It’s common to find a white, grainy or crystalline deposit at the bottom of a can or jar of olives. This harmless substance is caused by the curing and preservation process that olives undergo before they are packaged and sold.
What Causes the White Deposit in Olive Cans?
Olives are naturally very bitter when they are first picked from the tree. They contain a compound called oleuropein that must be removed or neutralized to make the olives palatable. There are a few different ways that olive producers reduce the bitterness:
- Lye-curing – Treating raw olives with a food-grade lye solution which hydrolyzes the oleuropein
- Salt-curing – Repeatedly soaking olives in salt brine to leach out the bitterness
- Water-curing – Soaking olives in plain water and changing it daily to remove oleuropein
After the curing process, olives are usually packed in a salted brine solution for preservation. This brine may also contain acids like acetic acid (vinegar) or lactic acid to enhance preservation.
During storage and transport, chemical changes take place between the olive brine, olive flesh, metals from the can, and even the air trapped in the can. These reactions result in the formation of pale crystallized deposits, usually consisting of calcium carbonate or magnesium carbonate.
Are the Crystals Harmful?
The white sediment found in olive cans is harmless and completely safe to consume. The crystalline compounds are naturally occurring minerals that come out of solution due to chemical shifts during storage. The deposit develops separate from the olives themselves.
Some of the exact compounds that can precipitate out include:
- Calcium carbonate
- Magnesium carbonate
- Calcium phosphate
- Magnesium hydroxide
- Magnesium oxide
- Calcium oxalate
These are all naturally present in the olive brine and safe for human consumption. The white sediment may have an unpleasant texture, but it is not dangerous or a sign of olive spoilage.
Why Do Olives Develop Sediment While Other Canned Goods Don’t?
There are a few reasons why olives are more prone to developing crystalline buildup than other canned products:
- Olives undergo a complex curing process – The lye, salt, and acid steps involved in olive curing lead to chemical instability.
- Olives are packed in brine – The salted water provides reactive ions like calcium, magnesium, carbonate, and phosphate.
- Olives are not heat-sterilized – Most canned vegetables are heat processed which deactivates microbes and enzymes that could cause reactions.
- Olives are stored a long time – Months to years between packing and consumption allows precipitates to slowly develop.
Other pickled products like sauerkraut that also skip the sterilization step will sometimes have sediment, but not to the same degree as olives.
Does the Deposit Affect Olive Quality and Safety?
The crystallized sediment does not negatively impact the quality, safety, or nutrition of olives:
- It’s non-toxic and tasteless.
- It does not degrade the olive flesh or brine.
- No vitamins or nutrients are lost.
- The olives do not spoil faster.
- The texture and flavor is unaffected.
As long as the olives look, small, and taste normal, they are perfectly fine to eat. Some brands market “sediment-free” olives, but this is purely cosmetic and not a safety concern.
Are Cloudy Olives Safe to Eat?
Olive brine naturally becomes cloudier and less transparent the longer the can sits on the shelf. This cloudiness is caused by the growth of harmless lactic acid bacteria which thrive in the salty, acidic brine.
Cloudy brine does not mean the olives have spoiled. As long as the olives look and smell normal, they are perfectly safe to eat. Some cloudiness and sediment is typical in commercially cured olives.
Can the Deposit be Avoided or Removed?
While harmless, the crystalline sediment is unsightly and can have an unpleasant crunchy texture. Some methods to avoid or remove it include:
- Purchase fresher olives – Newly packed cans will have less precipitate accumulation.
- Refrigerate after opening – Cold temperatures slow down chemical reactions.
- Filter the brine – Pour olives into a strainer and rinse to catch debris.
- Use within 2 weeks – Rapidly consume opened cans before sediment forms.
- Select sediment-free brands – Some companies use modified brines to prevent deposits.
Unfortunately, there is no way to keep canned olives pristine forever. Some sediment will eventually form, but it can be minimized with proper handling and consumption.
Can Olives With Sediment Still be Eaten?
Yes, olives with white sediment at the bottom of the can are perfectly safe and fine to eat. To minimize the gritty texture:
- Swirl or shake the can to disperse sediment before pouring.
- Rinse off individual olives under running water.
- Avoid shaking up sediment if serving olives as a garnish.
- Scoop olives out with a fork rather than pouring out brine.
- Use olives immediately in a recipe instead of plain.
The edibility of the olives is not affected, but the coarse deposit itself has an unappealing mouthfeel. With a few simple measures, olives with sediment can still be enjoyed without an unwanted crunch.
How to Store Canned Olives
To maximize freshness and minimize sediment formation in canned olives:
- Buy only intact, well-sealed cans – Avoid dented, leaking, or bulging cans.
- Check the ‘best by’ date – Consume within 1-2 years for peak quality.
- Store unopened cans in a cool, dry pantry – Avoid temperature extremes.
- Refrigerate opened cans – Cold temperatures slow sediment formation.
- Use within 2 weeks once opened – Finish quickly or transfer to airtight container.
- Rinse off olives as needed – Rinsing removes some unwanted debris.
- Don’t store opened cans at room temperature – Warmth accelerates chemical reactions.
With proper storage and handling, commercially canned olives can retain good quality and flavor for years, even though some crystallization is inevitable.
What’s the White Buildup on My Olives?
If white spots, webby deposits, or fuzzy growth forms directly on your olives, it is likely mold growth rather than normal sediment. This can occur if olives are exposed to air for too long after opening.
Signs of actual olive spoilage include:
- White/blue/green spots on the olive flesh
- Soft, shriveled olives
- Cheesy, bitter, or moldy smell
- Dry, cracked olive skins
- Gas production inside the can
- Slimy olive texture
- Rancid or rotten aroma
Any olives showing these warning signs should be discarded. Always practice proper storage and hygiene to minimize microbial contamination.
Frequently Asked Questions
Is the white sediment made of salt?
No, the white deposit is not pure salt. It is usually calcium carbonate and other insoluble minerals that naturally precipitate from the olive brine over time.
Why is there sometimes sediment and sometimes not?
Many factors influence sediment formation including olive variety, curing method, brine ingredients, canning, and age. Some brands also use additives to intentionally inhibit crystallization.
Can olives with sediment make you sick?
No, the harmless sediment cannot cause illness or toxicity. As long as the olives look and smell normal, they are safe to eat.
How can sediment be avoided?
Choosing fresher cans, proper storage, and quickly using opened cans help minimize sediment. But some will always form over months or years.
Should cans with sediment be returned?
No, the sediment is normal and not a sign of spoiled or defective product. There is no need to return or discard cans due to harmless precipitation.
The Bottom Line
Finding white crystalline buildup in canned olives is common and not a cause for concern. The harmless sediment forms naturally over time from compounds in the olive brine. While unsightly and crunchy, it is non-toxic and does not make the olives unsafe or inedible. Storing cans properly, consuming quickly after opening, rinsing off olives, and buying fresher stock can help control sediment. With a few simple precautions, you can continue safely enjoying canned olives even if they contain some gritty deposits.
