Fresh fava beans, known for their rich nutritional profile and versatility in global cuisines, face a significant challenge: their short shelf life. After harvest, these beans quickly lose quality due to high respiration rates (a process where plants consume stored sugars and oxygen, releasing carbon dioxide and heat), microbial growth (the proliferation of bacteria, molds, and yeasts on the bean surface), and enzymatic browning .

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These factors contribute to annual global waste of approximately 800,000 tons of fava beans. A recent study published in LWT – Food Science and Technology (2025) offers a promising solution by combining two advanced technologies—electron beam irradiation (EBI) and modified atmosphere packaging (MAP).

How Electron Beam Irradiation Preserves Fresh Fava Beans

Fresh fava beans are highly perishable, often deteriorating within days due to their biological and environmental vulnerabilities. Once harvested, they undergo rapid respiration, a metabolic process where stored carbohydrates and oxygen are broken down into energy, carbon dioxide, and water.

This process depletes nutrients and softens the beans’ texture. Additionally, surface microbes like bacteria and molds thrive in the moist environment of freshly harvested beans, accelerating spoilage. Enzymes such as polyphenol oxidase (PPO) and lipoxygenase (LOX) further degrade quality by triggering browning and off-flavors. Traditional preservation methods, such as chemical treatments or refrigeration, have limitations.

Chemicals like sulfur dioxide can leave harmful residues,
while refrigeration alone cannot fully inhibit microbial growth or enzymatic activity.

To address these challenges, researchers turned to electron beam irradiation (EBI) and modified atmosphere packaging (MAP). EBI uses high-energy electrons (generated by accelerators) to sterilize food by disrupting the DNA of microbes, effectively reducing contamination without heat or chemicals.

This process is non-thermal, meaning it preserves the food’s texture and nutritional content. MAP, on the other hand, involves sealing food in packaging with a controlled gas environment—typically low oxygen (O₂) and high carbon dioxide (CO₂)—to slow down respiration and microbial activity.

The gas composition in MAP is critical: low oxygen levels reduce oxidation (a chemical reaction that degrades fats and vitamins), while high carbon dioxide inhibits microbial growth. Together, these methods create a dual defense system: EBI targets microbes directly, while MAP maintains an optimal storage environment.

Key Steps in Testing Fava Bean Preservation Methods

The research team from Qinghai University and Northwest A&F University in China conducted a series of experiments to determine the optimal conditions for preserving fava beans. The process began with selecting the most suitable packaging material. Four types of polyethylene (PE) films were tested:

microporous film (with tiny holes for airflow),
PE 0.02 mm,
PE 0.03 mm, and
PE 0.05 mm.

These films differed in their gas transmission rates (the rate at which gases like oxygen and carbon dioxide pass through the material), influencing how quickly oxygen and carbon dioxide entered or exited the packaging.

For instance, the microporous film allowed 248,000 mL of oxygen per square meter per day, while the thicker PE 0.05 mm film permitted only 2,860 mL.

Furthermore, gas transmission rates are crucial because they determine how well the packaging can maintain a stable internal atmosphere, balancing the beans’ respiration with the need to suppress microbial growth. After identifying the best-performing film, the team tested various EBI doses (0, 0.5, 1.0, 1.5, 2.0, and 2.5 kGy) on fava beans stored in the selected packaging.

Irradiation dose refers to the amount of energy absorbed by the food during treatment, measured in kilograys (kGy). For context, doses below 10 kGy are considered safe and effective for food preservation by regulatory bodies like the FDA and WHO. Over 20 days, the beans were stored at 4°C, and their quality was assessed every four days using a range of metrics.

These included gas composition inside the packaging , microbial counts, color changes , nutrient levels, enzyme activity, and structural integrity observed through scanning electron microscopy (SEM), a technique that magnifies surface structures up to 100,000 times to detect physical damage or microbial colonization.

How Modified Atmosphere Packaging Extends Fava Bean Freshness

The study revealed that the combination of 2.0 kGy EBI and PE 0.03 mm MAP delivered the best results. Beans treated with this method retained their green color, firm texture, and nutritional value for up to 20 days, compared to untreated beans, which began spoiling after just eight days. One of the most critical factors was the gas composition inside the packaging.

