🫒 Californian-style black olives
Half-ripe olives treated with lye, darkened by air and sterilised in cans.
Californian black olives are olives that turn black not on the tree but during processing: oxygen from the air blackens them in an alkaline solution. Green-yellow fruit is used, and before processing it is kept in brine or in acidified solutions.
The bitterness is removed with several treatments in a weak 1–2 per cent solution of caustic soda, each lasting a few hours, over 3–7 days, until the lye reaches the stone. Between treatments the olives lie in water with air bubbled through it from below. The oxygen oxidises the fruit's natural phenolic compounds, and the skin gradually turns black.
This colour is unstable, so it is fixed with iron salts, either gluconate or lactate. The International Olive Council standard limits them to no more than 0.15 grams of iron per kilogram. The olives are then rinsed for a long time and packed in cans with a weak brine of about 3 per cent.
These olives have low acidity, so the cans must be sterilised to destroy the spores of botulism bacteria. The result is an even black colour, a soft texture and a mild taste with no bitterness. The main variety for them in California is Manzanilla de Sevilla, known there as Manzanillo.
How it connects to Olives
🫒 Californian-style black olives → kind of → 🫒 Table olives → kind of → 🫒 Olives
Links
- Packed in
- 🫙 Jar
- What is needed
- 🧪 Sodium hydroxide (lye), 🧂 Brine
- Traditions
- 🌍 North America
- Part of
- 🫒 Table olives
- Similar and different
- 🫒 Greek-style black olives
- From which cultivars
- 🫒 Manzanilla de Sevilla
Frequently asked questions
Why are canned olives such an even black?
They are blackened with air during processing, and the colour is fixed with iron salts.
What is ferrous gluconate in the ingredients?
An iron salt that keeps the black colour; there may be no more than 0.15 g of iron per kilogram.
Why are these olives sterilised?
Their acidity is low, so sterilisation is needed to destroy botulism spores.
Comparisons
What to read next
- 🧪 Sodium hydroxide (lye) — An alkali; a weak 2–3.5 % solution of it removes bitterness from green olives.
- 🫙 Jar — Glass (three-litre) or tin (condensed milk).
- 🫒 Greek-style black olives — Nearly ripe olives fermented for months in strong brine without lye.
- 🌍 North America — The United States and Canada: cheeses brought by European settlers and missionaries, such as California's Monterey Jack.
Similar
🫒 Spanish-style green olives · 🫒 Greek-style black olives · 🫒 Table olives
Sources
- International Olive Council: Trade Standard Applying to Table Olives, COI/OT/NC no. 1 (2004)
- Campus M. et al. Technologies and Trends to Improve Table Olive Quality and Safety. Frontiers in Microbiology 2018, 9:617
- Charoenprasert S., Mitchell A. (UC Davis). Factors Influencing Phenolic Compounds in Table Olives. J. Agric. Food Chem. 2012