R. R. Sharma

Pre-harvest fruit bagging: a useful approach for plant protection and improved post-harvest fruit quality – a review

Summary Several good agricultural practices (GAP) are becoming popular throughout the World for the production of high quality fruit with less dependence on man-made chemicals. Among such practices, pre-harvest fruit bagging has emerged as an effective method. Bagging is a physical protection method which not only improves the visual quality of fruit by promoting skin colouration and reducing blemishes, but can also change the micro-environment for fruit development, which can have several beneficial effects on internal fruit quality. Pre-harvest bagging of fruit can also reduce the incidence of disease, insect pest and/or mechanical damage, sunburn of the skin, fruit cracking, agrochemical residues on the fruit, and bird damage. Due to its many beneficial effects, fruit bagging has become an integral part of peach, apple, pear, grape, and loquat cultivation in Japan, Australia, China and the USA. Moreover, countries such as Mexico, Chile, and Argentina do not import apples unless they are bagged. Several studies have been conducted to identify the desirable effects of pre-harvest fruit bagging on skin colour development and quality, but contradictory results have been reported. These may be due to differences in the type of bag used, the stage of fruit development when bagged, the duration of fruit exposure to natural light following bag removal, and/or fruit- and cultivar-specific responses. Bagging is laborious and its cost:benefit ratio must be investigated in order to promote adoption of the method in much of the World. The aim of this review is to improve our understanding of the beneficial effects of bagging in different fruit by collecting otherwise scattered information so that more growers could consider using this method on a commercial scale.

Validation of drying models and rehydration characteristics of betel ( Piper betel L.) leaves

Effect of temperature on drying behaviour of betel leaves at drying air temperatures of 50, 60 and 70°C was investigated in tunnel as well as cabinet dryer. The L* and b* values increased whereas, a* values decreased, as the drying air temperature increased from 50 to 70°C in both the dryers, but the colour values remained higher for cabinet dryer than tunnel dryer in all cases. Eleven different drying models were compared according to their coefficients of determination (R2), root mean square error (RMSE) and chi square (χ2) to estimate drying curves. The results indicated that, logarithmic model and modified Page model could satisfactorily describe the drying curve of betel leaves for tunnel drying and cabinet dryer, respectively. In terms of colour quality, drying of betel leaves at 60°C in tunnel dryer and at 50°C in cabinet dryer was found optimum whereas, rehydration at 40°C produced the best acceptable product.

Enhanced biodegradation of PAHs by microbial consortium with different amendment and their fate in in-situ condition.

Microbial degradation is a useful tool to prevent chemical pollution in soil. In the present study, in-situ bioremediation of polyaromatic hydrocarbons (PAHs) by microbial consortium consisting of Serratia marcescens L-11, Streptomyces rochei PAH-13 and Phanerochaete chrysosporium VV-18 has been reported. In preliminary studies, the consortium degraded nearly 60-70% of PAHs in broth within 7 days under controlled conditions. The same consortium was evaluated for its competence under natural conditions by amending the soil with ammonium sulphate, paddy straw and compost. Highest microbial activity in terms of dehydrogenase, FDA hydrolase and aryl esterase was recorded on the 5(th) day. The degradation rate of PAHs significantly increased up to 56-98% within 7 days under in-situ however almost complete dissipation (83.50-100%) was observed on the 30(th) day. Among all the co-substrates evaluated, faster degradation of PAHs was observed in compost amended soil wherein fluorene, anthracene, phenanthrene and pyrene degraded with half-life of 1.71, 4.70, 2.04 and 6.14 days respectively. Different degradation products formed were also identified by GC-MS. Besides traces of parent PAHs eleven non-polar and five polar products were identified by direct and silylation reaction respectively. Various products formed indicated that consortium was capable to degrade PAHs by oxidation to mineralization.

Bio-active compounds in mango (Mangifera indica L.) and their roles in human health and plant defence – a review

Summary Mango (Mangifera indica L.) is one of the most important tropical fruits in the World. Mango leaves, bark, and fruit (pulp, peel, and stone) are rich sources of bio-active compounds (BaCs) such as proteins [0.36 – 0.40 g 100 g–1 fresh weight (FW) of pulp; 1.76 – 2.05% (w/w) of peel; 66.1 g kg–1 of kernel flour; and 3.0% (w/w) of leaves], vitamin A [0.135 – 1.872 mg 100 g–1 FW pulp; 15.27 International Units (IU) in kernels; 1,490 IU in leaves], vitamin C [7.8 – 172.0 mg 100 g–1 FW of pulp; 188 – 349 µg g–1 FW of peel; 0.17 g kg–1 DW of kernel flour; 53 mg 100 g–1 dry matter (DM) in leaves], carotenoids (0.78 – 29.34 µg g–1 FW of pulp; 493 – 3,945 µg g–1 FW of peel), mangiferin (1,690.4 mg kg–1 DM in peel; 4.2 mg kg–1 DW of kernel extract), phenolic compounds, dietary fibre (DF), carbohydrates, minerals, and other anti-oxidants known to have medicinal, nutritional, and industrial benefits. Bio-active compounds exist in functional foods and can protect us against diseases via several mechanisms. The anti-oxidant properties of several BaCs are important to protect against diseases related to oxidative stress. Fruit intake provides us with anti-oxidants that may act in a synergistic way to offer protection. In mango fruit, only the pulp is used, while all other parts are discarded and cause environmental pollution. The importance of all the different parts of mango fruit and trees should not be disregarded. With a global increase in health issues there is an increasing demand for natural foods. Hence, there is need to study all the bio-active constituents in mango to provide greater insights into their medical, nutritional, and industrial applications, as well as their role(s) in defending of the plant. This review aims to assist in the proper utilisation of mangoes to improve nutrition and health, as well as to improve our understanding of the defence mechanisms in plants that depend on these compounds.

