Sugar losses during storage – impact of different harvesting modes and storage scale

Cut-to-crush delays have been assessed regularly in Réunion. However, these assessments primarily occur at the scale of small-growers’ quantities (bundles of 1–1.5 m in height, weighing about 100 kg). In Réunion, two concerns led to this study: how to improve the management of the mill-storage area and to assess the impact of local harvesters (mini diggers equipped with a claw and a saw) on cane degradation. Cane degradation in small-growers’ bundles was compared to two larger scales: 25 t of cane stored in delivery trucks (with a design enabling core sampling) and batches of 400 t. Changes in cane temperature, mass and composition of three harvesting modes were assessed: 1) billeted cane (every 12 h up to 3 days); 2) manually cut long stalk cane; and 3) long stalk cane harvested using the local harvester (both every 48 h up to 8 days). For the 400 t batches, intermediate data could not be collected. Samples were cutter-ground and analyzed using a hydraulic press procedure that determines the cane’s sugar and fiber content, and the purity and pH of the press juice. Results showed that mass loss proportion was greater in smaller bundles than in batches of 25 t or 400 t. This is probably due to higher evaporation rates. However, sugar loss (sugar content · mass) was greater for larger batches (400 t) than for truckloads (25 t) and growers’ bundles (100 kg). Purity and pH dropped accordingly. Manually cut canes degraded less than mechanically harvested ones. This is well known for billeted cane, but when comparing the slopes between a 3-day deterioration of billeted cane to 8-days deterioration of mechanically harvested stalks, the latter shows higher degradation rates (for all parameters). Temperatures in the long stalk mechanically harvested canes were higher, and steam and fungi were observed during storage. It is thought that the local harvester’s claw and disc damage the stalks and exacerbate microbiological contamination. This study will be used to estimate sugar losses and other deterioration metrics in cane storage areas. Results from this work can be used to discuss how to manage better losses that occur during cane storage.