Efficacy of Lemon Myrtle Essential Oil as a Bio-Fungicide in Inhibiting Citrus Green Mould.

The effectiveness of lemon myrtle (LM) (Backhousia citriodora) essential oil (EO) was investigated to combat Penicillium digitatum by in vitro agar diffusion and vapour assay and in artificially infected oranges. The main constituent of LM EO was revealed as citral when analysed in gas chromatography-mass spectrometry. Pure citral was also included in the experiment for comparison. The in vitro fungal growth was significantly inhibited by LM EO at 1, 2, 3, 4 and 5 µL per disc while complete growth inhibition by both the pure citral and LM EO occurred at 4 and 5 µL per disc. Inoculated fruits treated by dipping in 1000 µL L-1 LM EO solutions for 5, 10, 15, 30 and 120 s showed significantly lower fungal wounds compared to control. While longer dipping times led to some rind injuries, fruits with a 5 and 10 s dip were found free from any injury. The evaluation after dipping and storage confirmed that the fruits maintained the sensory attributes and were not compromised by the incorporation of the essential oil. The results of this study indicate that LM EO can be a promising alternative to synthetic fungicides for preserving the quality of citrus fruits during storage.

Beneficial impact of exogenous arginine, cysteine and methionine on postharvest senescence of broccoli.

This study examined the ability of l-arginine, l-cysteine and l-methionine, to inhibit postharvest senescence of broccoli. Florets were dipped in aqueous solutions of the amino acids at concentrations from 1.0 to 100 mM and stored at 10 °C. A 5 mM dip was found to be optimal in delaying senescence as measured by retention of green colour, vitamin C and antioxidant activity, and a lower level of ethylene production, respiration, weight loss, phenylalanine ammonia lyase (PAL) activity and ion leakage with the benefits being similar for all three amino acids. Arginine, cysteine and methionine have Generally Recognised As Safe (GRAS) status and should have few impediments in obtaining regulatory approval for commercial use if similar effects were found for other leafy vegetables.

Improving the storage quality of Tahitian limes (Citrus latifolia) by pre-storage UV-C irradiation.

UV-C (180-280 nm) has been shown to extend the postharvest shelf-life of many horticulture crops. In this study, Tahitian limes (Citrus latifolia) were exposed to 0, 3.4, 7.2 and 10.5 kJ m-2 UV-C then stored for 28 days in air at 10 °C and 80% RH. Weight loss, peel colour, calyx abscission, ethylene production, respiration rate, total soluble solids (TSS), titratable acidity (TA) and acceptability index were assessed. The results showed that UV-C treatment maintained lime peel green colour and retained calyx attachment after 28 days storage. UV-C treatment also affected endogenous ethylene production and respiration rate, where the highest UV-C treatment (10.5 kJ m-2) maintained low ethylene production and low respiration rates after 28 days storage with no differences between the different UV-C intensities. In terms of fruit acceptability, limes were exposed to 10.5 kJ m-2 UV-C had a 60% acceptability index after 28 days storage, while untreated control fruit retained acceptability of 39%. In general, the pre-storage UV-C treatments did not affect fruit weight loss, TSS or TA contents during storage.

Starch-based films: Major factors affecting their properties.

Starch is the most popular plant polysaccharides, which has been widely used for the development of edible coating films because of its abundance, cost-effectiveness, and excellent film-forming abilities. Starch-based films have good optical, organoleptic and gas barrier properties, however, they have poor mechanical properties. Many attempts have been made to overcome these limitations, such as the addition of co-biopolymers or other secondary additives to improve the mechanical and tensile properties of the films. Properties of the starch-based films can be influenced by many factors, including types of starches, temperature and time during film formation, plasticizers, co-biopolymers, and storage conditions. Understanding the mechanisms of these factors is very important for future studies on the development of starch-based films. This review focuses on starch as a film/coating material and comprehensively discusses the effects of major factors on properties of starch-based films.

Long Term Exposure to Low Ethylene and Storage Temperatures Delays Calyx Senescence and Maintains 'Afourer' Mandarins and Navel Oranges Quality.