The PE 0.03 mm film achieved a stable balance of 9.22% oxygen and 6.15% carbon dioxide by the third day of storage.

This equilibrium slowed the beans’ respiration rate, reducing nutrient loss and delaying aging. Respiration rate is a key indicator of metabolic activity; lower rates mean slower degradation of sugars and proteins.

In contrast, thinner films (e.g., PE 0.02 mm) allowed too much oxygen, accelerating spoilage, while thicker films (e.g., PE 0.05 mm) restricted gas exchange excessively, leading to carbon dioxide buildup and potential tissue damage.

Microbial growth was another major focus. Untreated beans showed aerobic bacteria counts (a measure of bacteria that thrive in oxygen-rich environments) of 2.33 log CFU/g on day zero, rising to 3.53 log CFU/g by day 20.

However, beans irradiated at 2.0 kGy had significantly lower counts, with aerobic bacteria reduced to 1.46 log CFU/g and molds/yeasts to 1.70 log CFU/g. Log CFU/g (colony-forming units per gram) is a logarithmic scale used to quantify microbial populations; a reduction of 1 log CFU/g represents a 90% decrease in microbes.

This reduction is crucial because microbial activity not only causes spoilage but also produces off-flavors and harmful compounds like mycotoxins (toxic substances produced by molds). Nutrient retention was equally impressive.

Chlorophyll, the pigment responsible for the beans’ green color and a marker of freshness, remained at 0.0227 g/kg in irradiated samples, compared to 0.0162 g/kg in untreated beans.
Soluble sugars, which contribute to flavor and sweetness, peaked at 3.3% in treated beans, while untreated beans reached only 2.9%.
Meanwhile, antioxidant activity, measured through DPPH and ABTS⁺ radical scavenging rates (tests that evaluate a food’s ability to neutralize free radicals linked to aging and disease), increased by 27% and 20%, respectively.

Free radicals are unstable molecules that damage cells, and higher scavenging rates indicate better protection against oxidative stress. However, enzyme activity played a dual role in preservation. Beneficial enzymes like peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD)—which neutralize harmful free radicals—showed increased activity in irradiated beans.

For example, SOD activity rose by 30%, helping protect cellular structures from oxidative damage. Conversely, enzymes linked to spoilage, such as polyphenol oxidase (PPO) and lipoxygenase (LOX), were suppressed.

PPO activity dropped by 50%, reducing browning, while LOX activity decreased by 35%, slowing fat oxidation and off-flavor development.

Lipid oxidation is a process where fats break down, producing rancid odors and reducing nutritional quality. Structural integrity, observed through scanning electron microscopy (SEM), provided visual confirmation of these benefits.

However, untreated beans developed cracks and microbial colonies on their surfaces, while irradiated beans maintained smooth, intact cell walls and starch granules. Starch granules are carbohydrate storage units in plants; their preservation is vital for maintaining texture and preventing moisture loss.

Implications for Reducing Food Waste and Improving Safety

The success of this method has far-reaching implications. By extending the shelf life of fava beans from days to weeks, farmers and distributors can reduce post-harvest losses (waste occurring after crops are harvested) significantly. For context, if this technology were adopted globally, it could save approximately 400,000 tons of fava beans annually—enough to feed millions of people.

From a health perspective, the absence of chemical residues makes EBI+MAP a safer alternative to traditional preservatives. Consumers benefit from beans that retain higher levels of antioxidants, compounds that protect cells from damage caused by free radicals.

Antioxidants are linked to reduced risk of chronic diseases like heart disease and cancer. Additionally, the suppression of harmful enzymes like PPO and LOX ensures that the beans not only look and taste fresh but are also free from compounds that could affect digestibility or flavor.

Economically, longer shelf life opens new markets for fava beans. Regions that previously could not export fresh beans due to spoilage risks can now access distant markets, boosting farmers’ incomes and stabilizing prices. For example, countries in Africa and the Mediterranean, where fava beans are a staple crop (a primary food source for a population), could expand their trade networks significantly.