Response of kiwifruit (Actinidia deliciosa cv. Allison) to post-harvest treatment with 1-methylcyclopropene

Summary Experiments were conducted to observe the effect of different concentrations of 1-methylcyclopropene (1-MCP) on the post-harvest life and quality of ‘Allison’ kiwifruit (Actinidia deliciosa). Fruit were treated with 1-MCP at 0.5 µl l–1, 1.0 µl l–1, or 2.0 µl l–1, un-treated fruit served as controls. Each 1-MCP treatment was applied for 24 h at 20°C. After treatment, fruit were transferred to ambient temperature storage (22º ± 4ºC; 65 – 70% relative humidity) for 18 d, during which time observations on various physical, physiological, and biochemical parameters were recorded at 3 d intervals. Our results indicated that 2.0 µl l–1 1-MCP was the most effective treatment to delay softening and ripening in ‘Allison’ kiwifruit, as such fruit showed the lowest mean weight loss (9.8 ± 0.2%), the highest mean fruit firmness value (32.7 ± 0.2 N), and began to ripen only after 12 d in storage, whereas untreated fruit started ripening on day-6 of storage. The activities of fruit softening enzymes such as polygalacturonase (PG; 58.5 ± 0.3 µg galacturonic acid g–1 FW h–1), and lipoxygenase (LOX; 3.96 ± 1.3 µmoles linoleic acid oxidised min–1 g–1 FW h–1) were lower, and total phenolics (TP) contents (24.3 ± 0.3 mg 100 g–1) and anti-oxidant (AOX) activities (12.5 ± 0.03 µmol Trolox g–1 FW h–1) were higher in 1-MCP-treated fruit than in untreated fruit (PG, 98.3 ± 0.5 µg galacturonic acid g–1 FW h–1; LOX, 4.39 ± 1.0 µmoles min–1 g–1 FW h–1; TP, 5.3 ± 0.6 mg 100 g–1; AOX, 4.7 ± 0.02 µmol Trolox g–1 FW h–1, respectively). In addition, 1-MCP-treated fruit exhibited lower rates of respiration (48.3 ± 0.4 ml CO2 kg–1 h–1) and ethylene production (30.2 ± 0.02 µl kg–1 FW h–1) than untreated fruit (58.9 ± 0.6 ml CO2 kg–1 h–1; 38.7 ± 0.04 µl kg–1 FW h–1, respectively). Similarly, 1-MCP-treated fruit had higher titratable acidity (TA; 1.33 ± 0.3%) and ascorbic acid (AA) contents (115.9 ± 2.6 mg 100 g–1 pulp) and lower soluble solids contents (SSC; 8.33º ± 0.2º Brix) than untreated kiwifruit (TA, 1.0 ± 0.2 %; AA, 105.3 ± 2.2 mg 100 g–1 pulp; SSC, 13.7º ± 0.3º Brix, respectively). Thus, 2.0 µl l–1 1-MCP can be used for the post-harvest treatment of ‘Allison’ kiwifruit to enhance its shelf-life and marketability by approx. 6 d.

An efficient and rapid method for the isolation of RNA from different recalcitrant tissues of mango (Mangifera indica L.)

Summary The isolation of high quality RNA from different tissues of mango (Mangifera indica L.) is relatively challenging due to the presence of interfering substances such as polysaccharides, polyphenols, and proteins. All these compounds render available isolation protocols useless by reducing the quality (purity and integrity) and quantity of the RNA that can be recovered. Several tissue-specific protocols for the isolation of RNA have been developed specifically for mango, however they are cumbersome, expensive and time-consuming. To overcome these drawbacks, we have developed a comprehensive (CTAB-free, guanidine-free, and LiCl-free) RNA isolation protocol using SDS (sodium dodecyl sulphate) plus phenol which works well for most mango tissues such as leaves, flowers, and fruit, at different stages of development or ripening, as well as fruit peel and seed kernels.This rapid protocol allowed us to process large numbers of samples (12 - 15) simultaneously in a single day. Using this method, we obtained good quantity RNA (16 - 80 ?g g-1 tissue) from various mango tissues at different stages of development. RNA isolated by this method was pure and amenable to various downstream molecular applications such as RT-PCR and the construction of a cDNA library.

Cold Plasma Technology for Surface Disinfection of Fruits and Vegetables

Abstract Various methods of preservation have been developed and commercialized since ancient times for the preservation of fresh as well as processed foods. Though most of these methods could effectively control the spoilage/pathogenic microbes and enzymes, they have certain negative effects on the sensory as well as nutritional parameters of the treated foods. Thus, the perishable food industry was in great need of alternative, nonthermal technologies that could be used to meet the food safety measures with minimal or no impact over their nutritional and sensory quality. One such demand-driven nonthermal preservation technique is cold plasma technology, which uses cold ionized gases for surface disinfection of fresh fruits and vegetables. It was shown to effectively reduce the foodborne pathogens, viz., Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, Staphylococcus aureus, and Shigella spp. Being flexible and antimicrobial in nature, cold plasma has a great potential for use with a wide variety of food materials. The exact clear mechanism of antimicrobial mode of action of cold plasma treatment systems was not established so far, hence there is a great need for research in that direction. Understanding the mode of action is a key step toward optimization of the technology for specific applications in the food processing industry.