Effect Of Hot Air Treatment Research Articles

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

Effect of Hot Air Treatment on Physio-Chemical Properties of Pomegranate Arils

Hot air treatment has been applied on a wide range of horticultural crops to control postharvest decay and to maintain quality characteristics. To evaluate the effect of hot air treatment on physio-chemical properties of pomegranate arils, an experiment was carried out in a factorial experiment using a completely randomized design with four replications in 2015. About 200 g of ‘‘Rabab-e-Neyriz’’ pomegranate arils were placed in 350 mg polypropylene boxes with three holes on top for ventilation. Boxes were heated at 35 °C, 40 °C and 45 °C and 80% relative humidity for 30, 60, and 120 min in oven. After being cooled at an ambient temperature, boxes were stored at 5 °C (RH= 70-80%) for 15 days. The scored results of decay assay showed that heated “Rabab” arils at 35 °C till 45 °C decayed lesser than those untreated during storage period. Hot air temperature at 45 °C for 120 min resulted in the highest weight loss at the end of storage period. The highest total soluble solids content was belonged to the arils heated at 45 °C for 30 min. Hot air treatments increased pH and TSS/TA ratio of aril juice. Hot air temperature treatment decreased antioxidant activity, total phenolic compounds and total anthocyanin of arils during storage period, whilst hot air treatment had no significant effect on color values. Generally, the application of mild heat treatments could be considered as a non-contaminant postharvest tool to maintain functional and nutritive properties of arils during postharvest storage.

Effects of hot air treatment and chitosan coating on citric acid metabolism in ponkan fruit during cold storage.

In citrus fruit, citric acid is the predominant organic acid which influence fruit taste, flavor and quality. The effect of hot air treatment (HAT 40°C, 48 h) and 1.0% chitosan coating on the change of organic acids and the related gene expression of citric acid synthesis and degradation in ponkan (Citrus reticulata Blanco) fruit during cold storage have been studied. The results showed that citric acid was the main organic acid in fruit, the trend change of citric acid content was consistent with total organic acids and titratable acidity (TA) content, which decreased with the prolongation of storage time, hot air treatment significantly promoted but chitosan coating treatment significantly delayed citric acid degradation in Ponkan fruit. Hot air treatment could induced CitAco2/3, CitIDH2/3, CitGAD4, CitACLs, CitPEPCKs and CitFBPases expression during fruit storage period, but had no significant effect on CitGSs expression, The enhanced expression of degradation-related genes was closely related to the degradation of citric acid. The expressions of CitAco3, CitGAD4 CitACLα2/β, CitPEPCKs and CitFBPases were inhibited, which leading to the degradation rate of citric acid was slowed by chitosan coating during storage. These results showed that the degradation of citric acid in fruit was regulated by ATP citrate lyase (ACL) pathway and γ-aminobutyric acid (GABA) pathway.

Effects of hot air treatment on the quality attributes of semidry-milled Indica rice

To investigate the effects of hot air treatment (HAT) on the quality attributes of Indica rice semidry-milling, HAT was applied at various temperatures (45–120 °C) and processing times (0–240 min). The changes in grain-surface cracking, moisture absorption rate, damaged starch, rheological properties, microbial decontamination, and texture qualities were evaluated. HAT induced many cracks in the rice grains, shortening the soaking time to reach maximum water content (28%) to 8 min. However, at high temperatures, extending the HAT time slowed the water absorption rate. Under the optimum HAT conditions and soaking time, the total viable counts in the rice flour were similar to those of dry-milled rice flour (102–103 cfu/g), with no coliforms and few yeasts and molds. The damaged starch content, rheological and texture properties were similar to those of wet-milling. Therefore, an appropriate HAT can shorten the soaking time of the rice and clean it during the milling process.

