Nuts Archieven - VacQPack Group

Peanuts travel long distances and often remain in storage for extended periods. During that time, quality loss is a persistent concern. Rising free fatty acids, flavour deterioration and mould risks are not uncommon in global supply chains. Many companies rely on low-oxygen storage as a solution.

Yet experience shows that quality issues can still occur.

For traders, processors and logistics managers, this creates uncertainty. When and why does hermetic storage protect quality, and when does it fail? In this article, we explore what scientific research reveals about oxygen, humidity and peanut stability, and what this means for bulk storage and transport strategies.

Hermetic storage: promise and complexity

Hermetic storage is designed to limit oxygen availability by using gas-tight packaging systems. Reduced oxygen slows insect development and decreases oxidative reactions. This makes hermetic storage an attractive alternative to chemical fumigation in many bulk applications.

However, peanuts are biologically active seeds with a high oil content. Their quality is shaped not only by oxygen exposure but also by moisture conditions. Hermetic systems create stable atmospheres, yet internal biological processes still respond to humidity levels.

The complexity lies in this interaction. Oxygen reduction can slow degradation, but it cannot compensate for excessive moisture. Understanding this balance is essential for effective quality preservation.

What research reveals about peanuts, oxygen, and humidity

A detailed scientific study titled “Analyses of metabolic activity in peanuts under hermetic storage at different relative humidity levels” examined how peanuts behave under varying storage conditions. The research compared storage in normal air and nitrogen-rich environments across a wide range of water activity levels.

Over nearly three months, the researchers monitored metabolic activity, oxygen consumption, lipid oxidation and free fatty acid development. The results show that oxygen and moisture interact in defining quality stability.

Oxygen drives oxidation — but only when moisture allows it

Peanuts contain high levels of unsaturated fatty acids. These fats are sensitive to oxidation, which directly affects flavour and shelf life. When oxygen is present and moisture levels rise above a critical threshold, oxidative processes accelerate.

Under these conditions, storage can result in:

Increased lipid oxidation
Rapid growth of free fatty acid levels
Decline in sensory quality

The research identified a critical tipping point around a water activity of 0.7. Below this level, peanuts remained relatively stable. Above it, metabolic activity increased rapidly, especially when oxygen was available.

Why nitrogen makes the difference

Replacing oxygen with nitrogen significantly changes the internal storage environment. Nitrogen is inert and does not participate in oxidative reactions. By reducing oxygen availability, nitrogen suppresses the biochemical pathways responsible for lipid oxidation.

The study demonstrated that peanuts stored under nitrogen showed far lower levels of oxidation and free fatty acid formation compared to those stored in air. Nitrogen therefore acts as a stabilising factor, particularly when moisture remains within safe limits.

However, nitrogen is not a universal safeguard. Its effectiveness depends on the surrounding moisture conditions.

Humidity remains the critical control point

While low-oxygen environments reduce oxidative damage, excessive moisture activates other degradation mechanisms. At higher water activity levels, fermentation and microbial activity may occur, even when oxygen is limited.

When moisture exceeds safe thresholds, storage stability declines due to:

Increased metabolic activity
Formation of ethanol and fermentation by-products
Reduced seed viability over time

This confirms a key insight. Oxygen control reduces risk, but moisture ultimately determines long-term stability. Effective storage must therefore manage both parameters simultaneously.

Implications for bulk storage and transport

In practice, peanuts are often transported in permeable packaging materials. During maritime transport, temperature gradients may cause condensation and moisture migration within the cargo. Even properly dried peanuts can experience local increases in humidity.

Hermetic systems with strong barrier properties help stabilise oxygen conditions. However, they must be combined with proper drying and humidity control from the start. Bulk storage strategies should focus on integrated environmental management rather than single-parameter solutions.

For decision-makers, this means viewing storage as a dynamic process. Quality preservation requires monitoring, stable atmospheres and moisture discipline throughout the logistics chain.

Conclusion: controlled atmospheres need controlled moisture

Hermetic storage offers clear benefits for peanut preservation. By limiting oxygen, it reduces lipid oxidation and slows quality deterioration. Scientific research confirms that nitrogen-rich environments significantly improve stability under controlled moisture conditions.

Yet the same research makes one point equally clear. Oxygen reduction alone does not guarantee protection. When moisture exceeds critical levels, degradation processes accelerate despite low-oxygen conditions.

For resilient supply chains, atmosphere control must be combined with strict humidity management. Only by stabilising both oxygen and moisture can long-term peanut quality be preserved predictably and sustainably.

If you would like to explore how integrated atmosphere and moisture control can strengthen your bulk peanut storage strategy, our specialists are happy to share practical insights tailored to your supply chain.

Scientific reference

Groot, S.P.C., van Litsenburg, M-J., et al.
Analyses of metabolic activity in peanuts under hermetic storage at different relative humidity levels.
Food Chemistry, 373 (2022) 131020.

