Keeping the colour light: enhancing walnut kernel value through MAP
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 (O?) and releasing carbon dioxide (CO?). 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.
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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:
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.
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