Olives (Olea europaea L.)

The term olive refers to the fruits of Olea europaea L., a tree species typical of Mediterranean climate regions, cultivated in particular in Italy, Spain, Greece, and Portugal, with production also in North Africa and the Middle East. Olive trees find their ideal environment in areas characterised by mild winters, hot, dry summers, and generally well-drained soils, often shallow, of calcareous or mixed nature, with moderate water availability. Cropping systems range from traditional olive groves with low planting density, sometimes on terraces and slopes, to intensive and super-intensive orchards in flat areas, with varying levels of mechanisation and agronomic management.

From a botanical standpoint, the olive is a drupe consisting of epicarp (skin), mesocarp (pulp) and endocarp (stone), which contains the seed. The numerous cultivars selected over time differ in terms of yield, composition and fruit characteristics. There are cultivars intended mainly for oil production, with small or medium-small drupes, a high percentage of lipids and good extraction yield, and cultivars for table olives, with larger fruits, greater pulp thickness and a favourable pulp-to-stone ratio. A smaller share of total production is processed into table olives through curing, brine fermentation, or other preservation processes.

The composition of olives depends on the cultivar, ripening stage, and pedoclimatic conditions. The fatty acid profile is dominated by monounsaturated fatty acids, particularly oleic acid, with a variable presence of polyphenols (oleuropein, hydroxytyrosol and derivatives), pigments, aromatic substances, and a certain proportion of water. The content of phenolic compounds, the structure of the pulp, and technological parameters influence the characteristics of the oil obtained, its shelf-life, and its suitability for use as a table olive. Olive growing includes management systems that maintain high varietal biodiversity, with numerous local cultivars and agronomic practices that reflect both local traditions and increasing levels of technological innovation.

Overall, the olive is the core of the olive–oil supply chain, representing the primary raw material for the olive oil market and a significant component of table olive production, with a key economic, cultural, and agricultural role in Mediterranean areas.

Botanical classification
Common name: green olive, olive tree
Clade: Angiosperms
Order: Lamiales
Family: Oleaceae
Genus: Olea
Species: Olea europaea L.

Cultivation and growth conditions

Climate
The olive tree is a typically Mediterranean species, adapted to warm–temperate climates with mild winters and hot, dry summers. It tolerates short periods of cold, but is sensitive to intense, prolonged frost, especially below about –7 / –10 °C. The most delicate stages in relation to low temperatures are flower bud differentiation, flowering and fruit set. For the production of green olives, a regular thermal pattern is important to allow good fruit growth without marked stress.

Exposure
Olive trees require full sun to fully express their production potential. Good exposure promotes differentiation of flower buds, uniform fruit colour and adequate oil content. Orchards that are too shaded (narrow valleys, buildings, taller trees nearby) show lower vigour, reduced yield and greater alternation between high– and low–yield years.

Soil
The species adapts to a wide range of soils, but shows its best performance in soils that are:

• well drained,

• from sandy–loam to loam,

• with pH from slightly alkaline to neutral (about 6.5–8).

Soils prone to waterlogging increase the risk of root rots and reduce tree longevity. A moderate level of organic matter improves structure and water-holding capacity, especially in dry environments.

Irrigation
Although traditionally considered a dryland crop, modern olive growing increasingly uses supplementary irrigation, particularly in intensive orchards and for table olive production (green and black olives). It is important to:

• maintain moderate soil moisture during stone hardening and fruit enlargement;

• avoid prolonged drought, which reduces fruit size and yield;

• prevent excess water, which favours diseases and excessively vigorous vegetative growth at the expense of fruiting.

Drip irrigation systems allow good control of water supply and reduce wastage.

Temperature
Optimal temperatures for vegetative growth are around 18–28 °C. The olive tree also requires a certain number of chilling hours in winter for proper flower induction, but it is damaged by severe frosts. Prolonged high temperatures, combined with drought and hot winds, can cause flower and fruit drop, reducing the production of green olives of suitable calibre.

Fertilization
The tree has medium nutritional requirements, but for table olive production fertilization must be carefully balanced in nitrogen (N), phosphorus (P) and potassium (K):

• Nitrogen supports growth of shoots and formation of new flower buds, but in excess it favours vegetative growth at the expense of fruiting and increases susceptibility to diseases.

