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Note: This article was AI-translated from Arabic and is currently under manual review. The author is not responsible for any translation errors. Please refer to the original Arabic text for the most accurate and authoritative information.
Professor of Oils and Fats at the National Research Centre; Vice-President of the Egyptian Food Safety Association; WHO National Consultant for the iTFA programme.
The company did everything right... yet they overlooked the water.
In a hypothetical scenario summarizing a preventable industrial issue, an olive oil producing company implemented Good Agricultural Practices (GAP): selecting appropriate varieties, managing irrigation and fertilization, timing the harvest meticulously, and rapidly transporting the olives in well-ventilated crates.
At the mill, they adhered to Good Manufacturing Practices (GMP), utilized a state-of-the-art extraction line, and closely monitored hygiene, malaxation temperatures, and storage conditions. Everyone anticipated a high-value extra virgin olive oil.
However, the resulting oil lacked the expected vibrant green aroma, possessed a limited phenolic content, and subsequently lost part of its oxidative stability and sensory quality during storage—reducing its competitiveness and failing to achieve the targeted market price.
When the entire process was thoroughly audited, the neglected variable emerged: the water used in the olive oil mill.
"Mill water" here refers to all water utilized inside the olive oil processing plant, starting from fruit washing to malaxation, separation, and equipment cleaning.
The characteristics of the well water had shifted during the season, fruit washing water replacement was delayed, water was added to the paste without verifying the actual requirement, and an excessive amount was used in the vertical centrifuge.
Is mill water merely a supportive utility, or is it a crucial hidden factor that directly influences the oil's aroma, polyphenols, shelf stability, and price? The answer begins in the orchard and ends only after the last drop of water is separated from the oil.
Rainfall and irrigation water directly influence fruit size, moisture, yield, and oil composition, though the relationship is not uniform under all conditions.
While full irrigation may increase total crop yield and fruit moisture, phenolic compounds and volatile profiles are heavily influenced by irrigation levels, cultivar, season, and ripeness stage. Therefore, it is inaccurate to claim that rain-fed olive oil is always superior, or that irrigation inherently lowers quality.
A more precise approach connects irrigation management with actual mill data, including:
An irrigation decision made in the field can eventually become a technical advantage—or a bottleneck—inside the malaxer and decanter.
Mills located near orchards often rely on groundwater wells or storage tanks, where water may contain elevated levels of iron, manganese, salts, sand, and hardness.
Conversely, urban and industrial park mills typically use municipal tap water. However, water quality can degrade within the facility due to:
Consequently, water quality must be evaluated at the point of use rather than solely at the source. Critical control points include:
Meeting drinking water standards is an absolute essential, but it may not be sufficient on its own to protect the oil's quality during processing. Mills must actively monitor:
Iron and copper are of critical importance: as transition metals, they act as potent catalysts that accelerate lipid oxidation and consume natural antioxidants. Thus, their concentrations must be kept as close to zero as practically possible, rather than merely staying under standard drinking limits.
Fruit washing aims to remove soil, mud, sand, and surface residues. However, wash water does not remain clean throughout an operational shift.
During continuous operation, wash water accumulates:
Without proper management, wash water transitions from a cleaning agent into a vehicle for cross-contamination across processing batches.
Mills should never wait until wash water turns dark or develops an unpleasant odor, as these signs indicate that acceptable quality thresholds were breached long ago.
Optimal water replacement schedules depend on:
Best operational practices include removing leaves and loose sand before washing, filtering recirculating water, continuously purging a portion of the basin water while supplying fresh water, cleaning basins regularly, and applying a final fresh-water rinse when necessary.
Golden Rule: Wash water must be refreshed before it shifts from a cleaning agent into a vector for microbes and trace metals.
Adding water during malaxation should never be a routine default for every batch. Instead, it must be a technical decision dictated by fruit moisture, paste consistency, cultivar, ripeness, and the extraction system used.
While dry or difficult-to-process pastes may require minor water additions, the impact of added water is not uniform across all olive varieties.
Unnecessary water addition can lead to:
Sound operational decisions should rely on trial runs that evaluate:
In modern malaxers, heating water circulates within an outer jacket without coming into direct contact with the olive paste. Therefore, the critical metric is not the jacket water temperature, but the actual temperature profile of the paste over time.
Moderate heat reduces viscosity and promotes oil droplet coalescence; however, elevated temperatures or extended malaxation times can negatively impact:
Volatile aroma compounds and subtle phenolics can degrade long before chemical indicators like peroxide value, K232, or K270 reflect noticeable damage. In short, the oil may remain within official chemical limits while losing the distinctive sensory attributes that command premium prices.
Under European regulations, terms like "Cold Extraction" for virgin or extra virgin olive oils are restricted to operations where extraction occurs via centrifugation or filtration below 27°C (80.6°F).
However, staying under 27°C does not automatically guarantee superior quality—poor-quality fruit, processing delays, inadequate hygiene, or excessive oxygen exposure can still degrade the final product.
Traditional 3-Phase Decanters typically require added process water to facilitate phase separation, producing oil, a liquid waste stream (vegetation water), and dry pomace.
Modern 2-Phase Decanters operate with minimal or no added water, yielding oil and a moist pomace.
Multi-Phase Decanters (DMF) operate without conventional water addition during primary extraction, producing oil along with wet pomace and a pitted pulp phase known as Pâté.
Technology alone cannot guarantee quality; the inherent benefits of advanced extraction systems can easily be negated by high processing temperatures, prolonged malaxation, degraded fruit, or inadequate line sanitation.
Vertical separators are used to remove residual water droplets and fine suspended particles from oil exiting the decanter. However, excessive washing water can result in:
Operational Rule: Use the absolute minimum water required to achieve clarity, in the shortest time, with minimal air exposure.
A facility's Water Footprint (ISO 14046) extends far beyond the water meter at the front gate. It evaluates water consumption and environmental impacts across the entire production lifecycle—from field irrigation and washing to malaxation, separation, cleaning, and wastewater treatment.
Key metrics that olive oil mills should measure include:
Two facilities may use the exact same total volume of water, yet one may have a significantly higher environmental footprint due to reliance on scarce water sources, generation of highly polluted effluent, or higher loss of product quality.
Not every mill requires a Reverse Osmosis (RO) system; technological choices should strictly align with comprehensive water analysis and site-specific needs.
UV disinfection systems may underperform in highly turbid water, while Reverse Osmosis increases energy consumption and generates a reject stream that requires management. Therefore, treatment technologies must target actual risks rather than serving as generic solutions.
The true cost of water extends far beyond purchasing or pumping expenses. It includes:
Rather than solely asking "How much water did we save?", mill managers must evaluate: "How much value did we preserve in every liter of olive oil produced?"
A company can implement flawless GAP and GMP standards and invest in the latest extraction technology, only to lose premium value due to a neglected storage tank, unrefreshed wash water, unmonitored transition metals, or improper temperature control.
The future belongs to olive oil producers who digitally integrate water quality metrics with fruit moisture, malaxation heat, oil yields, phenolic retention, volatile profiles, shelf stability, and environmental footprints.
Water never appears on an olive oil label, but its footprint is unmistakable in the oil's aroma, phenolic richness, stability, official grade, market price, and brand reputation.