Maple Syrup

Maple syrup is a thin syrup made from the sap of the sugar maple tree (Acer Saccharum). It is used as a natural and unrefined sweetener and has a mild sweet taste. The syrup is used in the production of various products, used as lemonade syrup and eaten on pancakes, waffles, and suchlike.

The sap of the sugar maple tree consists approximately for 97% of water. The remaining 3% mainly consists of sugars (sucrose) and minerals. Maple sap is rich in potassium and calcium, and includes, among other things, magnesium, iron, phosphorus and vitamin B. To produce 1 liter of syrup, 40 liter of sap has to be evaporated and reduced.

The Northeastern part of North America is the only place on earth where the climate is suitable for the sugar maple to grow. Hence a maple leaf can be found on the national flag of Canada.

Maple syrup is available in three categories of quality: A, B and C. This quality indication is based on the flavor and clarity of the syrup.

Over the course of the draining period, the syrup gets darker in colour, as more and more organic substances get into the sap. The best quality is A-grade. This syrup is obtained at the first draining and has a light brown color. Grade B and C are of a darker color and C-quality syrup also has a stronger caramel flavor.

Maple syrup production

Drain

There are several different types of maple trees, only two of which are of importance for the production of maple syrup. The sugar maple is the main syrup source. In addition, the sap of the black maple (Acer nigrum) has a similar quality (2 to 3% sugar, light and bright colors and tasteful) and length of draining season. The black maple is less common in North America.

A maple can only be taken in production if it has a diameter of 25 cm, measured 1.3 meters above the ground. Per season per tree, depending on its size and condition, 1 to 4 draining holes are made at a distance of 60 to 90 cm above the ground. These will provide a maximum of 1 liter of concentrated juice per year. When the draining is done carefully, a tree can remain productive for more than 150 years. It is very important that new draining holes are drilled at a distance of at least 15 cm from the previous holes. In this way, large scars on the tree are prevented, which otherwise could lead to diseases of the tree. Often a germicidal tablet is put in the draining hole in order to prevent microbial growth.

Mid-February, slightly sloping draining holes of 1 cm wide to 5 cm deep are drilled into the sapwood of the maple trees, after which immediately plastic drain gutters are attached. These draining holes are connected with each other through polyethylene tubing and then to a pumping station, where the sap is stored in stainless steel tanks, or is immediately fed to the 'sugar home’. With the use of a vacuum pump it is possible to increase sap yield and to obtain a constant flow of sap through the tubes. It is important that the bark is not damaged during the draining process, as this can cause air to come in contact with the sap and thus have a negative influence on its taste.

From mid-February, the freezing and thawing cycle causes the pressure in the tree to change and the sap begins to flow. This phenomenon can be explained by the production of large quantities of carbon dioxide during freezing. Gravity and the pressure difference caused by this gas will cause the sap to flow from the trees at temperatures above the freezing point. This so-called bleeding takes place only until the beginning of April. In April the trees begin to bloom, resulting in a chemical reaction that negatively impacts the taste of the maple sap. 

Pre-concentration

In the sugar house, the sap is further processed as quickly as possible in order to produce a quality syrup as high as possible. Until the time of processing, the sap is stored cold to prevent bacterial contamination. Nowadays, the sap is concentrated by using membrane filtration (reverse osmosis). In this way, the energy consumption is greatly reduced, making it possible to evaporate 75 to 80% of the water at a lower temperature.

Evaporation

Next, the sap flows to an evaporator, where it is evaporated to a sugar content of 66.7°Brix. In a pre-heater, the temperature of the sap is raised to about 85°C, with the help of the steam from the evaporator. Next, the sap is passed through an evaporation unit for a gradual, constant evaporation, after which the evaporation is completed in a long, shallow pan.

The rate of evaporation is important because it determines the colour, flavour and texture of the syrup. During the evaporation process, a complex chain of reactions takes place, which provides the characteristic flavour and colour of the maple syrup.

The sugar content of the syrup is measured with a hydrometer. The boiling point of the syrup can also be used as a measurement tool. When this has been raised to 104°C, the evaporation process can be stopped. The regulation of the sugar content is important, because the syrup will crystallize if the sugar content is too high, while the likelihood of spoilage greatly increases when the sugar content is too low.

Filter

After the evaporation process, the calcium residues and other contaminants are removed with the aid of a filter press.

Temporary storage

Before the maple syrup can be bottled, first the quality of the syrup, like the colour and the mineral content, are determined. To do this, the syrup is temporarily stored in barrels cleaned with steam. Only high-quality maple syrup is used for retail.

Bottling

Before the maple syrup is automatically filled in glass bottles or metal containers, the syrup is heated again to 82°C. This will make the product sterile before bottling. It is important that the maple syrup is bottled without headspace and is sealed airtight. The maple syrup contains no preservatives. Nevertheless, a shelf life of 4 years can be obtained. The final step of the maple syrup production process is labeling the packages

Food Safety & Hygienic Design

A high sugar content prevents microorganisms from withdrawing any water from the syrup in order to grow. In fact, the water from the microorganisms themselves is extracted and they dehydrate. A large number of microorganism species do not survive at high concentrations of sugar.

A low sugar content is an ideal breeding ground for microorganisms. The maple sap gets its long shelf life through low temperature (<7°C). If the temperature is higher, the sap can be spoiled within a day.

A lower temperature is the absolute requirement in the preliminary stages of the production process.

A sugar content of 66.7°Brix is enough to prevent de-sporulation (converting microbial spores to vegetative microorganism). Pasteurization of Maple syrup should be sufficient. Except, if during the storage and transport condensation drops occur in the bottle and fall to the syrup, an environment is created where fungal spores can develop. The mold growth continues until the condensation droplet is completely consumed. For this reason, the maple syrup is sterilized. The sterilization of the syrup deactivates any microbial spores that could be present.

The production equipment and machinery must be of a GMP-class. This means that the machinery and equipment must be visibly clean before use. In case that the machinery cannot be emptied fully (and set aside clean and dry), the machinery has to be thoroughly cleaned and disinfected before the production process can start again. Cleanability to a microbial level (hygienic design) is not necessarily required for this process. A light microbial contamination should not be a problem.

During the concentration step of the production process, when the equipment is operating at temperatures between 7 and 63°C, substantial microbial growth can take place. This part of the machinery must be hygienically designed, meaning cleanable to microbial level. After cleaning it, the last microorganisms are killed during the disinfection step. The crude product must then be subjected to a heat treatment before it is concentrated. The processing temperature, speed of de-sporulation and growth determine the length of the production run.

After closing the packaging, the product undergoes a heat treatment. However, this is not a license to be less careful during the pre-processing phase or to clean the processing equipment less frequently or not fully, or extending the production run. Large amounts of heat-stable toxins, coming from microorganisms (in particular, toxins of S.aereus), may still be toxic after sterilization and will be a threat to consumer health.