Chitosan disrupts Penicillium expansum and controls postharvest blue mold of jujube fruit

Chitosan has been shown to be effective for control of postharvest diseases on various fruit. However, little is known about the effect of chitosan on blue mold caused by Penicillium expansum on jujube fruit. Here we show that application of chitosan reduced disease development of blue mold caused by P. expansum in wounded and inoculated jujube fruit at 25 °C. Chitosan also provided an inhibitory effect on natural decay of jujube fruit during storage at 0 °C. Application of a chitosan coating to fruit had hardly any significant effect on the changes of weight loss, soluble solid contents, titratable acidity, and vitamin C, as storage time increased. To investigate the mechanisms underlying the effectiveness of chitosan against blue mold on jujube fruit, we analyzed the growth of P. expansum after chitosan treatment. Results indicated that spore germination, germ tube length and mycelial growth of P. expansum were significantly inhibited by chitosan in a concentration-dependent mode. Using the fluorescent probe propidium iodide, we found that the plasma membrane of P. expansum collapsed significantly after chitosan treatment. Further observation by electron microscopy revealed that plasma membrane of P. expansum was gradually disrupted after chitosan application. Our data suggest that chitosan may be potentially used for controlling postharvest diseases in jujube fruit without negative effect on fruit quality.     

Antifungal activity of five different essential oils in vapour phase for the control of Colletotrichum gloeosporioides and Lasiodiplodia theobromae in vitro and on mango

Mango fruit has high commercial value; however, major postharvest losses are encountered throughout the supply chain due to postharvest diseases. These results lead to the search for natural fungicide for postharvest diseases control. The antifungal effects of five essential oils (thyme, clove, cinnamon, anise and vitex) were assessed by disc volatilisation method. Thyme oil vapours at 5 μL per Petriplate, and clove and cinnamon oil at 8 μL per Petriplate showed 100% growth inhibition of mango pathogens in vitro. GC/MS analysis of essential oil showed thymol (23.88), o‐cymol (23.88) and terpinolene (23.88) as the major constituents of thyme oil. Clove and cinnamon oils contain 3‐allyl‐2‐methoxyphenol (37.42%) and benzofuran 3‐methyl (17.97%), respectively. Thyme oil as a fumigant at 66.7 μL L^?1 showed a significant (P < 0.05) inhibition on postharvest pathogens of mango fruits stored at 25 °C for 6 days. Results of our study suggest the possibility of using thyme oil as an alternate natural fungicide to manage postharvest diseases in mango.     

Triple bag hermetic technology for controlling a bruchid (Spermophagus sp.) (Coleoptera,Chrysomelidae) in stored Hibiscus sabdariffa grain

We assessed the performance of hermetic triple layer Purdue Improved Crop Storage (PICS) bags for protecting Hibiscus sabdariffa grain against storage insects. The major storage pest in the grain was a bruchid, Spermophagus sp.. When we stored infested H. sabdariffa grain for six months in the woven polypropylene bags typically used by farmers, the Spermophagus population increased 33-fold over that initially present. The mean number of emergence holes per 100 seeds increased from 3.3 holes to 35.4 holes during this time period, while grain held for the same length of time in PICS bags experienced no increase in the numbers of holes. Grain weight loss in the woven control bags was 8.6% while no weight loss was observed in the PICS bags. Seed germination rates of grain held in woven bags for six months dropped significantly while germination of grain held in PICS bags did not change from the initial value. PICS bags can be used to safely store Hibiscus grain after harvest to protect against a major insect pest.     

