Κ232 and Κ270 show UV absorption in 232nm and 270nm and can give us information about quality and oxidative alteration. More specifically, in 232nm primary oxidation products show absorption (conjugated peroxides) and in 270nm secondary oxidation products show absorption (aldehydes and ketones).
K232 is considered a critical marker for good quality extra virgin olive oil. Oxidation can be the result of natural aging or indicative of poor handling or heating during the refining process.
In case of fraud, usually refined oils are added to the extra virgin olive oil. Refining results to formation of dienes and trienes that also absorb in 232nm and 270nm. That is why high index of K232 and K270 may indicate fraud of extra virgin olive oil. Peroxide index should be taken into consideration in order to clarify if fraud or rancidity occurs.
K232 generally increase due to inappropriate storage of olive fruits or old-fashioned extraction or standardization procedure.
K270 increases when extra virgin olive oil is not fresh, which means that our product consists of extra virgin olive oil of a previous harvesting or a blend of extra virgin olive oil of previous harvesting along with the fresh one.
DK indicates blending of extra virgin olive oil with a non extra virgin olive oil, for example virgin olive oil, or other seed oils.
The lower K 232, K 270 and DK in an extra virgin olive oil, the better it is.
The limits for K232, K270 and DK for extra virgin olive oil has to be < 2.5, < 0.22 and < 0.01 respectively.