Hot air treatment‐induced arginine catabolism is associated with elevated polyamines and proline levels and alleviates chilling injury in postharvest tomato fruit

To understand whether arginine catabolism might be involved in hot air (HA)-induced chilling tolerance mechanism in tomato fruit, we investigated the effect of HA treatment on endogenous arginine catabolism in relation to chilling injury. Tomato fruit were harvested at mature green stage and treated with HA at 38°C for 12 h and then stored at 2°C for 21 days. The effects of HA treatment on fruit chilling injury and gene expression levels or enzyme activity, and metabolites related to arginine catabolism were evaluated. HA treatment reduced the chilling injury symptoms of tomato fruit and enhanced the accumulation of endogenous polyamines, especially putrescine and proline. This accumulation is associated with the increased transcript levels of genes encoding arginase (LeARG1 and LeARG2), arginine decarboxylase (LeADC), ornithine decarboxylase (LeODC) and ornithine aminotransferase (LeOAT) at most sampling times. However, HA treatment had little effect on nitric oxide synthase activity and nitric oxide concentration. These results revealed that the reduction in chilling injury by HA treatment may be due to the accumulation of putrescine and proline induced primarily by activating the catabolism of endogenous arginine.

Hot Air Treatment and its Effect on Nectarine Metabolism var. Big Top Stored at Different Temperatures

The effect of hot air treatment (35 °C / 36 h) on Big Top nectarines prior storage at 0 and 5 °C for 6, 18 and 27 days followed by 6 days at 20 °C (shelf life, sl) was evaluated. Respiratory activity was twice as much in fruits at 5 °C (24 mg CO2 kg-1h-1), compared to those kept at 0 °C during the respiratory peak. At 0 °C, the treated fruits showed between 2 and 5 % more respiratory activity. The total polyphenols were not affected by temperature or treatment (0.22 and 0.24 mg galic acid equivalent g-1 fw) but almost doubled in sl, especially in fruits from 0 °C. At some analysis moments, the total antioxidant capacity of untreated fruits stored at 0 °C (0.42 and 0.45 mg equivalent ascorbic acid g-1 fw) doubled the values of the treated ones, although this situation was reversed in sl. The superoxide dismutase activity was considerably higher in fruits treated and stored at 0 °C (15-30 units of activity mg-1 of protein), as opposed to the observed at 5 °C. The activity of polygalacturonase and pectinmethyl esterase, as well as the development of mealiness in sl and in untreated fruits from 5 °C, would indicate that the heat treatment had a protective effect reducing the occurrence of damage. However, the little or no response observed in other variables make it necessary to confirm the effect of heat treatment in future studies.

Effect of hot air treatment on organic acid- and sugar-metabolism in Ponkan (Citrus reticulata) fruit

Organic acid and sugar balance is an important trait for fruit quality. The mandarin, Ponkan (Citrus reticulata Blanco cv. Ponkan) is rich in organic acids even at maturity, thus the fruit provide good material for the study of organic acid degradation. In the present research, hot air (40°C, 2d) treatment (HAT) was found to have significant effects on both degradation of the organic acids, especially on citric acid, and accumulation of soluble sugars, especially on fructose and glucose. Genes related to citric acid degradation related (CitAco1, CitAco2, CitAco3, CitIDH1, CitIDH2, CitIDH3, CitGAD4, CitGAD5 and CitGS2) and sucrose metabolism (CitAI1, CitAI3, CitNI1 and CitNI3) were isolated and transcription analyzed. HAT significantly up-regulated CitAco3, CitIDH2/3 and CitGAD4 expression, while having little effect on CitGS2. Sucrose metabolism related genes also differentially responded to HAT, with CitAI genes were induced and CitNI genes were relatively unchanged. It is proposed that HAT drove citric acid degradation via the GABA shunt pathway (especially by modulating CitAco3–CitIDH2/3–CitGAD4 cascade), but not the glycolysis pathway.

