|Pakistan is one of the largest producers of mangoes which are known world over for their quality, aroma and taste. Reportedly about 100,000 ton of mangoes are exported from Pakistan annually. Due to presence of certain post harvest diseases and insects like anthracnose, stem-end rot and fruit fly, export of mango is limited.
In order to reach high end markets of the World (China, Iran, Japan, Australia, New zeland) the mangoes of Pakistan must meet WTO/HACCP/ISO and SPS requirements. For the said purpose, quarantine of mangoes through physical or chemical treatment is essentially required. Chemical treatment face severe restrictions from different countries, therefore, physical methods such as hot water treatment (HWT), vapour heat treatment (VHT) and irradiation are preferred. Among the physical methods of quarantine, HWT is most economic and safe.
The HWT procedure consist of dipping/immersion of freshly harvested mangoes in hot water at 45-55ºC for 3 to 75 minute depending on type of disease/insect, variety and fruit size. After dipping/immersion of the mangoes in hot water, mangoes are dried and processed for packing. In order to achieve this goal AMRI has got a project from PARB “optimization and standardization of operational parameters of hot water treatment (HWT) system to control post harvest diseases and insects of mangoes”.
The hot water treatment system comprise of a feeding conveyor, hot water dipping tank, drying system and packing tray. Each component except packing tray is mounted on wheels for ease of transportation. The water tank is made of stainless steel in order to avoid rusting. The water is heated through three gas burners.
The required temperature of the water tank is adjusted in the panel, when the water temperature reaches to the adjusted temperature burners automatically off. Eight no thermo couples are fitted in the water dipping tank in order to check the temperature at different sites of the tank. The water is agitated with a power full two no re circulation pumps. This agitation keeps the water evenly mixed and helps maintain temperature evenly. The size of the tank is big enough that there is no appreciable drop in temperature in the tank when the fruit is dipped. In the drying system mangoes are dried with the help of two no high speed electric fans. After drying the fruits are allowed to drop in the packing tray from where theses are packed.
An electric panel is fitted out side the water dipping tank. All the motors, pumps and fans are controlled from here.
The main objectives of this study are:
To generate data on the basis of which operational parameters of HWT system will be optimized and standardized for different varieties and sizes of mangoes for subsequent adaptation by the processor and exporters.
To know the effect of HWT system for the control of diseases and insects.
The HWT system was initially tested to check the working of plant. After that the speed of the variable electric speed motors of different systems were determined at different hertz in order to carried out different treatments of different varieties of mangoes at different temperatures and different dipping times.
Different varieties of mangoes were treated in different times. First of all SINDHRI was treated. The mangoes were procured from a common orchard which was not properly managed according to required pre harvest management criteria in order to check the effectiveness of HWT system in the control of diseases and fruit fly. The procured mangoes were washed in the food grade lime water and peduncle was detached in the lime water in ordered to save the skin of the fruit from the sap. Then these mangoes are again washed in the clean water. After washing they are graded into three categories that are large, medium and small. Different treatments were carried out as proposed in the project.
At last sensation was treated but due to non availability of required quantity of mangoes all the treatments were not carried out.