polylysine on microorganisms and the refrigerated quality of fresh-cut jackfruit. After being treated with distilled water (control), nisin (0.5 g/L), ε-polylysine (0.5 g/L), and the combination of nisin (0.1 g/L) and ε-polylysine (0.4 g/L), microporous modified atmosphere packaging (MMAP) was carried out and stored at 10 ± 1°C for 8 days. The microorganisms and physicochemical indexes were measured every 2 days during storage. The results indicated that combined treatment (0.1 g/L nisin, 0.4 g/L ε-polylysine) had the best preservation on fresh-cut jackfruit. Compared with the control, combined treatment inhibited microbial growth (total bacterial count, mold and yeast), reduced the weight loss rate, respiratory intensity, polyphenol oxidase and peroxidase activities, and maintained higher sugar acid content, firmness, and color. Furthermore, it preserved higher levels of antioxidant compounds, reduced the accumulation of malondialdehyde and hydrogen peroxide, thereby reducing oxidative damage and maintaining high nutritional and sensory qualities. As a safe application of natural preservatives, nisin combined with ε-polylysine treatment has great application potential in the fresh-cut jackfruit industry.

Application of ultrasound technology for the effective management of waste from fruit and vegetable

Food waste presents a continuous challenge for the food industry, leading to environmental pollution and economic issues. A substantial amount of waste, including by-products from fruits and vegetables, non-edible food items, and other waste materials, is produced throughout the food supply chain, from production to consumption. Recycling and valorizing waste from perishable goods is emerging as a key multidisciplinary approach within the circular bio-economy framework. This waste, rich in raw by-products, can be repurposed as a natural source of ingredients. Researchers increasingly focus on biomass valorization to extract and use components that add significant value. Traditional methods for extracting these bio-compounds typically require the use of solvents and are time-consuming, underscoring the need for innovative techniques like ultrasound (US) extraction. Wastes from the processing of fruits and vegetables in the food industry can be used to develop functional foods and edible coatings, offering protection against various environmental factors. This comprehensive review paper discusses the valorization of waste from perishable items like fruits and vegetables using US technology, not only to extract valuable components from waste but also to treat wastewater in the beverage industry. It also covers the application of biomolecules recovered from this process in the development of functional foods and packaging.

Effects of konjac glucan-nan/low-acyl gellan edible coatings loaded thymol-β-cyclodextrin microcapsules on postharvest blueberry

This study developed an edible antimicrobial coating using a blend of konjac glucomannan (KGM) and low acyl gellan gum (LAG) hydrogel to incorporate thymol nanoparticles (TKL). The optimized TKL formulation (TKL60) comprised 0.22% thymol microcapsules (TMs), 0.075% total polysaccharide content (KGM:LAG = 1:2), and 99.63% distilled water. When applied to blueberries, TKL60 significantly extended their shelf life to 42 d at 2 ± 0.5 °C, tripling that of control fruit. TKL60 reduced decay rate, weight loss, and respiration rate, delayed softening and senescence during cold storage. It preserved the outer epidermis by retaining cuticular waxes, curbing lipid oxidation, and sustaining defense-related enzyme activities. Flavor analysis revealed altered volatile compound concentrations in TKL60-treated berries, including decreased terpenes and benzaldehyde, and increased esters and aldehydes like 2-methylbutanol, 3-methylbutanol, and linalool. Discriminant Analysis highlighted TKL60's efficacy in delaying aroma deterioration by over 21 d. TKL60 exhibits potential as a substitute for synthetic coatings and chemical insecticides.