• Phosphorus is important for the root system and flowering.

• Potassium affects fruit quality, oil content and tolerance to water stress.

Periodic applications of well–matured organic amendments, integrated with targeted mineral fertilization based on soil analysis and, where possible, leaf analysis, are recommended.

Crop care
Main management practices include:

• Pruning for training and production, aimed at maintaining an open canopy, well lit and balanced between wood and fruit.

• Weed control with shallow tillage, controlled ground cover or mulching.

• Soil management to improve water infiltration and limit erosion.

• Monitoring of pests (e.g. olive fruit fly, moths, scale insects) and diseases (peacock spot, olive anthracnose) with integrated pest management strategies.

• Possible fruit thinning in table–olive orchards to obtain green olives with more uniform size.

A well–managed canopy and balanced nutrition help reduce alternate bearing.

Harvesting
Green olives are harvested at an early maturity stage, when fruit size is fully developed but the skin is still green or only slightly changing colour (onset of veraison). Harvesting is carried out:

• by hand, with combs or hand–held rakes, taking care not to damage the skin;

• or with gentle mechanical systems, where orchard structure allows it.

After harvesting, olives destined for table processing (brining, lye treatment, other curing methods) must be processed quickly to limit undesired fermentations and pulp deterioration.

Propagation
Olive trees are propagated mainly by vegetative means:

• semi–hardwood or hardwood cuttings;

• grafting onto selected rootstocks;

• in nurseries, sometimes by micropropagation of clonal material.

Propagation by seed is used almost exclusively for rootstock production and does not preserve varietal traits (fruit size, shape and technological behaviour of olives, green or black). In commercial orchards, grafted plants or certified clones are therefore used, selected for good yield of green olives and suitable characteristics for table processing.

Indicative nutritional values per 100 g (green table olives, drained)

(Average values; they vary with cultivar, process and residual brine.)

• Energy: 140–170 kcal

• Water: 70–75 g

• Protein: 0.8–1.5 g

• Total fat: 14–16 g

  • SFA (Saturated Fatty Acids): ~2–3 g

  • MUFA (mainly oleic acid): ~10–12 g

  • PUFA: ~1–1.5 g

• Available carbohydrates: 2–4 g

  • Sugars: ~0–1 g

• Total dietary fibre: 2–4 g

• Sodium: 2–3.5 g (high, due to brine)

These data confirm that the caloric value of olives derives almost entirely from the lipid fraction, with a fat profile dominated by monounsaturated fatty acids.

Key constituents

• Triglycerides with a predominance of oleic acid (omega-9), plus palmitic acid (saturated), linoleic acid (n-6) and small amounts of other fatty acids

• Phenolic compounds: oleuropein (more abundant in green olives), hydroxytyrosol, tyrosol and derivatives

• Phytosterols (e.g. β-sitosterol)

• Tocopherols (vitamin E, especially α-tocopherol)

• Pigments: chlorophylls and carotenoids (responsible for green and yellow shades)

• Dietary fibre (cellulose, hemicelluloses, pectins in the cell wall)

• Minerals: especially sodium (from brine), with smaller amounts of calcium and potassium

• Vitamins: small amounts of vitamin E and B-group vitamins

Production process
(Standard “Spanish-style” or similar processing of green table olives.)

1. Harvesting

   • Olives are harvested at the “green” or “green–waxy” stage, when fruits are intact, firm and uniformly coloured.

2. Sorting and washing

   • Selection to remove damaged or defective fruits; washing to eliminate soil, dust and foreign matter.

3. Alkaline treatment (lye)

   • Immersion in a dilute sodium hydroxide solution to reduce bitterness (hydrolysis of oleuropein); time and concentration are adjusted according to cultivar and fruit size.

4. Washing

   • Several washing steps with water to remove residual lye to the required level.

5. Brining and fermentation

   • Immersion in brine (NaCl, typically 6–10%) that allows spontaneous lactic fermentation, driven by the natural microflora; this reduces pH and develops characteristic flavour.

6. Stabilisation and packaging

   • Final adjustment of salt and acidity; optional pasteurisation; packaging in brine or other packing media (brine, oil, flavourings).