Calyx browning and internal quality loss are major physiological causes for the loss of quality in citrus fruit during storage. While the symptoms of calyx senescence are only superficial, it can affect the appearance and consumer acceptability of citrus fruit. In this study, continuous ethylene exposure at different storage temperatures was investigated to assess their effect on calyx senescence and internal qualities in 'Afourer' mandarin and Navel orange fruit during storage. 'Afourer' mandarin fruit were stored at ≤0.001 (equivalent to ethylene-free air), 0.01, 0.1 and 1 µL L-1 of ethylene at either 5, 10 or 20 °C, whilst in a parallel experiment, Navel oranges were exposed to ≤0.001, 0.1 and 1 µL L-1 ethylene at either 1 or 10 °C. Changes in external and internal postharvest quality parameters were assessed for up to 8 weeks for 'Afourer' mandarins and 10 weeks for Navel oranges. At all storage temperatures, high levels of ethylene were found to increase the level of calyx senescence, weight loss, loss of fruit firmness and respiration rates. Also, there were significant effects of ethylene and storage temperatures on total soluble solids (TSS) content, titratable acidity (TA), and ethanol accumulation in both citrus species. Continuous exposure to high ethylene also significantly reduced vitamin C and ferric reducing antioxidant power (FRAP) in 'Afourer' mandarins after 8 weeks of storage. Overall, ethylene treatments had a significant effect on both the external and internal qualities of the fruit during storage. The relationship between ethylene concentrations and storage temperatures demonstrate that lowering atmospheric ethylene levels at reduced storage temperatures maintain fruit quality during long term storage.

Combined postharvest UV-C and 1-methylcyclopropene (1-MCP) treatment, followed by storage continuously in low level of ethylene atmosphere improves the quality of Tahitian limes.

The green Tahitian limes (Citrus latifolia) were exposed to 7.2 kJ m-2 UV-C and 0.5 µL L-1 1-methylcyclopropene (1-MCP) treatments both separately and in combination. After treatment, fruit were stored in ethylene free (i.e. air containing < 0.005 µL L-1) or 0.1 µL L-1 ethylene at 20 °C and 100% RH. The results showed that UV-C treatment delayed skin degreening and reduced endogenous ethylene production compared to untreated control fruit, however these effects reduced over the storage time. As expected, 1-MCP inhibited ethylene production, reduced calyx abscission and retained peel greenness during the storage. Both of the combination treatments, 1-MCP + UV-C and UV-C + 1-MCP reduced endogenous ethylene production and delayed skin yellowing. In all treatments, UV-C and 1-MCP resulted in lower fruit respiration rates than untreated control fruit, however this effect diminished during 7 and 14 days storage for fruits stored in air and 0.1 µL L-1 ethylene atmosphere, respectively. There was no difference in weight loss, SSC, TA and SSC/TA ratio between the treatments and storage conditions. The results suggest that a pre-storage UV-C treatment, followed by storage at low level of ethylene improves the quality of limes, with the additional improvement when combined with 1-MCP treatment prior or after UV-C irradiation.

Encapsulation of Citrus By-Product Extracts by Spray-Drying and Freeze-Drying Using Combinations of Maltodextrin with Soybean Protein and ι-Carrageenan.

The effect of different combinations of maltodextrin (MD) coating agents (MD, MD + soybean protein, and MD + ι-carrageenan) on the encapsulation of lemon by-product aqueous extracts using freeze-drying and spray-drying were investigated. The total phenolic content (TPC), total flavonoid content (TFC), and ferric ion reducing antioxidant power (FRAP) of the microparticles were evaluated. Freeze-drying with the mixture of MD + soybean protein resulted in the highest retention of TPC, TFC, and FRAP (1.66 ± 0.02 mg GAE/g d.b., 0.43 ± 0.02 mg CE/g d.b., and 3.70 ± 0.05 mM TE/g, respectively). Freeze-drying resulted in microparticles with lower moisture content (MC) and water activity (aw) than those produced by spray-drying. Specifically, the MC and aw of the microparticles produced by freeze-drying ranged from 1.15 to 2.15% and 0.13 to 0.14, respectively, while the MC and aw of the microparticles produced by spray-drying ranged from 6.06% to 6.60% and 0.33 to 0.40, respectively. Scanning electron microscopy revealed that spray-drying resulted in the formation of spherical particles of different sizes regardless of the type of coating agent. Although freeze-drying resulted in microparticles with amorphous glassy shapes, the mixture of MD + soybean protein resulted in the formation of spherical porous particles. X-ray diffraction revealed a low degree of crystallinity for the samples produced by both techniques.

