How Does Bruise Susceptibility in Fresh Produce Impact Quality and Harvest Timing?

• Bruise susceptibility varies based on the species, cultivar, and physical and physiological properties of fresh produce.
• The critical bruising threshold estimates the bruise susceptibility of fruits at different firmness.
• A critical bruising threshold has been used to develop a harvest maturity index that identifies the minimum firmness (or maximum maturity) for harvesting stone fruits.

Bruising is the leading type of mechanical damage that occurs from the preharvest to the retail stages, leading to quality loss and food safety issues. It is one of the critical quality parameters that guide customers’ purchasing choices for fresh fruit. Hence, bruising is used to inform several key decisions in the fresh produce supply chain. Find out how bruise measurements are shaping fresh produce quality control decisions.

Bruising Impacts

Approximately 30–40% of fresh produce is affected by mechanical damage, including bruising, between the farm gate and the market, resulting in significant economic losses for the entire supply chain. Avoiding or limiting bruising can improve profits and reduce food loss.

Bruising is damage to the fruit tissue due to external force without skin rupture, and the impact is not immediately visible. Bruising can cause internal browning and alter various physiological processes—the respiration of the bruised tissue increases, leading to higher ethylene production and quicker ripening and senescence. Bruises can lead to rapid and significant moisture loss, causing the fruit to shrivel and reducing its weight. Bruised areas are also more susceptible to microbial spoilage, making the fruit unsafe to consume. Bruised fresh produce is also more prone to postharvest decay and rots than undamaged produce.

Bruising also degrades fresh produce quality. The internal changes can affect the firmness, sugar, and acidity content, and the internal browning soon spreads to blemish the skin, spoiling the fruit’s appearance.

Dropping from height, compaction, and rough handling by machines during harvest, sorting, packing, transport, and storage can cause bruising.

Fresh produce supply chains strive to control these factors to minimize the impact of bruising.

Bruising Susceptibility

All fruits and vegetables can be bruised, but some are more prone to damage.

Bruise susceptibility is the ease with which fresh produce bruises. Some factors make fresh produce more susceptible to bruising. These are species, cultivar, soft skin, harvest maturity, and ripeness. However, it remains unclear which of these factors contributes most to bruise susceptibility. The physical and physiological conditions that determine bruise susceptibility can be assessed by measuring mechanical properties.

Postharvest storage duration, high temperatures, and humidity can exacerbate bruising impacts (see Figure 1).

Knowing the bruise susceptibility or resistance of fresh produce is crucial in developing strategies to overcome its effects.

Figure 1:  “Different levels of bruising in avocado,” Opara  & Pathar (2014). (Image credits: https://d1wqtxts1xzle7.cloudfront.net/35491084/dx.doi.org/10.1016/j.postharvbio.2013.12.009)

Bruising Threshold

The point when fresh produce starts to show bruising symptoms is called the bruise threshold. If the bruise threshold is exceeded due to the application of mechanical load, a bruise is formed. The quantity of mechanical energy that fresh produce absorbs during compression, impact, or vibration determines the severity of bruising.

Scientists have established that two physical properties of the impact determine the severity of bruising: peak acceleration (or maximum g) and velocity change (m s−1), representing the area impacted by the acceleration.

In the 1990s, a device called ‘artificial fruit,’ also known as an instrumental sphere (IS) or impact recording device (IRD), recorded the magnitude of acceleration, velocity changes, and recording time, which ranged from seconds to hours. The device is designed to mimic the shape, size, weight, and appearance of each type of fresh produce. The bruise threshold of several fresh produce items, such as apples, oranges, onions, potatoes, avocados, kiwifruits, and even berries, has been recorded using artificial fruit against different surfaces from varying drop heights.

Bruise threshold values of species and cultivars can help us assess the effects of bruising and have various applications.

Critical Bruising Threshold

The critical bruising threshold is calculated by measuring the susceptibility to bruising at various fruit firmness levels. It is expressed as acceleration G.