Physical properties

• Shape: ovoid or ellipsoidal drupe, with wide variation among cultivars

• Colour: green to yellow-green; may shift towards more yellowish tones during storage

• Texture: firm, compact flesh, with resistance to compression (key quality parameter)

• Water activity: high in brined products; reduced only in partially dehydrated or dried olives

• Relatively high density, with pulp/stone ratio depending on cultivar

Sensory and technological properties

• Taste: predominantly salty due to high salt content; initial strong bitterness reduced considerably by processing; mild acidity in more fermented products

• Aroma: vegetal and slightly fruity notes, possibly with herbal or spicy nuances according to cultivar, fermentation and added flavourings

• Texture: crisp or firm; loss of firmness (soft, mushy texture) is seen as a major defect

• Technological behaviour:

  • good stability in brine and in jars/pouches;

  • sensitive to surface oxidation (browning) if pH, salt and oxygen exposure are not properly controlled.

Food uses

• Direct consumption as a savoury snack or appetiser

• Component of mixed salads, rice salads and cold dishes

• Ingredient for pizzas, focaccias and savoury baked goods

• Preparation of pâtés/tapenades and spreads

• Use in meat, fish, legume and vegetable dishes in Mediterranean recipes (stews, braises, sauces)

Nutrition and health

Green olives are:

• a food with high lipid density, dominated by monounsaturated fats (mainly oleic acid) compared with lower shares of saturated and polyunsaturated fats;

• a moderate source of dietary fibre;

• a significant source of sodium, which can represent a substantial proportion of the daily intake.

The fat profile, with a predominance of MUFA (oleic acid), is generally considered favourable within a balanced diet, especially when replacing fats rich in saturated fatty acids. Phenolic compounds (oleuropein, hydroxytyrosol, etc.) and vitamin E contribute to the antioxidant potential of the product.

However, the high salt content of green table olives requires attention to total sodium intake, particularly in individuals with hypertension, cardiovascular disease or those following low-sodium diets. Consumption should therefore be integrated into a varied and balanced diet, with portion size adjusted according to the overall sodium load of the meal.

Portion note

• Typical household portion: 20–30 g (about 5–8 medium/large olives) as appetiser or snack.

• In sodium-restricted diets, portion size can be reduced and olives can be rinsed before consumption to partially lower surface salt.

Allergens and intolerances

• Olives are not among the major mandatory allergens.

• Rare individual reactions (hypersensitivity to the fruit or certain components) may occur.

• In industrial products it is important to consider:

  • possible allergenic ingredients in fillings (e.g. cheese, fish, nuts);

  • potential cross-contamination in facilities that process other allergens (gluten, soy, milk, etc.).

Storage and shelf-life

• Packaged olives in brine (jars, cans, pouches):

  • store at ambient temperature if sealed and heat-treated, away from light and heat sources;

  • once opened, keep refrigerated, ensuring the olives remain submerged in the packing liquid, and consume within the period indicated by the manufacturer.

• Loose olives in brine (delicatessen counter):

  • store under refrigeration;

  • shorter shelf-life than pre-packed products (a few days).

Main causes of quality deterioration:

• growth of spoilage microorganisms when pH or salt are not adequate;

• surface rancidity of lipids under oxidative conditions;

• loss of firmness of the flesh.

Safety and regulatory aspects

• Table olives are subject to general legislation for processed vegetable foods and specific standards for table olives.

• Controls and limits address:

  • residues of plant protection products;

  • chemical contaminants and mycotoxins;

  • microbiological criteria (absence of pathogens, control of fermentations).

• Food operators must apply GMP/HACCP systems throughout the chain (harvest, processing, fermentation, packaging, distribution).

• Full traceability of batches is required, including indication of the origin of olives and the main processing steps.

Labelling

On retail packs of green table olives, the following information must be provided in accordance with current legislation:

• sales name (e.g. “green table olives in brine”, “pitted green olives”)

• ingredient list (olives, water, salt, acidifiers, antioxidants, flavourings, etc.)

• net weight and, where applicable, drained weight

• date of minimum durability or “use by” date

• storage conditions and instructions after opening

• name or business name and address of the food business operator

• nutrition declaration per 100 g (and optionally per portion)

• highlighting of any allergens present (especially in stuffed olives or mixed products)

Any nutrition claims (e.g. “rich in monounsaturated fats”) or health claims must comply with the relevant regulations.