Challenges and Considerations for Real-World Application

While the results are promising, several challenges must be addressed for widespread adoption. The cost of EBI technology is a primary concern. Industrial-scale electron beam accelerators (machines that generate high-energy electrons) can cost between $2 mi ll i o n an d$ 5 million, making them inaccessible for small-scale farmers.

To overcome this, researchers suggest establishing regional irradiation hubs (shared facilities where multiple farmers process crops) or government-funded programs to subsidize costs. However, consumer perception is another hurdle. Despite approvals from organizations like the FDA and WHO, some consumers remain wary of irradiated foods (foods treated with ionizing radiation).

Misconceptions about “radioactive” foods persist, even though EBI does not make food radioactive. Education campaigns emphasizing the safety and benefits of EBI—such as the absence of chemical residues and enhanced food safety—could alleviate these concerns. Clear labeling, such as “Irradiated for Freshness,” might also improve acceptance.

The study also noted that higher irradiation doses (e.g., 2.5 kGy) caused slight browning and texture changes, underscoring the importance of dose precision. The 2.0 kGy dose proved optimal, balancing microbial reduction with quality retention.

However, future research could explore combining EBI with natural antimicrobial agents (substances like clove oil or chitosan that inhibit microbes), to further enhance preservation at lower doses.

Future Directions and Broader Applications

Beyond fava beans, this technology holds potential for other perishable crops (foods that spoil quickly, like berries or leafy greens). For instance, preliminary studies on strawberries and cherry tomatoes have shown that irradiation combined with modified atmospheres extends shelf life by up to 50%.

Leafy greens, which are prone to wilting and microbial contamination, could particularly benefit from reduced respiration rates and microbial suppression. However, the research team highlighted several areas for future exploration.

One priority is testing lower irradiation doses (e.g., 1.5 kGy) to reduce costs while maintaining efficacy.
Another is evaluating the method’s performance in different climates, as humidity and temperature fluctuations could affect gas dynamics (how gases move and interact within the packaging) in MAP.

Furthermore, consumer preference studies are also essential. While the scientific metrics of preservation are clear, understanding how taste, texture, and appearance influence buyer choices will determine commercial success. For example, irradiated beans might need to be marketed as “premium fresh” or “longer-lasting” to appeal to quality-conscious consumers.

Conclusion

Electron beam irradiation (EBI) and modified atmosphere packaging (MAP) extend the shelf life of fava beans to 20 days, preserving their nutrition and sensory qualities.

With improvements like reduced microbial counts, chlorophyll retention, and increased antioxidant activity, this method offers a sustainable solution to food waste and security. Despite challenges, ongoing research and collaboration could revolutionize the preservation of perishable crops.

Power Terms

Electron Beam Irradiation (EBI):
A food preservation method that uses high-energy electrons to treat materials, altering their chemical and physical properties. EBI is a non-thermal, chemical-free technology that kills microbes, delays spoilage, and extends shelf life. In the study, 2.0 kGy EBI reduced harmful substances like malondialdehyde (MDA) and improved antioxidant levels in fava beans. For example, it slowed browning by inhibiting enzymes like polyphenol oxidase (PPO). EBI is widely used in food preservation for items like mushrooms and fruits.

Modified Atmosphere Packaging (MAP):
A technique where food is packaged in a gas-barrier material with adjusted gas levels (e.g., oxygen, carbon dioxide) to slow spoilage. In the study, MAP with 0.03 mm polyethylene (PE) film maintained stable oxygen (O₂) and carbon dioxide (CO₂) levels, reducing fava beans’ respiration rate and water loss. MAP is crucial for preserving freshness in fruits, vegetables, and meats by creating an optimal storage environment.

Malondialdehyde (MDA):
A harmful byproduct of lipid peroxidation (fat breakdown) in cells, indicating oxidative stress. High MDA levels signal cell membrane damage. In the study, EBI treatment lowered MDA content in fava beans, preserving their quality. MDA is measured using absorbance at specific wavelengths (e.g., 532 nm) and calculated with the formula:
*MDA (nmol/g) = 6.45 × (A532 – A600) – 0.56 × A450*.