Carvacrol Treatment Reduces Decay and Maintains the Postharvest Quality of Red Grape Fruits (Vitis vinifera L.) Inoculated with Alternaria alternata

In this study, we isolated and identified pathogenic fungi from the naturally occurring fruits of red grapes, studied their biological characteristics, screened fifteen essential oil components to find the best natural antibacterial agent with the strongest inhibitory effect, and then compared the incidence of postharvest diseases and storage potential of red grapes treated with two concentrations (0.5 EC50/EC50) of essential oil components (inoculated with pathogenic fungi) during storage for 12 d at room temperature. In our research, Alternaria alternata was the primary pathogenic fungus of red grapes. Specifically, red grapes became infected which caused diseases, regardless of whether they were inoculated with Alternaria alternata in an injured or uninjured state. Our findings demonstrated that the following conditions were ideal for Alternaria alternata mycelial development and spore germination: BSA medium, D-maltose, ammonium nitrate, 28 °C, pH 6, and exposure to light. For the best Alternaria alternata spore production, OA medium, mannitol, urea, 34 °C, pH 9, and dark conditions were advised. Furthermore, with an EC50 value of 36.71 μg/mL, carvacrol demonstrated the highest inhibitory impact on Alternaria alternata among the 15 components of essential oils. In the meantime, treatment with EC50 concentration of carvacrol was found to be more effective than 0.5 EC50 concentration for controlling Alternaria alternata-induced decay disease of red grapes. The fruits exhibited remarkable improvements in the activity of defense-related enzymes, preservation of the greatest hardness and total soluble solids content, reduction in membrane lipid peroxidation in the peel, and preservation of the structural integrity of peel cells. Consequently, carvacrol was able to prevent the Alternaria alternata infestation disease that affects red grapes, and its EC50 concentration produced the greatest outcomes.

Characterization of Sodium Alginate-Based Films Blended with Olive Leaf and Laurel Leaf Extracts Obtained by Ultrasound-Assisted Technology

Due to environmental concerns, there is an increasing need to reduce the use of synthetic and non-renewable packaging materials to reduce waste and increase sustainability. This study aimed to characterise sodium alginate edible-based films (SA) incorporated with laurel leaf extract (LLE) and olive leaf extract (OLE) obtained by ultrasound-assisted extraction. Determination of total phenolic content, antioxidant, and antimicrobial activity was performed for the extracts and films. Also, thickness, tensile strength, elongation at break, modulus of elasticity, opacity and colour, moisture content, water vapour permeability (WVP), Fourier-transform infrared spectroscopy (FTIR) spectra, and surface morphology by scanning electron microscope (SEM) analyses were performed for the films. LLE yielded better results in terms of phenolic content (195 mg GAE/g), antioxidant (2.1 TE/g extract) and antimicrobial activity (MIC at 1% for Listeria monocytogenes and Staphylococcus aureus, and 1.8% for Enterococcus faecalis). For the films, the simultaneous incorporation of LLE 1% (w/v) and OLE 1% (w/v) resulted in a significant reduction of approximately 2 log CFU/g against S. aureus. The addition of LLE and OLE extracts also proved to improve barrier properties (lower WVP for SA films with LLE 1% + OLE 1%, 3.49 × 10-11 g m-1 s-1 Pa-1) and promoted changes in resistance and flexibility. The results demonstrated that active alginate-based films can be valuable for enhancing food preservation.

Ultrasonic treatment decreases Lyophyllum decastes fruiting body browning and affects energy metabolism

Lyophyllum decastes is a common mushroom that is prone to browning during prolonged storage. In this study, the effects of ultrasonic treatment on metabolic gene expression, enzyme activity, and metabolic compounds related to L. decastes browning were investigated. Treatment of the fruiting body at 35 kHz and 300 W for 10 min reduced the browning index of L. decastes by 21.0 % and increased the L* value by 11.1 %. Ultrasonic treatment of the fruiting body resulted in higher levels of total phenols, flavonoids, and 9 kinds of amino acid with catalase (CAT) and peroxidase (POD) activities maintained at high levels. Higher cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), phosphofructokinase (PFK), and pyruvate kinase (PK) activities may be ascribed to increased antioxidant capacity. Moreover, ultrasonication retained higher adenosine triphosphate (ATP) concentrations with an increased energy charge, while there were lower levels of adenosine diphosphate (ADP) and reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD⁺), respectively. Meanwhile, lower lignin contents were observed, along with retarded polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Lower PPO activity reduced the fruiting body enzymatic browning rate through decreased expression of LdPpo1, LdPpo2, and LdPpo3 during storage at 4 °C for 16 days. This activity may be used to determine the effectiveness of ultrasonication.

