**3. Factors influencing quality**

#### **3.1 Pre-harvest factors**

*Site selection:* The soil properties of a given site for crop production will determine the ultimate compositional and physical quality of the harvested produce. Appropriate site selection, free from heavy metals, toxic materials and adequate fertility level is essential for maximum quality. The soil should be analysed, and the soil condition should be determined before planting.

*Genetic constituent of produce:* The potential quality of harvested produce is a factor in the genetic constitution of the plant. Varieties with shorter shelf lives have higher postharvest losses while those with thick peel, high firmness quality, low respiration rate and low ethylene production rates have longer shelf life. Their different quality traits characterise each variety; these peculiar genetic quality character traits make some varieties more desirable to producers and consumers. The choice of adequateyielding crop variety with desired qualities and longer shelf life is a vital decision for producers and an important pre-harvest factor that determines the shelf life of harvested produce [10]. The varieties that have the potential traits to withstand the rigours of marketing and distribution will have reduced losses after harvest. Varieties with resistance to low-temperature disorders, pathogens can be stored efficiently for longer duration with minimum storage losses. To prolong shelf life, enhance sustainable food availability and maintain good quality, producers must choose varieties that have inherently good quality and extended storage potential in addition to the high yield and pest resistance potentials. Failure to select an appropriate cultivar may lead to lower yield, low-quality fruits or less market acceptability. Fruits of different cultivars differ in size, colour, texture and flavour as well as storage potential. Getinet *et al*. [45] showed the influence of tomato cultivars on some postharvest qualities of tomatoes stored under different conditions, they established that tomato cultivar Roma VF has higher sugar content and lower weight loss compared to other cultivars. The genetic constituent of a produce is, therefore, critical to the postharvest storage life and utilisation qualities of such produce [37].

*Planting period:* The quality of crops planted during the dry season differ in size, firmness, fibre content and nutritional composition compared to those cultivated in rainy season when there is adequate water availability for chemical processes necessary for plant growth and development [46].

*Irrigation:* Some crops are not drought resistant hence, yield decreases in terms of size and nutritional quality after short periods of water stress. Proper irrigation planning is crucial for optimum crop development and adequate nutritional composition. Efficient water management scheme is vital to maintaining quality crop and maximum yield [47]. It is observed that deficit irrigation reduced fruit water accumulation and fresh fruit yield but increased fruit total soluble solids in tomatoes [48]. Mitchell *et al.* observed that deficit irrigation reduced fruit water accumulation and fresh fruit yield but increased fruit total soluble solids in tomato [48]. A higher level of moisture stress affects both yield and quality by decreasing cell enlargement. Crops which have higher moisture content generally have poorer storage characteristics. Some hybrid onions give a high yield of bulbs with low dry matter content and short storage life. Fully matured banana harvested soon after rainfall or irrigation may easily split during handling operations resulting in microorganism infection and rotting. If orange is too turgid at harvest, gland in the skin can be ruptured during harvesting, releasing phenolic compounds and causing oleocellosis or oil spotting (green spot on the yellow/orange coloured citrus fruit after degreening). In green leafy vegetables, too much rain or irrigation can make leaves harder and brittle, making them more susceptible to damage and decay during handling and transportation. Generally, crops with higher moisture or low dry matter content have poorer storage characteristics. Keeping quality of bulb crops like onion and garlic will be poor if irrigation is not stopped before 3 weeks of harvesting [11].

*Thinning and Pruning:* Thinning is a post-planting operation that reduces plant population, and competition between plants, increase maximum exposure to light, supply adequate water and nutrient to plants, consequently promoting good balance

#### *Pre-Harvest and Postharvest Factors Affecting Quality and Shelf Life of Harvested Produce DOI: http://dx.doi.org/10.5772/intechopen.111649*

in the vegetative stage during fruit production and also improves the quality of harvested produce. It affects fruit texture and size due to inadequate exposure to sunlight. Thinning also improves the textural characteristics of harvested produce, which consequently greatly affect firmness. Studies also revealed that fruit firmness positively correlated with fruit size, implying that larger fruits were slightly firmer at harvest than smaller ones [18]. Appropriate pruning enhances fruit texture characteristics by optimise light distribution to all fruit on the tree. Inappropriate pruning may result in fruit shading with consequent smaller undesirable under, ripe fruit with a hard and grainy texture. Pruning is done to control the number of flowers and fruits by reducing the competition between fruits. Pruning, therefore, ensures nutrients are channelled to fewer fruits which can lead to increased fruit size [49] and increased sugar content of fruits in some cases [50]. On the other hand, the effect of pruning on other quality traits of the fruit produced depends on many factors, including the sink developmental stage, fruit-to-leaf ratio, truss position, and genetic composition of the plant [51].