DPPH Radical Scavenging Rate:
A measure of antioxidant activity, showing how well a substance neutralizes free radicals. DPPH (2,2-Diphenyl-1-picrylhydrazyl) is a stable free radical. Higher scavenging rates mean better antioxidant capacity. In the study, EBI-treated fava beans had higher DPPH scavenging rates (up to 80%) compared to untreated ones. The rate is calculated as:
*(DPPH scavenging rate %) = [(A₀ – A₁) / A₀] × 100*, where A₀ is the control absorbance and A₁ is the sample absorbance.

ABTS⁺ Radical Scavenging Rate:
Another method to assess antioxidant activity using the ABTS⁺ (2,2-Azinobis-(3-ethylbenzothiazoline-6-sulphonate)) radical. Like DPPH, higher values indicate stronger antioxidant effects. EBI increased ABTS⁺ scavenging rates in fava beans, delaying oxidative damage. The formula is:
*(ABTS⁺ scavenging rate %) = [(Aᵢ – Aⱼ) / Aᵢ] × 100*.

Peroxidase (POD):
An enzyme that breaks down hydrogen peroxide (H₂O₂) into water and oxygen, protecting cells from oxidative damage. In the study, EBI boosted POD activity, helping fava beans resist browning and decay. High POD activity is linked to better stress tolerance in plants.

Phenylalanine Ammonia Lyase (PAL):
An enzyme that starts the phenylpropanoid pathway, producing compounds like phenolics to protect plants from stress. EBI-treated fava beans showed higher PAL activity, which delayed aging and maintained quality. PAL activity is measured in units per hour per gram (U/h·g).

Catalase (CAT):
An enzyme that detoxifies hydrogen peroxide into water and oxygen, reducing oxidative stress. CAT activity in fava beans decreased during storage but was higher in EBI-treated samples, slowing quality loss.

Superoxide Dismutase (SOD):
An enzyme that neutralizes harmful superoxide radicals, protecting cells. SOD activity spiked in fava beans under EBI treatment, helping combat oxidative damage. SOD levels are measured in units per gram (U/g).

Lipoxygenase (LOX):
An enzyme that oxidizes fats, leading to off-flavors and cell membrane damage. EBI reduced LOX activity in fava beans, preserving texture and freshness. Lower LOX activity slows lipid peroxidation.

Polyphenol Oxidase (PPO):
An enzyme causing browning by oxidizing phenolic compounds. EBI inhibited PPO activity in fava beans, keeping them green and fresh. PPO activity is measured in units per minute per gram (U/min·g).

Sensory Evaluation:
A quality assessment method where trained panelists score food attributes like color, texture, and taste. In the study, EBI-treated fava beans scored higher (e.g., 3.4/9 for color vs. lower scores in controls), indicating better consumer appeal.

Chromatic Aberration (ΔE):
A measure of color change over time. Higher ΔE values mean more browning. EBI kept ΔE lower in fava beans, maintaining their green color. ΔE is calculated as:
ΔE = √(ΔL)² + (Δa)² + (Δb)², where L, a, and b represent color parameters.

Browning Index (BI):
A numerical value indicating browning severity. Lower BI means less discoloration. EBI reduced BI in fava beans by slowing enzyme activity. BI is calculated using color values:
*BI = [100 × (x – 0.31)] / 0.172*, where x = (a* + 1.75L*) / (5.645L* + a* – 3.012b*).

Cell Membrane Permeability:
A measure of cell damage, where higher permeability means leaky membranes. EBI-treated fava beans had lower permeability, indicating healthier cells. It’s calculated using conductivity measurements:
*Permeability (%) = [(P₁ – P₀) / (P₂ – P₀)] × 100*, where P₀, P₁, and P₂ are conductivities of water, sample, and frozen sample.

Microbial Enumeration:
Counting microbes (e.g., bacteria, mold) to assess food safety. EBI reduced microbial growth in fava beans, with aerobic plate counts dropping by 1.03 log CFU/g. Results are expressed as log colony-forming units per gram (log CFU/g).

