Effect of carboxymethyl cellulose coating enriched with clove oil on postharvest quality of ‘Xinyu’ mandarin oranges

Identification of key sensory and chemical factors determining flavor quality of Xinyu mandarin during ripening and storage

Xinyu mandarin is popular for its good flavor, but its flavor deteriorates during postharvest storage. To better understand the underlying basis of this change, the dynamics of the sensory profiles were investigated throughout fruit ripening and storage. Sweetness and sourness, determined especially by sucrose and citric acid content, were identified as the key sensory factors in flavor establishment during ripening, but not in flavor deterioration during storage. Postharvest flavor deterioration is mainly attributed to the reduction of retronasal aroma and the development of off-flavor. Furthermore, sugars, acids and volatile compounds were analyzed. Among the 101 detected volatile compounds, 10 changed significantly during the ripening process. The concentrations of 15 volatile components decreased during late postharvest storage, among which α-pinene and d-limonene were likely to play key roles in the reduction of aroma. Three volatile compounds were found to increase during storage, associated with off-flavor development.

Carboxymethyl cellulose coating delays ripening of harvested mango fruits by regulating softening enzymes activities

The effect of carboxymethyl cellulose [(1%) CMC] was evaluated on mango fruits under storage at 20 ± 1 °C for 20 days. The CMC coating noticeably reduced weight loss and disease incidence. Application of CMC delayed climacteric peak of ethylene and respiration rate with significantly reduced relative ion leakage, malondialdehyde, superoxide anion and hydrogen peroxide content. The treated mangoes showed significantly lower L*, a*, b* and total carotenoids. The CMC treatment reduced the increase in cellulase, pectin methylesterase and polygalacturonase activity that delayed softening of mango fruits. In addition, activities of peroxidase, catalase, ascorbate peroxidase and superoxide dismutase were substantially higher in CMC-treated mango fruits. The treated fruits showed significantly lower soluble solids and higher titratable acidity which thereby reduced the ripening index of mangoes. In conclusion, CMC treatment could be considered a potential pre-storage treatment to delay postharvest ripening and to conserve the eating quality of ambient stored mango fruits.

Synergistic effect of gum Arabic and carboxymethyl cellulose as biocomposite coating delays senescence in stored tomatoes by regulating antioxidants and cell wall degradation

This study tested a novel combination of hydrocolloid gum arabic (GA) and carboxymethyl cellulose (CMC) to extend postharvest life of tomatoes. For this purpose, tomato fruits were coated with GA 10%, CMC 0.5% and GA 10% + CMC 0.5%, and stored for 20 days at 20 °C and 90 ± 2% RH. Application of biocomposite hydrocolloid coating reduced physiological weight loss, respiration rate, ethylene production, decay percentage and stress markers viz. malondialdehyde and hydrogen peroxide. Biocomposite hydrocolloid coating inhibited change in bioactive compounds (phenolics, ascorbic acid, and lycopene), color, organic acids, soluble sugars and up-regulated enzymatic ROS scavenging mechanism in tomato fruit more than GA or CMC coating. Moreover, biocomposite coatings delayed senescence by reducing activity of cell wall degrading enzymes and maintaining cell wall fractions. Conclusively, the biocomposite coating based on GA and CMC was superior to their individual coating in prolonging ripening phase, delaying senescence and increasing the acceptability of tomato fruits for longer duration.

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.

Paenibacillus brasilensis YS-1: A Potential Biocontrol Agent to Retard Xinyu Tangerine Senescence

The Xinyu tangerine (Citrus reticulata Blanco) is a non-climacteric fruit that is widely cultivated and consumed in China but highly susceptible to fungal infections. Antagonistic microorganisms can control postharvest diseases and extend the storage life of citrus fruits. However, little work has been done to investigate the effects of applying Paenibacillus brasilensis YS-1 by immersion to enhance the cold storability of Xinyu tangerines. Fruits were soaked with P. brasilensis YS-1 fermented filtrates for 10 min and in sterile water as the control. The decay incidence, weight loss, nutrient content, respiration rate, malondialdehyde (MDA) content, and defensive enzymes activities in citrus fruit were measured during cold storage at 5 ± 0.5 °C. The results showed that P. brasilensis YS-1 treatment significantly reduced postharvest decay and effectively maintained the nutritional quality compared to the control under cold storage. The weight loss, respiration rate, and MDA content were lower in P. brasilensis YS-1-treated fruits than the control fruits, indicating that P. brasilensis YS-1 treatment increased the activities of superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), and phenylalnine ammonia-lyase (PAL). According to the results, a postharvest application of P. brasilensis YS-1 can control the postharvest decay and maintain fruit quality, as well as increase the defensive enzyme activity, so as to achieve the purpose of retarding postharvest senescence in citrus fruit.

Pinocembrin-7-Glucoside (P7G) Reduced Postharvest Blue Mold of Navel Orange by Suppressing Penicillium italicum Growth

The current study aimed to examine the in vitro and in vivo antifungal potential of pinocembrin-7-glucoside (P7G). P7G is an antifungal flavanone glycoside isolated from Ficus hirta Vahl. fruit against Penicillium italicum, a causative pathogen of blue mold disease in citrus fruit, and this study elucidates its possible action mechanism. P7G had a prominent mycelial growth inhibitory activity against P. italicum, with an observed half maximal effective concentration, minimum inhibitory concentration and minimum fungicidal concentration of 0.08, 0.2, and 0.8 g/L, respectively. The data from the in vivo test show that P7G significantly reduced blue mold symptoms and disease development of P. italicum in artificially inoculated "Newhall" navel orange. Compared to the control, increases in the cell membrane permeability of P. italicum supernatant and decreases in the intracellular constituent (e.g., soluble protein, reducing sugar, and total lipid) contents of P. italicum mycelia were identified, supporting scanning electron microscopy and transmission electron microscopy observations. Furthermore, a marked decline in both chitin and glucanase contents of P. italicum mycelia treated with P7G was induced by increasing its related degrading enzyme activities, suggesting that the cell wall structure was destroyed. The current study indicated that P7G may be a novel alternative for reducing blue mold by suppressing mycelial growth of P. italicum via a cell membrane/wall-targeting mechanism.

