Antifungal Coatings on Fresh Strawberries (Fragaria × ananassa) to Control Mold Growth During Cold Storage

Degradable chitosan-based bioplastic packaging: Design, preparation and applications

Food packaging is an essential part of food transportation, storage and preservation. Biodegradable biopolymers are a significant direction for the future development of food packaging materials. As a natural biological polysaccharide, chitosan has been widely concerned by researchers in the field of food packaging due to its excellent film-forming property, good antibacterial property and designability. Thus, the application research of chitosan-based food packaging films, coatings and aerogels has been greatly developed. In this review, recent advances on chitosan-based food packaging materials are summarized. Firstly, the development background of chitosan-based packaging materials was described, and then chitosan itself was introduced. In addition, the design, preparation and applications of films, coatings and aerogels in chitosan-based packaging for food preservation were discussed, and the advantages and disadvantages of each research in the development of chitosan-based packaging materials were analyzed. Finally, the application prospects, challenges and suggestions for solving the problems of chitosan-based packaging are summarized and prospected.

A Review into the Effectiveness of Ozone Technology for Improving the Safety and Preserving the Quality of Fresh-Cut Fruits and Vegetables

In recent years, consumers have become increasingly aware of the nutritional benefits brought by the regular consumption of fresh fruits and vegetables, which reduces the risk of health problems and disease. High-quality raw materials are essential since minimally processed produce is highly perishable and susceptible to quality deterioration. The cutting, peeling, cleaning and packaging processes as well as the biochemical, sensorial and microbial changes that occur on plant tissue surfaces may accelerate produce deterioration. In this regard, biological contamination can be primary, which occurs when the infectious organisms directly contaminate raw materials, and/or by cross-contamination, which occurs during food preparation processes such as washing. Among the many technologies available to extend the shelf life of fresh-cut products, ozone technology has proven to be a highly effective sterilization technique. In this paper, we examine the main studies that have focused on the effects of gaseous ozone and ozonated water treatments on microbial growth and quality retention of fresh-cut fruit and vegetables. The purpose of this scientific literature review is to broaden our knowledge of eco-friendly technologies, such as ozone technology, which extends the shelf life and maintains the quality of fresh produce without emitting hazardous chemicals that negatively affect plant material and the environment.

Diversity of experimental designs for the fabrication of antifungal surfaces for the built environment

The fungal infestation in construction industries is a major problem with a very high removal cost that needs to be controlled not only to prevent the fouling of surfaces but also to prevent allergic reactions or respiratory problems especially in immunocompromised individuals. To combat fungal invasion, several experimental approaches to produce antifungal surfaces have been developed. Here, we reviewed the current strategies in designing antifungal surfaces and classified those approaches into two major categories: the chemical and/or physical modification of the actual material surface and nanoparticle-based coating formulations created using the functionalised nanoparticles. KEY POINTS: • Antifungal effect of micro- and nano-structured superhydrophobic surfaces. • Long-term antifungal effect conferred through biocides. • Advanced coatings based on functionalised silica, TiO₂ and ZnO nanoparticles.

Food Safety through Natural Antimicrobials

Microbial pathogens are the cause of many foodborne diseases after the ingestion of contaminated food. Several preservation methods have been developed to assure microbial food safety, as well as nutritional values and sensory characteristics of food. However, the demand for natural antimicrobial agents is increasing due to consumers' concern on health issues. Moreover, the use of antibiotics is leading to multidrug resistant microorganisms reinforcing the focus of researchers and the food industry on natural antimicrobials. Natural antimicrobial compounds from plants, animals, bacteria, viruses, algae and mushrooms are covered. Finally, new perspectives from researchers in the field and the interest of the food industry in innovations are reviewed. These new approaches should be useful for controlling foodborne bacterial pathogens; furthermore, the shelf-life of food would be extended.

Shelf life extension of fresh fruit and vegetables by chitosan treatment

Among alternatives that are currently under investigation to replace the use of synthetic fungicides to control postharvest diseases in fresh produce and to extend their shelf life, chitosan application has shown promising disease control, at both preharvest and postharvest stages. Chitosan shows a dual mode of action, on the pathogen and on the plant, as it reduces the growth of decay-causing fungi and foodborne pathogens and induces resistance responses in the host tissues. Chitosan coating forms a semipermeable film on the surface of fruit and vegetables, thereby delaying the rate of respiration, decreasing weight loss, maintaining the overall quality, and prolonging the shelf life. Moreover, the coating can provide a substrate for incorporation of other functional food additives, such as minerals, vitamins, or other drugs or nutraceutical compounds that can be used to enhance the beneficial properties of fresh commodities, or in some cases the antimicrobial activity of chitosan. Chitosan coating has been approved as GRAS substance by USFDA, and its application is safe for the consumer and the environment. This review summarizes the most relevant and recent knowledge in the application of chitosan in postharvest disease control and maintenance of overall fruit and vegetable quality during postharvest storage.

