Estimation of Whole Plant Photosynthetic Rate of Irwin Mango under Artificial and Natural Lights Using a Three-Dimensional Plant Model and Ray-Tracing.

Photosynthesis is an important physiological response for determination of CO2 fertilization in greenhouses and estimation of crop growth. In order to estimate the whole plant photosynthetic rate, it is necessary to investigate how light interception by crops changes with environmental and morphological factors. The objectives of this study were to analyze plant light interception using a three-dimensional (3D) plant model and ray-tracing, determine the spatial distribution of the photosynthetic rate, and estimate the whole plant photosynthetic rate of Irwin mango (Mangifera indica L. cv. Irwin) grown in greenhouses. In the case of mangoes, it is difficult to measure actual light interception at the canopy level due to their vase shape. A two-year-old Irwin mango tree was used to measure the whole plant photosynthetic rate. Light interception and whole plant photosynthetic rate were measured under artificial and natural light conditions using a closed chamber (1 × 1 × 2 m). A 3D plant model was constructed and ray-tracing simulation was conducted for calculating the photosynthetic rate with a two-variable leaf photosynthetic rate model of the plant. Under artificial light, the estimated photosynthetic rate increased from 2.0 to 2.9 µmolCO2·m-2·s-1 with increasing CO2 concentration. On the other hand, under natural light, the photosynthetic rate increased from 0.2 µmolCO2·m-2·s-1 at 06:00 to a maximum of 7.3 µmolCO2·m-2·s-1 at 09:00, then gradually decreased to -1.0 µmolCO2·m-2·s-1 at 18:00. In validation, simulation results showed good agreement with measured results with R² = 0.79 and RMSE = 0.263. The results suggest that this method could accurately estimate the whole plant photosynthetic rate and be useful for pruning and adequate CO2 fertilization.

Effect of high pressure and thermal processing on spoilage-causing enzymes in mango (Mangifera indica).

The aim of the present work was to model the effect of combined pressure-temperature processing on spoilage-causing enzymes in mango pulp; which conventionally are inactivated using high temperatures leading to inevitable quality losses. The inactivation of enzymes pectin methylesterase (PME), polyphenol oxidase (PPO) and peroxidase (POD) was studied in mango pulp within the pressure, temperature and hold-time ranges of 0.1 to 600MPa, 40 to 70°C and 1s to 90min, respectively. The enzyme inactivation was described as a dual process: initial change in activity during dynamic pressure build-up phase and subsequent decrease under isobaric-isothermal conditions. The former led to considerable increase in activities of all the three enzymes (p<0.05); however, the increased activity reduced with increased intensity of applied pressure-temperature. On the other hand, isobaric-isothermal conditions led to substantial inactivation (p<0.05), with 600MPa/70°C/20min treatment being most effective in reducing the activities of PME, PPO and POD to 32, 15 and 26%, respectively. The enzyme inactivation data was non-linear under isobaric-isothermal conditions and fitted to the nth-order reaction model, indicative of the occurrence of series of reactions possibly due to pressure-temperature interaction effects. The estimated reaction order 'n' was 0.815, 1.106 and 1.137 for PME, PPO and POD, respectively. The estimated reaction rate constant k (min-1) depicted PME to be the most baroresistant enzyme followed by POD and PPO. Temperature and pressure dependency of k was expressed in terms of activation energy and activation volume using the Arrhenius- and Eyring-type relations, respectively. An empirical model with good correlation between actual and predicted data (R2>0.90) was proposed to simulate the rate of enzyme inactivation under isobaric-isothermal conditions as a function of pressure and temperature.

Effects of ultraviolet light (UV-C) and heat treatment on the quality of fresh-cut Chokanan mango and Josephine pineapple.

The effects of ultraviolet (UV-C) and medium heat (70 °C) treatments on the quality of fresh-cut Chokanan mango and Josephine pineapple were investigated. Quality attributes included physicochemical properties (pH, titratable acidity, and total soluble solids), ascorbic acid content (vitamin C), antioxidant activity, as well as microbial inactivation. Consumers' acceptance was also investigated through sensory evaluation of the attributes (appearance, texture, aroma and taste). Furthermore, shelf-life study of samples stored at 4 ± 1 °C was conducted for 15 d. The fresh-cut fruits were exposed to UV-C for 0, 15, 30, and 60 min while heat treatments were carried out at 70 °C for 0, 5, 10 and 20 min. Both UV-C and medium heat treatments resulted in no significant changes to the physicochemical attributes of both fruits. The ascorbic acid content of UV-C treated fruits was unaffected; however, medium heat treatment resulted in deterioration of ascorbic acids in both fruits. The antioxidants were enhanced with UV-C treatment which could prove invaluable to consumers. Heat treatments on the other hand resulted in decreased antioxidant activities. Microbial count in both fruits was significantly reduced by both treatments. The shelf life of the fresh-cut fruits were also successfully extended to a maximum of 15 d following treatments. As for consumers' acceptance, UV-C treated fruits were the most accepted as compared to their heat-treated counterparts. The results obtained through this study support the use of UV-C treatment for better retention of quality, effective microbial inactivation and enhancement of health promoting compounds for the benefit of consumers.

