Table olives should be nutritious, tasty and safe to eat. The growth of micro-organisms (like bacteria and yeasts) and oxidation, can cause spoilage in table olives.
Micro-organisms are usually introduced during processing under poor hygienic conditions. If the levels of micro-organisms get controlled early in the processing, the risk of spoilage can be avoided.
Oxygen levels, temperature and moisture are factors of influencing the growth of micro-organisms. Temperatures during processing should be maintained at 15C – 25C. Lower temperatures slow down fermentation and prolong the processing time.
Salt dried and sun dried olives processed correctly, result in minimal microbial spoilage, due to low water content of the olives. When the levels of contaminating micro-organisms are high, the risk of spoilage is high also.
On the surface of the fermentation brines, oxidative moulds are growing, which are releasing metabolites that contaminate the olives.
The use of fresh herbs and spices also contaminate the olives. Moulds, yeasts and bacteria, over-riped and long time stored olives before processing, result in soft and defected olives. Although micro-organisms are the cause of the softening of the olives, it can be reduced by controlling the pH levels of the fermentation and packing brines. High levels of pH cause deterioration, low levels avoid it.
Greek researchers proposed that hygiene and good quality water, are of high importance in preventing spoilage.
When micro-organisms appear in the beginning of the fermentation, they are controlling the effectiveness of the whole process.
Spoilage of the olives also include:
Blistered skin (blisters between skin and flesh) that can be formed from lye solutions. The right lye concentration prevent blistering.
Darkening, when they stand in air during or after processing. This is an advantage for black olives, unlikely for the green olives reduces their visual beauty.
White spots. The micro-organisms and yeasts are forming residences under the skin and are visible on green olives after the processing. These spots are owed to low sugar levels in the brine. The problem can be reduced with the addition of fermentable sugar in the brine.
Gas pockets. They are blisters in the flesh, filled with gas in both green and black olives. This problem can not be corrected, and preventive measures should be taken. All the ingredients used for processing should be of high quality and the correct concentrations and starter cultures should be used.
Galazoma. It is a characteristic that turns the black olives into dark blue when exposed to air. Also the olives get an unpleasnt odor. Their quality of the olives is reduced along with their commercial value. The process in the right brine solutions, eliminate the development of galazoma.
Skin marks are formed when rough handling of the olives occurs from harvesting to processing time.
Processing and packaging under the right conditions are the keys to minimize the levels of spoilage. Poor handling and control in the beginning of processing of the table olives, can result in food poisoning if the olives are consumed.
Monitoring and controlling the processing can prevent problems and leads in the production of a high quality olive.