Coffea Arabica or simply Arabica (pronounced a-ra-bik-a) and Robusta are two of the species of the Coffea genus.  The primary differences between them are taste and the conditions under which the beans are grown and processed.

Arabica has a smoother, sweeter and less bitter taste and typically have less caffeine than Robusta coffees.  Arabica plants are delicate plants and require cooler tropical climates, high levels of moisture, fertile soil and an equal combination of shade and sun. These elements can be found between the Tropics of Cancer and Capricorn.  They are often handpicked and wet processed which is gentler on the beans and there is a higher chance that the beans will be perfectly ripe when harvested.

Robusta beans typically have a distinct earthy flavour with a less fragrant aroma.  Robusta coffees generally have a higher caffeine level than Arabica coffees. Probably named after its robust nature, Robusta beans are hardier and are less susceptible to pests and disease, and therefore require much less herbicide and pesticide than Arabica.   While still grown primarily in the same region as Arabica beans, Robusta beans are grown at lower elevations and are often machine picked and dry processed to remove the cherry.  These methods are less discerning between the ripe, under ripe and over ripe beans and the processing is not as gentle on the beans.   

The Italians traditionally use more Robusta than Arabica and the French will use about 30% Robusta with 70% Arabica.  Robusta is also often used to produce instant coffees, and in espresso blends to promote the formation of "crema".  

A good espresso blend needs a small percentage of Robusta because when the beans are ground the Robusta helps provide a better foundation for espresso extraction resulting in a thick crema which gives the coffee body.  In our opinion, a full-bodied crema (which you’ll only get with a little robusta mixed in) is more desirable for the devoted espresso coffee drinker than a thin or mostly non-existent crema from a 100% Arabica coffee.  

Next time you buy a pack of roasted coffee beans grab a handful of the beans and spread them out onto a flat surface. Look at both the shape and size.  Arabica beans will be larger than the Robusta bean. They will be more oval in shape as opposed to the Robusta’s round shape, and the Arabica will sit flatter than the more dome-like Robusta bean.  Work out the percentage of Robusta compared to the total bean count.  If the Robusta is less than 10% of the total beans and they are whole and in good shape then you have an ideal blend for espresso coffee making for milk based drinks.