Alcaparrones are the fruits of the caper bush, picked green with their stalks and fermented. In Spanish, alcaparra is both the
plant and its flower bud, the small caper sold in jars. The fruit that forms if the bud is left to flower is the alcaparrón, which the
Spanish Royal Academy’s dictionary defines as a fleshy berry shaped like a small fig, eaten pickled
(RAE dictionary). The word came into Spanish through Andalusi Arabic alkappárra, from Latin
cappăris and Greek kápparis (RAE: alcaparra).
The names change by region. A 1967 advisory leaflet from Spain’s Ministry of Agriculture, which calls the plant alcaparro or
tapanera, recorded it as alcaparrera, caparro or caparras in Aragón, tápenas in Valencia, Murcia and Albacete, and taparota in Almería
and Murcia; the buds were tápara, the fruits alcaparrón or tápena. It placed the crop in southern Murcia (Águilas, Lorca, Alhama,
Mazarrón, Librilla), southern Almería (Albox, Cuevas, Serón, Adra, Dalías), the Baza and Caniles area of Granada, and the Balearic
Islands. Spain, it noted, grows only the spiny form, while Sicily has one without spines (MAPA, 1967). In Catalan, spoken
in the Balearic Islands and, as Valencian, in Valencia, the fruit is taperot and the plant taperera
(Diccionari català-valencià-balear) or taparera (Herbari Virtual, University of the Balearic Islands).
Spain is one producer among several. A University of Jaén study names Greece, Italy, Turkey, Morocco and Spain as the main producers
of fermented caper berries, served as an appetizer with meat, olives, cheese and nuts, or with salads and pasta
(Pérez Pulido et al., 2005).
In Spain the alcaparrón is above all an aperitivo and salad food. Being larger than the bud, it is served on its own with drinks, like olives,
usually with part of its stalk still on, and in Murcia it is typical in tomate partío, the region’s tomato salad
(Directo al Paladar).
Why Fresh Capers Are Fermented at All
Fresh capers are bitter, so they are usually brined and eaten as pickles (Berkel Kaşıkçı and Bağdatlıoğlu, 2024).
Fermentation changes their chemistry. In caper berries the main compound is glucocapparin, a glucosinolate (the mustard-oil family),
and it breaks down during fermentation (Jiménez-López et al., 2018). In the buds, fermentation cut the total aroma
compounds by about two thirds; methyl isothiocyanate had the strongest aroma impact in the fresh bud and acetic acid in the fermented
one. The authors’ summary: “Fermentation makes the caper edible” (Sonmezdag et al., 2019).
What the Jaén Study Measured, Day by Day
The most detailed published record of a caper-berry fermentation we found is a University of Jaén study of a local company that
ferments them the traditional way. Berries of 1.5 to 2.5 cm across went into 150-litre vats of tap water, with no salt, and fermented at
ambient temperature for 6 days. Then concentrated salt was added to bring the vats to 10% (weight per volume), and the berries were
sampled once more after 24 hours in brine (Pérez Pulido et al., 2005).
The water soured fast. The pH fell from 7.50 to 4.37 during the first day and kept falling to 3.55 at the end. Enterobacteriaceae,
the gut-bacteria family that includes E. coli and Salmonella, were present at the start and gone from day 1 on.
Yeasts showed up only at the end, once the salt went in. The authors call the low pH “a key factor for safety and adequate preservation
of the final product” (same study).
Heat is part of the method. In the traditional process the berries are picked in June or July and ferment for about 5 to 7 days at 23
to 43°C, and containers left in the sun can pass 40°C (same study). That warmth, with the quick drop in pH, is the authors’ explanation
for why Leuconostoc, the bacterium that starts a cool sauerkraut, never appeared.
Not every traditional method skips the salt. Spain’s 1967 leaflet describes alcaparrones layered with salt in a wooden tub, covered
with sacks weighted with stones and topped up with water, for about fifteen days before the fruit was drained and salted; it gives no
salt amount (MAPA, 1967). The recipe on this page follows the Jaén vats because they are the only version with a measured
pH.
pH 3.55 is well below 4.6, the line that matters for botulism. Guidance for small fermented-vegetable businesses treats a steady,
sustained fall to below 4.6 as the critical control, and warns that with little or no salt the pH can be unstable and even rise back
above 4.6 (Snyder et al., 2020). Our pH chart of fermented foods explains that line and how to test
with strips or a meter. For a ferment with no salt in its first stage, testing is the only check you have.
