Understanding Lemons

Growing lemons is very much a science. It takes time and money to find the best cultivated varieties (cultivars) that produce abundant fruit and resist disease and tolerate bad weather. For commercial cultivation, lemon seedlings are grafted onto young trees, or rootstocks, of different citrus species such as orange or grapefruit. These rootstocks usually resist rotting disease better than lemon trees.

The origins of the lemon, citrus limon, are as old as civilisation itself. Some writers believe the lemon came from the borders of India and China. Others suggest the Middle East.

Wherever the lemon's geographical beginnings lie, by the first and second centuries AD lemons were cultivated in the Middle East and Greece. There is a mosaic of a lemon in the ruined Roman city of Pompeii. Other evidence suggests that by the second century Rome was importing lemons from North Africa.

The fruit spread throughout the Roman empire. It thrived in the warm climate of the Mediterranean region. The lemon reached the Americas about five hundred years ago.

Traditionally, the main varieties of lemons were the Lisbon, from Australia, and the Eureka, from California. But now more vigorous varieties have been developed, such as the Frost Lisbon and Frost Eureka. Some varieties are better for processing. Certain South American lemons, for example, yield more than 6 kg of oil for every tonne of fruit. There are three main methods to extract juice and oil from the lemon.

Growing lemons is very much a science.

It takes time and money to find the best varieties that produce lots of fruit.

• FMC: The most common method is the FMC extractor, widely used in orange processing worldwide. This extracts oil and juice at the same time. A cutter tube pierces the fruit and a strainer is pushed up inside. A mechanical hand squeezes the lemon. The pulp is pressed against the strainer, keeping the juice away from the strongly flavoured oils in the peel or 'flavedo'. At the same time, a fine mist of water is sprayed on the outside of the fruit. This creates an emulsion of water and oil that is piped away for further processing and finishing.
• BROWN: The Brown Oil Extractor (BOE) process first uses thousands of stainless steel needles to puncture the peel. This ruptures the lemon's oil cells. The processing takes place in a shallow pool of water, so no oil is lost to the atmosphere. The water-oil mixture is centrifuged to separate the water and to polish and finish the oil. This processing method is common in the Americas but less popular in Europe.
• PELATRICE: This is similar to the Brown process, but it uses rolling disc graters instead of needles. The discs rasp the flavedo. A water spray captures the oil, and the mixture is then separated by centrifuge. Almost all of the peel has been removed from the fruit, and juice can then be extracted easily by other equipment.

WINTERIZATION The oil needs more processing at very low temperatures to clarify it and remove wax. This is called 'winterization'. The lemon oil is stored for around three weeks as low as -30C. The wax settles at the bottom of the tank. Up to 10 per cent of the oil may be lost during clarification. The remainder is then stored at around 5C. Some wax will remain in the oil. This is normal. There is usually too little to be noticed. Waxes can continue to form after winterization. Again, this is natural and cannot be totally prevented. Filtration will remove excess wax. This is important if the lemon oil is to be used in some products, such as clear beverages or fine fragrance. PRODUCTION The Americas dominate lemon oil production. Argentina is the world's largest grower of the fruit; its lemons are mainly sold to processors. It produces 32,000 tonnes of lemon oil each year - around 45 per cent of world output. In Brazil and Mexico, lemon oil output is increasing. In Spain it is declining, since its lemons are now grown principally for the fresh-fruit market. The United States produces around 1,000 tonnes of lemon oil each year, although this too is falling. Lemon oil production is also decreasing in Italy and in Sicily in particular. Over the past decade, this once-dominant producer has found it difficult to compete against Argentina's lower costs from bigger scale of production.