How to Improve Post-harvest Quality in Fresh Produce

• Factors affecting post-harvest quality are determined by harvest time, method, and fresh produce maturity.
• Subsequent postharvest handling during precooling, sorting, grading, packaging, storage, and transport conditions will also influence fresh produce quality and marketing time.
• Significant differences exist in postharvest technology between developing and developed countries.

Fresh produce is highly perishable and suffers from physical injury, microbial spoilage, water loss, physiological disorders, and senescence in the post-harvest quality check stages. Appropriate handling and technology can somewhat slow unfavorable postharvest changes to increase shelf life, marketing time, and quality to improve food security. The factors that the supply chain must consider are discussed in this article.

Maturity Stage and Its Impact on Post-harvest Quality

Maturity at harvest influences quality and also determines postharvest handling conditions. Fresh produce must be harvested at the appropriate physiological and horticultural maturity, which varies with crop and varieties, storage and transport time, and intended end use.

Harvest Time and Method

The harvest method should be chosen depending on the fruits. Rough handling can cause bruising and physical injury, encouraging microbe entry, spoilage, and rotting. Three standard harvest methods are picking by hand, using secateurs/clippers/ scissors, or specially designed harvesters with precision technology.

Harvesting is done in the morning before 10 am when fresh produce has more water content to retain quality longer, avoid high-temperature damage, and ensure faster precooling.

Precooling

Cooling immediately after harvest removes field heat from fresh produce that has higher than ambient temperature due to exposure to direct sun. Rapid cooling to the optimum storage conditions is a must for almost all fruits, flowers, and some vegetables to slow down deterioration, especially if transport to cold storage requires more than a few hours. Precooling, a critical step in maintaining post-harvest quality, reduces the rate of fruit respiration and other physiological processes.

The precooling method depends on the crop and cost-to-benefit considerations and can be forced air, hydrocooling, vacuum and water spray, packaging ice, room cooling, and transport cooling. Precooling is a compulsory step in developed countries.

Sorting and Grading

Fresh produce sorting and grading is conducted several times in the supply chain, but at least once in the farmers’ field or packing house, to remove defective items and prevent ethylene-triggered ripening and senescence.

Fresh produce is sorted according to their maturity in different lots to ensure uniform ripening and quality of products. Producers also allocate lots to appropriate postharvest pathways like retailing, processing, or storage.

Producers grade fresh produce based on size, shape, color, and extent of defects. The grading system can be simple, manual, or done by machines fitted with quality monitoring sensors.

Packaging and Packaging Materials

Fresh produce is fragile and needs protection and proper storage conditions. Packing methods and packaging materials can vary from simple to active modified atmosphere packaging to have the appropriate mix of oxygen, carbon dioxide, etc.

Individual and lot packages must protect fruits from bruising, compression, and damage. Stacking should use separators and trays to avoid damage to fruit in the upper layer.

Table 1: CA storage potential at optimum temperatures and RH for fresh produce, Gross et al. 2016. (Credits: https://www.ars.usda.gov/arsuserfiles/oc/np/commercialstorage/commercialstorage.pdf)

Storage Type and Conditions

Fresh produce must be stored at optimal temperatures and relative humidity (RH) to reduce respiration, transpiration, and ethylene production rates.

Developing countries rely on natural cold air and more straightforward techniques, and developed countries use controlled atmosphere (CA) storage facilities to extend storage for months, see Table 1.

CA storage conditions depend on the fresh produce as discussed below:

• Cool conditions of 0-2^oC and 85-98% RH for most greens, vegetables, melons, and temperate fruits.
• Chill-sensitive citrus, Mediterranean, and some tropical fruits (avocado, guava, custard apples) require 7-10^oC and RH of 85-95%.
• The highest temperature group of tropical fruits and watermelons needs 13 to 18^oC and 85-95% RH.

Gas levels of oxygen, carbon dioxide, and ethylene and their combination are crucial and depend on the crop.

Transportation and Road Conditions

Transport distance and mode are crucial for fresh produce quality.

Developing countries’ road networks are inadequate for transport to local and export markets. Also, road conditions cause vibrations and physical injury, and sun exposure causes heat damage.

Developed countries use refrigerated trucks for road transport or cold storage containers for marine transport, where suppliers maintain optimal temperature and RH. However, the last mile transport, where fresh produce with varying temperature requirements is transported together, results in heat damage or chill injury for many crops.

Monitoring Postharvest Crops

In all steps, from measuring maturity, sorting, grading, and monitoring during storage, transport, and retailing, it is essential to monitor external and internal quality parameters. Precision instruments based on near-infrared spectroscopy, which are portable or fixed as inline and online sensors, can provide accurate real-time quality estimates to guide stakeholders.

Felix Instruments Applied Food Science’s portable F-750 Produce Quality Meter and the F-751 series measure dry matter, total soluble sugars, titrable acidity, internal and external color, and other traits. The device is simple, user-friendly, and suitable for use in the entire supply chain.

Sources

Ahmad, M.S., & Siddiqui, M.W. (2015). Factors Affecting Postharvest Quality of Fresh Fruits. In: Postharvest Quality Assurance of Fruits. Springer, Cham. https://doi.org/10.1007/978-3-319-21197-8_2

Arah, I.K., Amaglo, H., Kumah, E.K., & Ofori, H. (2015). “Preharvest and Postharvest Factors Affecting the Quality and Shelf Life of Harvested Tomatoes: A Mini Review”, International Journal of Agronomy, vol. 2015. https://doi.org/10.1155/2015/478041

Bekele. D. (2018). Review on Factors Affecting Postharvest Quality of Fruits. J Plant Sci Res. 5(2): 180. JPSR-2349-2805-5-180.html

Benedicta Adewoyin, O. (2023). Pre-Harvest and Postharvest Factors Affecting Quality and Shelf Life of Harvested Produce. IntechOpen. doi: 10.5772/intechopen.111649

Elik, A., Yanık, D.K., Istanbullu, Y., Guzelsoy, N., Yavuz, A., & Göğüş, F. (2019). Strategies to Reduce Postharvest Losses for Fruits and Vegetables. International Journal of Scientific and Technological Research.

Lufu, R., Ambaw, A., Opara, U.L. (2020). Water loss of fresh fruit: Influencing pre-harvest, harvest and postharvest factors. Scientia Horticulturae, 272. https://doi.org/10.1016/j.scienta.2020.109519.