Role Of SSC, Acidity, And Ethylene In Determining Fruit Maturity, Quality, And Storage Life In Horticultural Crops

How SSC, acidity, and SSC/TA ratio are used in determining fruit maturity for harvesting, determining quality and taste of horticultural produce?

1. How SSC, acidity, and SSC/acid ratio are used in determining fruit maturity for harvesting, determining quality and taste of horticultural produce? Cite two examples?

2. How SSC, acidity, and SSC/TA ratio used in meeting export quality standards in fresh produce with examples?

3. Role of harvest maturity in determining storage life and quality in different horticultural crops with examples

4. Role of harvest maturity in determining taste of fresh produce, cite examples

5. Implications of ethylene in fruit ripening and quality in different horticultural crops with examples

6. Relationship between ethylene and storage life of fresh produce, cite examples?

Soluble Solid Content (SSC), Titratable Acidity (TA) and SSC/TA ratio act as maturity indices, and are related to senescent phase of the plant ontogeny. It comprises of a series of irreversible events which ultimately result in the breakdown and death of the plant tissues and organs. As these events are irreversible therefore it is imperative to estimate the quality of produce as per the standards pertaining to these events, as these events eventually leave the produce spoiled and unfit for consumption by consumers. The indices of SSC and TA are used for chemical measurement (Dhatt & Mahajan, 2007). The soluble solid content of the fruits and vegetables comprises of sugars, acids, vitamins, proteins, pigments, phenolics, minerals, and proteins, and thus are indicative of the sugar content. Therefore, this parameter is used to determine the sweetness of the fresh horticultural produce. It is measured using refractometer, and the fruits with higher SSC values find higher acceptance amongst consumers, as these indicate to higher sweetness.  However, SSC does not prove to be a good indicator in case of blueberries, strawberries, and other less pigmented fruits. Thus in such cases, SSC:TA ratios prove to better measures, as these are not static and change with stages of fruit maturation and ripening. Therefore, these prove to be better measures of maturity and quality of the food, For example, in case of mangoes, the flesh acid concentration is found to be greater in younger fruits and it continues to decline with the development of the fruits. Whereas on the other hand the sugar content increase, hence the SSC increase but TA decreases, and overall ratio increases (Magwaza & Opara, 2015).

The three indices of SSC, TA and SSC:TA are known to act as important attributes for determining the quality of fruit at harvest. These indices are known to affect the taste and flavour of fruits, thus serve as important parameters in determining the standards for export. These quality indices also find relationship with the nutritive value of the fruits, and the right nutritive balance is essential to maintain the quality of fruits. Also, the produce needs to be at an appropriate stage of harvest so as to allow safe export, and the reception of undamaged goods. As these indices change with the different stages of development, these help in determining the quality and maturity of the produce being exported. Hence there are certain parameters which govern the export. For example, the New Zealand mandarins having the SSC: TA ratio below 10 cannot be exported to Japan as the acid proportion is too high (Brummell, 2014). The general acceptable level of SSC for export of kiwi fruit in New Zealand in 6.2%, whereas in California the acceptable level is 6.5%. In USA on the other hand the SSC levels of up to 15% have been recommended, and the rapid increase in SSC and softening act as notable characteristics for maturity of kiwi (Rees, Farrell, & Orchard, 2012).

How SSC, acidity, and SSC/TA ratio used in meeting export quality standards in fresh produce with examples?

Harvest maturity plays an important role in determining the storage life and quality of different horticultural crops. As the fruits and vegetables mature the biochemical alteration result in changes in the chemical components. For example the starch levels initially rise followed by a decrement, which is accompanied with a rise in soluble solid content. Further the acid levels also decrease which result in increase in perceived sweetness of the produce, as the sugar/acid ratio increases. Therefore, harvest maturity plays the highest importance in determining the post harvest life and quality of the produce. The fruits need to be picked at such a stage so that they are least susceptible to grater shrivelling and mechanical damage. Also, they should be of inferior quality, so that by the time they reach the consumer they are at their peak quality. But caution needs to be practiced as harvesting at too immature stage could lead to underdevelopment of characteristics.

Hence, the stage at which the fruit should be harvested is crucial for subsequent storage, quality, and marketable life. The stage of maturity of the fruit impacts the storage potential, and also the spoilage of fruits due to a number of storage disorders. Also, the stage at which the fruit is to be harvested, is also determined by the nature of the fruit, whether it is climacteric and non-climacteric. For example the climacteric fruits such as mango, banana, apple, kiwi, and others need to be subjected to ripening treatment before retailing. This treatment allows for uniform ripening of the fruits, and their availability could be managed as per the market demand. However, the non-climacteric fruits on the other hand, are harvested when they have developed appropriate ripening when attached to mother plant. Here the ripening treatment is not given before retailing (El-Ramady, Domokos-Szabolcsy, Abdalla, Taha, & Fári, 2015).

