As shown in Figure 4.5, oxygen from the air breaks down carbohydrates in the plant into carbon dioxide and water.Respiration uses stored starch or sugar and will stop when reserves of these are exhausted; ageing follows and the produce dies and decays.Air contains about 20 percent of the oxygen essential to normal plant respiration, during which starch and sugars are converted to carbon dioxide and water vapour.When the air supply is restricted and the amount of available oxygen in the environment falls to about 2 percent or less, fermentation instead of respiration occurs.When the concentration of this gas rises to between I and 5 percent in the atmosphere, it will quickly ruin produce by causing bad flavours, internal breakdown, failure of fruit to ripen and other abnormal physiological conditions.The surfaces of all plant parts are covered by a waxy or corky layer of skin or bark limiting water loss.Well-designed packaging materials and suitable stacking patterns for crates and boxes can contribute to controlled air flow through produce.Leafy green vegetables, especially spinach, lose water quickly because they have a thin waxy skin with many pores.The significant factor in water loss is the ratio of the surface area of the type of plant part to its volume.The fruit referred to here includes those used as vegetables or salads, such as aubergine, sweet pepper, tomato, breadfruit and avocado.Their eating quality suffers if they are harvested before they are fully ripe because their sugar and acid content does not increase further.The start of ripening is accompanied by a rapid rise in respiration rate, called the respiratory climacteric.After the climacteric, the respiration slows down as the fruit ripens and develops good eating quality.Ethylene gas is produced in most plant tissues and is known to be an important factor in starting off the ripening of fruits.This has made it possible for tropical fruits such as mangoes and bananas to be harvested green and shipped to distant markets, where they are ripened under controlled conditions;.citrus fruit grown in tropical areas remains green after becoming fully ripe on the tree.The gas concentration, temperature, humidity and ventilation have to be carefully controlled in specialized rooms, so degreening is economically viable only for high-value export or domestic markets.In most tropical countries fully ripe green citrus fruit is acceptable to local populations.The high moisture content and soft texture of fruit, vegetables and root crops make them susceptible to mechanical injury, which can occur at any stage from production to retail marketing because of:.unsuitable field or marketing containers and crates, which may have splintered wood, sharp edges, poor nailing or stapling;.careless handling, such as dropping or throwing or walking on produce and packed containers during the process of grading, transport or marketing.Although a few commodities are tolerant of slight freezing, it is advisable to avoid such temperatures because subsequent storage life is short.Effect of chilling injury Symptom Discoloration Internal or external or both, usually brown or black Skin piking Sunken spots, especially under dry conditions Abnormal ripening (fruits) Ripening is uneven or fails; off-flavours Increase in decay Activity of micro-organisms.and Hardenburg, R.E., 1966, The commercial storage of fruits, vegetables and florist And nursery storks, Agricultural Handbook No.Symptoms of chilling injury may not develop until the produce is removed from cold storage to normal market (i.e. ambient) temperatures.It will achieve a high rate of respiration and, if packed and transported without cooling or adequate ventilation, will become unusable.Long exposure to tropical sun will cause severe water loss from thin-skinned root crops such as carrots and turnips and from leafy vegetables.Insect pests that are mainly responsible for wastage in cereals and grain legumes are rarely a cause of post-harvest loss in fresh produce.Loss in quantity, the more serious, occurs where deep penetration of decay makes the infected produce unusable.In crops grown for local consumption, the result is less serious since the affected skin can often be removed and the undamaged interior can be used.Fungal and bacterial diseases are spread for the most part by microscopic spores, which are widely distributed in the air and soil and on dead and decaying plant material.through injuries caused by careless handling, by insect or other animal damage, or through growth cracks (see colour section, Figure 1);.Similarly, tropical fruits infected at any time during their development may show decay only during ripening.records may not truly represent a continuing situation; for example, losses may have been calculated only when unusually high or low;.loss figures may be deliberately over- or understated for commercial or other reasons in order to gain benefits or to avoid embarrassment.
Why Do Tomatoes Turn Red When They're Ripe?
When tomatoes are growing on the vine, they're not bright red like they are when they're ripe and ready to eat.Why do they grow green on the vine and then turn red when they're ripe and ready to eat?As harvest time approaches, days get shorter and temperatures fall.At that point, tomatoes start to produce an odorless, tasteless, and invisible chemical gas called ethylene.While it may take months for tomatoes to grow, the ripening process occurs quickly during a fairly-short period of time.As they're sent to market, they're treated with ethylene gas to jump-start the ripening process, so that they arrive at stores ripe and ready to eat.If you have an unripe tomato, simply place it in a paper bag and give it a little time.The trapped ethylene gas will help to speed the tomato along to full ripeness in a matter of days! .
