Asgar Ali

Effect of ozone pre-conditioning on quality and antioxidant capacity of papaya fruit during ambient storage

The objective of this study was to compare the physico-chemical characteristics and antioxidant activity of ozone-treated papaya fruit and untreated fruit. Freshly harvested papaya fruit were exposed continuously to ozone fumigation (0, 1.5, 2.5, 3.5 and 5ppm) for 96h prior to ambient storage at 25±3°C and 70±5% relative humidity (RH) for up to 14days. The fruit exposed to 2.5ppm ozone had higher levels of total soluble solids (25.0%), ascorbic acid content (12.4%), β-carotene content (19.6%), lycopene content (52.1%), and antioxidant activity (30.9%), and also reduced weight loss (11.5%) at day 10 compared to the control. The sensory attributes of papaya treated with 2.5ppm ozone was superior in sweetness and overall acceptability. These results support the application of ozone as a non-thermal and safe food preservation technique for papaya which can benefit both the producers and consumers.

Effect of a novel edible composite coating based on gum arabic and chitosan on biochemical and physiological responses of banana fruits during cold storage.

The composite effects of gum arabic (GA) (5, 10, 15, and 20%) and chitosan (CH) (1.0%) on the biochemical and physiological characteristics of banana fruits stored at 13 ± 1 °C and 80 ± 3% relative humidity (RH) for 28 days and afterward for 5 days at simulated marketing conditions (25 °C, 60% RH) were investigated. Significant (P ≤ 0.05) differences were observed for the entire GA plus CH treatments as compared to the control. However, the results showed that after 33 days of storage, the weight loss and soluble solids concentration of fruits treated with 10% GA plus 1.0% CH composite coating were 24 and 54% lower, whereas fruit firmness, total carbohydrates, and reducing sugars were 31, 59, and 40% higher than the control, respectively. Furthermore, the composite edible coating of 10% GA plus 1.0% CH delayed color development and reduced the rate of respiration and ethylene evolution during storage as compared to the control. Similarly, sensory evaluation results also proved the effectiveness of 10% GA plus 1.0% CH composite coating by maintaining the overall quality of banana fruits. Consequently, the results of scanning electron microscopy also confirmed that the fruits coated with 10% GA plus 1.0% CH composite edible coating had very fewer cracks and showed a smooth surface. These findings suggest that 10% GA plus 1.0% CH as an edible composite coating can be used commercially for extending the storage life of banana fruits for up to 33 days.

Potential of chitosan-loaded nanoemulsions to control different Colletotrichum spp. and maintain quality of tropical fruits during cold storage

To investigate the antifungal activity of conventional chitosan and chitosan‐loaded nanoemulsions against anthracnose caused by Colletotrichum spp. isolated from different tropical fruits.

Role of H2O2 in the fluctuating patterns of COD (chemical oxygen demand) during the treatment of palm oil mill effluent (POME) using pilot scale triple frequency ultrasound cavitation reactor

Palm oil mill effluent (POME) is a highly contaminating wastewater due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Conventional treatment methods require longer residence time (10-15 days) and higher operating cost. Owing to this, finding a suitable and efficient method for the treatment of POME is crucial. In this investigation, ultrasound cavitation technology has been used as an alternative technique to treat POME. Cavitation is the phenomenon of formation, growth and collapse of bubbles in a liquid. The end process of collapse leads to intense conditions of temperature and pressure and shock waves which assist various physical and chemical transformations. Two different ultrasound systems i.e. ultrasonic bath (37 kHz) and a hexagonal triple frequency ultrasonic reactor (28, 40 and 70 kHz) of 15 L have been used. The results showed a fluctuating COD pattern (in between 45,000 and 60,000 mg/L) while using ultrasound bath alone, whereas a non-fluctuating COD pattern with a final COD of 27,000 mg/L was achieved when hydrogen peroxide was introduced. Similarly for the triple frequency ultrasound reactor, coupling all the three frequencies resulted into a final COD of 41,300 mg/L compared to any other individual or combination of two frequencies. With the possibility of larger and continuous ultrasonic cavitational reactors, it is believed that this could be a promising and a fruitful green process engineering technique for the treatment of POME.

Application of lemongrass oil in vapour phase for the effective control of anthracnose of ‘Sekaki’ papaya

To evaluate the potential use of lemongrass essential oil vapour as an alternative for synthetic fungicides in controlling anthracnose of papaya.