*Maturity Stage:* Fruit maturity stage influences the total antioxidant capacity of the produce. These changes are determined by crop type and stage of maturity. For example, in tomato, pepper, mango, and prunus species, total antioxidant capacity increases as carotenoids and vitamin C accumulate during ripening [52]. Adewoyin and Babatola observed that pepper fruits harvested at 10% ripe (breakers stage) retained firmness, and weight loss was minimal compared to those harvested at 100% ripe stage (fully ripe) in all storage medium studied [53]. Wang and Lin observed that the shelf life of all tomatoes is longest when harvested at green mature stage though fruit nutritional values and appearance may be affected when harvested green [54]. Delays between harvest and consumption or processing can result in losses of flavour and nutritional quality. The magnitude of these losses increases with exposure to inappropriate temperatures, relative humidity and concentrations of O2, CO2, and C2H4 [26]. During berry ripening, anthocyanins accumulate while phenolic acids decrease [55] in products in which anthocyanins or chlorophylls dominate, carotenoids decrease during development; in cherry, ascorbic acid accumulates during ripening [56].

*Climatic condition:* Many plants are very sensitive to environmental conditions, and thus quality will not be optimised when crop is produced under adverse conditions. Poor weather at harvesting time affects the operations and functionality of harvesting machines or human labour and usually increases the moisture content of the harvested products, consequently resulting in loss of quality and reduced shelf life [57].

*Heat management:* Physiological and biochemical processes involved in plant growth, yield and maturation is influenced by temperature. Higher temperature during field conditions decreases shelf life and quality of the produce. At high temperatures, plants respire at a faster rate, and stored carbohydrates in harvested produce are depleted rapidly during respiration. High temperature during the fruiting season of tomato leads to quick ripening of fruits. Orange grown in the tropics have higher sugar content and total soluble solids than those grown in the subtropics. Tropically grown oranges tend to be green in colour and peel less easily. This is due to the higher temperature that occurs in the tropics, which results in rapid maturation of fruit which halts the process of the typical temperate orange colour development [58].

*Light:* Light regulates several physiological processes like chlorophyll synthesis, phototropism, respiration and stomatal opening. The duration, intensity and quality of light affect the quality of fruits and vegetables at harvest. Most of the produce needs high light intensity. Absorption of red light through pigments, phytochrome, is essential for carbohydrate synthesis, which determines the shelf life of the produce.

Citrus and mango fruits produced in full sun generally had thinner skin, a lower weight, low juice content and lower acidity but a higher total soluble solid. Citrus fruits grown in the shade may be less susceptible to chilling injury when stored in cold storage. In tomatoes, leaf shading of fruits produced a deeper red colour during the ripening than in the case of those exposed to light. The side of the fruit that was exposed to the sun was firmer than those that were not exposed to sunlight, the lower the light intensity, the lower the ascorbic acid content of plant tissues. In leafy vegetables, leaves are larger for those exposed to adequate light and thinner under conditions of low light intensity.

*Humidity:* High humidity during the growing season results in thin rind and increased size in some horticultural produce, and this produce is more prone to a high incidence of disease during postharvest period. Humid atmosphere may cause the development of fungal and bacterial diseases, which damages produce during storage and transport. Damaged produce removes water very quickly and emits a larger ethylene concentration than healthy ones. Low humidity may cause browning of leaf edge on plants with thin leaves or leaflets. High humidity can maintain the water-borne pollutants in a condition so that they can be more easily absorbed through the cuticles or stomata. Reduced transpiration leads to calcium and other elemental deficiency [59].

*Rainfall:* Rainfall affects the water supply to the plant and influences the composition of the harvested plant part. This affects its susceptibility to mechanical damage and decay during subsequent harvesting and handling operations. Excess water supply to plants results in the cracking of fruits such as orange, cherries, plums and tomatoes. If root and bulb crops are harvested during heavy rainfall, the storage losses will be higher [60].

*Seasons:* Seasonal fluctuation and time of the day at harvest will greatly affect the postharvest quality of produce. Synthesis of higher amount of carbohydrates during the day and its utilisation through translocation and respiration at night is responsible for the variation in the longevity of some harvested produce. Roses and tuberose have been found to show longer keeping quality in the winter under ambient conditions than in the summer. Produce harvested early in the morning or in the evening hours exhibits longer postharvest life than produce harvested during hot time of the day. If long-day onion (temperate) is grown during short-day (tropics) conditions, it will result in very poor storage quality [61].

