Five Significant Research Findings on Fruit Quality Management in 2024

• Fruit quality studies in 2024 aim to future-proof food production against the vagaries of climate change and to meet increasing demand.
• As in previous years, the focus remains on eradicating chemicals to improve food and environment safety.
• Research on AI-based models and tools is a standard theme, but it is diversifying to produce cost-effective versions for wide global adoption to modernize fruit quality estimations.

Yield is no longer the single critical criterion for research or food production. Scientific efforts aim to improve quality to increase nutritional value, marketability, storability, and consumer acceptance. It shows that the challenges in the entire food supply chain are being addressed to increase food production rather than only at the farms. Find out some of the 2024 research findings on improving fruit quality management.

1. Climate Change Influences Citrus Fruit Quality

Figure 1: “Graphical abstract,” Dong et al. (2024). (Image credits: https://doi.org/10.1016/j.scitotenv.2024.171406)

Climate change has far-reaching agricultural and economic impacts. In the last 130 years, Earth’s temperature has risen by about 1 °C. China experienced the warmest decade from 2012 to 2021 in 70 years. The cumulative change in temperature, daylight (photoperiods), and rainfall affect flowering, fruit set, growth, and ripening. These effects can significantly impact citrus fruit development and quality, introducing uncertainties in its supply chain.

Experiment

Dong et al. (2024) conducted a nine-year experiment in Yunnan province, China, to determine the effects of climate change on Bingtang sweet orange fruit development and quality. The study years were divided into two distinct climatic sets. The years 2014-2018, or group A, had lower temperatures, and group B, or 2019-2022, had heavy rainfall followed by less rainfall.

Principal component analysis showed significant differences in fruit quality in the two climatic groups, chiefly in total soluble sugars (TSS) and titrable acidity (TA) content, see Figure 1. Citrus fruit acidity and sugar-to-acid ratio define fruit flavor and consumer acceptance.

The soluble sugars- fructose, sucrose, and glucose- comprise 70% of citrus’s TSS, and the juice vesicles’ primary acids are citric acid, malic acid, and malic acid.

High rainfall over 220 mm and low cumulative temperature of less than 3150°C increased TA by 1.8% in fruits. The decrease in TA was rapid in the initial phases of fruit expansion during 120 to 180 DAF (days after flower), after which it slowed down when rainfall of 300-400 mm, low diurnal temperature range of <10°C, and cumulative temperature less than 2400°C occurred. Higher temperatures and more light are needed to speed up TA decrease.

In contrast, sugars accumulated more during lower rainfall <220 mm, a high diurnal temperature range of >14°C, and a high cumulative temperature over 3150°C. Rainfalls less than 100 mm were necessary for the 1.5% increase in TSS during fruit expansion (195-225 DAF).

The scientists used the over nine years of observed TA and TSS accumulation relationships to climate to develop a regression model to predict future citrus fruit quality.

Moreover, based on their findings, they make suggestions to optimize citrus quality in the changing climate. Since irregular rains affect citrus acidity, they suggest medium soil moisture maintenance during the fruit expansion phase to increase acidity, but not too much, as that would reduce fruit acidity.

Takeaway: Climate changes affect fruit acidity dynamics, especially in the early (0-120 DAF) and expanding (120-180 DAF) phases of fruit development. Growers should provide growing conditions that adjust acidity due to its impact on citrus flavor for quality management.

2. UV-C Radiation And Magnetic Field Effects On Postharvest Fruit Properties

Fungi, common pathogens in fruits, are controlled by synthetic chemicals. Fungicide use is decreasing due to resistance buildup and adverse environmental and health effects. Ultraviolet radiation (UV-C) and magnetic fields (MFs) are increasingly being tried as chemical-free alternatives to control fruit diseases. They directly impact pathogens and leave no residue. Nor do they lead to environmental effects or resistance. However, they have limitations such as lower efficiency, less uniform results, and difficulty in application. Hence, more studies are needed to understand the mechanisms behind their actions and optimize their use.

Figure 2.: “Magnetic field effects on plant physiology.” Gąstoł et al. (2024). (Image credits: https://doi.org/10.3390/agriculture14071167)

Review

Gąstoł et al. (2024) reviewed recent research findings on  MFs and UV-C to see how they impact fruit processes, quality, and storability.

Magnetic fields: MF effects were studied for the entire crop cycle. The magnetic field affects plant metabolism and alters cell membrane permeability. MFs can accelerate seed germination and vegetative and reproductive development. This occurs as MFs increase plant energy and the distribution of biomolecules within cells.

MFs also stimulate enzyme activity, photosynthesis, protein, and carbohydrate synthesis in young plants with low MF induction and water and nutrient uptake in older plants to increase growth and biomass accumulation. MFs reduce oxidative stress in plants, making them resilient and increasing their tolerance to environmental stressors. MFs also enhance plant drought tolerance by increasing calcium and water uptake and decreasing stomatal conductance.