Avocado Fruit Quality Management during the Postharvest Supply Chain

Avocados are a popular subtropical fruit of high economic importance, and the European Union is the biggest importer of the bulk of the fruit coming from countries such as South Africa, Chile, and Israel. The fruit is highly nutritious, being rich in vitamins A, B, C, minerals, potassium, phosphorus, magnesium, iron, and antioxidants. The biggest challenge is that the fruit is highly susceptible to qualitative and quantitative postharvest losses. Successful maintenance of avocado fruit quality during the supply chain depends on many aspects, including adequate orchard management practices, harvesting practices, packing operations, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are mostly attributed to flesh softening, decay, physiological disorders, and improper temperature management. Management of the supply chain is solely done to provide the fruit with the most favorable conditions to extend storage life, and retain quality and nutritional attributes of the fruit. The focus of this review is therefore to study the findings that have emanated from research done to retain overall avocado fruit quality and to reduce postharvest losses during the supply chain through the adoption of appropriate and novel postharvest technologies.     

Mild heat and calcium treatment effects on fresh-cut cantaloupe melon during storage

The effect of mild heat fruit pre-treatment on some properties of fresh-cut cantaloupe melon during storage was determined. Whole fruit, previously held at 4 °C, was immersed in heated water (60 °C) with and without dissolved calcium lactate (1%). Fresh-cut processing was done immediately, either after treatment or after storage at 4 °C for 24 h. Headspace gas accumulation during storage indicated reduced respiration in heat-treated fruit. Reduced lipase activity occurred in heat treated fruit during storage at 10 °C, while the fruit that was cut 24 h after treatment had a reduced peroxidase activity, unlike fruit that was processed immediately after heating. Isoelectric focussing indicated production of heat shock proteins (PI = 5.1 and 6.5) as a result of heat-treatment. Textural measurements showed increased hardness, chewiness and cohesiveness, but springiness decreased in heat-treated fruit. Presence of calcium in the treatment solution did not affect respiration and textural changes caused by heat treatment. Lipase activity was, however, higher in fruit heated in calcium solutions. Results indicated the potential improvement of shelf life of cut cantaloupe melon by mild heat pre-treatment of the fruit, and that the addition of calcium to the treatment water did not further improve product quality.     

The effect of postharvest calcium application on tissue calcium concentration, quality attributes, incidence of flesh browning and cell wall physicochemical aspects of peach fruits

The effects of postharvest calcium applications on cell wall properties and quality attributes of peach fruits (Prunus persica L. Batsch, cv. ‘Andross’) after harvest or cold storage up to 4 weeks were determined. The fruits were immersed in deionised water or in different calcium sources (calcium chloride, calcium lactate and calcium propionate) at two calcium concentrations (62.5 and 187.5 mM Ca). Calcium concentration profiles in fruits (peel and flesh), in cell wall and in pectin fractions were determined. The calcium content in the peel increased up to 2.7-fold, whereas flesh calcium increased up to 74%, 1 day after immersion. The increase of flesh calcium was accompanied by increase of cell wall calcium, which corresponded to a significant increase of calcium in the water-insoluble pectin fraction. However, calcium became saturated in the water-insoluble, but not water-soluble, pectin fraction with 62.5 mM Ca treatment. Treatment with 62.5 mM Ca salts was as effective as higher concentrations of calcium chloride maintaining tissue firmness during storage. Inversely, calcium lactate and calcium propionate at high concentrations (187.5 mM Ca) caused toxicity symptoms on the fruit surface, expressed as skin discoloration and superficial pitting, leading to additional chemical changes and reduced tissue firmness. Postharvest calcium applications limited the intense of chilling injury symptoms, expressed as flesh browning after 4 weeks cold storage. Peach fruits with severe flesh browning symptoms were characterized by reduced ethylene production, and reduced activities of the pectin modifying enzymes poly-galacturonase and pectin-methyl-esterase.     