Hot Air Treatment Improved the Chilling Resistance of Loquat Fruit under Cold Storage

Absract Hot air treatment at 38C for 36 h significantly improved the chilling resistance of loquat during 4C storage for 28 days, appeared as higher extractable juice, lower firmness, internal browning and decay development. This treatment reduced hydrogen peroxide level by improving superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase activities, then maintained higher unsaturated/saturated fatty acid ratio and lower permeability of membrane at the end of storage. It also reduced phenylalanine ammonia lyase, peroxidase and polyphenol oxidase activities, and total phenolic content to control internal browning and lignin synthesis; the enhanced antioxidant enzyme activities also contribute to control them. Meanwhile, heat-treated fruits showed significantly higher levels of water- and chelator-soluble pectins and lower Na2CO3-soluble pectin than controls at the later of storage. It was suggested that the improved chilling resistance by heat treatment maybe mainly due to the enhanced scavenging capacity of oxygen species and solubilization of cell wall polysaccharides. Practical Applications Loquat fruit is very perishable because of microbial decay and mechanical damage after harvest. Low-temperature storage is an effective method to control pathogenic decay and preserve quality. However, loquat fruit are chilling-sensitive, and chilling injury limits the storage period and shelf-life. This work investigated the effects of hot air treatment on the chilling resistance of loquat fruit. It was found that heat treatment at 38C for 36 h can enhance the chilling resistance, reduce the chilling symptoms and maintain higher quality after storage at 4C for 28 days. The information obtained from this study suggested that this heat treatment may be a suitable method for the commercial application on loquat fruits.

A COMBINATION OF HEAT TREATMENT AND CHITOSAN COATING DELAYS RIPENING AND REDUCES DECAY IN “GALA” APPLE FRUIT

ABSTRACTApples (Malus domestica Borkh. cv. Gala) were heat‐treated at 38C for 4 days (heat treatment [HT]) before or after coated with 1% chitosan (CTS). Following treatment, apples were stored at 0C for 8 weeks and 20C for 7 days as shelf life. The effectiveness of the combined treatments on the ripeness, quality and decay development caused by Penicillium expansum and Botrytis cinerea was evaluated. Severe heat damage was observed on the fruits heat‐treated after CTS coating (CTS + HT), appeared as external decay and internal brown after treatment. However, no damage on fruits heated before CTS coating (HT + CTS) during the whole storage. Besides the completely control of blue mold and gray mold on artificially inoculated fruits during storage, the HT + CTS treated fruit showed the lowest respiration rate, ethylene evolution, malondialdehyde and membrane leakage, and the highest firmness and consumer acceptance among the treatments. At the same time, this combined treatment could inhibit the lost of green color, titratable acidity and weight loss compared with HT alone.PRACTICAL APPLICATIONS“Gala” apple fruits become more popular in the world because of its high productivity and good quality. Hot air treatment alone has been used to delay ripening of Gala but caused the loss of peel green, titratable acidity and weight. This work investigated the effects of hot air treatment combined with chitosan (CTS) coating on the ripening, quality and decay development for Gala apple fruits. Compared with fruits heat‐treat alone, fruits heat‐treated before CTS coating (heat treatment + CTS) preserved original peel color, maintained titratable acidity and weight, completely control decay development and showed the highest consumer acceptance after storage. The information obtained from this study suggested that this combined treatment may be a suitable method for the commercial application on Gala apple fruits.