*Fertiliser application:* Poor fertiliser management will increase physiological disorders due to deficiencies of some minerals or increase of others, leading to toxicity. In both cases, quality will be negatively affected. The use of trace elements or the practice of soilless tomato production can be made possible during irrigation, where fertilisers are added to the irrigation water in a form of solution and administered. These trace elements are selected depending on the specific postharvest quality traits needed in the fruits. Nutrient balance is crucial for maintaining optimal fruit texture and size: fruits from nitrogen deficient trees are usually smaller with firmer texture, while excess nitrogen leads to rapid loss of firmness and decreased storability. Potassium deficiency also leads to textural changes resulting in small, poorly coloured fruit that may not ripen, leaving fruit hard and inedible. A lack of boron can result in fruits with a mealy texture [62–64].

*Pest and Disease Management:* Pathogens and insects have very negative effects on quality of harvested produce. The effect of insect is more pronounced on grains but can also cause a lot of damages in fruits and vegetables. Nematodes cause various injuries to fruits and vegetables and continue the deterioration during storage. Parasites are therefore seen to be important in damage to farm produce as well as food

#### *Pre-Harvest and Postharvest Factors Affecting Quality and Shelf Life of Harvested Produce DOI: http://dx.doi.org/10.5772/intechopen.111649*

preservation. In the case of insects, produce attacked by them in agriculture may consume over 50% of the harvest. Insects at times lay eggs in the produce, making it almost impossible to eliminate all insects pest in the produce. Parasites like nematodes and amoeba may infect the produce, and the same is true when produce comes in contact with water; this is very common in Africa. Rodents contaminate food with their urine and droppings. They also produce large litter, for example, two rats can give up to 30,000 litres per year. Through their contamination, they spread diseases like salmonellosis, plague and typhoid fever. Various efforts to control the detrimental effects of these organisms have resulted in great hazard to human health due to misuse of the chemicals [65].

*Weed management:* Failure to control weeds will result in a lot of damage to crop quantity and quality. Weeds harbour diseases and pests that easily infest crops both on the field and in the store. Weeds also contaminate harvested produce by mixing with the seeds [66].

*Presence of heavy metals:* The site for crop production must not be just any site or dump site which is loaded with heavy metals. Appropriate soil tests should be done to ascertain the soil condition because some crops absorb heavy metals, which are easily assimilated by human system [66–69].

*Harvesting methods and time:* The time of the day at which harvesting is done must be considered to avoid excessive field heat, which can cause rapid deterioration of the harvested produce. Loss is also caused by improper harvesting methods such as rough handling, untimely harvesting, lack of appropriate and poorly-designed harvesting tools, equipment, and harvesting containers [70].

*Method of Processing:* Processing can decrease phenolic antioxidants [71]. Anthocyanin losses in processed berries are reduced by blanching, indicating enzymatic degradation [71]. A study conducted comparing manually tearing lettuce into strips to shredding with a sharp knife showed that the retention of ascorbate in lettuce sliced by a machine was 25–63% lower than in lettuce shredded by manual tearing [72]. Effects of slicing and shredding radishes on quality during storage at 1, 5, and 10°C were determined [73]; on the 10th day, intact radishes stored at 1°C had the lowest respiration rate, while sliced radishes stored at 10°C had the highest. Shredded radishes showed the most undesirably low levels soluble solids, higher weight loss, ascorbic acid, and lightness as compared to intact or sliced radishes [74].

## **4. Postharvest factors**

Harvested produce are living tissues and subject to continual changes after harvest. Such changes cannot be stopped but can be controlled within certain limits by using various postharvest procedures. Postharvest factors that affect quality of harvested produce include the following: temperature is the most important tool to extend shelf life and maintain quality of harvested produce [75]. Delays between harvesting and cooling or processing can result in direct loss due to water loss and decay; indirect losses such as off-flavour and deterioration in nutritional quality can also occur. For instance, the temperature range and the extent of vitamin C loss depended on the type of citrus fruit. In general, the extent of loss in ascorbic acid (AA) content in response to elevated temperature was greater in vegetables than in acidic fruits such as citrus. Ascorbic acid is more stable under acidic conditions [76]. Reported that retention of vitamin C ranged from 56 to 98% for six broccoli cultivars stored at 2°C for 3 weeks.