Clove Essential Oil as an Alternative Approach to Control Postharvest Blue Mold Caused by Penicillium italicum in Citrus Fruit

Penicillium italicum causes blue mold disease and leads to huge economic losses in citrus production. As a natural antifungal agent, clove essential oil (CEO), which is a generally recognized as safe (GRAS) substance, shows strong in vitro activity against fungal pathogens. However, few studies on CEO for controlling postharvest blue mold disease caused by P. italicum in citrus fruit have been reported. Our aims were to investigate the control efficacy and possible mechanisms involved of CEO against P. italicum. In the present study, CEO treatment inhibited the disease development of blue mold when applied at 0.05% to 0.8% (v/v), and with the effective concentration being obtained as 0.4% (v/v). Besides its direct antifungal activity, CEO treatment also spurred a rapid accumulation of H₂O₂ compared with untreated fruits, which might contribute to enhancing an increase in the activities of defense-related enzymes, such as β-1,3-glucanase (β-Glu), chitinase (CHI), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) in citrus fruit. Results of real time-quantitative polymerase chain reaction (RT-qPCR) showed that the gene expressions of β-Glu, CHI, PAL, POD and PPO were up-regulated in CEO-treated fruits. At the same time, CEO treatment led to down-regulated expression of the LOX gene in citrus fruit. Clove essential oil effectively control the disease incidence of blue mold decay in citrus fruit by motivating the host-defense responses, suppressing the malondialdehyde (MDA) accumulation while enhancing the activities and gene expressions of defense-related enzymes. Our study provides an alternative preservative applying CEO to reduce postharvest fungal decay in citrus fruit.

Preservation of Xinyu Tangerines with an Edible Coating Using Ficus hirta Vahl. Fruits Extract-Incorporated Chitosan

Xinyu tangerine is a citrus fruit that has enjoyed great popularity in China for its fewer dregs and abundant nutrients. However, it is considered an easily perishable fruit that is vulnerable to various pathogenic fungal infections, especially by Penicillium italicum, which reduces its storage life and commercial value. Normally, to reduce the losses caused by fungal deterioration of harvested fruit, polysaccharide-based edible coating, containing natural antimicrobial agents (e.g. plant extracts), have been applied. In current study, we evaluated the effects of Ficus hirta Vahl. fruits extract (FFE)⁻incorporated chitosan (CS) edible coating on Xinyu tangerines during cold storage at 5 °C. The results showed FFE has efficacy as an antifungal against P. italicum in a dose-dependent manner in vivo, with an EC₅₀ value of 12.543 mg·mL^-¹. It was found that the edible coating of FFE⁻CS exhibited a higher reduction of total soluble solid (TSS), titrable acid (TA), and ascorbic acid (AsA) content by reducing the fruit decay rate, weight loss, respiration rate, and malondialdehyde (MDA) content during cold storage at 5 °C. Moreover, the activities of protective enzyme such as superoxide dismutase (SOD), peroxidase (POD), and phenylalanine ammonia-lyase (PAL), which have been linked with reactive oxygen species (ROS) and the phenylpropanoid pathway, were higher in the FFE⁻CS-coated fruits. On the basis of these study results, the FFE⁻CS edible coating could reduce postharvest loss and enhance the storability of Xinyu tangerines due to the in vivo antifungal activity of FFE.

Chitosan-Based Coating Enriched with Hairy Fig (Ficus hirta Vahl.) Fruit Extract for “Newhall” Navel Orange Preservation

A novel coating based on 1.5% chitosan (CH), enriched with or without hairy fig (Ficus hirta Vahl.) fruit extract (HFE), was applied to “Newhall” navel orange for improving the preservation effect. Changes in physicochemical indexes were analyzed over 120 days of cold storage. Uncoated fruit were used as the control. The CH-HFE coating, based on 1.5% CH enriched with HFE, exhibited the best preservation effect and showed the lowest decay rate (5.2%) and weight loss (5.16%). The CH-HFE coating could postpone the ripening and senescence of navel oranges, and maintain higher fruit quality by inhibiting respiration, decreasing the accumulation of malondialdehyde (MDA), and enhancing the activities of protective enzyme, including superoxide dismutase (SOD), peroxidase (POD), chitinase (CHI), and β-1,3-glucanase (GLU), which suggests that CH-HFE coating has the potential to improve the postharvest quality of “Newhall” navel orange and prolong the storage life.

Antifungal Activity of Ramulus cinnamomi Explored by ¹H-NMR Based Metabolomics Approach

A ¹H nuclear magnetic resonance (NMR)-based approach to metabolomics combined bioassay was used to elucidate the antifungal activity of cinnamaldehyde (the main active compound of Ramulus cinnamomi) isolated from Ramulus cinnamomi (RC). Orthogonal signal correction partial least-squares discriminant analysis (OSC-PLS-DA) of NMR data was constructed to analyze all the P. italicum data acquired from the control and treatment groups at 4, 8, and 12 h. Metabolic profiles disclosed metabolic changes that were related to the antifungal effects of cinnamaldehyde against P. italicum including oxidative stress, disorder of energy metabolism, amino acids, and nucleic acids metabolism in treatment group. This integrated metabolomics approach provided an effective way to detect the antifungal effects of cinnamaldehyde against P. italicum dynamically.