Hot Air Roasting

A key part of our philosophy to coffee is exemplified by the fluid bed roasting method we have perfected over three decades. Originally developed by Michael Sivetz, the fluid bed roasting process, also known as hot air roasting, uses forced hot air to agitate and roast coffee beans. The perfectly controlled hot air flows over a tilted bed and circulates through the beans, roasting each bean evenly. This hot air reaches temperatures of between 450 and 485 degrees fahrenheit.

During the roasting process, the green coffee beans go through two major “pops” or “cracks” The first occurs when the internal temperature of the bean reaches approximately 356 degrees fahrenheit. By this point the silverskin or chaff has been expelled from the bean as it expands to double its original size. In the fluid bed roasting process, this chaff is blown out of the roaster into a separate chamber and not burned up with the coffee. Because coffee is so absorbent, if this chaff were burnt within the roasting chamber, the beans would soak up this unwanted flavor and present itself in the cup. In the same way, the hot air blows out any other impurities from the batch, so the only thing that is roasted and tasted is the coffee itself. This process of eliminating chaff and impurities is a unique and important aspect of the fluid bed roasting method that we employ each day.

Another advantage stems from the greater efficiency in heat transference that is possible with hot air roasters. The beginning stages of coffee roasting are focused on driving moisture from the bean; this moisture content can be as much as 12% by weight. The bean can not actually be roasted until the moisture is removed, so this step is critical. When the coffee bean still contains this moisture, prolonged exposure to high heat results in “cooking” rather than “roasting” of the bean. The longer it cooks, the greater the formation of acids such as acetic and quinic. Since the fluid bed roaster can reach higher temperatures in half the time of typical cylindrical roasters, the time for these acidic compounds to form is greatly reduced. Many have found that these acidic compounds can cause stomach irritation, and we have many customers that had given up on coffee but can now drink ours comfortably.

Longbottom coffees are characterized by a smooth, rich flavor that reflects the roast level and true essence of each bean.