Nuts

Walnuts are a rich source of omega-3 fatty acids, vitamin E, B-complex vitamins, copper, manganese, and iron. That is why they are enjoyed all over the world. And while in-shell walnuts are popular for festive displays or gifting, it is mostly the shelled walnuts (the kernels) that are exported from, for example, walnut-producing California to Asian and European markets for direct consumption, or to food manufacturing companies, where they may be stored in bulk for a longer period of time.

Walnuts are seeds from the walnut tree (Juglans regia or other species) and, as such, they contain the potential to grow into a new tree. If the conditions are right – think water, oxygen, and warmth – raw, unprocessed walnuts can germinate. To sustain their viability, these living organisms continue to respire after harvest, consuming oxygen (O₂) and releasing carbon dioxide (CO₂). While this process is natural, it accelerates deterioration.

Proper storage in cool and dry environments helps maintain the walnut’s viability while slowing down respiration, ensuring freshness for consumption. In storage solutions, reducing oxygen levels to below 2% helps prevent oxidation and slows the release of carbon dioxide, both of which contribute to maintaining the quality of the kernels.

The importance of walnut kernel colour in bulk storage

The quality of walnut kernels is defined by several factors, including texture, taste, odour, and colour. These attributes collectively determine the ‘consumer acceptance score,’ which reflects the appeal of walnuts to buyers and directly impacts their market value. Among these, colour is particularly significant when discussing the commercial value of walnuts.

Colour is assessed using the DFA score, which stands for Dark, Fine, and Amber, and their various nuances. Light-coloured walnuts are associated with freshness, quality, and superior taste. Walnut processors, buyers, and exporters use DFA scores to classify kernels for different market segments. The higher the DFA score (e.g., Fine, Light, or even Extra Light), the higher the price. Conversely, darker or amber grades are sold at lower rates.

Maintaining these light-coloured kernels, however, requires addressing several storage challenges that can threaten their quality and value.

Challenges in bulk walnut storage

Bulk storage of walnut kernels presents significant challenges, including oxidation, rancidity, and microbial growth. Walnuts are particularly susceptible to quality degradation due to their high-fat content, which makes them prone to rancidity—a process exacerbated by exposure to oxygen, moisture, and elevated temperatures.

Without adequate measures, these conditions can result in darkened kernels, reduced freshness, and significant economic losses. Proper storage is therefore essential to prevent oxidation and maintain the quality of walnut kernels, including their desirable colour.

Modified atmosphere packaging (MAP): a game-changer for walnut storage

These challenges necessitate an innovative approach—modified atmosphere packaging (MAP). By mitigating the risks described in the previous paragraph, MAP ensures walnut kernels maintain their colour, freshness, and quality over extended storage periods. By precisely controlling the storage environment, MAP effectively slows respiration and oxidation processes, preserving the natural characteristics of walnuts, and elongating shelf life.

The VacQPack solution, a leading technology in MAP systems, offers a comprehensive approach to walnut storage. It combines vacuum sealing with precise atmospheric control, reducing oxygen levels to below 2% and optimising carbon dioxide concentrations to suppress microbial growth and deter pests. This carefully regulated environment significantly extends shelf life while safeguarding the kernels’ visual appeal and nutritional value.

Advantages of MAP in bulk walnut packaging

MAP technology directly addresses the challenges discussed above, providing a range of benefits that improve walnut storage and profitability for walnut producers, exporters, and processors:

Preservation of colour: Reduced oxygen exposure prevents kernel darkening, ensuring walnuts retain their high DFA scores. This preservation of light and uniform shades directly translates into higher market prices.
Extended shelf life: By slowing down respiration and oxidation, MAP significantly extends the storage duration of walnut kernels, reducing losses from spoilage.
Quality retention: MAP safeguards not only the colour but also the texture, taste, and aroma of walnuts, ensuring a superior consumer acceptance score.
Pest control: The controlled atmosphere suppresses the activity of pests like moths and beetles, eliminating the need for chemical fumigation.
Economic benefits: With fewer losses due to spoilage and downgrades, MAP ensures a higher return on investment for walnut producers and distributors.
Environmental sustainability: By minimising waste and reducing the reliance on chemical treatments, MAP supports more sustainable storage practices.

Conclusion: a bright future for walnut storage

Maintaining walnut kernel colour and quality in bulk storage is crucial for preserving their market value. With the DFA score serving as a critical determinant of price and consumer acceptance, ensuring proper storage conditions is paramount.

The adoption of MAP solutions, such as the VacQPack solution, represents a transformative step forward. By combining low-oxygen environment sealing with precise atmospheric control, VacQPack not only protects walnut kernels from the detrimental effects of oxidation and microbial activity but also preserves their colour, texture, and flavour for extended periods.

For producers and exporters looking to secure their harvest’s value and reputation in competitive markets, MAP technology is an investment in quality, sustainability, and profitability. To learn more about VacQPack and how the VacQPack solution can transform your walnut storage, contact our expert advisors today.