Effects of hot air treatment on postharvest quality of ‘cat Hoa loc’ mangoes

Effects of hot air treatment on postharvest quality of 'cat Hoa loc' mangoes. Abstract — Introduction. Vietnam is among the world's top 20 mango producing countries. In this country, the 'cat Hoa loc' variety is predominant, with 17 692 ha under cultivation with an annual produc- tion of 58 471 t; it is considered to be the best mango variety in the Mekong delta. Ripening of the fruit is typically expressed by a skin colour change from green to bright yellow. This variety is highly prized by local and foreign consumers, but subject to different disorders, especially fruit fly infestations. Heat treat- ment is a safe alternative to chemical treatments. It can impair mould development and control fruit infes- tation by destroying fruit fly eggs and larvae. It may have a greater or lesser effect on fruit physiology. If the treatment temperature and duration are incorrectly handled, skin burns may result and the internal qua- lity of the fruit may be affected. Materials and methods. 'Cat Hoa loc' mangoes at the commercially mature stage were subjected to hot air treatment (47 °C and 90% RH) of different durations ((0, 20, 40, 60, 90, 120 and 180) min from the fruit core attaining the temperature). After treatment, the fruits were stored at 25 °C and quality parameters evaluated (weight loss, peel and flesh colour, percentages of fruit with burns and rots, burn index, ripening percentage, firmness, TSS, TA, vitamin C content, pH, reducing and total sugars, and taste test). Results and discussion. For the 'cat Hoa loc' variety, heat treatment accele- rated ripening of the fruit in the initial storage period and colour changes occurred more quickly. However, after 7 days' storage, the difference in Hue value between the treated and control fruits disappeared. Hot air treatment at 47 °C of different durations ((20 to180) min) did not affect the internal coloration changes of 'cat Hoa loc' mangoes, but did affect the flesh firmness. We found that, after 3 d, hot air treatment at 47 °C led to significantly faster weight loss than control fruits but this difference disappeared after 7 d. Total sugar content was not affected by the treatment, but titratable acidity decreased more quickly in treated fruits. Vietnam /Mangifera indica/ fruits / postharvest control / heat treatment / quality

Effect of hot air treatment in combination with Pichia guilliermondii on postharvest anthracnose rot of loquat fruit

Effect of heat treatment (hot air at 38 °C for 36 h) and Pichia guilliermondii ( P. guilliermondii), either alone or in combination, against anthracnose rot caused by Colletotrichum acutatum ( C. acutatum), in loquat fruit was investigated. Results showed that the combined treatment significantly reduced natural decay, and disease incidence and lesion diameter in artificially inoculated fruit. Fruit given the combined treatment maintained low activities of catalase (CAT) during the early storage period, but CAT and superoxide dismutase (SOD) activities both rose later in storage. This corresponded with a high level of H 2O 2 in the early storage period and a lower level of H 2O 2 in the later period. At the same time, induced activity of phenylalanine ammonia-lyase (PAL) and β-1,3-glucanase stimulated synthesis of lignin, thus eliciting disease resistance. Moreover, the combined treatment significantly inhibited mycelial growth and spore germination of C. acutatum, reducing anthracnose rot of loquat fruit.

Effect of hot air treatment on postharvest mould decay in Chinese bayberry fruit and the possible mechanisms

The effect of hot air treatment (HAT) on reducing natural fungal decay and green mould decay caused by Leptographium abietinum on postharvest Chinese bayberry fruit and the possible mechanisms were investigated. Freshly harvested Chinese bayberry fruit were firstly pretreated with hot air at 36–60 °C for 1–3 h, and then stored at 20 °C for 3 d or at 1 °C for 12 d to investigate the optimum condition of hot air treatment (HAT) for inhibiting decay development. Results demonstrated that HAT at 48 °C for 3 h was the most effective in reducing natural decay without impairing quality. This treatment also enhanced the resistance of Chinese bayberry fruit against green mould rot caused by L. abietinum and reduced the severity of the disease. The activities of defense-related enzymes including chitinase, β-1, 3-glucanase, peroxidase and polyphenol oxidase were significantly enhanced by HAT. In addition, the in vitro experiment showed that HAT significantly inhibited spore germination, germ tube elongation and mycelial growth of L. abietinum. These results indicate that HAT can effectively reduce fruit decay possibly by directly inhibiting pathogen growth and indirectly inducing disease resistance.

Effect of hot-air treatment on the ripening of ‘Qingnai’ plum (Prunus salicina Lindl.)