Maturity impacts the taste of the produce as well. For example the juice content of many fruits tends to increase as the fruit continues to mature on trees. The volume of the juice contained in the fruits, is related to the original mass of the juice contained in the fruit, and is hence proportional to the level of maturity. Furthermore, as the climacteric fruits continue to mature, the carbohydrate accumulates in the form of starch, which is broken down into sugar as the fruit ripens. Whereas in the non-climacteric fruits the sugar content is accumulated at the time of maturation. Hence the difference in the nature of harvest maturity determines the taste of the fresh produce. If the fruit is harvested too early then it results in poor flavour potential, and also makes the fruit highly susceptible to physiological disorders , water loss, and abrasion Also, on the other hand if the fruit is left for too long and harvested too late then its ability to ripen gets compromised. This further makes the fruit highly susceptible to decay, off-flavour profile, and bruising (Ahmad & Siddiqui, 2015).

Role of harvest maturity in determining storage life and quality in different horticultural crops with examples

Even after the fruits and vegetables have been harvested, they still comprise of living tissues. These living tissues continue to respire and release biochemical compounds during their post-harvest life.  Ethylene is one such compound produced naturally by plants, and acts as a regulator of plant growth. It is a colourless gas which is known to trigger ripening process by inducing changes in texture, colour and tissue quality thereby impacting the colour and quality of the produce. For optimal quality of produce ethylene is required in optimum concentrations, and inadvertent exposure to ethylene could result in loss of quality of the produce. The climacteric crops produce large quantities of ethylene, and thus exhibit the capability of ripening in the post harvest period. The fruits such as banana, peaches, apples and others, therefore tend to get sweeter and softer post harvest. The non climacteric produce such as the leafy vegetables do not ripen after harvesting as these produce very low amounts of ethylene (Silva, 2010). The rotting and softening in such crops is brought about due to external factors of loss of moisture, decay, and deterioration of tissues. The different types of horticulture produce is impacted differently by ethylene, such as yellowing or loss of green color in cucumber, kale, broccoli; discoloration and deterioration of flavour in sweet potatoes; increased ripening and softening of green tomatoes; development of a bitter flavour profile in carrots and parsnips; browning of pulp of eggplant etc (Mahajan, Caleb, Singh, Watkins, & Geyer, 2014).

Explain relationship between ethylene and storage life of fresh produce comprehensively with clear and meaningful examples.

As ethylene is involved in stimulation and regulation of the different processes which result in ripening of mostly the climacteric fruits, therefore it has serious implications on the storage life of the fresh produce as well. It is highly important to block the effect of the respective plant hormone, so as to avoid rapid spoilage of the produce due to rapid ripening. Ethylene tends to increase the respiratory activity of most of the fruits and vegetables, which tends to impact their physical and chemical characteristics (Subramaniam & Wareing, 2016). Therefore, by controlling ethylene gas in the storage room allows for the preservation of quality and freshness, and extends the life cycle of the produce. This further allows the maintenance and storage of the produce for longer times. Correspondingly, the rate at which ethylene is produced by the produce also depends on conditions of temperature and concentration of carbon dioxide and oxygen. Oxygen and carbon dioxide concentrations tend to play role in biosynthesis and action of ethylene. Hence the storage life of the produce needs to be carefully balanced with respect to the different factors which impact ethylene production, and the quantity of ethylene produced by the specific produce. Therefore it has been recommended to remove ethylene from storage rooms to avoid the development of undesirable disorders (Fragoso & Mujica-Paz, 2016).

References:

Ahmad, M. S., & Siddiqui, M. W. (2015). Postharvest quality assurance of fruits: Practical approaches for developing countries. Springer.

Brummell, D. A. (2014). Fruit growth, ripening and post-harvest physiology. Retrieved March 28, 2018, from https://plantsinaction.science.uq.edu.au/book/export/html/70

Dhatt, A. S., & Mahajan, B. V. C. (2007). Horticulture post harvest technology harvesting, handling and storage of horticultural crops. Ludhiana.

El-Ramady, H. R., Domokos-Szabolcsy, É., Abdalla, N. A., Taha, H. S., & Fári, M. (2015). Postharvest management of fruits and vegetables storage. Sustainable Agriculture Reviews, 65–152.

Fragoso, A. V., & Mujica-Paz, H. (2016). Controlled atmosphere storage: effect on fruit and vegetables. In Encyclopedia of food and health (pp. 308–311). Academic Foundation.

Magwaza, L. S., & Opara, U. L. (2015). Analytical methods for determination of sugars and sweetness of horticultural products—A review. Scientia Horticulturae, 184, 179–192.

Mahajan, P. V., Caleb, O. J., Singh, Z., Watkins, C. B., & Geyer, M. (2014). Postharvest treatments of fresh produce. Phil. Trans. R. Soc. A, 372, 20130309.

Rees, D., Farrell, G., & Orchard, J. (2012). Crop post-harvest: Science and technology, volume 3: perishables. John Wiley & Sons.

Silva, E. (2010). Respiration and ethylene and their relationship to postharvest handling. Retrieved March 28, 2018, from https://articles.extension.org/pages/18354/respiration-and-ethylene-and-their-relationship-to-postharvest-handling

Subramaniam, P., & Wareing, P. (2016). The stability and shelf life of food. In The stability and shelf life of food (p. 612). Woodhead Publishing.