BEST IELTS Academic Reading Test 445

BEST IELTS Academic Reading Test 445

IELTS Academic Reading Test

Tomato Ripening

When tomatoes are exposed to the air, they release trace amounts of the gas ethylene, which is responsible for kickstarting the ripening process. However, tomatoes ripen at unpredictable intervals if left to nature. Tomatoes can be ripened using the trickling ethylene gas procedure by exposing them to a low concentration of ethylene gas in a specially designed tomato-ripening room. This procedure originates and regulates the natural ripening and coloration of the tomatoes.

The grower can sell tomatoes of a more uniform hue and quality with controlled ripening and coloring than with green or field-ripened produce. Controlled ripening and coloring can be used to optimize yields and resource utilization by determining when to harvest and sell.

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Ripening Conditions

For controlled ripening to be successful, all fruit must be fully developed while still in the mature green stage at harvest. The effects of relative humidity on tomato ripening appear to be minor. Due to the relatively impermeable quality of the tomato skin, little moisture is lost from the tomatoes during the ripening process.

The time it takes for the fruit to ripen depends on the temperature at which it is kept; however, if the temperature is above 24 degrees Celsius, the fruit will turn out yellow or orange instead of red. Capabilities in both heating and cooling should be sufficient to bring the tomatoes to the ideal ripening temperature in under 24 hours.

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General Arrangement

Figure 1 depicts a typical setup for a tomato ripening chamber, complete with labels for all of the system’s most crucial parts.

Room Size and Construction

On-farm tomato ripening facilities are often designed to accommodate the average daily tomato pick during peak harvest times for the sake of efficiency and convenience. Typically, a room may hold anything from two to ten metric tonnes of tomatoes, while larger rooms are available upon request. Since most fruits only need three or four days to ripen, having various storage areas on a single farm is quite advantageous.

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Air Circulation and Ventilation System

In order to maintain a steady temperature and distribute the ethylene gas evenly throughout the ripening chamber, a fan-driven ventilation system is essential. As a rule of thumb, a circulation rate of two air volumes per minute in a given space is advised. This is the same as about 480 cubic meters of air each hour for every tonne of tomatoes. With a heating or cooling capability of 0.6 to 1.2 kW per tonne of tomatoes, this results in a 3.5 to 7°C air temperature differential.

Achieving a suitable rate of heating or cooling the tomatoes requires such high rates of air circulation as to restrict temperature variation within the room to tolerable levels. Continuously introducing a tiny percentage of new air and exhausting an equal volume of air, the ventilation system circulates the air in the room. This eliminates carbon dioxide released by the fruit during respiration and prevents ethylene gas from building up in the room. If the concentration of carbon dioxide in the air were permitted to rise to dangerous levels, the ripening process would be stymied.

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Temperature Control System

There is a strong correlation between the temperature in the ripening room and the level of ripeness achieved by the tomatoes. In fact, in most cases, the product heat load accounts for roughly 80% of the total heat load. The remainder is caused by the pace at which the room’s air is exchanged for new air and by heat transfer via the room’s exterior walls.

The need for both heating and cooling systems can arise while trying to keep a room at a specific temperature. Increasing the temperature can hasten the ripening process to a lesser amount. Tomato ripening rooms do not appear to benefit greatly from humidity control, therefore reverse cycle air conditioners can be utilized for both heating and cooling with success.

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Supply and Control Systems

The trickling ethylene gas system uses a constant, tiny, controlled flow of gas to keep the ethylene concentration in the ripening room at around 10 parts per million (ppm). High-pressure ethylene gas comes from a bottle and is metered into the ripening room via a pressure regulator. A gas pressure regulator is used to modify the pressure of the gas leaving the appliance, and a small needle valve controls the volume of gas leaving the appliance.

For safety reasons, the ethylene gas supply line has a normally closed solenoid valve that prevents gas from being released into the room unless the ripening room’s fans and ventilation system are running. An airflow switch and an electrical interlock regulate the solenoid valve, which controls the ventilation system’s fan operation.

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For precise regulation of gas delivery, a gas control thermostat is installed. The thermostat’s temperature sensor is inserted into a tomato to measure the temperature of the room based on the pulp temperature of tomatoes placed in different locations.

Assuming the ethylene gas supply and control systems are set up properly, the concentration of ethylene gas in the room won’t go above the safe, ripening threshold while remaining well below the explosive threshold. Certain Electricity Commissions have ruled that tomato ripening rooms erected on farms and used only for ripening fruit produced by the owner do not constitute a dangerous place under these terms.

(This is an edited version of an essay first published in the October 1989 issue of the “Electrofarming Notebook” by Brian Hesse for the South East Queensland Electricity Board.

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IELTS Academic Reading Test

Complete the table in the box below. Use NO MORE THAN THREE WORDS OR A NUMBER for each answer.

Requirements for successful use of the Ethylene Gas System for Tomato Ripening:

When tomatoes are 27_____________, they are ready to be harvested.

The room must be 28_____________ degrees Celsius.

Fruit must ripen at the ideal temperature, which must be attained 29_______________.

IELTS Academic Reading Test

Complete the flowchart below using information from the text. 

Use NO MORE THAN THREE WORDS for each answer. 

The harvest of tomatoes

– A device used in the ripening room to control the ripening and 30__________.

– Cooling is controlled by the room’s airflow 31 ______________.

– Air conditioning controls temperature & humidity

– The Ideal temperature is reached

– The amount of 32_________ and 33 __________________ is regulated by the facility’s ventilation system.

– Ethylene gas is supplied in pressurized form

– Tomatoes are ripened & removed

– Tomatoes are marketed.

IELTS Academic Reading Test

Below is a list of assumptions. Using the information given in the passage, choose:

TRUE                             if it is a reasonable assumption

FALSE                            if it is not a reasonable assumption

NOT GIVEN                   if it is not possible to assume the information in the text.

34.  An explosion could happen if ethylene gas builds up to a dangerous level.

35.  Maturation can be hurried along by raising the temperature.

36.  The quantity of supplemental heating required in the ripening chamber depends      on the ambient air temperature.

37.  Humidity levels must be controlled for optimal tomato ripening.

38.   It’s not always safe to set up ethylene gas ripening rooms.

39.  Ripening is not helped by carbon dioxide.

40.  Maintenance of the solenoid valve is a must.

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BEST IELTS Academic Reading Test 445

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34. TRUE

35. TRUE



38. TRUE



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