Troubleshooting

Common quality defects

• Soft or mushy texture

  • excessive or poorly controlled alkaline treatment;

  • unsuitable brine composition;

  • mechanical damage during harvesting or processing.

• Surface browning

  • phenolic oxidation due to excessive exposure to air or inadequate pH/salt conditions;

  • insufficient acidification or poor process control.

• Off-odours / unwanted fermentations

  • brine salinity too low;

  • microbiological contamination;

  • lack of acidity or inadequate hygiene.

Preventive measures

• Accurate control of lye treatment parameters according to cultivar.

• Correct management of brine (salt concentration, pH, fruit/liquid ratio).

• Microbiological monitoring and strict application of good hygiene practices.

• Use of appropriate packaging to limit oxygen ingress and external contamination.

Main INCI functions (cosmetics)

Olive-derived ingredients (including from green olives) used in cosmetics include, among others:

• Olea Europaea Fruit Extract

• Olea Europaea Fruit Oil

According to INCI classifications, key cosmetic functions are:

• skin conditioning (helps maintain skin in good condition, with emollient and nourishing effect)

• antioxidant (contributes to protecting both the formulation and, to some extent, the skin from oxidation)

• emollient / nourishing, improving skin softness and elasticity

• soothing roles in some products designed for sensitive skin

• in certain hair products, additional functions such as hair conditioning

Use levels and purity must comply with cosmetic regulations and safety assessments of the finished product.

Conclusion

The green olive is a fatty drupe transformed into a table olive through de-bittering, brining and controlled fermentation. From a nutritional standpoint it is a concentrated source of monounsaturated fats, with phenolic compounds and tocopherols of functional interest, but also a notable source of sodium, which requires careful management in everyday diets.

Technologically and sensorially, green olives are a characteristic component of the Mediterranean diet, providing flavour, texture and aromatic complexity in appetisers, compound dishes and baked products. In cosmetics, fruit extracts and olive oil are widely used as emollient, conditioning and antioxidant ingredients, within the limits of safety and regulatory requirements.

Mini-glossary

• SFA: Saturated Fatty Acids. Fatty acids that, when consumed in excess, are associated with increased cardiovascular risk; in olives they are present but lower than the monounsaturated fraction.

• MUFA: MonoUnsaturated Fatty Acids. Fats (notably oleic acid) considered favourable for lipid profile when they replace part of dietary saturated fats.

• PUFA: PolyUnsaturated Fatty Acids. Include essential fatty acids; in olives they are present at lower levels than MUFA.

• GMP/HACCP: Good Manufacturing Practices / Hazard Analysis and Critical Control Points. Organisational systems that ensure hygiene, quality and safety along food and cosmetic chains.

• BOD/COD: Biochemical Oxygen Demand / Chemical Oxygen Demand. Parameters used to assess the biodegradable and oxidisable organic load of wastewater, important for environmental monitoring of processing plants.

Studies

In the olive there are bioactive compounds useful for human health such as polyphenols, proteins (1).

The amount of phenolic compounds is significant and explains the antioxidant activity of olive and olive oil:

• phenols are present in quantities between 317mg/100g and 2657mg/100g.
• gallic acid from 7mg/100g to 35mg/100g
• 3,4-Dihydroxybenzoic acid 33mg/100g to 25mg/100g

These values change substantially depending on the type of oleander, harvest period and other parameters (2).

The good protein and amino acid content of olive and in particular maslinic acid, a tripenoid, have shown that, together with moderate exercise, they can increase muscle mass, grip strength, knee pain and thus prevent disability related to mobility in older people (3).

Olive cultivation is damaged by the so-called "Olive Fly" (Bactrocera oleae).

Green olive studies

Olive fruit fly

References________________________________________

(1) Montealegre C, Esteve C, García MC, García-Ruiz C, Marina ML. Proteins in olive fruit and oil.   Crit Rev Food Sci Nutr. 2014;54(5):611-24. doi: 10.1080/10408398.2011.598639. Review.

