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Solutions
for
Soluble Coffee

BY DR. TERRY MABBETT

In every single respect, the invention and development of soluble coffee was a logical and sensible step forward. Socially, commercially and scientifically, soluble coffee was an “instant” impact waiting to happen.

The flavor compounds (or their precursors) that coffee lovers pine for, and the caffeine stimulant that coffee addicts crave, start their “journey” by being dissolved -- to a greater or lesser extent -- in the lively and watery fluid of freshly picked coffee. And at the journey’s end, now molded and modified by roasting, they are re-dissolved and infused in the bland boiled water of the coffee drinker’s cup.

Water (dihydrogen oxide or H2O) is the basis of life, and the life-giving force to coffee solutions. Water is the only ubiquitous, plentiful and normally liquid compound on this planet with the ability to dissolve and carry solid chemicals. Thus, coffee chemicals can be conveyed by a solution in water from coffee beans, for the nourishment and enjoyment of the coffee drinker, and according to supporters of soluble coffee, the quicker the better.

When a coffee chemical is taken in through the mouth, as a component of a coffee solution, or if it diffuses up the nostrils as vapor, it cannot express a flavor profile in the absence of liquid water. This is true whether the chemical comes from the inner secrets of the percolator or from the simplicity of some 3 grams of instant coffee granules in a cup of boiling water. It requires the coffee infusion to pass into the taste bud cells on the surface of the tongue, or for the vapor to dissolve and cover the delicate membranes across the sensory cells in the nasal passage, to then reveal its hidden aroma to the coffee drinker.

However, without the invention of a soluble coffee product, this enjoyable drink would have remained preserved for the leisured and moneyed classes with all the time in the world, or all of someone else’s time, to brew their beverage.

As in the case of many other important inventions, it took major international conflict to commercialise soluble coffee. The U.S. Government, more than most, has always appreciated that fighting men and women lack tenacity on a “rusty” palate, as well as on an empty stomach. When American soldiers consigned to the mud and mire of Northern France in 1917-18, this was no exception.

The billions of sachets of instant coffee dispatched by a grateful government to its fighting men provided instant home comforts, and in the long term laid the commercial foundation for today’s mighty soluble coffee sector.

But the snobbery that surrounded coffee drinking two centuries ago still exists today, with a lingering attitude against instant coffee. Many so-called coffee connoisseurs claim that soluble coffee is no more than an instant excuse to mask and hide “rough-edged” Robusta from Africa, and ‘anonymous’ unwashed Arabica from Brazil.

If instant coffee has a rough edge, then this “expert” assessment is equally harsh. It may be really necessary to mask the organoleptic properties and effects of some coffee origins, but then they have to be hidden by something else that is presumably better. However, success may be achieved through mutual organoleptic enhancement of separate coffee origins, and then the satisfaction score of the blend is higher than the total of its component parts.

Be that as it may, the initial stages of manufacturing coffee are essentially the same, whether the finished retailed product ends up in a fine foil bag and destined for the pot, or in a hermetically sealed glass jar with a cup or mug as its direct and final destination. This equality of opportunity for real and instant coffee includes the need to blend green coffee beans, from several or more different origins before or after roasting, depending on similarity or diversity, as well as the roasting process itself.

If instant coffee is so awful, then why do countless consumers from different communities and countries, with ripe coffee cherry trees, literally in the back yard, drink large volumes of instant coffee with considerable relish?

The entry of Brazilian manufacturers into the soluble market some 40 years ago, using their own homegrown and unwashed Arabica instead of the traditional Robusta, represented a significant step forward. Until then, Robusta had ruled the roost as a cheap source of beans with twice the caffeine content of Arabica (2% to 1%), and offering higher general extraction yields at lower temperatures.

The Robusta extract, however, contained more tars, which are highly proteinaceous in nature and generally insoluble in water. Overall, the Brazilian manufactured soluble coffee made from Arabica was much better tasting, and still highly competitive because there were no export taxes, like those on green coffee beans exported from Brazil. Coincidentally, it was at this juncture in 1965 that freeze-drying for coffee was widely adopted in the manufacture of soluble products around the world.

Within two years, Brazilian manufacturers had captured almost 15% of the U.S. market, but this initial rapid growth failed to last when unfair competition was cited. In the following years, Brazil was forced to slap export taxes on soluble coffee and lift export taxes on green coffee beans to soluble coffee manufacturers in the U.S. Be that as it may, the Brazilian experience was clearly an important stepping stone in the continuing general selection of better tasting and superior coffee origins for the manufacture of soluble coffee products world wide.