Symptoms of frost, freezing and chilling injury on vegetables
Chilling injury occurs at temperatures well above freezing point.Symptoms include surface lesions/pitting, internal discoloration, water soaking of the tissue, failure to ripen normally and increased susceptibility to decay organisms such as Alternaria.Maturity at harvest also affects the susceptibility to chilling injury in products such as tomatoes, honeydew melons and peppers.It can also occur during cold storage if temperatures were below the freezing point of the product.Researchers have categorized fruits and vegetables into three groups based on their sensitivity to freezing (Table 1): most susceptible are those that are likely to be injured by one light freeze, moderately susceptible are those that will recover from one or two light freezes and least susceptible are those that can be lightly frozen several times without serious injury.Symptoms of freezing, chilling injury.Asparagus: Freezing injury (water-soaked appearance leading to extreme softening) will likely result at temperatures of 30.9°F (-0.6°C) or lower.Chilling Injury occurs when spears are held more than 10 days at 32°F (0°C) and symptoms of chilling injury include loss of sheen or glossiness and graying of the tips.Freezing injury occurs at temperatures of 30.7°F (-0.7°C) or below.The typical symptom of chilling injury in snap beans stored below 41°F (5°C) but above freezing point for longer than 5-6 days is a general opaque discoloration of the entire bean.The most common symptom of chilling injury is the appearance of discrete rusty brown spots which occur in the temperature range of 41-45°F (5-7.5°C).No discoloration occurs on beans stored at 50°F (10°C).Bell Pepper: Freezing injury symptoms include dead, water-soaked tissue in part or all of the pericarp surface; pitting, shriveling, and decay follow thawing.Symptoms of chilling injury include surface pitting, water-soaked areas, decay (especially Alternaria spp.Frozen and thawed areas on the florets appear very dark and translucent, may discolor after thawing and are very susceptible to bacterial decay.Cabbage: Freeze damage appears as darkened translucent or water-soaked areas that will deteriorate rapidly after thawing.Leaves become water-soaked, translucent, and limp upon thawing; the epidermis can also separate from the leaf as it does in lettuce.Cauliflower: Freezing injury will be initiated at 30.6°F (- 0.8°C).Symptoms of freezing injury include a water-soaked appearance on thawing and wilted leaves.Symptoms of freezing injury include a water-soaked pulp becoming brown and desiccated in appearance over time.Eggplant fruit are chilling sensitive at temperatures below 50°F (10°C).At 41°F (5°C) chilling injury will occur in 6-8 days.Symptoms of freezing injury include a water-soaked appearance of bulb or leaves and wilted or gelatinous leaves, after thawing.Freeze damage can occur during storage if the lettuce is held at 31.7°F (<-0.2°C).The blistered dead cells of the separated epidermis on outer leaves become tan and there is increased susceptibility to physical damage and decay.Okra: Freeze damage occurs at temperatures of 28.7°F (-1.8°C) or below.The typical symptoms of chilling injury in okra are discoloration, pitting, water-soaked lesions and increased decay (especially after removal to warmer temperatures, as during marketing).Onion: Freezing injury symptoms include soft water-soaked scales that rapidly decay from subsequent microbial growth.Symptoms of freezing injury include a water-soaked appearance, glassiness, and tissue breakdown on thawing.Turnip: Freezing injury symptoms include small water-soaked spots or pitting on the surface. .
Induced Ripening Agents and Their Effect on Fruit Quality of Banana
Banana is one of mostly consumed fruit crops in the world.Ethylene gas, acetylene gas liberated from calcium carbide, and ethephon are some of the commercial ripening agents used successfully in the trade and they have been widely studied for their effectiveness on initiating and accelerating the ripening process and their effect on fruit quality and health related issues.Lauryl alcohol was also shown as a ripening agent for bananas.However volatile profiles of artificially ripened bananas were shown to be considerably different from naturally ripened bananas in some studies.These changes include changes in carbohydrate content, increment of sugar content, changes in colour, texture, aroma volatiles, flavour compounds, phenolic compounds, and organic acids.Based on regulatory mechanisms leading to fruit ripening, fruits can be divided into two groups: climacteric and nonclimacteric fruits.Although climacteric fruits are considered as ethylene dependent, it has been shown that in climacteric fruits some ripening changes occur independently of ethylene; also there are some changes in nonclimacteric fruits which are ethylene dependent.System 1 represents ethylene biosynthesis during the preclimacteric stage of climacteric fruits as well as during the whole ripening process of nonclimacteric fruits.System 2 operates during the ripening of climacteric fruit and is an autostimulated process which is responsible for high levels of ethylene production .Figure 2 shows the mechanism of ethylene biosynthesis from methionine.Changes during Ripening.Carotenoid biosynthesis during ripening has been studied using tomato plant as a model.It has been reported that ethylene is involved in regulation of genes related to anthocyanin biosynthesis .Many fruits emit volatile compounds which are responsible for flavour and aroma of the certain fruit.Ethylene treatments can enhance the aroma volatile production in mangoes and honeydew melons [21, 22].Further [23, 24] showed that aroma production is reduced when ethylene biosynthesis is inhibited by using aminoethoxyvinylglycine (AVG) or 1-methylcyclopropane (1-MCP) indicating that aroma synthesis is correlated with ethylene production and action in fruits.According to a case study in Sri Lankan crop sector  currently there are 55 local cultivars in Sri Lanka.According to Agricultural statistics in Sri Lanka, 2015, the total