Crisosto (2023) used the critical bruising threshold to determine the maximum maturity index and establish the optimal harvest time. Harvest is one of the essential stages where decisions can reduce bruising. Fruits and vegetables picked before they are very ripe or in advanced stages of maturity will be firmer and suffer less bruising during harvest and in postharvest stages. However, care must be taken to ensure that the fruits are not immature; otherwise, they will not ripen properly.

Crisosto utilized critical bruising thresholds to determine the minimum firmness and the corresponding soluble sugar content levels at which bruising occurs. Since firmness decreases with increasing maturity and associated sweetness, critical bruising thresholds help identify the maximum harvest maturity or the point at which fruits can be harvested late, thereby ensuring optimal quality that meets consumer satisfaction. A harvest maturity index identifying optimal firmness and soluble sugar content levels based on bruising thresholds can improve the fruit quality of the harvest.

Some points on the fruits are more susceptible to damage than others. So, the minimum firmness must be measured at the weakest point of the fruit.

The critical bruising threshold varies for different fruits and cultivars. Plums have more resistance to bruising than yellow flesh peach and nectarine, and can be harvested at later stages of fruit maturity.

Other Bruise-Based Indices

Other maturity indices use bruised portions of fruits to quantify the intensity of damage. In these cases, bruise impacts can also be measured by manually estimating the injured area or volume,  imaging the bruised tissue, or through non-destructive measurement and analysis by near-infrared (NIR) spectroscopy. Felix Instruments Applied Food Science offers NIR-based quality meters that can measure internal and external color changes to detect bruising and discoloration.

Besides adjusting harvest time, bruise detection and measurement are crucial for fruit grading and the elimination of damaged produce, thereby improving quality.

Find out more about Felix Instruments Applied Food Science quality meters for estimating color and SSC levels to monitor maturity and bruising impacts during research and in supply chains.

Sources

Crisosto, C. H., Slaughter, D., Garner, D., & Boyd, J. (2001). Stone fruit critical bruising thresholds. Journal of the American Pomological Society, 55(2), 76.

Crisosto, C. H. (2023). Establishing a Consumer Quality Index for Fresh Plums (Prunus salicina Lindell). Horticulturae, 9(6), 682. https://doi.org/10.3390/horticulturae9060682

Hussein, Z., Fawole, O. A., & Opara, U. L. (2020). Harvest and postharvest factors affecting bruise damage of fresh fruits. Horticultural Plant Journal, 6(1), 1-13. https://doi.org/10.1016/j.hpj.2019.07.006

Komarnicki, P., Stopa, R., Szyjewicz, D., & Młotek, M. (2016). Evaluation of bruise resistance of pears to impact load. Postharvest Biology and Technology, 114, 36-44. https://doi.org/10.1016/j.postharvbio.2015.11.017

Li, Z., & Thomas, C. (2014). Quantitative evaluation of mechanical damage to fresh fruits. Trends in Food Science & Technology, 35(2), 138-150.

Opara, U. L., & Pathare, P. B. (2014). Bruise damage measurement and analysis of fresh horticultural produce—A review. Postharvest Biology and Technology, 91, 9-24.

Opara, U. L., & Hussein, Z. (2024). Factors affecting bruise damage susceptibility of fresh produce. In Mechanical Damage in Fresh Horticultural Produce: Measurement, Analysis and Control (pp. 21-44). Singapore: Springer Nature Singapore.

Öztekin, Y. B., & Güngör, B. (2020). Determining impact bruising thresholds of peaches using electronic fruit. Scientia Horticulturae, 262, 109046.

Pathare, P. B., & Opara, U. L. (2024). Importance of Bruise Assessment and Control in Fresh Produce Industry. In Mechanical Damage in Fresh Horticultural Produce: Measurement, Analysis and Control (pp. 337-350). Singapore: Springer Nature Singapore.

Ruiz-Altisent, M., Moreda, G.P. (2011). Fruits, Mechanical Properties and Bruise Susceptibility. In: Gliński, J., Horabik, J., Lipiec, J. (eds) Encyclopedia of Agrophysics. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-3585-1_63