Use of response surface methodology (RSM) to optimize pea starch-chitosan novel edible film formulation.

The aim of this study was to develop an optimal formulation for preparation of edible films from chitosan, pea starch and glycerol using response surface methodology. Three independent variables were assigned comprising chitosan (1-2%), pea starch (0.5-1.5%) and glycerol (0.5-1%) to design an empirical model best fit in physical, mechanical and barrier attributes. Impacts of independent variables on thickness, moisture content, solubility, tensile strength, elastic modulus, elongation at break and water vapor permeability of films were evaluated. All the parameters were found to have significant effects on physical and mechanical properties of film. The optimal formulation for preparation of edible film from chitosan, pea starch and glycerol was 1% chitosan, 1.5% pea starch and 0.5% glycerol. Edible films with good physical and mechanical properties can be prepared with this formulation and thus this formulation can be further applied for testing on coating for fruit and vegetables.

Characterization of rice starch-ι-carrageenan biodegradable edible film. Effect of stearic acid on the film properties.

The main aim of this study was to develop rice starch (RS), ι-carrageenan (ι-car) based film. Different formulations of RS (1-4%, w/w), ι-car (0.5-2%, w/w) was blended with stearic acid (SA; 0.3-0.9%, w/w) and glycerol (1%, w/w) as a plasticizer. The effect of film ingredients on the thickness, water vapour permeability (WVP), film solubility (FS), moisture content (MC), colour, film opacity (FO), tensile strength (TS), elongation-at-break (EAB) of film was examined. Interactions and miscibility of partaking components was studied by using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Hydrocolloid suspension solution of mix polysaccharides imparted a significant impact (p<0.05) on the important attributes of resulting edible film. TS and EAB of film were improved significantly (p<0.05) when ι-car was increased in the film matrix. Formulation F1 comprising 2% ι-car, 2% RS, 0.3% SA, Gly 30% w/w and 0.2% surfactant (tween®20) provided film with good physical, mechanical and barrier properties. FT-IR and XRD results reveal that molecular interactions between RS-ι-car have a great impact on the film properties confining the compatibility and miscibility of mixed polysaccharide. Results of the study offers new biodegradable formulation for application on fruit and vegetables.

Impact of different solvents on the recovery of bioactive compounds and antioxidant properties from lemon (Citrus limon L.) pomace waste.

The effects of different solvents on the recovery of (i) extractable solids (ES), (ii) total phenolic compounds (TPC), (iii) total flavonoid content (TFC), (iv) vitamin C, and (v) antioxidant activity from lemon pomace waste were investigated. The results revealed that solvents significantly affected the recovery of ES, TPC, TFC, and antioxidant properties. Absolute methanol and 50% acetone resulted in the highest extraction yields of TPC, whereas absolute methanol resulted in the highest extraction of TFC, and water had the highest recovery of vitamin C. 50% ethanol, and 50% acetone had higher extraction yields for TPC, and TFC, as well as higher antioxidant activity compared with their absolute solvents and water. TPC and TFC were shown to be the major components contributing to the antioxidant activity of lemon pomace.

Enhancing the Total Phenolic Content and Antioxidants of Lemon Pomace Aqueous Extracts by Applying UV-C Irradiation to the Dried Powder.

Several studies have shown that UV-C (ultraviolet C) irradiation promotes the bioactive compounds and antioxidants of fresh fruits and vegetables. The aim of this study was to apply UV irradiation in dried lemon pomace powder for enhancing its phenolic content and antioxidant properties, thus more bioactive compounds should be available for extraction and utilization. Lemon pomace dried powder was placed under a UV lamp and treated with dosages of 4, 19, 80 and 185 kJ·m-2, while untreated powder was used as a control. UV-C irradiation significantly affected the total phenolic content, total flavonoid content, proanthocyanidins, and antioxidant capacity measured by cupric reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP) of the lemon pomace dried powder, while it did not affect the vitamin C content. UV-C irradiation of 19 kJ·m-2 resulted in 19% higher total phenolic content than the control, while UV-C irradiation of 180 kJ·m-2 resulted in 28% higher total flavonoid content than the control. The antioxidant capacity was reduced when UV-C irradiation more than 4 kJ·m-2 was applied. The results of this study indicate that UV-C treatment has the potential to increase the extraction of bioactive compounds of dried lemon pomace at relatively high dosages.