Roasters

i.) Roasters

There are many options available for roasting samples for flavour testing. These include:

Static oven tray roasters such as table top toaster ovens and home ovens.
Converted small scale rotary type coffee roasters and rotisserie ovens.
Lab scale non ventilated box ovens.
Mechanically ventilated convention ovens.
High efficiency convection ovens.

The heating systems in these various roasting options vary from electric elements to infrared heaters with or without air or ventilation control and temperature or timer settings. At the very least, there should be some form of either temperature or timer control.

Critical factors for the most optimal roasting method to prepare samples for flavour testing include:

Thermal uniformity of the air flow throughout the oven cavity unloaded and loaded.
Thermal recovery time from door opening to set point.
Air volume movement through a circulating fan.

ii.) Roasting trays

Roasting trays should be a wide mesh stainless steel (preferred) or non-treated, mild steel wire mesh tray with mesh size small enough to prevent beans from falling through but large enough to promote optimal air flow across the beans. Galvanized or plastic coated screens should not be used to construct roasting trays. Rotary type ovens should have either mesh screen or evenly perforated drums. Solid drums are not recommended. Loading and unloading should also be uncomplicated and allow for complete discharge and cleaning which is always necessary to ensure uniformity of air flow.

Ideally, static tray ovens should be loaded with a single, wide mesh screen tray. Beans should be loaded as a single bean depth across the loading area. Where there is insufficient sample to fill the tray, filler beans should be used so that all roasts are carried out with the same bean loading. It is important to note that filler beans cannot be used to ensure uniform charge size for rotary drum roasters and so these are limited to applications where sufficient beans are always available.

iii.) Roasting conditions

Roasting conditions should be chosen to maximize the flavour potential for each type of cocoa bean and would need to be mapped according to temperature, time and loading capacity for each variety and for the specific type of roaster used.

Typically the following temperature and time combinations are suggested as a starting guide for individual roast mapping using a convection tray roaster according to aromas identified in the cut test and dominant genetic type of cocoa beans (if known):

Low roast - 112°C for 25 minutes
Medium roast - 120°C for 25 minutes
High roast - 130°C for 25 minutes

Time is measured starting from 2°C below the set point. Note that these times are based on an oven recovery time of 5 – 7 minutes from the time that the door is closed to 2° C below the set point.

Although a low roast would commonly be used for traditional Criollo types, most modern Criollo types will usually be roasted following the Medium roast conditions. This is because they are generally much closer genetically and in terms of processing requirements to traditional Trinitario beans which are normally given a Medium roast.

Roasting conditions should be selected that will promote the expression of the intrinsic fruity and floral complementary flavours whilst preserving any delicate nutty/ caramel notes of Criollo types. The high roasting conditions may be best suited for “Forastero” to bring out any complementary flavours as well as the maximum cacao intensity inherent in these types.

Both bean size and moisture content of the beans prior to roasting are important considerations and samples with very low moisture contents (< 6.5%) or very high moisture contents (≥ 8.5%) may require adjustment to be made to the roasting conditions to ensure a standardized roast for flavour evaluation. Similarly, beans may need to be sorted for size consistency before roasting. As long as bean size is in the range of 70 – 130 beans/100 g, the roasting conditions should not need adjustment for bean size.

Roasting Adjustment for both moisture content and bean size to ensure optimum roasting of beans are provided in Table 49 of the Guide for the Assessment of Cacao Quality and Flavour (Cacao of Excellence, 2023) (see www.cacaoofexcellence.org/)