STATEMENT ON THE GLASS-LIKE CRYSTALS SOMETIMES FOUND
IN CANNED SALMON, TUNA, & OTHER CANNED MARINE PRODUCTS

On occasion small crystals having some resemblance to pieces of broken glass may be found in canned fishery products. They are colourless, transparent and tasteless. The size varies; sometimes they are so small as to impart only slight “grittiness” to the product, whereas sometimes several crystals up to 0.25" (6 mm) long may be found.

WHAT ARE THEY?
Such crystals have been frequently analysed and invariably have been identified as the chemical substance magnesium ammonium phosphate.

ARE THEY HARMLESS?
Yes. In fact, the chemical substances in the crystals are necessary in one form or another for normal health. The crystals have about the same hardness as a crystal of ordinary salt; hence they will not injure the enamel of healthy teeth. They are practically insoluble in the saliva of the mouth, but should they be swallowed, no harm will result as they dissolve in the digestive juices of the stomach.

WHERE DO THEY COME FROM?
The separate chemical substances capable of uniting to form crystals of magnesium ammonium phosphate are always present in the bodies of fishes, animals, and man, but it is only under certain conditions that these substances unite to form crystals. Crystals of magnesium ammonium phosphate are found as the naturally occurring mineral “struvite”, and the same substance has also been found in the healthy human body in the tartar film on teeth and elsewhere.

HOW MAY THEY BE DISTINGUISHED FROM PIECES OF BROKEN GLASS?
Their crystalline structure renders them sufficiently friable to be readily crushed between the fingernail and a hard surface without scratching the fingernail. They will not actually scratch the surface of an aluminum cooking utensil or copper coin, although they may make a mark on the oxidized surface layer of the metal. Polishing the mark with a cloth will disclose that no actual scratching of the metal has taken place, whereas glass easily scratches these two metals. A convincing test is to place a suspected crystal in a teaspoon, then add a few drops of 10% hydrochloric acid, and heat by means of a match, candle, or cigarette lighter until the acid is hot. The crystals will dissolve, whereas a fragment of glass will not dissolve.

Since these crystals may sometimes be mistaken for broken glass, this statement as to their nature and harmlessness has been prepared for the protection of the marine products canning industry of British Columbia.