Chlorophyll Content:
A pigment critical for photosynthesis; its retention indicates freshness. EBI preserved chlorophyll in fava beans, with treated samples having 40% higher levels. Chlorophyll is calculated using absorbance at 645 nm and 663 nm:
*Chlorophyll (g/kg) = [(20.0 × A645 + 8.02 × A663) × V] / (1000 × W)*, where V is extract volume and W is sample weight.

Soluble Sugar:
Carbohydrates that affect taste and energy metabolism. EBI increased soluble sugar content in fava beans, peaking at 3.3% vs. 2.9% in controls. Measured using a sucrose-based standard curve:
*y = 0.0035x + 0.0874 (R² = 0.9991)*.

Soluble Protein:
Proteins dissolved in water, important for enzymatic activity. EBI maintained higher soluble protein levels in fava beans, averaging 0.87 mg/g vs. 0.81 mg/g in controls. Calculated using a Coomassie Brilliant Blue assay:
*y = 0.002x + 0.4305 (R² = 0.9997)*.

O₂ and CO₂ Content:
Gases in packaging affecting respiration and spoilage. MAP with 0.03 mm PE film stabilized O₂ at ~9.22% and CO₂ at ~6.15%, slowing fava bean aging. Measured using a gas analyzer.

Respiration Rate:
The speed at which plants consume O₂ and release CO₂. High respiration accelerates spoilage. MAP reduced fava beans’ respiration by creating a low-O₂ environment, extending shelf life.

Reactive Oxygen Species (ROS):
Harmful molecules (e.g., free radicals) causing oxidative damage. EBI increased antioxidant enzymes (SOD, CAT) to neutralize ROS, protecting fava bean cells.

Lipid Peroxidation:
The breakdown of fats by ROS, producing MDA. EBI reduced lipid peroxidation in fava beans, preserving membrane integrity and freshness.

Starch Granules:
Energy-storing structures in plants. EBI-treated fava beans had larger, more abundant starch granules, indicating delayed breakdown during storage. Observed via scanning electron microscopy (SEM).

Scanning Electron Microscope (SEM):
A tool to visualize surface structures at high magnification. SEM showed EBI preserved fava beans’ cuticle and stomata, reducing water loss and microbial invasion.

Shelf Life:
The time food remains safe and high-quality. Combining EBI and MAP extended fava beans’ shelf life to 20 days by slowing microbial growth, enzyme activity, and oxidative damage.

Antioxidant Capacity:
The ability to neutralize free radicals. EBI boosted fava beans’ antioxidant capacity via higher DPPH/ABTS⁺ scavenging rates and enzyme activity, delaying spoilage.

Polyethylene (PE) Film:
A gas-barrier packaging material. PE films (0.03 mm thickness) optimized gas exchange in MAP, balancing O₂ and CO₂ to preserve fava beans.

Log CFU/g:
Logarithm of colony-forming units per gram, quantifying microbes. EBI reduced log CFU/g in fava beans, ensuring safety. For example, mold counts dropped from 2.40 to 1.40 log CFU/g.

Respiratory Quotient (RQ):
The ratio of CO₂ produced to O₂ consumed. MAP maintained a stable RQ in fava beans, indicating balanced aerobic respiration and delayed aging.

Stomata:
Pores on plant surfaces regulating gas exchange. SEM showed EBI preserved fava bean stomata structure, preventing moisture loss and microbial entry.

Irradiation Dose (kGy):
Energy absorbed during irradiation. A 2.0 kGy dose optimally preserved fava beans by balancing microbial reduction and quality retention, while higher doses (2.5 kGy) caused damage.

Sulfur Dioxide Preservatives:
Chemicals used to inhibit spoilage. The study compared EBI to traditional methods like sulfur dioxide, noting EBI’s safety and lack of chemical residues.

γ-Irradiation:
A similar preservation method using gamma rays. The study focused on EBI but referenced γ-irradiation’s role in reducing LOX activity in other foods.

Free Radicals:
Unstable molecules damaging cells. Antioxidants in EBI-treated fava beans neutralized free radicals, reducing oxidative stress and extending freshness.

Postharvest Quality:
The condition of crops after harvest. EBI and MAP improved fava beans’ postharvest quality by retaining nutrients, color, and texture during storage.