UV-B irradiation alleviates the deterioration of cold-stored mangoes by enhancing endogenous nitric oxide levels.

Effects of UV-B radiation on chilling injury, ripening and endogenous nitric oxide (NO) levels in mango fruit were evaluated. Chilling injury index, ion leakage, and malondialdehyde (MDA) content of the fruit pretreated with 5kJm(-2) UV-B for 4h were significantly lower than those of the control during fruit ripening at ambient temperature following cold storage at 6°C for 10days. Fruit firmness of the mangoes irradiated with UV-B was significantly higher than the control during the ripening period. Endogenous NO levels of the UV-B-irradiated fruit were rapidly increased after UV-B treatment. Pre-treatment of mangoes with the NO specific scavenger, not only abolished UV-B-triggered NO accumulation, but also suppressed the UV-B-reduced chilling injury, oxidative damage, and ripening delay of the fruit. Together, the results suggest that UV-B treatment may enhance chilling tolerance and delay fruit ripening of mangoes by triggering endogenous NO generation in the fruit.

Attenuation coefficients and absorbed gamma radiation energy of different varieties of potato, mango and prawn at different storage time and physiological condition.

Attenuation coefficients of different varieties of gamma irradiated potato (Kufri Chandramukhi, Kufri Jyoti, and Kufri Sindhuri), mango (Himsagar, Langra, Dashehri and Fazli) and prawn (Tiger prawn and Fresh water prawn) of different storage time and physiological stages were determined. After six months storage attenuation coefficient of Kufri Chandramukhi was decreased by 30.8% with decrease of density and moisture content. Decreasing trend of attenuation coefficient during storage was more prominent (almost 50%) in other two varieties of potato. On the other hand in all four varieties, unripe mango consisted of significantly less (p ≤ 0.05) attenuation coefficient (around 11-14%) than the ripe one due to changes in physiological properties and density. Different varieties of prawn had different attenuation coefficients due to subtle differences in their proximate composition. Due to having different attenuation coefficients, different food components, even different varieties of same food component absorbed different gamma radiation energy though exposed to same radiation dose.

Total phenolics, carotenoids, ascorbic acid, and antioxidant properties of fresh-cut mango (Mangifera indica L., cv. Tommy Atkin) as affected by infrared heat treatment.

UNLABELLED: Mango (Mangifera indica L.) is a major tropical fruit that has not been exploited for fresh-cut or minimally processed products on a scale similar to apples, pineapples, or melons. The objective of this study was to investigate the effect of infrared (IR) treatment on total phenolics, carotenoids, ascorbic acid, and antioxidant properties of fresh-cut cubes from 'Tommy Atkin' mangoes. Mango cubes were IR treated (5, 10, 15 min) and evaluated at 4-d intervals during 16-d storage at 4 ± 1 °C. Total phenolics, carotenoids, and ascorbic acid content in fresh-cut control mango cubes were 43.33, 1.37, and 15.97 mg/100 g FW, respectively. IR treatments increased total phenolics (59.23 to 71.16 mg/100 g FW) and decreased ascorbic acid (12.14 to 15.38 mg/100 g, FW). Total carotenoids showed a mixed trend (1.13 to 1.66 mg/100 g, FW). The IR treatment showed a significant positive impact on antioxidant properties (µM TE/100 g, FW) of mango cubes, as assayed by ABTS (261.5 compared with 338.0 to 416.4), DPPH (270.5 compared with 289.4 to 360.5), and ORAC (6686 compared with 8450 to 12230). Total phenolics, carotenoids, ascorbic acid, and antioxidant capacity decreased over 16-d storage. However, IR treated samples had consistently higher ABTS, DPPH, and total phenolics during storage. It was demonstrated that IR treatment can be effectively used in improving antioxidant properties of fresh-cut mangoes with minimal effect on the visual appearance. PRACTICAL APPLICATION: Various methods/treatments are in use for extending the quality of fresh-cut fruits, including mild heat treatment. This study explored the application of infrared (IR) heat for processing fresh-cut mango cubes and evaluated its effect on vitamin C and antioxidant capacity during 16-d storage. This is the first study reporting on the use of IR heat in fresh-cut fruits. IR treatment was shown to be effective in retaining antioxidant properties of fresh-cut mango cubes with minimal effect on the visual appearance.

Preharvest bagging with wavelength-selective materials enhances development and quality of mango (Mangifera indica L.) cv. Nam Dok Mai #4.