MF reduces plant disease index, improving fruit’s internal and external quality. In postharvest fruits, MFs improve firmness, increase sugar content and acidity, and reduce weight loss to extend shelf-life, see Figure 2.

UV-C radiation: UV-C improves fruit quality by decreasing postharvest fruit diseases and delaying ripening and senescence. UV-C light application combats postharvest infections by destroying microbes on the fruit surface and by triggering the plant defense mechanisms. Moreover, UV-C hormetic doses can improve the accumulation of various phytochemicals like polyphenols to increase fruits’ nutritional and antioxidant value. The advantages of UV-C for fresh produce are its low energy consumption and fast application.

However, UV-C has limitations. It is not effective when used alone, as it can’t penetrate deeper layers beyond 50–300 nm to destroy microbes in the deeper tissues or handle wounds. Hence, it is primarily useful for packaging surface disinfection.

UV-C radiation can be used for fresh produce in combination with other methods like MF, chemicals, heat treatment, gamma radiation, edible nano-coating, and modified atmosphere storage.

Takeaway: Magnetic fields can be used alone or in combination with UV-C radiation to control pathogens without leaving residues. However, more precise and repeatable methods of applications designed for the food industry are needed.

3. Cultivar and Location Affect Organic Apple Fruit Quality

Figure 3.: “Principal component analysis was performed on sugar contents (A, B) and organic acid contents (C, D),” Natic et al. (2024). (Image credits: https://doi.org/10.3390/plants13010147).

Apple consumption is significant and accounts for nearly 39% of temperate fruit cultivation area. Globally, organic apple cultivation uses 2% of land in organic areas. In Norway, the popularity of organic apples is growing, as is the area it covers. However, organic apple quality is known only for fruits from the Ullensvang fjords.

Experiment

Hence, Natic et al. (2024) aimed to study apple quality from organic systems across Norway. Twelve apple cultivars, including commercial varieties Discovery, Red Aroma, Gravenstein, Summerred, Elstar, and Rubinstep, organically grown in three regions, Ullensvang, Telemark, and Viken, were analyzed to determine the growing conditions in different climates.

The scientists wanted to identify cultivars with superior-quality fruits to start a breeding program for organic apples in Norway. Most apple varieties were grown in Ullensvang, followed by Telemark. The popular organic production varieties are Rubinstep, Discovery, and Red Aroma.

The fruit quality parameters analyzed were sugars, organic acids, minerals, sugar alcohols, total phenolic content, and radical scavenging activity (RSA).

The major carbohydrates in Norway apples were fructose, sucrose, glucose, and sorbitol, while the primary organic acids were malic acid and quinic acid, see Figure 3. Kaempferol-3-O-glucoside and chlorogenic acid accounted for 85.5% of polyphenols.

Principal component analysis (PCA) showed that location significantly impacted apple quality.

• Ullensvang apples had the most sugar, organic acids (quinic, galacturonic, and shikimic), polyphenols, and RSA. Galacturonic acid’s high content can be a marker for Ullensvang apples.
• Viken apples had the highest acidity.
• Telemark fruits have the most mineral content and malic acid.

Regardless of location, the cultivar Discovery had the most sugar and polyphenol contents. Discovery “Rose” grown in Telemark had the highest mineral levels (24,094.5 mg/kg dry weight).

Discovery, Red Aroma, and Rubinstep cultivars have the highest polyphenol content, RSA, and TPC values and lower sucrose and glucose levels, making them the healthiest apples and suitable for people with diabetes.

Takeaway: All the apple cultivars in Norway are of good quality and can be used in future breeding programs and promoted in areas with similar climates and soils. Consumers can choose varieties based on the nutrition profile of individual cultivars.

4. Fruit Quality Assessment For Small Agricultural Operations

Fruit quality assessment is a standard practice to ensure food safety, marketability, consumer satisfaction, and lower production costs. Non-destructive, rapid, and precise technologies like spectroscopy, machine learning, and imaging replace traditional slow, laborious manual chemical tests. However, the high costs of many new techniques hinder their use by small producers in resource-limited areas.

Figure 4: “Proposed workflow for fruit classification and quality assessment using deep learning and traditional computer vision,” Zarate and Hernández. (Image credits: https://doi.org/10.3390/app14188243)

Experiment

Zárate & Hernández (2024) wanted to develop a precise and cost-effective method to address these challenges, see Figure 4. The research explores two approaches based on deep learning techniques. One was training a convolutional neural network (CNN) model, and the other was fine-tuning a pretrained MobileNetV2 model through transfer learning. The performances of the two models were tested on a subset of the Fruits-360 data, which covers many fruits and conditions, to simulate small-scale producers’ reality.

