Harvesting & Post-harvest Handling

• When is the harvest season?

• How to harvest?

• Elderberry toxicity

• Post-harvest handling

• Cost of labor

When is the harvest season?

Blue elderberry has a long harvest season that runs from mid-June to mid-September. Peak harvest depends on environmental factors but has typically been reported in August. In California, blue elderberries, unlike American elderberries, hold on the tree longer which allows for less frequent harvests. Harvest frequency can range from weekly to monthly.

How to harvest?

Flowers

Elderberry flowers grow on large cymes and can be easily harvested by snipping the main stem and placing into a wide crate or bin. Flowers should be harvested when freshly opened. They will first have a creamy yellow color and as fruit development progresses, will turn white. Flowers are present alongside maturing berries for much of the harvest season, allowing harvesting of both flowers and berries at the same time.

Berries

Harvesting of blue elderberries is carried out by hand, as no mechanical harvesters are currently available. Harvesting consists of removing entire cymes and later removing berries from the stems (“destemming”). Cymes can be cut using clippers or a knife, or plucked by hand.

When the berries develop a white, dusty bloom, this is an indicator that the berries are ripe. As they continue to ripen on the tree, the white bloom will fade and the berries will change to a dark blue-black color. While berries can be harvested when the white bloom develops, the flavor will generally be sweeter and more evenly ripened after the bloom fades. Whole cymes can be cut off when all berries have ripened and no green tinge is present.

Elderberry toxicity

European black elderberry is known to contain a compound, sambunigrin, which is a cyanogenic glycoside that breaks down to hydrogen cyanide after ingestion and can cause gastrointestinal disorders such as nausea, vomiting, weakness, and dizziness when ingested in large quantities. The leaves, seeds, bark, and unripe berries of black elderberry are known to contain relatively high concentrations of sambunigrin, while ripe berries contain lower concentrations.²

Heating black elderberries while processing them into final food products such as juice, jelly, liqueur, or tea, has been shown to reduce the levels of sambunigrin by 44% to 96%, depending on the amount of heating. The resulting levels are deemed safe to consume in normally accepted serving sizes for these products, as the human body has some natural capacity to break down a limited concentration of cyanide.²

Research on American elderberries conducted at the University of Missouri found only low levels of cyanide in fresh berries, and cyanide levels in juice & seeds were lower than those in stems & green berries. ³

The level of sambunigrin in blue elderberry is unknown. Some individuals of Native American descent have reported eating raw ripe berries, likely in small quantities, with no ill effects, even as children, suggesting that concentrations may be low, but levels of sambunigrin in blue elderberry have not been confirmed by laboratory analysis. However, when processing ripe berries and flowers, it is a best practice to remove all stems and leaves from the finished product to completely eliminate plant parts highest in cyanogenic glycoside.

Post-harvest Handling

How should berries be handled after harvest?

Elderberries are highly perishable, and to preserve as many of their healthful phenolic compounds as possible, it is advisable to place berries into a cooler in the field, and refrigerate them soon after harvest, within 2-4 hours.¹ It is also best to minimize storage time before processing. 

Destemming berries

Stem removal can be accomplished through available mechanical options, small-scale designs, or by hand. Perforated baskets can be purchased or made using steel or other materials to create a basket with holes the size of the berries. Shaking and moving the berries over the holes will cause the berries to fall through, leaving the stems behind in the basket.

One California farm in the Central Valley destems their elderberries by placing the entire cymes, immediately after harvest, into large plastic bags, then putting the bags into stacking crates inside a freezer. Once the berries are completely frozen, they roughly massage the plastic bag, resulting in the frozen berries separating from the stem. The contents of the bag are then poured into a large metal bowl, which is agitated in a circular motion, causing loose stems and leaves to rise to the top, where they can be picked out by hand. The remaining berries that are still attached to stems can be pulled off by hand. Although labor intensive this method it does not require expensive, specialized equipment. Alternatively, the contents of the bag could be dumped onto a large sieve or screen, which is then agitated, allowing the frozen berries to fall through and leaving the stems and debris remaining. 

Some mechanical destemmers are available for elderberry and others may be made by adapting equipment intended for other fruit. An elderberry grower in California’s Central Coast region modified a wine grape destemmer for a total cost of around $3,000 (including the purchase price). Modifications involved fabricating a new metal basket with smaller holes sized to elderberry fruit, removing one of the rollers (to avoid crushing berries) and replacing the existing motor with a slower motor.

River Hills Harvest in Missouri has designed both a mechanized destemmer and a handheld destemmer.

Cost of labor

The estimated cost of labor for hand-harvest and hand-destemming, calculated from data collected in a 2018/2019 Sacramento Valley field demonstration study, is shown in TABLE (see below).  Harvest labor estimates were made by timing the hand-harvest of mature elderberry trees using orchard ladders.  Destemming labor estimates were made by timing hand destemming of frozen berries. 

Average amount and cost of hand harvest and hand destemming labor per pound of destemmed berries (@ wage of $15/hr). Berry cymes were frozen whole then destemmed by hand.  Berries were harvested by hand-plucking whole ripe cymes within safe reach of an 8-foot orchard ladder (approximately 10-12 feet from the ground). 

References

1. Wilson, R. et al. 2016. Growing Elderberries: A Production Manual and Enterprise Viability Guide for Vermont and the Northeast. University of Vermont Extension Center for Sustainable Agriculture.
2. Senica M, Stampar F, Veberic R, Mikulic-Petkovsek M. 2016. Processed elderberry (Sambucus nigra L.) products: A beneficial or harmful food alternative? LWT-Food Science and Technology 72:182-188.
3. Thomas, Andrew L. 2019. Elderberry Flower Production and Cyanide Concern (presentation). University of Missouri Division of Plant Sciences, Southwest Research Center Mt. Vernon, MO.