*Ethylene management:* Ethylene (C2H4) is an odourless and colourless two-carbon natural plant hormone which is triggered at maturity in climacteric fruits. It is also known as the 'natural ageing, death or ripening hormone', it is active at small traces and its accumulation can led to fruit decay and waste during postharvest stage of harvested produce. It is regulated in various physiological processes of plant growth, germination, development, ripening, maturity and senescence. It also plays a major role in the abscission of plant organs. Several strategies of crop management, coordination of postharvest and pre-harvest factors and various techniques of plant breeding have been investigated to understand ethylene regulation pathways, biochemical and physiological processes in extending produce shelf life and improve the postharvest quality of harvested produce [77]. Some fruits are either ethylene producers or absorbers. Fruits such as apples, bananas, melons, pears and peaches are ethylene producers, while broccoli, cabbage, and cauliflower are ethylene sensitive. The respiration rate of non-climacteric crops is not influenced by the presence ethylene. Examples of non-climacteric produce are leafy vegetables, watermelon, strawberries and grapes. Non-climacteric crops will not respond to ripening with ethylene gas. Exposure of climacteric fruits to ethylene will advance the onset of an irreversible rise in respiration rate and rapid ripening. Appropriate packaging can delay the onset of climacteric and prolong shelf life of fruits by reducing ethylene production and sensitivity [28]. Ethylene production rates is influenced by type of produce, and it increases with maturity at harvest, physical injuries, disease incidence, increased temperature up to 30°C and water stress [30]. The response of various types of crops to ethylene is shown in **Table 3**.

*Chemical Treatments:* Calcium dips may be used to reduce physiological disorders and maintain firmness in apples and cherries. Dehydrated pineapples and guava pretreated with cysteine hydrochloride had increased vitamin C retention and reduced colour change during storage [76, 78].

*Irradiation:* Ionising radiation may be used for sprout inhibition, insect control or delay of ripening of certain fruits and vegetables. Irradiation of horticultural crops at relatively low doses of 75–100 krad irreversibly inhibited the sprouting of potatoes regardless of storage temperature. Losses in vitamin C were lower in potato irradiated for sprout control and subsequently stored at 15°C than in non-irradiated tubers stored at 2–4°C 78].


#### **Table 3.**

*Classification of crop according to ethylene production.*

#### *Pre-Harvest and Postharvest Factors Affecting Quality and Shelf Life of Harvested Produce DOI: http://dx.doi.org/10.5772/intechopen.111649*

*Respiration:* The respiration rate in harvested produce will influence its metabolic activities. High temperatures can hasten the rate of respiration and CO2 production in harvested produce. CO2 production in stored climacteric products like tomatoes can trigger ethylene production, depending on other factors like O2 or CO2 levels, exposure time, and ripening stage [79].

*Relative Humidity:* Moisture loss from harvested produce is predominantly caused by the amount of moisture present in the air expressed as relative humidity [80]. Harvested fruits and vegetables maintain their nutritional quality, appearance, weight and flavour at very high relative humidity. On the contrary, this is adverse for grain crops such as maize, millet, wheat, rice, beans and soybean. Harvested fruits shrivel with little percentage moisture loss while grain crops require low moisture content for optimum storage conditions after harvest. The optimal values of relative humidity to maintain quality of mature green tomatoes are within the range of 85–95% (v/v) and 90–95% (v/v) for firmer ripe fruits [81].

*Physical Handling:* The handling of produce from the moment of detachment from the parent plant, packing from the farm gate to the market, and then the final consumption of produce are significantly associated with mechanical injuries such as bruising, scarring, scuffing, cutting or puncturing. Some of these mechanical injuries may result from careless handling, the use of inappropriate harvesting containers, inappropriate vehicles, careless loading and unloading and packaging materials. According to Miller [82], the consequences of these mechanical injuries are cumulative, leading to a total breakdown of the cell structure accompanied by unwanted metabolic activities such as increased ethylene production, accelerated respiration rates, and ripening, resulting in either reduced shelf life or poor quality [83]. It is, therefore, important to handle harvested produce with care during harvest and postharvest activities to minimise mechanical injuries to avoid losses.

*Gases:* The combination of different gases in a storage environment is very important in extending the shelf life of harvested produce. The optimal ambient condition required to inhibit senescence in matured harvested produce is very low supply of oxygen [84–86]. Carbon monoxide (CO) has been investigated as a gas to speed up ripening, and it is therefore necessary to balance the carbon monoxide with low oxygen to delay senescence in harvested produce [86].

### **5. Conclusion**

Huge amount of crops are being produced annually, but most is lost at various stages of handling due to pre-harvest and postharvest factors affecting quality and shelf life of harvested produce. Every unit of produce preserved converts to added unit available for productive utilisation and food security. The use of any postharvest method or handling practices can only maintain quality. Understanding and controlling the various roles of pre-harvest factors like fertiliser application, pruning, maturity stage, cultivar selection, and irrigation can play major role in improving quality of harvested produce and prolonging their shelf life after harvest. Using best postharvest handling practices or factors such as optimum temperature, right relative humidity, right gases in storage and the best physical handling procedures to maintain the quality after harvest is also critical. Postharvest factors alone cannot maintain quality but the pre-harvest factors during production are also important. Until both factors are managed properly, quality loss will still be a major challenge in maintaining quality and prolonging shelf life of harvested produce.

*New Advances in Postharvest Technology*