The results show that both approaches produced models of high accuracy, but the transfer learning model performed better and had faster convergence, especially with less data availability.

Hence, MobileNetV2 was selected for its efficiency, compact size, and compatibility for devices with limited computational capacity. It is suitable for developing a cost-effective and accessible fruit quality tool for small-scale producers and farmers.

The feature map visualizations highlighting damaged areas in fruits provide insight into the model’s decision-making process and make its results easy to interpret. Testing on two fruits showed the model was useful for diverse fruit types.

However, the model must be trained on more diverse data and use more techniques to provide a robust performance in the real world.

The study did not aim to revolutionize quality testing but focused on practical applications that are potentially suitable for wide adoption in resource-limited regions.

Takeaway: Identifying a machine learning-based model that balances precision and cost helps modernize fruit quality testing by providing efficient and interpretable tools for small-scale producers to increase food security and sustainability.

5. Maintaining Strawberry Fruit Quality to Improve Marketability

Figure 5: “Graphical abstract, Zhang et al. (2024). (Image credits: https://doi.org/10.1016/j.fochx.2024.101252)

Strawberries are perishable in the postharvest stage, being susceptible to mechanical damage, water loss, and diseases, resulting in economic losses for the supply chain. There is a lack of safe, environmentally friendly preservation techniques that do not damage fruit quality to replace chilling and chemical fungicides.

 

Experiment

Zhang et al. (2024) decided to try the γ-aminobutyric acid (GABA), which is naturally produced by plants and animals and is known to maintain health-promoting functions. They tested the effect of postharvest external GABA application on strawberry’s appearance, internal quality, and antioxidant levels during storage to prolong the fruit’s shelf-life. They separated 120 strawberries into four groups and treated them for 15 minutes with 0, 5, 10, and 15 mM GABA solution. Another set of 30 strawberries’ quality was tested on harvest day.

The quality parameters tested were skin color, firmness, weight loss, soluble sugar content, titrable acidity, anthocyanin, total flavonoid content (TFC), and total phenolic content (TPC). The scientists also determined reactive oxygen species (ROS), malondialdehyde (MDA), and antioxidant activities.

The results show that GABA-treated strawberries had more sugar, titrable acidity, anthocyanins, and TFC, whereas the 10 mM GABA results were the best. The 10 mM GABA treatment had significantly less weight loss than the control and more fructose and acids (oxalic and succinic) accumulation.

GABA treatments did not change fruit skin color and firmness.

Treatment with GABA also improved antioxidant activities and reduced oxidative damage. GABA increased DPPH radical scavenging, total anthocyanins, and total flavonoids in strawberries. The 10 mM GABA had the most antioxidant activities, and the 5 mM had less ROS and MDA.

Takeaway: The results show that 10 mM GABA was the best treatment to improve strawberry quality, antioxidant activities, and storability.

Rapid and Precise Quality Measurements

Many studies have used chemical methods to estimate external and internal quality parameters. While these are the standard laboratory methods, scientists also use visible and near-infrared spectroscopy-based tools for precise analysis and estimations of quality in real time. Felix Instruments Applied Science provides several quality meters that are accurate, small, portable, easy to use, and interpret. Research on fruit quality is becoming more complex, and researchers are trying to find the effects of real-world conditions on internal quality. In these cases, modern precision tools can be a valuable asset for scientists in sustainably increasing the production of safe, healthy, high-quality fresh produce.

Check out Felix Instruments’ Quality Meters range for your research.

 

Sources

1. Dong, Z., Chen, M., Srivastava, A. K., Mahmood, U. H., Ishfaq, M., Shi, X., … & Zhang, F. (2024). Climate changes altered the citrus fruit quality: A 9-year case study in China. Science of The Total Environment, 923, 171406.

 

2. Gąstoł, M., & Błaszczyk, U. (2024). Effect of magnetic field and UV-C radiation on postharvest fruit properties. Agriculture, 14(7), 1167.

 

3. Natić, M., Dabić Zagorac, D., Jakanovski, M., Smailagić, A., Čolić, S., Meland, M., & Fotirić Akšić, M. (2024). Fruit Quality Attributes of Organically Grown Norwegian Apples Are Affected by Cultivar and Location. Plants, 13(1), 147.

 

4. Zárate, V., & Hernández, D. C. (2024). Simplified Deep Learning for Accessible Fruit Quality Assessment in Small Agricultural Operations. Applied Sciences, 14(18), 8243.

 

5. Zhang, Y., Lin, B., Tang, G., Chen, Y., Deng, M., Lin, Y., … & Tang, H. (2024). Application of γ-aminobutyric acid improves the postharvest marketability of strawberry by maintaining fruit quality and enhancing antioxidant system. Food Chemistry: X, 21, 101252.