STORING OF RADICCHIO
The cold storage of radicchio is a practice which allows product availability throughout the year, that is during those periods when fresh produce directly from the field is not available (March-April, at the end of the production).
To learn more about this important process, it’s necessary to consider two elements:
The first element is the correlation between cycle and shelf life:
To best perform this technique it is crucial to take advantage from the selection that the enviroment conducted on this species over decades. Since radicchio is an utumn/winter species, its cold resistance is directly related to its ability to react positively to cold storage. Based on that, it’s possible to classify radicchio according to a gradient of shelf life, based on the length of the cycle:
- Early: short (2 weeks) cold storage, intended for direct fresh market.
- Medium: suitable for short (1 month) cold storage.
- Late: suitable for long (3-5 months) cold storage. Product harvested a few days before ripening, with a portion of the root.
The second element is the “tenderness” gradient:
it’s important to highlight that, among the various types, some are more suited to cold storage, others less so, and others not al all. The most suitable types are Cicoria Rossa di Chioggia, Cicoria Rossa di Treviso Precoce, Sugar Loaf Chicory, Cicoria Rossa di Verona. Cicoria variegata di Castelfranco and Cicoria Rossa di Treviso 2 (Tardivo da forzare) are intermediate types for cold storage. Cicoria Variegata di Lusia, Cicoria Rosa and Cicoria Goriziana are more delicate and therefore less suitable for cold storage.
Cold storage requires very careful planning in the field, by adopting nutritional and plant health management techniques. Careful field management is essential for excellent cold storage results.
- Adopt a less generous nitrogen anagament regime that is typically used for direct-sale production.
- Harvest before full commercial maturity (about 2 weeks), when the heads are still soft.
- Harvest radicchio when the central rib is still slightly green.
- Harvest radicchio preserving 1-2 cm of root (check image on the right), to allow plant to continue ripening in the refrigerator.
- The small piece of root will allow the plant to continue its physiological maturation process, allowing us to extract from the cold storage heads that are firmer than those that entered and with the ribs completely white.
- Best in the afternoon, when the plant is drier. Residual humidity from morning dew is a enemy for a good conservation.
- Avoid picking or even touching plants that are still frozen in the field. Frozen tissue, if touched, will shows signs of damage, blackened at the point of contact, during defrosting.
- Harvest only healthy heads, avoiding those with damaged outer leaves and signs of rot. Be sure to leave two or three extra leaves, which will be removed when the product is removed from the cold storage room and ready for sale.
- Optimal storage would be in suitably stacked crates. If storing in bins, it’s
recommended not to overfill each bin, being careful to arrange an upside-down crate inside the container, to build an empty space that promotes airflow between the stored product. - When the heads are removed from the cells (at the end of the cold storage process), they may have some damaged leaves. Inside, however, the heads remain intact and
qualitatively perfect.
Environmental, climatic and meteorological factors are also very important. A favorable growing season, in absence of excessively high temperatures and rainfall is essential for the success of the process. This is essential for the success of the process.
Cold storage can be divided into “short” and “long” storage, based on the lenght of time the product is kept inside the cells:
- Short-term storage: up to one month, with storage rooms set at constant temperature of +2°C (35.6°F).
- Long-term storage: managed in small refrigerated rooms under stable conditions, where the average core temperature of radicchio is -0.5°C (31.1°F), while the internal air avarages -1.5°C (29.3°F).
- To be processed, radicchio is removed from the cold room the evening before processing and processed the following morning, avoiding touching it directly while it’s still frozen to prevent damage of the product.
- During processing, if it’s necessary, the product can be soaked in water to rehydrate, remove the slimy leaves and process more easily. At this stage the excess root is removed, allowing for a new non-oxidized cut near the taproot.
- Controlled atmosphere (with CO₂ management): it’s a highly professional approach, which ensures the preservation of a perfectly healthy product. After this process, the product removed from the cell will deteriorate very rapidly. For this reason, it must be sold and consumed within a few days.
Thanks to Shawn Linehan for the photos.