Ultrasound-assisted fabrication of biopolymer materials: A review

There is an urgent need to develop technologies that can physically manipulate the structure of biocompatible and green polymer materials in order to tune their performance in an efficient, repeatable, easy-to-operate, chemical-free, non-contact, and highly controllable manner. Ultrasound technology produces a cavitation effect that promotes the generation of free radicals, the fracture of chemical chain segments and a rapid change of morphology. The cavitation effects are accompanied by thermal, chemical, and biological effects that interact with the material being studied. With its high efficiency, cleanliness, and reusability applications, ultrasound has a vast range of opportunity within the field of natural polymer-based materials. This work expounds the basic principle of ultrasonic cavitation and analyzes the influence that ultrasonic strength, temperature, frequency and induced liquid surface tension on the physical and chemical properties of biopolymer materials. The mechanism and the influence that ultrasonic modification has on materials is discussed, with highlighted details on the agglomeration, degradation, morphology, structure, and the mechanical properties of these novel materials from naturally derived polymers.

Supramolecular nanogels based on gelatin-cyclodextrin-stabilized silver nanocomposites with antibacterial and anticancer properties

An effective method for reducing silver ions using gelatin (Gel) and 2-hydroxypropyl-β-cyclodextrin (HPCD) hydrogels, which stabilize silver at various concentrations is described. The formation of AgNPs in solution, as well as Gel-HPCD nanogels, is confirmed by the surface plasmon resonance (SPR) band at 420-440 nm in the UV-Vis spectrum. The resulting Gel-HPCD and Gel-HPCD/AgNPs composites are characterized using various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). SEM images showed that the porous structure and the AgNPs are homogeneously dispersed throughout the Gel-HPCD/AgNP composites network. The AgNPs in the Gel-HPCD/AgNPs composite is crystalline, with spherical particles having an average size of 7.0 ± 2.5 nm, as determined by TEM. The Gel-HPCD/AgNPs composites are strongly effective against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The assembled antibacterial Gel-HPCD/AgNPs composites are also assessed for their cytotoxic and anticancer activities using HCT-116 cancer cells. The results suggest that Gel-HPCD/AgNPs composites could be used as effective therapeutics in the future in tissue engineering applications, as their bactericidal properties and low toxicity make them ideal for clinical use.

Characterization and Antimicrobial Activity of Silver Nanoparticles Synthesized with the Peel Extract of Mango

The green synthesis of silver nanoparticles (AgNPs) from biological waste, as well as their excellent antibacterial properties, is currently attracting significant research attention. This study synthesized AgNPs from different mango peel extract concentrations while investigating their characteristics and antibacterial properties. The results showed that the AgNPs were irregular with rod-like, spherical shapes and were detected in a range of 25 nm to 75 nm. The AgNPs displayed antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), showing a more significant impact when synthesized with 0.20 g/mL of mango peel extract. Therefore, the antibacterial effect of different diluted AgNP concentrations on the growth kinetic curves of E. coli and S. aureus after synthesis with 0.20 g/mL mango peel extract was analyzed. The results indicated that the AgNP antibacterial activity was higher against S. aureus than against E. coli, while the AgNP IC50 in these two strains was approximately 1.557 mg/mL and 2.335 mg/L, respectively. This research provides new insights regarding the use of postharvest mango byproducts and the potential for developing additional AgNP composite antibacterial materials for fruit and vegetable preservation.

Antibacterial Biodegradable Films Based on Alginate with Silver Nanoparticles and Lemongrass Essential Oil-Innovative Packaging for Cheese

Replacing the petroleum-based materials in the food industry is one of the main objectives of the scientists and decision makers worldwide. Biodegradable packaging will help diminish the environmental impact of human activity. Improving such biodegradable packaging materials by adding antimicrobial activity will not only extend the shelf life of foodstuff, but will also eliminate some health hazards associated with food borne diseases, and by diminishing the food spoilage will decrease the food waste. The objective of this research was to obtain innovative antibacterial films based on a biodegradable polymer, namely alginate. Films were characterized by environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR) and microscopy, complex thermal analysis (TG-DSC-FTIR), UV-Vis and fluorescence spectroscopy. Water vapor permeability and swelling behavior were also determined. As antimicrobial agents, we used silver spherical nanoparticles (Ag NPs) and lemongrass essential oil (LGO), which were found to act in a synergic way. The obtained films exhibited strong antibacterial activity against tested strains, two Gram-positive (Bacillus cereus and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Salmonella Typhi). Best results were obtained against Bacillus cereus. The tests indicate that the antimicrobial films can be used as packaging, preserving the color, surface texture, and softness of cheese for 14 days. At the same time, the color of the films changed (darkened) as a function of temperature and light presence, a feature that can be used to monitor the storage conditions for sensitive food.

