Dextrose is a form of glucose, or simple sugar, derived when starchy plants such as corn (and less commonly, wheat or rice) are broken down into monosaccharides using enzymes. About 20% less sweet than sucrose, dextrose is one of the most commonly used ingredients in packaged and processed foods because of its affordability and wide availability. It is used in sauces, cookies, cake mixes, candies, energy drinks and frozen desserts. It may also be used in savory foods like cured meats, canned foods, pretzels, pickles and crackers. Dextrose also helps dough rise and brown, is known to enhance and stabilize food colorings and can also extend the shelf-life of packaged foods.

Dextrose is also used in the pharmaceutical industry. Because dextrose has a high glycemic index, meaning it quickly raises blood sugar levels, it is commonly used in intravenous (IV) preparations and injections in hospital settings for low blood sugar and dehydration, and IV feeding.

Due to its high demand in the food and pharmaceutical industries, dextrose manufacturing companies are looking at more efficient and economical manufacturing processes rather than the conventional centrifugation, ion exchange, evaporation, freeze concentration, freeze drying or other dewatering techniques used. Membrane filtration is quickly gaining acceptance in the sugar, starch and sweetener industry with producers benefiting from improved yields, reduced costs, more efficient use of power and natural resources and the opportunity of producing specialty products.

DEXTROSE PURIFICATION (OR DEXTROSE ENRICHMENT) PROCESS

One of the largest membrane applications in the sweetener industry is dextrose purification, also referred to as dextrose enrichment. This process involves a separation of monosaccharides (sugars with a degree of polymerization of 1, also referred to as DP1s), most commonly dextrose (molecular weight: 180 Da), from disaccharides (sugars with a degree of polymerization of 2, also referred to as DP2s) most commonly sucrose (molecular weight: 342 Da). The desired result of this separation is a product with a dextrose purity of around 99.5%.

Dextrose purification typically uses nanofiltration membranes rated in the 200 Dalton (Da) molecular weight cut-off (MWCO) range. The process is most commonly run in the 24-31 bar (350-450 psi) range with a pH in the 4-5 range, since the peak stability pH for dextrose is 4.5. There are two common temperature ranges used in dextrose purification: 45-50°C (113-122°F) and 65-70°C (149-158°F).

MICRODYN-NADIR has two nanofiltration membranes that have proved successful in dextrose purification applications. For more information, please contact MICRODYN-NADIR.

A typical sugaring season lasts 4 to 6 weeks, usually somewhere between the months of February through April. By late spring when the trees begin to produce leaves and flowers, a chemical change occurs in the sap giving it an unpleasant “buddy” taste. A pattern of freezing and thawing temperatures (below freezing at night and 4.4-7.2°C or 40-45°F during the day), builds up enough pressure within the maple trees, causing the sap to flow through from the tap holes. The sap collected in buckets must be gathered by hand, while sap from pipelines is drawn back to storage tanks at the sugarhouse using a vacuum pump. From the storage tanks, the sap is sent through a reverse osmosis system to remove a large percent of water from the sap before boiling.

REVERSE OSMOSIS FOR CONCENTRATING MAPLE SAP

Maple sap is pumped through a series of reverse osmosis (RO) elements to remove water and to produce a more concentrated maple sap product. Concentrating maple sap with RO significantly increases the efficiency and profitability of processing sap into syrup by reducing the amount of both fuel and time required to concentrate the material to syrup density in the evaporator.

Spiral-wound RO elements are used to remove 75% or more of the water from maple sap before it reaches the evaporator. Standard maple sap RO elements may increase the sugar concentration to as high as 22% while high brix maple sap RO elements may be used to concentrate the sugars up to as high as 25-40%. MICRODYN-NADIR offers both standard maple sap RO elements as well as high brix maple sap RO elements. TRISEP® Maple XP-8040 elements may be used to concentrate the sugars up to 22%, while TRISEP® Maple HB-8040 elements may be used to concentrate sugars up to 25-40%. For more information, please contact MICRODYN-NADIR.

After being concentrated by reverse osmosis, the sap is sent to the evaporation process. As the sap boils, water evaporates, and the sap becomes denser and sweeter. The evaporation process concentrates the sugar to approximately 66.9-68.9%, producing the final product known as maple syrup. The syrup is then filtered and bottled.