The Bacteria in a Caper-Berry Vat
Lactic acid bacteria run the fermentation. Of 75 distinct isolates, 37 were Lactobacillus plantarum, the usual leader in
vegetable ferments, followed by Pediococcus pentosaceus (14), L. brevis (9), L. fermentum (6) and L.
pentosus (5), with a few others (Pérez Pulido et al., 2005). Many of the lactobacilli could break down raffinose and
stachyose, sugars people digest poorly (Pulido et al., 2007).
The same group also studied 17 enterococci from caper fermentations. Some carried genes linked to virulence, and all 17 were
resistant to rifampicin, erythromycin and ciprofloxacin, though none to vancomycin. The authors asked for closer study of enterococci in
foods, “especially those of a higher risk-like home-made foods” (Pérez-Pulido et al., 2006). That is a laboratory
finding about bacterial traits, not a record of illness, but it is one reason to keep a home batch clean and quick.
A starter helps. In a trial at the University of Palermo, caper berries fermented with a chosen L. pentosus strain soured
faster, carried fewer spoilage organisms and tasted less bitter than berries left to ferment on their own
(Francesca et al., 2016). We know of no caper starter culture sold to home cooks, so the recipe below relies on warmth
and pH testing.
Biogenic amines were low in commercial jars. In a survey of packed table olives and pickles, capers and caperberries had under 60 mg
of total biogenic amines per kg, which the authors judged no risk to health; caperberries had the highest histamine of the products
tested, 38 mg per kg (García-García et al., 2001). Home batches weren’t measured.
Capers Are Cured Differently From the Berries
The buds take longer and more salt. In a Turkish trial, mid-sized buds pickled in brines of 5, 10, 15 and 20% salt showed the most
lactic acid bacteria activity at 5% and partly at 10%, and took 40 to 50 days to reach the right flavour, smell, acidity and pH
(Özcan and Akgül, 1999). Spain’s 1967 leaflet described the trade method for buds: barrels of brine at 25° Baumé, about
25 kg of salt to 85 litres of water by its own rough figure, for about 25 days of fermentation, then a fresh brine for about a month.
The same leaflet records buds sold in vinegar and in dry salt (MAPA, 1967).
Salted capers from the Italian island of Pantelleria, a protected geographical indication, are dry salted with sea salt only. The
specification calls for 30 to 40% of the capers’ weight for about 8 to 10 days, mixed to encourage lactic fermentation; then the liquid
is poured off and another 20 to 25% is added (Cappero di Pantelleria PGI specification). In a Turkish comparison,
dry-salted buds and berries kept more of their phenolic compounds than brined ones (Aksay et al., 2021).
Caper berries are the quicker ferment. Brine-cured olives share their Mediterranean setting but take months; our
guide to brine-curing olives at home gives that longer method.
Making Them at Home: What the Study Doesn’t Tell You
The recipe below scales the Jaén vats down to a jar, and some numbers have to be filled in. The study gives no ratio of berries to
water, no vessel other than its vats, and “ambient” for the temperature; the traditional range is 23 to 43°C. It followed the berries
for only one day in brine, so there is no tested shelf life. The card uses a glass jar, enough water to keep the berries covered, a
measured warm spot (23°C or above) and pH testing, and says plainly where those choices are ours. Because the first stage has no salt,
the pH test is required: the card gives a 48-hour limit for getting to 4.6 or lower, and a 7-day limit for the unsalted stage.
You need fresh berries from a true caper bush (Capparis spinosa), picked green with their stalks, as Spain’s leaflet
describes. Fresh berries are rarely sold outside caper-growing areas, so this is a project for people with access to a bush. Don’t use
this method for “capers” made from other plants, such as nasturtium seeds: they are different species and need their own preparation.
For the salting step, dissolve 100 g of salt in each litre of the fermentation liquid. That makes the liquid about 10%, close to the
study’s 10% weight per volume. Salt then moves into the berries, so the brine around them ends weaker; the acidity, not the salt, is
what keeps them safe. Our salt and brine calculator works out other amounts. If a jar goes soft, slimy or grows a
film, our fermentation troubleshooting guide covers which signs mean throw it out, and our
guide to storing fermented foods covers keeping them in the fridge.