Thiobarbituric Acid (TBA):
A reagent used to measure MDA levels. In the study, TBA reacted with MDA to form a pink complex, quantified via spectrophotometry.

Gas Transmission Rate:
The speed gases pass through packaging. PE films with low O₂/CO₂ transmission rates (e.g., 4767 mL/m²·day for O₂) created ideal MAP conditions for fava beans.

Water Vapor Transmission Rate:
A measure of packaging’s moisture resistance. PE films with low rates (e.g., 3.67 g/m²·day) reduced water loss in fava beans, maintaining crispness.

Plate Counting Agar (PCA):
A growth medium for bacteria. PCA incubated at 36°C for 48 hours measured aerobic plate counts in fava beans, assessing microbial safety.

Red Bengal Medium (RBM):
A medium for growing molds/yeasts. RBM incubated at 28°C for 96 hours quantified fungal contamination in stored fava beans.

Conductivity Meter:
A device measuring electrical conductivity to assess cell membrane damage. Higher conductivity in untreated fava beans indicated greater leakage and spoilage.

Duncan’s Multiple Range Test:
A statistical method comparing group means. The study used it to confirm significant differences (p < 0.05) between EBI treatments and controls.

SEM Observation:
Microscopic imaging of surface structures. SEM revealed EBI preserved fava beans’ cuticle and starch granules, reducing physical degradation.

Antimicrobial Nanocomposite Films:
Packaging materials with nanoparticles to inhibit microbes. The study compared MAP to such films, highlighting EBI’s standalone efficacy.

Cold Storage:
Preservation at low temperatures (e.g., 4°C). Combined with EBI and MAP, cold storage extended fava beans’ shelf life by slowing metabolic activity.

Oxidative Aging:
Degradation caused by oxygen exposure. EBI delayed oxidative aging in fava beans by enhancing antioxidant defenses and reducing ROS.

Electrostatic Field Treatment:
A non-thermal method inhibiting browning. The study referenced it as an alternative to EBI but focused on irradiation’s superior performance.

Phenylpropanoid Pathway:
A metabolic route producing antioxidants. EBI activated this pathway in fava beans, increasing phenolic compounds and stress resistance.

Respiratory Metabolism:
Cellular processes using O₂ to produce energy. MAP reduced respiratory metabolism in fava beans, conserving nutrients and delaying senescence.

Storage Condition:
Environmental factors (temperature, humidity) affecting preservation. The study used 4°C and 90% humidity with MAP/EBI for optimal fava bean storage.

Chemical Treatments:
Preservatives like chlorine dioxide. The study noted EBI’s advantage over chemicals by avoiding residues and health risks.

Micro-Frozen Treatment:
A physical preservation method. While safer than chemicals, the study found EBI more effective for fava beans due to better enzyme regulation.

β-Glucan/Polyvinyl Alcohol/Clove Film:
An antimicrobial packaging material. The study compared EBI to such films, showing irradiation’s broader impact on quality retention.

Silver Dichromate Dosimeters:
Tools to measure irradiation dose accuracy. Placed on fava beans, they ensured consistent 2.0 kGy EBI application.

Texture Analysis:
Assessing firmness and softness. EBI-treated fava beans scored higher in texture (e.g., 62% less softening), indicating better consumer appeal.

Ultrastructure:
Microscopic cellular details. SEM showed EBI maintained fava beans’ cell walls and starch structures, preventing mushiness.

Postharvest Senescence:
Aging after harvest. EBI delayed senescence in fava beans by reducing ethylene production and oxidative stress.

Consumer Acceptance:
Willingness to buy/eat a product. Higher sensory scores for EBI-treated fava beans suggested greater marketability and consumer preference.

Reference:

Wang, K., Iqrar, I., Yu, J., Shi, Y., Nian, S., Dang, B., & Kou, L. (2025). Effect of electron beam irradiation treatment on preservation of freshly fava bean (Vicia faba L.) in modified atmosphere packaging. *LWT – Food Science and Technology, 218*, 117488. https://doi.org/10.1016/j.lwt.2025.117488

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