Chitosan films and coatings containing essential oils: The antioxidant and antimicrobial activity, and application in food systems

Chitosan edible films and coatings have shown great promise for their application in food preservation and also are promising systems to be used as essential oil (EO) carriers. This review reports the most recent and relevant studies concerning chitosan films and coatings containing EOs. The effect of EO incorporation on the antioxidant, antibacterial and antifungal activities of chitosan films and coatings in vitro and in vivo, as well as their applications in food systems have been discussed. In general, incorporation of EOs significantly increased the antioxidant, antibacterial and antifungal efficacy of chitosan films and coatings in vitro. EO-incorporated films and coatings also showed greater effectiveness against postharvest fungi and foodborne bacteria in food systems than pure films and coatings. The application of chitosan films and coatings containing EOs usually led to an extension of the shelf-life and reduction of lipid peroxidation of fish and meat products over pure chitosan films and coatings. In addition, chitosan coatings incorporated with EOs were more effective in maintaining fruit and vegetable quality, and controlling their postharvest decay during storage and shelf life than pure chitosan coatings.

Non-Conventional Tools to Preserve and Prolong the Quality of Minimally-Processed Fruits and Vegetables

The main topic of this paper is a focus on some non-conventional tools to preserve the microbiological and physico-chemical quality of fresh-cut fruits and vegetables. The quality of fresh-cut foods is the result of a complex equilibrium involving surface microbiota, storage temperature, gas in the headspace and the use of antimicrobials. This paper proposes a short overview of some non-conventional approaches able to preserve the quality of this kind of product, with a special focus on some new ways, as follows: (1) use of edible or antimicrobial-containing coatings (e.g., chitosan-based coatings) on fruits or vegetables; (2) alternative modified atmospheres (e.g., high O2-modified atmosphere packaging (MAP)) or the use of essential oils in the headspace; (3) conditioning solutions with antimicrobials or natural compounds for fruit salad; and (4) biopreservation and use of a probiotic coating.

Edible Active Coatings Based on Pectin, Pullulan, and Chitosan Increase Quality and Shelf Life of Strawberries (Fragaria ananassa)

Edible active coatings (EACs) based on pectin, pullulan, and chitosan incorporated with sodium benzoate and potassium sorbate were employed to improve the quality and shelf life of strawberries. Fruits were washed, disinfected, coated by dipping, packed, and stored at 4 °C for 15 d. Application of EACs reduced (P < 0.05) weight loss and fruit softening and delayed alteration of color (redness) and total soluble solids content. In contrast, pH and titratable acidity were not affected (P > 0.05) throughout storage, and ascorbic acid content was maintained in pectin-EAC coated strawberries. Microbiological analyses showed that application of EACs reduced (P < 0.05) microbial growth (total aerobic counts, molds, and yeasts) on strawberries. Chitosan-EAC coated strawberries presented the best results in microbial growth assays. Sensory quality (color, flavor, texture, and acceptance) improved and decay rate decreased (P < 0.05) in pectin-EAC, pullulan-EAC, and chitosan-EAC coated strawberries. In conclusion, EACs based on polysaccharides improved the physicochemical, microbiological, and sensory characteristics, increasing the shelf life of strawberries from 6 (control) to 15 d (coated fruits).

The effect of chitosan and whey proteins-chitosan films on the growth of Penicillium expansum in apples

BACKGROUND

Penicillium expansum causes a major post-harvest disease of apples. The aim of this study was to investigate the inhibition effect of chitosan and whey proteins-chitosan films containing different amounts of quince and cranberry juice against P. expansum on the simulation medium and on apples. The mechanical properties of films were also evaluated.

RESULTS

The presence of cranberry and quince juice in the composition of chitosan and whey proteins-chitosan films caused a significant (P ≤ 0.05) increase in elasticity and decrease in tensile strength of films. Chitosan and whey proteins-chitosan films with quince and cranberry juice demonstrated a significant (P ≤ 0.05) inhibition effect against P. expansum growth on the simulated medium and apples. The presence of cranberry juice in the composition of chitosan and whey proteins-chitosan films resulted in a longer lag phase and a lower P. expansum growth rate on the simulation medium in comparison with films made with the addition of quince juice. These differences were not evident when experiment was conducted with apples.

