Control of Rhizopus soft rot and quality responses in plums (Prunus domestica L.) coated with gum arabic, oregano and rosemary essential oils

Abstract

This study evaluated the efficacy of coatings comprising gum arabic (GA) and essential oils from Origanum vulgare L. (OVEO) and Rosmarinus officinalis L. (ROEO) to control Rhizopus soft rot and quality of plums (Prunus domestica L.) during storage at room (25°C; 12 days) and cold (12°C; 24 days) temperatures. GA (1 mg/ml) and OVEO (0.25 μl/ml) or OVEO (0.06 μl/ml) plus ROEO (0.25 μl/ml) inhibited the mycelial growth, spore germination and sporulation of R. stolonifer. GA‐OVEO and GA‐OVEO‐ROEO coatings delayed the occurrence of soft rot and decreased the rotted plums at the end of storage compared to GA alone. Plums coated with GA‐OVEO and GA‐OVEO‐ROEO exhibited greater firmness decreased weight loss and lower decrease of sugars and phenolics at the end of storage compared to uncoated plums. GA‐OVEO and GA‐OVEO‐ROEO coatings enhanced the color and flavor, while GA‐OVEO coating affected negatively the aftertaste of plums. GA‐OVEO‐ROEO coating is a promising postharvest treatment for plums. Practical applications In plums, the reduction of postharvest quality losses resulting from decay caused by Rhizopus stolonifer contamination or by the ripening process is a major goal of postharvest technology, which increase attention to use environmental friendly methods as postharvest treatment of fruit. Edible coatings can reduce the use of synthetic fungicides, thus are in agreement with the increased consumer's demand by products obtained with the minimum quantities of synthetic products. Gum arabic is largely used in food industry, however underexplored as coating component, particularly in combination with natural antifungal substances such as essential oils. Edible coatings containing essential oils are considered environmentally friendly technologies because these substances when incorporated in polissacharydes can be released on surfaces of fruit and increase the storage time. This study evaluated coatings containing reduced amounts of oregano and rosemary essential oils in combination as postharvest treatment to control Rhizopus soft rot in plums (Prunus domestica), as well as their effects on the quality attributes of this fruit during storage. The tested coatings are presented as alternative technologies to control soft rot and preserve the quality of plums during storage.

An Analysis of the Published Literature on the Effects of Edible Coatings Formed by Polysaccharides and Essential Oils on Postharvest Microbial Control and Overall Quality of Fruit

“…Twelve studies used other polysaccharides or gums combined with CH, such as CS (de Aquino et al., ), hydroxypropylmethylcellulose (Sánchez‐González et al., ), and locust bean gum (Aloui et al., ), or as the only ingredient to formulate coatings, such as gum arabic (GA; Andrade et al., ; Etemadipoor, Ramezanian, Mirzaalian Dastjerdi, & Shamili, ; Maqbool et al., ), mesquite gum (Bosquez‐Molina, Jesús, Bautista‐Baños, Verde‐Calvo, & Morales‐López, ), flaxseed gum (Yousuf & Srivastava, ), pullulan (Gniewosz & Synowiec, ), pectin (Guerreiro, Gago, Faleiro, Miguel, & Antunes, ; Rodriguez‐Garcia et al., ), and sodium alginate (Guerreiro et al., ).…”

“…Twenty‐four out of the 30 selected studies used EOs for the formulation of edible coatings, such as the EO from cinnamon (Etemadipoor et al., ; Maqbool et al., ; Xing, Li et al., ; Xing et al., , ), lemongrass (Athayde et al., ; Maqbool et al., ; Oliveira et al., ; Vu et al., ; Yousuf & Srivastava, ), peppermint (de Oliveira et al., ; Guerra et al., , ; Vu et al., ), bergamot (Aloui et al., ; Cháfer et al., ; Sánchez‐González et al., ), oregano (Andrade et al., ; Barreto et al., ; dos Santos et al., ; Rodriguez‐Garcia et al., ; Vu et al., ), rosemary (Andrade et al., ), clove (Shao et al., ), thyme (Bosquez‐Molina et al., ; Cháfer et al., ), tea tree (Cháfer et al., ), Mexican lime (Bosquez‐Molina et al., ), and Lippia gracilis (Azevedo et al., ; de Aquino et al., ). Only five studies used ICs to formulate edible coatings, to cite: carvacrol (de Souza et al., ; Sun et al., ), cinnamaldehyde and trans ‐cinnamaldehyde (Sun et al., ), thymol (Gniewosz & Synowiec, ), citral and eugenol (Guerreiro et al., ), and limonene (Vu et al., ).…”

“…Twelve studies tested more than one EO or IC to select the concentration most effective to inhibit the target microorganism and/or with improved abilities to preserve the quality parameters of coated fruit (Aloui et al., ; Andrade et al., ; Azevedo et al., ; Bosquez‐Molina et al., ; Cháfer et al., ; de Aquino et al., ; Guerra et al., , ; Guerreiro et al., ; Maqbool et al., ; Sun et al., ; Vu et al., ).…”

“…The type and concentration of the polysaccharide as well as of the EO or IC used to formulate the edible coatings used in in situ assays were selected overall considering their antimicrobial effects determined firstly in in vitro assays, as measured through the determination of the minimum inhibitory concentration (MIC; Aloui et al., ; Andrade et al., ; Azevedo et al., ; Bosquez‐Molina et al., ; de Aquino et al., ; de Souza et al., ; dos Santos et al., ; Gniewosz & Synowiec, ; Guerreiro et al., ; Maqbool et al., ; Sun et al., ; Xing et al., ).…”

“…Hydroxypropylmethylcellulose (1%, w/v) was dissolved in distilled water (80 C for 2 hr) under overnight stirring at room temperature (Sánchez‐González et al., ). Three studies used GA to formulate coatings and this polysaccharide was firstly dissolved in ultra‐purified water and stirred at 40 °C for 60 min (Andrade et al., ; Etemadipoor et al., ; Maqbool et al., ). One study used pullulan or mesquite gum to formulate coatings.…”