Influence of virgin coconut oil on the inhibitory effect of emulsion-based edible coatings containing cinnamaldehyde against the growth of Colletotrichum gloeosporioides (Glomerella cingulata)

Eco-sustainable, edible, biodegradable and antioxidant pectin and bacterial cellulose films loaded with coconut oil for strawberry preservation

Strawberry is one of the most problematic fresh fruits susceptible to damage or mold due to their sensitive skin. For this, we developed films made of bacterial cellulose [BC, 25 % (w/w)], pectin [P, 75 % (w/w)] loaded with coconut oil for strawberry preservation. XRD patterns of the BC showed three distinct peaks at Bragg angles (2θ) of 14.6°, 16.9°, and 22.7°, indicating the structural characteristics of cellulose I. CG-MS demonstrated that coconut oil contained triacylglycerols like lauric acid, linoleic acid, and dodecanoic acid. Moreover, coconut oil showed antioxidant activity of about 50 % and antimicrobial activity in yeast extracted from strawberries. FTIR spectroscopy, TGA/DTG, mechanical testing, water vapor permeability, AFM and SEM images showed that the oil was successfully incorporated into the film. Next, mass loss and swelling degree and wettability studies revealed that formed films maintained hydrophobic characteristics. In fact, these films presented a high-water vapor barrier because preserved a major part of the characteristics of the biocellulose, turning the bioplastics inert to water. In addition, coconut oil loaded into BC + P bioplastic presented low release due to its hydrophobicity character. Despite this, our bioplastic worked as a mechanical barrier, protecting the fruits from microorganisms and other forms of damage. Furthermore, antioxidant activity from both film-formed was similar (28 %), and these bioplastics preserved the strawberries for 192 h, whereas uncoated fruits degraded at 72 h. Indeed, our bioplastics were more effective in reducing fruit mass loss, especially BC + P + O film. Our findings showed that the essential oil acted as a reducing agent of strawberry mass loss, decreasing its skin transpiration, being an inexpensive and feasible alternative for fruits preservation.

Modelling the In Vitro Growth of Phytopathogenic Filamentous Fungi and Oomycetes: The Gompertz Parameters as Robust Indicators of Propolis Antifungal Action

Propolis is a resinous mixture produced by honeybees, mainly from plant exudates. With a rich chemical composition including many phenolic compounds, mostly responsible for its biological properties, namely antimicrobial ones, propolis may be a promising alternative to synthetic pesticides. The study of propolis from the south of Portugal and of its potential against phytopathogenic agents are still very recent and different methodological approaches hinder a comparison of efficacies. In this context, we aimed to test the value of a mathematical model for the multiparametric characterization of propolis' antifungal action on solid medium assays. An ethanol extract (EE) of a propolis sample harvested in 2016 from Alves (A16) was characterized in terms of phenolic composition and antimicrobial potential against five phytopathogenic species. A16.EE (500-2000 µg/mL) inhibited the mycelial growth of all the species, with Phytophthora cinnamomi and Biscogniauxia mediterranea being the most susceptible and Colletotrichum acutatum being the least affected. The Gompertz mathematical model proved to be a suitable tool for quantitatively describing the growth profiles of fungi and oomycetes, and its parameters exhibit a high level of discrimination. Our results reveal that propolis extracts may have potential applications beyond traditional uses, particularly within the agri-food sector, allowing beekeepers to make their businesses more profitable and diversified.

Essential oils and plant extracts for tropical fruits protection: From farm to table

The tropical fruit industry in Malaysia makes up a large proportion of the agriculture sector, contributing to the local economy. Due to their high sugar and water content, tropical fruits are prone to pathogenic infections, providing optimal microorganism growth conditions. As one of the largest exporters of these fruits globally, following other Southeast Asian countries such as Thailand, Indonesia and the Philippines, the quality control of exported goods is of great interest to farmers and entrepreneurs. Traditional methods of managing diseases in fruits depend on chemical pesticides, which have attracted much negative perception due to their questionable safety. Therefore, the use of natural products as organic pesticides has been considered a generally safer alternative. The extracts of aromatic plants, known as essential oils or plant extracts, have garnered much interest, especially in Asian regions, due to their historical use in traditional medicine. In addition, the presence of antimicrobial compounds further advocates the assessment of these extracts for use in crop disease prevention and control. Herein, we reviewed the current developments and understanding of the use of essential oils and plant extracts in crop disease management, mainly focusing on tropical fruits. Studies reviewed suggest that essential oils and plant extracts can be effective at preventing fungal and bacterial infections, as well as controlling crop disease progression at the pre and postharvest stages of the tropical fruit supply chain. Positive results from edible coatings and as juice preservatives formulated with essential oils and plant extracts also point towards the potential for commercial use in the industry as more chemically safe and environmentally friendly biopesticides.

Enhanced antifungal and antioxidant activities of new chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties

In this work, chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties were successfully prepared via amidation reaction. Specific structural characterization was implemented using FTIR and ¹H NMR, and the DS of chitosan derivatives were quantitatively calculated by ratio of hydrogen proton integral. Meanwhile, the antifungal activity against two common plant pathogenic fungi (Fusarium oxysporum f. sp. cubense and Glomerella cingulata) was assayed in vitro by hyphal measurement, and data proved that the introduction of functional groups including benzene/heterocyclic compounds and Schiff base groups greatly enhanced the antifungal activity. Besides, the antioxidant efficiency was investigated in vitro, and all chitosan derivatives exhibited significantly increased antioxidant activity. Specially, the scavenging effect of 2SATCS was 96.62% at 1.6 mg/mL, which was close to the positive control VC (98.84%). These results indicated that chitosan derivatives with enhanced antifungal and antioxidant activities could serve as potential biomaterial for antifungal and antioxidant applications.