production of banana is nearly 530, 124 MT annually.Fruit ripening is a combination of physiological, biochemical, and molecular processes leading to changes in pigments, sugar content, acid content, flavour, aroma, texture, etc.Bananas can be artificially ripened using different ripening agents.Further this study showed that increment in respiration depends on time of treatment whereas 12-hour treatment was slightly effective than 6 hours treatment.Mostly in developing countries including Sri Lanka, calcium carbide is widely used for artificial ripening of bananas, though it is prohibited by the government regulations.It was shown in this study that acetylene emits from calcium carbide can enhance banana ripening as treated fruits were uniformly yellow with good flavour, medium starch content, and comparatively soft texture after 120 hours while control samples were remain unripe after same period of time.Further it was shown in this study that there is no significant difference in sensory attributes between bananas treated with ethylene and acetylene at 1ml/L when they are compared at same stage of ripeness.Ethephon.Adane  compared ethephon treatment and traditional kerosene smoke treatment and their effect on ripening of “Cavendish” bananas, where it was shown that ethephon treated fruits demonstrated higher sensory quality.One of the traditional methods used in Sri Lanka, as well as in many other countries, is smoking.Ethylene is also emitted from fruit that have already initiated to ripen and can be used to enhance ripening of other fruits.Effect of Induced Ripening Agents on Quality of Bananas.Another study which was conducted to examine comparative effect of acetylene and ethylene gas on banana ripening showed that fruits treated with acetylene at 1ml/L exhibited the similar colour score and soluble solids content in fruits treated with ethylene gas.However in this study it was further recorded that sensory quality is the same in the fruits treated with ethylene gas and acetylene gas when compared at same stage of ripeness .Similar research was conducted by Sarananda  where effect of acetylene liberated from calcium carbide on ripening of “Embul” (Musa acuminata, AAB) banana.It was clearly exhibited in this study that naturally ripened fruits have excellent sensory quality with flesh colour, flavour, taste, and overall acceptability compared to calcium carbide treated fruits at the stage of fully yellow (Colour Index-6).Gandhi  compared natural ripening agents including apple, pear, and tomato with calcium carbide.However calcium carbide treated fruits exhibited the least organoleptic quality compared to naturally ripened and ethephon treated bananas in .Reference  compared aroma compounds in naturally ripened and ethylene treated ripened banana (Musa acuminata).According to the data obtained by this study total aromatic concentration was higher in naturally ripened bananas (60 437 μg/kg) compared to that (55,243 μg/kg) of ethylene treated bananas.The banana ripening process can be enhanced using artificial ripening agents such as ethylene gas, ethephon, acetylene (emitted from calcium carbide), ethylene glycol, and alkyl alcohols (containing 6-14 carbon atoms such as lauryl alcohol).Many studies on the effect of different ripening agents on fruit quality appear to show that naturally ripened bananas exhibit better sensory characteristics compared to treated fruits. .
Ripening 101: Climacteric vs. Non-Climacteric Fruits
Another factor that is essential in fruit ripening is ethylene, a naturally occurring gas that triggers and promotes the ripening process.Knowing which fruits will ripen or which may be in danger of rotting can help you determine when to eat them.Climacteric Fruits. .
Blossom-End Rot: Preventing Blossom-End Rot on Tomatoes
Here are tips on how to identify, control, and prevent blossom-end rot on your tomatoes and other garden plants.When the demand for calcium exceeds the supply, the tissues in the fruit break down and blossom-end rot occurs.Be aware of these causes when caring for tomatoes and other garden plants in order to prevent blossom-end rot.Some blossom-end rot is more or less normal in the first tomatoes of the season, since the plants are usually under stress during the initial fruit set. .
What Type of Acid Is in Tomatoes?
The primary acids in tomatoes are citric and malic acid.Citric acid, ascorbic acid and malic acid are all found in tomatoes, and all of these provide help to the body's cellular functions.Malic Acid in Tomatoes.The most prominently found acids in tomatoes are citric, malic and ascorbic acid.Otherwise known as vitamin C, ascorbic acid is key to the production of proteins in the body.Malic acid is often paired with citric acid to create an effective antimicrobial, but in food it is often used to provide a distinct, sour taste to products like sour candies and fruit drinks as an additive.As a food additive, malic acid quantities have to be carefully maintained as too much or too little can encourage product deterioration.Therapeutically, malic acid has been used to treat ulcers and wounds, as well as used intravenously in the treatment of liver disorders.Citric Acid in Tomatoes.It is particularly used in soft fruit drinks to provide that sharp flavor.Citric acid can be a highly beneficial to your overall health as well.Along with a reduced chance of kidney stones, increased consumption of citric acid has been linked to a reduced risk of gout.An older study published in the journal Endocrine Research in 2010 tested a total of 70 subjects and found that increased citric acid intake also increased the acidity of urine and the excretion of uric acid, meaning that uric acid was less likely to build up and form crystals that could lead to gout.Ascorbic Acid in Tomatoes.Ascorbic acid, more commonly known as vitamin C, is found in significant quantities in tomatoes.It's a highly beneficial vitamin for the body due to its role in cell maintenance and repair.The most common sugars found in tomatoes are glucose and fructose, both of which play a key role in the production and release of energy in the body. .