Our resident expert from Modern Olives, Claudia Guillaume, explains some of the negative attributes associated with an olive oil sensory analysis.

1. FUSTY

Characteristic flavour of oil obtained from olives piled or stored for too long have undergone an advanced stage of anaerobic fermentation.
Presence of bacteria (Enterobacter, Clostridium, Pseudomonas). Some descriptors to identify this defect are: pomace paste, tapenade, olive mill waste pond, mushy black brined olives, horse poo.

2. WINEY

Characteristic flavour of certain oils reminiscent of wine or vinegar. This flavour is mainly due to a process of aerobic fermentation in the olives or in olive paste left on pressing mats which have not been properly cleaned and leads to the formation of acetic acid, ethyl acetate and ethanol.  Presence of yeast and Acetobacter. Some descriptors to identify this defect are: red apple fermented, nail polish, solvent, yeasty, bad quality wine, apple vinegar, cider.

3. MUSTY

Characteristic flavour of oils obtained from fruit in which large numbers of mould have developed as a result of it being stored in humid conditions for several days/weeks. Also, olives that have been crushed with dirt or mud on them. Presence of moulds (Aspergillus, Penicillium). Some descriptors to identify this defect are: sweaty socks, gym clothes bag, wet carpet, mouldy hay, yeasty, mushroom.

4. FROST

Flavour of oils made from frosted fruit on the tree which has been thawed. Some descriptors to identify this defect are: vanilla, wet wood, wet hay, stewed fruit.

5. DRIED

Flavour of oils made from olive fruit affected by drought or desiccated through extended refrigeration in cool room (also ‘dry frost’). This defect also is assigned in oil made with mummified fruit (fruit left in the tree from previous years). Some descriptors to identify this defect are: dry hay, pip, wood, mouldy straw.

6. GRUBBY

Flavour of oils made from olive fruit affected by olive fly (Bactrocera oleae).
The olive fly can lay eggs in developing olives and the larvae feed on the pulp. The larvae give a distinctive dirty flavour to the oil.

7. EARTHY

Flavour of oils produced from olives which have been collected with earth or mud on them and not washed. Some descriptors to identify this defect are: earth, dirty, sandy feeling in the mouth.

8. METALLIC

Flavour of oils which have been in prolonged contact with metallic surfaces during crushing, mixing or storage. Some descriptors to identify this defect are: metals, tins, rusty nails, grinding dust.

9. BURNT/HEATED

Flavour of oils caused by excessive temperature and /or prolonged heating during malaxation. Some descriptors to identify this defect are: burnt caramel, honey, boiled vegetables.

10. RANCID

Flavour of oils which have undergone intense process of oxidation. Inadequate storage conditions (exposure to light, heat, air or age) are the main reasons. Some descriptors to identify this defect are: old oils, stale walnuts, old butter, meat, wax crayons, old lipstick, play-doh.

11. MUDDY

Characteristic flavour of oil which has been left in contact with the sediment that settles in underground tanks and vats and which also has undergone a process of anaerobic fermentation. Some descriptors to identify this defect are: salami, bacon, fetid milk, baby vomit, sewer dregs, pig farm waste pond, cheese.