Biodegradable Alginate Films with ZnO Nanoparticles and Citronella Essential Oil-A Novel Antimicrobial Structure

The petroleum-based materials could be replaced, at least partially, by biodegradable packaging. Adding antimicrobial activity to the new packaging materials can also help improve the shelf life of food and diminish the spoilage. The objective of this research was to obtain a novel antibacterial packaging, based on alginate as biodegradable polymer. The antibacterial activity was induced to the alginate films by adding various amounts of ZnO nanoparticles loaded with citronella (lemongrass) essential oil (CEO). The obtained films were characterized, and antibacterial activity was tested against two Gram-negative (Escherichia coli and Salmonella Typhi) and two Gram-positive (Bacillus cereus and Staphylococcus aureus) bacterial strains. The results suggest the existence of synergy between antibacterial activities of ZnO and CEO against all tested bacterial strains. The obtained films have a good antibacterial coverage, being efficient against several pathogens, the best results being obtained against Bacillus cereus. In addition, the films presented better UV light barrier properties and lower water vapor permeability (WVP) when compared with a simple alginate film. The preliminary tests indicate that the alginate films with ZnO nanoparticles and CEO can be used to successfully preserve the cheese. Therefore, our research evidences the feasibility of using alginate/ZnO/CEO films as antibacterial packaging for cheese in order to extend its shelf life.

Application of Furcellaran Nanocomposite Film as Packaging of Cheese

There is a serious need to develop and test new biodegradable packaging which could at least partially replace petroleum-based materials. Therefore, the objective of this work was to examine the influence of the recently developed furcellaran nanocomposite film with silver nanoparticles (obtained by an in situ method) on the quality properties of two cheese varieties: a rennet-curd (gouda) and an acid-curd (quark) cheese. The water content, physicochemical properties, microbiological and organoleptic quality of cheese, and migration of silver nanoparticles were examined. Both the number of Lactococcus and total bacteria count did not differ during storage of gouda regardless of the packaging applied. The number of Lactococcus decreased in analogous quark samples. The use of the film slowed down and inhibited the growth of yeast in gouda and quark, respectively. An inhibitory effect of this film on mold count was also observed; however, only regarding gouda. The level of silver migration was found to be lower in quark than in gouda. The film improved the microbiological quality of cheeses during storage. Consequently, it is worth continuing research for the improvement of this film in order to enable its use in everyday life.

Electrospun nanofibers food packaging: trends and applications in food systems

Food safety is a bottleneck problem. In order to provide information about advanced and unique food packaging technique, this study summarized the advancements of electrospinning technique. Food packaging is a multidisciplinary area involving food science, food engineering, food chemistry, and food microbiology, and the interest in maintaining the freshness and quality of foods has grown considerably. For this purpose, electrospinning technology has gained much attention due to its unique functions and superior processing. Sudden advancements of electrospinning have been rapidly incorporated into research. This review summarized some latest information about food packaging and different materials used for the packaging of various foods such as fruits, vegetables, meat, and processed items. Also, the use of electrospinning and materials used for the formation of nanofibers are discussed in detail. However, in food industry, the application of electrospun nanofibers is still in its infancy. In this study, different parameters, structures of nanofibers, features and fundamental properties are described briefly, while polymers fabricated through electrospinning with advances in food packaging films are described in detail. Moreover, this comprehensive review focuses on the polymers used for the electrospinning of nanofibers as packaging films and their applications for variety of foods. This will be a valuable source of information for researchers studying various polymers for electrospinning for application in the food packaging industry.