CONCLUSION

Addition of quince and cranberry juice to the chitosan and whey proteins-chitosan films as natural antifungal agents has some potential for prolonging the shelf life of apples.

Evaluating food additives as antifungal agents against Monilinia fructicola in vitro and in hydroxypropyl methylcellulose-lipid composite edible coatings for plums

Common food preservative agents were evaluated in in vitro tests for their antifungal activity against Monilinia fructicola, the most economically important pathogen causing postharvest disease of stone fruits. Radial mycelial growth was measured in Petri dishes of PDA amended with three different concentrations of the agents (0.01-0.2%, v/v) after 7 days of incubation at 25 °C. Thirteen out of fifteen agents tested completely inhibited the radial growth of the fungus at various concentrations. Among them, ammonium carbonate, ammonium bicarbonate and sodium bicarbonate were the most effective while sodium acetate and sodium formate were the least effective. The effective agents and concentrations were tested as ingredients of hydroxypropyl methylcellulose (HPMC)-lipid edible coatings against brown rot disease on plums previously inoculated with M. fructicola (curative activity). 'Friar' and 'Larry Ann' plums were inoculated with the pathogen, coated with stable edible coatings about 24h later, and incubated at 20 °C and 90% RH. Disease incidence (%) and severity (lesion diameter) were determined after 4, 6, and 8 days of incubation and the 'area under the disease progress stairs' (AUDPS) was calculated. Coatings containing bicarbonates and parabens significantly reduced brown rot incidence in plums, but potassium sorbate, used at 1.0% in the coating formulation, was the most effective agent with a reduction rate of 28.6%. All the tested coatings reduced disease severity to some extent, but coatings containing 0.1% sodium methylparaben or sodium ethylparaben or 0.2% ammonium carbonate or ammonium bicarbonate were superior to the rest, with reduction rates of 45-50%. Overall, the results showed that most of the agents tested in this study had significant antimicrobial activity against M. fructicola and the application of selected antifungal edible coatings is a promising alternative for the control of postharvest brown rot in plums.

Optimization of antimicrobial and physical properties of alginate coatings containing carvacrol and methyl cinnamate for strawberry application

Increasing strawberry consumption has led to a growing safety concern because they are not washed after harvest. An antimicrobial edible coating could be an effective postharvest technique to ensure microbial safety and, at the same time, retain overall quality of the fruits. Response surface methodology was used to optimize the antimicrobial activity against Escherichia coli O157:H7 and Botrytis cinerea and several physical properties (turbidity, viscosity, and whitish index) of an alginate coating. A full factorial design was used to select the concentrations of carvacrol and methyl cinnamate on the basis of their effect against E. coli and B. cinerea. A central composite design was then performed to evaluate the effects/interactions of the two antimicrobials on the coating characteristics. The results from analysis of variance showed the significant fitting of all responses to the quadratic model. To attain the desirable responses, the optimal concentrations were 0.98% (w/w) carvacrol and 1.45% (w/w) methyl cinnamate.

Chitosan-caffeic acid-genipin films presenting enhanced antioxidant activity and stability in acidic media

The use of chitosan films has been limited due to their high degradability in aqueous acidic media. In order to produce chitosan films with high antioxidant activity and insoluble in acid solutions caffeic acid was grafted to chitosan by a radical mechanism using ammonium cerium (IV) nitrate (60 mM). Genipin was used as cross-linker. This methodology originated films with 80% higher antioxidant activity than the pristine film. Also, these films only lost 11% of their mass upon seven days immersion into an aqueous solution at pH 3.5 under stirring. The films surface wettability (contact angle 105°), mechanical properties (68 MPa of tensile strength and 4% of elongation at break), and thermal stability for temperatures lower than 300 °C were not significantly influenced by the covalent linkage of caffeic acid and genipin to chitosan. Due to their characteristics, mainly higher antioxidant activity and lower solubility, these are promising materials to be used as active films.

Refrigeration and edible coatings in blackberry (Rubus spp.) conservation

An experiment was conducted to evaluate the conservation of blackberry, cv. Tupy, stored under refrigeration and coated with different edible coatings. Four treatments were carried out: control T1 (uncoated), T2 (chitosan 1.5 %), T3 (cassava starch 2.5 %) and T4 (kefir grains in water 20 %), stored at temperatures of 0 and 10 °C; 1.0 % (m/v) sorbitol/glycerol was added as plasticizers. Chemical and physical-chemical evaluations (weight loss, firmness, pH, titratable acidity, soluble solids, SS/TA ratio and anthocyanins) were made, besides rot incidence. The results showed that cooling to 0 °C combined with T2 showed an effect in reducing the physiological loss of weight (4.41 %), in retaining fruit firmness (19.1 N) and presenting lower incidence of rot (6.19 %). Likewise, in physical and chemical parameters: SS did not alter significantly during the whole period of 18 days of storage.