Summary‘Qingnai’ plums are popular as “green” fruit throughout south-east Asia. However, the fruit soften rapidly after harvest, limiting commercial exports from China. Traditionally, the crop is sold mostly to the local population. We evaluated the potential of hot-air treatment (HAT) to delay ripening of ‘Qingnai’ plum fruit as a potential technology to expand the marketing of “green” plums. Fruit were stored at 20°C after being exposed to 20°C (control), 40°C (HAT40), 45°C (HAT45), or 50°C (HAT50) air for 5 h. Information was collected on fruit firmness, peel colour, chlorophyll contents, chlorophyllase activities, soluble solids contents (SSC), titratable acidities (TA), the rates of respiration and ethylene production, and the activities of cell wall hydrolysing enzymes. Fruit softening was accompanied by a progressive decrease in hue angle (h°), chlorophyll content, and TA, and increases in chlorophyllase, pectin methylesterase (PME) and polygalacturonase (PG) activities. Hot-air treatment delayed the onset of the climacteric peaks of CO2 and ethylene production, delayed fruit softening, and delayed the peaks of PME and PG activities. Heat-treated fruit changed from green-to-yellow at a slower rate than control fruit, with a delay in the peak of chlorophyllase activity. Heat-treated fruit could be stored for up to 18 d, and non-treated fruit for only 12 d. These results suggest that HAT can extend the post-harvest life of ‘Qingnai’ plums by up to 6 d.

Effect of hot air treatment on quality and ripening of Chinese bayberry fruit

AbstractBACKGROUND: Postharvest decay and softening are the major factors limiting the extension of storage life of Chinese bayberry fruit. To evaluate the effects of hot air treatment (HAT) on Chinese bayberry fruit, fruits were stored at 2 °C after exposure to 20 °C (control), 40 °C (HAT40), 45 °C (HAT45) or 50 °C (HAT50) hot air for 3 h. The effects of HAT on firmness, disease incidence, soluble solid content (SSC), titratable acidity (TA), respiration, ethylene production, pectic substances and activities of pectinmethylesterase (PME) and polygalacturonase (PG) were examined.RESULTS: HAT inhibited decrease in firmness, SSC and TA and retarded increase in disease incidence, while it promoted decrease in respiration rate and ethylene production. HAT suppressed the activities of PME and PG, which resulted in delaying the depolymerisation of chelator‐soluble and alkali‐soluble pectic substances and reducing the increase in water‐soluble pectic substances compared with control fruits.CONCLUSION: The present findings show that HAT can maintain postharvest quality and delay ripening of Chinese bayberry fruit and suggest that HAT could be considered for commercial use to extend the postharvest life of Chinese bayberry fruit. Copyright © 2008 Society of Chemical Industry

400 Effects of Hot Air Treatments on the Postharvest Physiology and Quality of Mango Fruit

Heat treatments have several potential positive effects in fruit, including insect and decay control, amelioration of chilling injury, and delay of ripening and senescence. Hot water treatment (46.1°C for 65-90 min, depending on fruit weight) has been used in Mexico and some other countries as a quarantine insect control treatment for mangoes. Hot air treatments can provide several advantages compared to hot water in regard to installations, costs, reduced injury, and compatibility with other systems such as controlled atmospheres. In this work we have investigated the effect of hot air treatments at 44 to 48°C and 50% relative humidity for 160 and 220 min, on the physiology and quality of `Manila' and `Óro' mango fruit stored at 10°C and 85% relative humidity for up to 4 weeks. No injury was observed in both cultivars exposed for 160 min, but some injury was observed when fruit were exposed for 220 min. Some of these fruit also failed to ripen. Heat treatment (especially for 160 min) delayed ripening of fruit, as measured with color and texture changes, compared to the control. Heat treatment changed the protein composition of the fruit and affected the activity of peroxidases.