The sugar mill

From the sugar cane fields to the mill

Historically, the sugar was cut by hand and transported to the mill on tumbrels powered by oxen. Up until the late 1990s, one could still occasionally see the oxen transporting sugar cane to the nearest factory. Since then, technology has replaced man for cutting sugar cane in most parts of the island, and sugar is transported by trucks, lifted by a crane upon arrival and then weighted before being loaded into the mill for the sugar making process.

The sugar-making process

The first step in the sugar making process is the extraction of juice from the sugar cane. One of the oldest types of mills was called a “frangourinier” or “flangourinier”, a type of vertical mill with two cylinders made of basalt – in essence, grinding stones. As technologies improved, the stones were replaced with big iron cylinders.  Most of these vertical mills were powered by oxen. The horizontal mill made of cast iron cylinders appeared later in 1794 and was brought to Mauritius by Charles Telfair during his tenure of the Bel Ombre estate. He imported the machinery from London at the cost of 1,006 pounds in June 1819. The cylinders crushed the sugar cane extracting the sugar cane juice. The horizontal mill resulted in higher efficiency.  Gradually, windmills with hydraulic wheels then steam driven mills fuelled by bagasse replaced oxen, and three cylinders instead of two allowed for[1]  maximum juice extraction.

Once the juice is extracted, it is clarified using lime. In order to help the clarification process, the juice is heated at 105°C and the impurities left to decant. The clarified sugar cane juice is brought to the next step, evaporation, while the resulting residue is used as a fertilizer in the sugar cane fields, Historically, evaporation was carried out in vats made of cast iron, and later was done with equipment known as “Wetzell”, which used vapour diffused through tubes turning on a horizontal axis. In Bel Ombre, another innovation took place: the condenser used for the evaporation process required large amounts of water – up to 400,000 litres an hour – and the estate used seawater for this process^[1]. 

The final step for the sugar making process is crystallization, whereby the remaining syrup is boiled at low temperature in a vacuum pan which provokes the growth of crystals, and results in a mix of crystals and molasses.  Before the introduction of centrifuges, the mix was left to cool off in terracotta and wooden moulds, which allowed the juice to decant. The remaining sugar would be dried in the sun before being stored in bags prior to their dispatch to the port for export.