Fungal inactivation by Mexican oregano (Lippia berlandieri Schauer) essential oil added to amaranth, chitosan, or starch edible films

Edible films can incorporate antimicrobial agents to provide microbiological stability, since they can be used as carriers of a wide number of additives that can extend product shelf life and reduce the risk of pathogenic bacteria growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of low antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition of Aspergillus niger and Penicillium spp. by selected concentrations of Mexican oregano (Lippia berlandieri Schauer) essential oil added to amaranth, chitosan, or starch edible films. Oregano essential oil was characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan, and starch edible films were formulated with essential oil concentrations of 0%, 0.25%, 0.50%, 0.75%, 1%, 2%, and 4%. Mold radial growth was evaluated inoculating spores in 2 ways: edible films were placed over inoculated agar, Film/Inoculum mode (F/I), or the edible films were first placed in the agar and then films were inoculated, Inoculum/Film mode (I/F). The modified Gompertz model adequately described growth curves. There was no significant difference (P > 0.05) in growth parameters between the 2 modes of inoculation. Antifungal effectiveness of edible films was starch > chitosan > amaranth. In starch edible films, both studied molds were inhibited with 0.50% of essential oil. Edible films added with Mexican oregano essential oil could improve the quality of foods by controlling surface growth of molds.

Review of antimicrobial and antioxidative activities of chitosans in food

Interest in chitosan, a biodegradable, nontoxic, non-antigenic, and biocompatible biopolymer isolated from shellfish, arises from the fact that chitosans are reported to exhibit numerous health-related beneficial effects, including strong antimicrobial and antioxidative activities in foods. The extraordinary interest in the chemistry and application in agriculture, horticulture, environmental science, industry, microbiology, and medicine is attested by about 17,000 citations on this subject in the Scopus database. A special need exists to develop a better understanding of the role of chitosans in ameliorating foodborne illness. To contribute to this effort, this overview surveys and interprets our present knowledge of the chemistry and antimicrobial activities of chitosan in solution, as powders, and in edible films and coating against foodborne pathogens, spoilage bacteria, and pathogenic viruses and fungi in several food categories. These include produce, fruit juices, eggs and dairy, cereal, meat, and seafood products. Also covered are antimicrobial activities of chemically modified and nanochitosans, therapeutic properties, and possible mechanisms of the antimicrobial, antioxidative, and metal chelating effects. Further research is suggested in each of these categories. The widely scattered data on the multifaceted aspects of chitosan microbiology, summarized in the text and in 10 tables and 8 representative figures, suggest that low-molecular-weight chitosans at a pH below 6.0 presents optimal conditions for achieving desirable antimicrobial and antioxidative-preservative effects in liquid and solid foods. We are very hopeful that the described findings will be a valuable record and resource for further progress to improve microbial food safety and food quality.

Inhibition of Penicillium digitatum and Penicillium italicum by hydroxypropyl methylcellulose-lipid edible composite films containing food additives with antifungal properties

New hydroxypropyl methylcellulose (HPMC)-lipid edible composite films containing low-toxicity chemicals with antifungal properties were developed. Tested chemicals were mainly salts of organic acids, salts of parabens, and mineral salts, classified as food additives or generally recognized as safe (GRAS) compounds. Selected films containing food preservatives were used for in vitro evaluation (disk diameter test) of their antifungal activity against Penicillium digitatum (PD) and Penicillium italicum (PI), the most important postharvest pathogens of fresh citrus fruit. Mechanical properties and oxygen (OP) and water vapor permeabilities (WVP) of selected films were also determined. Film disks containing parabens and their mixtures inhibited PD and PI to a higher extent than the other chemicals tested. Among all organic acid salts tested, potassium sorbate (PS) and sodium benzoate (SB) were the most effective salts in controlling both PD and PI. The use of mixtures of parabens or organic acid salts did not provide an additive or synergistic effect for mold inhibition when compared to the use of single chemicals. Barrier and mechanical properties of films were affected by the addition of food preservatives. Results showed that HPMC-lipid films containing an appropriate food additive should promise as potential commercial antifungal edible coatings for fresh citrus fruit.