Conceptualization, design and evaluation of a hyperbaric respirometer

Hyperbaric treatment consists of exposing fruit or vegetable to compressed air in a range lower than 10 atm. Unlike heat or UV processing, where temperature or radiation gradients are established, pressure treatment offers a very rapid establishment of homogeneous conditions as they act instantaneously and uniformly around each single produce or throughout an entire mass of food, independently of its size, shape or composition.A hyperbaric respirometer was designed, built and tested to explore the possibility of using hyperbaric treatment on postharvest commodity. It consisted of an air tight vessel that could be pressurized from 1 to 7 atm and instrumented to automatically monitor gas concentration along time using computer controlled valves, flow meter and CO₂ gas analyzer. Calibration of the system and hyperbaric treatments were performed on tomato fruit to evaluate the performance of the respirometer. Results showed that respiration rate was inversely proportional to pressure application.     

Papaya Fruit Quality Management during the Postharvest Supply Chain

Papayas are popular in tropical and subtropical regions and are being exported in large volumes to Europe, the United States, and Japan. The fruit has a sweet, exotic flavor and is rich in vitamins A and C and antioxidants. However, due to its highly perishable nature, it has not emerged as a major traded fruit. Papayas are highly susceptible to qualitative and quantitative postharvest losses. Maintenance of papaya fruit quality during the supply chain depends on orchard management, harvesting practices, packing operations, postharvest treatments, temperature management, and transportation and storage conditions. Postharvest losses are attributed to mechanical damage, rapid flesh softening, decay, physiological disorders, pest infestation, and improper temperature management. The aim of postharvest technology and management in the supply chain is to provide favorable conditions to extend storage life and retain quality and nutritional attributes. This review focuses on the available research findings to retain overall papaya fruit quality and to reduce postharvest losses during the supply chain via adopting appropriate or novel postharvest technologies.     

Browning on the surface of cut lettuce slices inhibited by short term exposure to nitric oxide (NO)

Freshly cut lettuce slices (Latuca sativa L.) were fumigated with nitric oxide (NO) gas at concentrations between 5 and 1000 μl/l in air at 20 °C for 1–4 h or dipped in an aqueous solution of the NO-donor compound, 2,2′-(hydroxynitrosohydrazino)-bisethanamine (DETANO) at concentrations between 10 and 1000 mg/l for 15 s to 60 min at 20 °C. Development of browning on the cut surfaces was inhibited during subsequent storage at 0 °C. The most effective treatments for extending postharvest life of lettuce slices were fumigation with 500 μl/l NO for 1 h, and dipping in 500 mg/l DETANO for 5 min. Dipping in DETANO solution was, however, more effective as it generated a 100% increase in postharvest life compared with a 70% increase due to NO gas. Solutions of DETANO in water were found to be relatively stable as the same extension in postharvest life was obtained for five batches of lettuce sequentially dipped in the same solution.     

Changes in fatty acid composition and electrolyte leakage of ‘Hayward’ kiwifruit during storage at different temperatures

Exposure to low storage temperature induces changes in electrolyte leakage and fatty acids composition, in a way depending on the plant tissue. Those changes alter the response of the fruit to storage conditions. The influence of storage temperature on ripening, fatty acids composition and electrolyte leakage of ‘Hayward’ kiwifruit were investigated. Harvested fruit were stored at 0, 5, 10, 15 and 20 °C for 5, 12 and 17 days. Measurements of SSC, firmness, flesh colour, fatty acid composition and electrolyte leakage were performed during the experiment. Kiwifruit did not fully ripen during the 17 days storage at any temperature. The major fatty acid component in ‘Hayward’ kiwifruit consisted of linolenic, followed by oleic, palmitic, linoleic and stearic acid. Membrane permeability and unsaturated/saturated fatty acid ratio increased during storage in all treatments. The highest increase was during the first 5 days and at the lowest temperatures. The increase in unsaturated/saturated fatty acid ratio was caused mainly by a decrease in palmitic and an increase in oleic acids. Stearic, linoleic and linolenic acids had insignificant changes during storage. The main increase in electrolyte leakage and unsaturated/saturated fatty acid ratio occurred during the first storage days and at lower temperatures, probably as a response of the tissue to an adaptation to the new stress storage conditions.