September 3, 2012

Hydrocolloids are a major group of chemicals most people have never heard of.  They serve very important functions both as food ingredients and for industrial applications.  The three principal hydrocolloids are pectin, xanthan gum, and carrageenan.

For many years Vincent screw presses have been used in the production of pectin, a polysaccharide food ingredient used for thickening.  Since most pectin is extracted from lemon and lime peel, we probably got into this market because of our roots in the citrus industry.  What was different about the pectin presses was that they had to be manufactured in a vapor-tight configuration.

Vapor tight presses are also suitable for other hydrocolloids where flammable solvents are used, including xanthan gum.  Xanthan gum is produced using a grain (usually corn) fermentation process.  Alcohol is used to precipitate and wash the gum following fermentation.  The flow from the fermenter may or may not be pre-thickened ahead of the screw press.  If pre-thickening is used, generally this is done with a screen.

For xanthan gum, as with pectin and soybean protein concentrate, vapor-tight presses are used to separate the aqueous alcohol solution ahead of a dryer.  Safety standards for our presses, especially those built with the European ATEX certification, are very stringent.  Explosion proof motors and tightly sealed covers are just a start.  Today RTD's (remote temperature detectors) are installed on the cone bushings, bearings and other potential hot spots.  Besides temperatures, a variety of other variables should be monitored.

Inert gas, usually nitrogen, may be pumped into the press compartment containing the screens.  The system can be either slightly pressurized so that air does not leak in, or under a slight vacuum to prevent alcohol from leaking out.  An oxygen meter may be used to monitor the oxygen concentration inside he press.  The system can be designed with alarms and automatic shutdown if the oxygen concentration increases above safe levels.

The cake discharge is usually enclosed, but it works well in an "open to atmosphere" system.  Ventilation can be used to ensure that the solvent concentration stays below the lower explosive limit.

Products related to xanthan gum include welan and gellan, with gellan gum falling in the food-grade category.  It is promoted as an alternate to pectin.  Welan is used industrially in applications such as oilfield drilling mud.  Gums used in frac drilling are vital and highly specialized.


In Wikipedia we read (somewhat edited for brevity):

Xanthan gum was discovered by an extensive research effort by Allene Rosalind Jeanes and her research team at the United States Department of Agriculture, which involved the screening of a large number of biopolymers for their potential uses. It was brought into commercial production by the Kelco Company under the trade name Kelzan in the early 1960's.

One of the most remarkable properties of xanthan gum is its ability to produce a large increase in the viscosity of a liquid by adding a very small quantity of gum, on the order of one percent. In most foods, it is used at 0.5%, and can be used in lower concentrations. The viscosity of xanthan gum solutions decreases with higher shear rates.  This means that a product subjected to shear, whether from mixing, shaking or even chewing, will thin out, but once the shear forces are removed, the food will thicken back up.  A practical use would be in salad dressing: the xanthan gum makes it thick enough at rest in the bottle to keep the mixture fairly homogeneous, but the shear forces generated by shaking and pouring thins it, so it can be easily poured.  When it exits the bottle, the shear forces are removed and it thickens back up, so it clings to the salad.

In foods, xanthan gum is most often found in salad dressings and sauces. It helps to prevent oil separation by stabilizing the emulsion, although it is not an emulsifier. Xanthan gum also helps suspend solid particles, such as spices. Also used in frozen foods and beverages, xanthan gum helps create the pleasant texture in many ice creams. Toothpaste often contains xanthan gum, where it serves as a binder to keep the product uniform.  Xanthan gum also helps thicken commercial egg substitutes made from egg whites, to replace the fat and emulsifiers found in yolks.

In the oil industry, xanthan gum is used in large quantities, usually to thicken drilling mud. These fluids serve to carry the solids cut by the drilling bit back to the surface.  When the circulation stops, the solids still remain suspended in the drilling fluid. The widespread use of horizontal drilling and the demand for good control of drilled solids has led to its expanded use. It has also been added to concrete poured underwater, to increase its viscosity and prevent washout.

In cosmetics, xanthan gum is used to prepare water gels, usually in conjunction with bentonite clays. It is also used in oil-in-water emulsions to help stabilize the oil droplets against coalescence. It has some skin hydrating properties.

Issue 249