Speed and convenience of preparation are clearly not the only and total answer to the continuing success of soluble coffee. Over the years the technology used to manufacture soluble coffee products has brought gradual improvements to the look, feel, taste and longevity of the final instant product, and their infusion in boiling water. As technology becomes more sophisticated and refined, and able to improve and enhance the instant coffee product, the makers have become increasingly inclined to risk finer origins in the manufacturing process.

Such have been the advances achieved, especially in the last decade, that supermarket shelves are now stacked with attractively shaped jars carrying exotic names, real-life labels and fine-flavored coffee. Indeed, they are vacuum-packed with rich and deeply colored granules, and dedicated to partially fermented (washed), uniform-roasted and full flavor Arabicas, originating from those special coffee places like Kenya, Guatemala and Java, which are equally “hot” in taste, high on aroma and full in flavor.

This is now the state and stage of sophistication in the retail sector for branded soluble coffee, “tight” on taste and quality, and a far cry from earlier “loose” talk about rough-edged Robusta and anonymous unwashed Arabica.

Improvements Down the Line
In addition to investing in more exciting and expensive origins in the manufacture of soluble coffee, the industry has continued to make quality enhancing changes and adjustments to the process itself. Now, some 40 years from the widespread commencement of freeze drying in the manufacture of soluble coffee, and considerably longer since spray drying began, it is hard to believe that coffee solutions used for making soluble products was first dried in hot revolving drums.

The spray drying process, which is less costly to set up and operate, has always catered to the largest slice of the soluble market, but in recent years, the more sophisticated and expensive freeze-drying process has started to even things up. Technology is clearly advancing hand-in-hand with the improved and higher-priced single origins, and blends now being used to resource the manufacture of soluble coffee products.

Spray drying typically produces a powder with particle sizes averaging between 200 and 300 µm (micron), whereas much larger granules are formed directly by freeze-drying. Since 1968, spray-dried coffees have been agglomerated, that is, treated so that particles cling together to form much larger granules. Agglomeration methods fall into one of two distinct categories, either the rewet method or the straight-through. Both, however, cause the cohesion (mutual attraction and sticking together) of particles of spray dried product to form granules.

Granules facilitate the rapid solution of the coffee in boiling water. Though useful, this is not the main underlying reason why spray-dried coffees are agglomerated, either at the same time or after the drying process. The move is for the more favorable, physical appearance they present to the consumer. Agglomerated spray dried formulations, now comprising of darker colored and irregular shaped granules of 1400 µm average diameter, make the product look, feel, move and sound more like roast ground coffee.

The volatile compounds produced by roasting coffee can be grouped into those which essentially give rise to the so-called “headspace” aroma from the dry product, and others that mainly furnish flavor to the brew. Those responsible for headspace aroma only occur in very small quantities that can be rapidly lost during subsequent drying operations. This potential loss of aroma is rectified by re-incorporation of volatile compounds. Coffee oil in minute quantities (less than 1% w/w), either original coffee oil or that fortified with aromatics from non-coffee sources, is “plated-on” to the final instant coffee product, usually when it is being packed into jars or other containers.

A cup of coffee is 98% water. And irrespective of how coffee is made, the taste and quality of water used will impact on cup quality. This has long been appreciated in brewed coffee where the instructions are clear. Use fresh water free of any off-tastes or odors. And unless you happen to live in one of those rare areas where tap water quality is high, only use water filtered through a simple carbon taste-and-odor filter. Would be coffee makers are warned against using very hard water (excess calcium and magnesium carbonates and bicarbonates), but should appreciate the benefits of at least some mineral content in the water. In areas where sulphur and saline (salt) intrusion is a problem, don’t take a chance. Use bottled water.

These potential problems with quality of drinking water supplies to coffee shops and households clearly have the capacity to impart off-tastes to cupped coffee, or at least mask natural flavors. Soluble coffee flavor is becoming better and more evident with the increasing use of improved single origins and blends. And therefore instant users should pay more attention to the quality of water used to dissolve the coffee granules, because in essence, water is where soluble coffee begins and ends.


Tea & Coffee - May/June, 2005
Sintercafe

ASIC 2014


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