Abstract
The fermentation stage is considered to be one of the critical steps in coffee processing due to its impact on the final quality of the product. The objective of this work is to characterise the temperature gradients in a fermentation tank by multi-distributed, low-cost and autonomous wireless sensors (23 semi-passive TurboTag® radio-frequency identifier (RFID) temperature loggers). Spatial interpolation in polar coordinates and an innovative methodology based on phase space diagrams are used. A real coffee fermentation process was supervised in the Cauca region (Colombia) with sensors submerged directly in the fermenting mass, leading to a 4.6 °C temperature range within the fermentation process. Spatial interpolation shows a maximum instant radial temperature gradient of 0.1 °C/cm from the centre to the perimeter of the tank and a vertical temperature gradient of 0.25 °C/cm for sensors with equal polar coordinates. The combination of spatial interpolation and phase space graphs consistently enables the identification of five local behaviours during fermentation (hot and cold spots).
Highlights
Coffee is one of the most popular and highly consumed food products in the world
II-G in Eckmann and Ruelle 1985), the best way to reconstruct the phase space from a time series is by using time delays
The analysis showed that height had a relevant effect (F=41.4, p
Summary
Coffee is one of the most popular and highly consumed food products in the world. According to the International Coffee Organization, during the 2012–2013 harvest, 145 million 60kg bags were produced globally. The quality of coffee beverage is strongly related to the chemical composition of the roasted beans but is dependent on the postharvest processing (Illy and Viani 2005). To produce coffee beans suitable for transport and roasting, there is a need to separate the seeds from the outer layers. Coffee cherries are processed by either “dry” or “wet” methods to separate the beans from the pulp. In this method, the coffee cherries are first depulped to remove the skin (exocarp) and the pulp (outer mesocarp).
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