A combination of gum arabic and chitosan can control anthracnose caused by Colletotrichum musae and enhance the shelf-life of banana fruit

Summary Anthracnose, caused by Colletotrichum musae, is the major disease affecting the quality of banana fruit during storage. To control banana anthracnose, the combined effects of coatings with gum arabic [GA; at 5, 10, 15 or 20% (w/v)] and 0.75% (w/v) chitosan (CH) were investigated and compared to untreated controls. In vitro results showed significant (P < 0.05) inhibition of mycelial growth and conidial germination of C. musae in all combined treatments compared to the untreated controls after 7 d of incubation at room temperature (25°C). However, potato dextrose agar (PDA) plates amended with 10% (w/v) GA gave the most promising results among all test treatments in suppressing mycelial growth (86%) and inhibiting conidial germination (80%), while no effective inhibition of conidial germination was observed in the controls. In vivo results confirmed that 10% (w/v) GA was the optimum concentration to control fruit decay (70%), while showing efficacy on the reduction of growth of C. musae on artificially inoculated banana fruit. The combined coatings of GA + CH also significantly delayed ripening in terms of weight loss, fruit firmness, soluble solids content, and titratable acidity. These results support the possibility of using 10% (w/v) GA combined with 0.75% (w/v) CH as an alternative strategy to control post-harvest anthracnose disease in banana fruit.

Photoprotection as a Trait for Rice Yield Improvement: Status and Prospects

Solar radiation is essential for photosynthesis and global crop productivity but it is also variable in space and time, frequently being limiting or in excess of plant requirements depending on season, environment and microclimate. Photoprotective mechanisms at the chloroplast level help to avoid oxidative stress and photoinhibition, which is a light-induced reduction in photosynthetic quantum efficiency often caused by damage to photosystem II. There is convincing evidence that photoinhibition has a large impact on biomass production in crops and this may be especially high in rice, which is typically exposed to high tropical light levels. Thus far there has been little attention to photoinhibition as a target for improvement of crop yield. However, we now have sufficient evidence to examine avenues for alleviation of this particular stress and the physiological and genetic basis for improvement in rice and other crops. Here we examine this evidence and identify new areas for attention. In particular we discuss how photoprotective mechanisms must be optimised at both the molecular and the canopy level in order to coordinate with efficient photosynthetic regulation and realise an increased biomass and yield in rice.

Ultrasound treatment on phenolic metabolism and antioxidant capacity of fresh-cut pineapple during cold storage

Ultrasound treatment at different power output (0, 25 and 29W) and exposure time (10 and 15min) was used to investigate its effect on the phenolic metabolism enzymes, total phenolic content and antioxidant capacity of fresh-cut pineapple. Following ultrasound treatment at 25 and 29W, the activity of phenylalanine ammonia lyase (PAL) was increased significantly (P<0.05) by 2.0 and 1.9-fold, when compared to control. Meanwhile, both the activity of polyphenol oxidase (PPO) and polyphenol peroxidase (POD) in fresh-cut pineapple was significantly (P<0.05) lower than control upon subjected to ultrasound treatment. In the present study, induction of PAL was found to significantly (P<0.001) correlate with higher total phenolic content and thus higher antioxidant capacity in fresh-cut pineapple. Results suggest that hormetic dosage of ultrasound treatment can enhance the activity of PAL and total phenolic content and hence the total antioxidant capacity to encounter with oxidative stress.

Advances in postharvest technologies to extend the storage life of minimally processed fruits and vegetables

ABSTRACT Minimally processed fresh produce is one of the fastest growing segments of the food industry due to consumer demand for fresh, healthy, and convenient foods. However, mechanical operations of cutting and peeling induce the liberation of cellular contents at the site of wounding that can promote the growth of pathogenic and spoilage microorganisms. In addition, rates of tissue senescence can be enhanced resulting in reduced storage life of fresh-cut fruits and vegetables. Chlorine has been widely adopted in the disinfection and washing procedures of fresh-cut produce due to its low cost and efficacy against a broad spectrum of microorganisms. Continuous replenishment of chlorine in high organic wash water can promote the formation of carcinogenic compounds such as trihalomethanes, which threaten human and environmental health. Alternative green and innovative chemical and physical postharvest treatments such as ozone, electrolyzed water, hydrogen peroxide, ultraviolet radiation, high pressure processing, and ultrasound can achieve similar reduction of microorganisms as chlorine without the production of harmful compounds or compromising the quality of fresh-cut produce.

Colletotrichum gloeosporioides (Anthracnose)

Abstract Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most widespread and serious postharvest disease of many tropical fruits including mango, papaya, pitaya, and avocado. The most damaging phase of the disease begins as a quiescent infection, when the fruit is in the preclimacteric phase of development. Growth of the pathogen is resumed only after harvest when the fruit starts to ripen and postharvest anthracnose develops leading to significant decay losses during storage and marketing. The disease is traditionally controlled by synthetic chemical fungicides and hot water treatment, in the case of papaya and mango. However, when harvested fruits are treated with fungicides, there is greater likelihood of direct human exposure to them and of development of resistance in pathogens. This chapter brings to light the key emerging environmentally friendly techniques, in particular, use of edible coatings and essential oils. It is well recognized that there is a need to develop new and effective methods of controlling postharvest diseases that are perceived as safe by the public and pose negligible risk to human health and the environment.