Abstract. This paper is a comprehensive review grouping the information on the extraction, characterization, and quantitation of olive and olive oil proteins and providing a practical guide about these proteins. Most characterized olive proteins are located in the fruit, mainly in the seed, where different oleosins and storage proteins have been found. Unlike the seed, the olive pulp contains a lower protein content having been described a polypeptide of 4.6 kDa and a thaumain-like protein. Other important proteins studied in olive fruits have been enzymes which could play important roles in olives characteristics. Part of these proteins is transferred from the fruit to the oil during the manufacturing process of olive oil. In fact, the same polypeptide of 4.6 kDa found in the pulp has been described in the olive oil and, additionally, the presence of other proteins and enzymes have also been described. Protein profiles have recently been proposed as an interesting strategy for the varietal classification of olive fruits and oils. Nevertheless, there is still a lot of knowledge without being explored requiring new studies focused on the determination and characterization of these proteins.

(2)  Özcan MM, Fındık S, AlJuhaimi F, Ghafoor K, Babiker EE, Adiamo OQ. The effect of harvest time and varieties on total phenolics, antioxidant activity and phenolic compounds of olive fruit and leaves.  J Food Sci Technol. 2019 May;56(5):2373-2385. doi: 10.1007/s13197-019-03650-8.

Abstract. The effect of harvest periods on total phenol, antioxidant activity, individual phenolic compounds of fruit and leaves of Tavşan Yüreği, Memecik, Edremit, Ayvalık and Gemlik olive varieties grown in Turkey were investigated. The highest total phenol (317.70 mg/100 g and 2657.81 mg/100 g) were observed in Tavşan Yüreği olive fruit and Ayvalık leaves harvested in December, respectively. The highest antioxidant activities (83.84%) were determined in Edremit fruit harvested in August and 83.33% in either Edremit olive leaves harvested in November and Tavşan Yüreği leaves harvested in December. The olive fruit contained gallic acid ranging from 7.18 mg/100 g (August) to 35.85 mg/100 g (December) in case of Ayvalık and 2.09 mg/100 g (November) to 21.62 mg/100 g (December) in Edremit. Gemlik olives showed higher gallic acid contents compared to the other varieties, however it depended significantly on harvest time in all cases. 3,4-Dihydroxybenzoic acid contents ranged from 33.11 mg/100 g (October) to 25.17 mg/100 g (September) in Memecik olives; 12.17 mg/100 g (August) to 33.11 mg/100 g (December) in case of Tavşan Yüreği olives depending on harvest time. The 3,4-dihydroxybenzoic acid contents of Memecik leaves ranged between 122.25 mg/100 g (September) to 196.58 mg/100 g (August) and that of Tavşan Yüreği leaves changed between 99.38 mg/100 g (November) and 179.90 mg/100 g (August). The leaves of these two varieties contained significantly (p < 0.01) higher 3,4-dihydroxybenzoic acid contents than other varieties. The highest gallic acid (144.83 mg/100 g) was detected in Memecik leaves (September) whereas lowest were found in Gemlik leaves collected in October.

(3) Nagai N, Yagyu S, Hata A, Nirengi S, Kotani K, Moritani T, Sakane N. Maslinic acid derived from olive fruit in combination with resistance training improves muscle mass and mobility functions in the elderly.   J Clin Biochem Nutr. 2019 May;64(3):224-230. doi: 10.3164/jcbn.18-104.

Abstract. Maslinic acid, derived from olive fruit, reduces pro-inflammation cytokines, which are involved in muscle fiber atrophy. Therefore, the maslinic acid ingestion may enhance the muscular response to resistance training through anti-inflammatory action. We therefore conducted a parallel, double-blind, randomized, placebo-controlled trial that examined whether a combination of maslinic acid supplementation and resistance training improve mobility functions in community-dwelling elderly persons. Over a 12-week period, 36 participants underwent moderate resistance training and are assigned to the maslinic acid supplementation (n = 17, 60 mg/day) or the placebo (n = 19) group. At baseline and at 12-weeks, we assessed body composition, grip strength, walking speed, leg strength, mobility functions, and knee pain scores. Following the 12-weeks, skeletal muscle mass, segmental muscle mass (right arm, left arm, and trunk) and knee pain score of the right leg were significantly improved in the maslinic acid group, while there was no change or parameters had worsened in the placebo group. Grip strength of the better side significantly increased only in the maslinic acid group. These results suggest that maslinic acid supplementation combined with moderate resistance training may increase upper muscle mass and grip strength, and reduce knee pain, could be effective for preventing mobility-related disability in elderly persons. Clinical trial registration number: UMIN000017207.