BACKGROUND: Preharvest bagging has been shown to improve development and quality of fruits. Different light transmittance bags showed different effects on fruit quality. This study presents the benefits of using newly developed plastic bagging materials with different wavelength-selective characteristics for mangoes (cv. Nam Dok Mai #4). Mangoes were bagged at 45 days after full bloom (DAFB) and randomly harvested at 65, 75, 85, 95, and 105 DAFB. The bags were removed on the harvest days. The wavelength-selective bags (no pigment, yellow, red, blue/violet, blue) were compared with the Kraft paper bag with black paper liner, which is currently used commercially for several fruits, and with non-bagging as a control. RESULTS: Bagging significantly (p⩽0.05) reduced diseases and blemishes. Mango weight at 95 DAFB was increased approximately 15% by VM and V plastic bagging, as compared to paper bagging and control. Plastic bagging accelerated mango ripening as well as growth. Plastic-bagged mangoes reached maturity stage at 95 DAFB, while non-bagged mangoes reached maturity stage at 105 DAFB. Paper bagging resulted in a pale-yellow peel beginning at 65 DAFB, while plastic bagging improved peel glossiness. CONCLUSION: Preharvest bagging with different wavelength-selective materials affected mango development and quality. Bagging mangoes with VM and V materials could reduce peel defects and diseases, increase weight, size, and sphericity, improve peel appearance, and shorten the development periods of mangoes. The results suggest a favorable practice using the newly developed VM and V plastic bags in the production of mangoes, and possibly other fruits as well.

ESR study of free radicals in mango.

An electron spin resonance (ESR) spectroscopic study of radicals induced in irradiated fresh mangoes was performed. Mangoes in the fresh state were irradiated with gamma-rays, lyophilized and then crushed into a powder. The ESR spectrum of the powder showed a strong main peak at g=2.004 and a pair of peaks centered at the main peak. The main peak was detected from both flesh and skin specimens. This peak height gradually decreased during storage following irradiation. On the other hand, the side peaks showed a well-defined dose-response relationship even at 9 days post-irradiation. The side peaks therefore provide a useful means to define the irradiation of fresh mangoes.

Dosimetry during mango irradiation using Gafchromic HD-810 film.

The dosimetric characteristics of Gafchromic HD-810 film were evaluated for its possible use as a high-dose dosimeter for routine dosimetry during mango irradiation. The film dosimeter sample of size 2 x 2 cm(2) was used throughout the course of this work. The irradiation of the film dosimeter for characterisation and calibration purposes was carried out in a gamma irradiator. The dose-response of the Gafchromic HD-810 film dosimeter at 550 nm was found to be linear in the dose range 50-1000 Gy, which indicates the feasibility of using this film for dosimetry up to 1000 Gy. The mean inter-dosimeter variation was within 2%, which gives better dose-response consistency of the HD-810 film. The radiation absorbed dose measured by the Gafchromic HD-810 film dosimeter during mango irradiation was compared with that measured by a standard Ceric-cerous dosimeter. This study establishes the Gafchromic HD-810 film as a convenient and technically suitable dosimeter for high-dose dosimetry up to 1.0 kGy during mango irradiation.

Improving antioxidant capacity of fresh-cut mangoes treated with UV-C.

The effect of UV-C irradiation time on total phenol, flavonoids, beta-carotene, ascorbic acid contents, and antioxidant capacity (ORAC, DPPH(*)) of fresh-cut "Tommy Atkins" mango stored for 15 d at 5 degrees C was investigated. Fresh-cut mango was irradiated for 0, 1, 3, 5, and 10 min prior to storage at 5 degrees C. UV-C irradiation for 10 min induced a hypersensitive defense response resulting in the phenols and flavonoids accumulation which was positively correlated with ORAC and DPPH(*) values. However, beta-carotene and ascorbic acid content of fresh-cut mangos decreased with irradiation time during storage. Antioxidant capacity (ORAC, DPPH(*)) was increased in fresh-cut mangoes treated with UV-C irradiation. In conclusion, UV-C irradiation appears to be a good technique to improve the total antioxidant capacity of fresh-cut mango.

Electron-beam ionizing radiation stress effects on mango fruit (Mangifera indica L.) antioxidant constituents before and during postharvest storage.

The effect of electron-beam ionizing radiation stress and storage on mango fruit antioxidant compounds was evaluated in a dose range of 1-3.1 kGy. Phenolic high-performance liquid chromatography (HPLC) profiles were not affected right after the irradiation process; however, an increase in flavonol constituents was observed after 18 days in storage (3.1 kGy). Total phenolics by the Folin Ciocalteu method and antioxidant capacity (ORAC) were not affected, while reduced ascorbic acid decreased approximately 50-54% during storage (>/=1.5 kGy). No major changes in carotenoid HPLC profiles indicated a delay in ripening of irradiated mangoes (1-3.1 kGy) compared to nonirradiated fruits. However, irradiation dose >/=1.5 kGy induced flesh pitting due to localized tissue death. A summary of the potential roles of reactive oxygen species generated by the irradiation stress on different antioxidant constituents of mango fruits is presented.