Performances et amélioration de quelques systèmes traditionnels de récolte et de conservation post récolte du macabo (Xanthosoma sagittifolium L.)

Abstract

Corms from 2 varieties of cocoyam (Xanthosoma sagittifolium L.), the red and the white fleshed were pre or post harvest handled and tested with different factors in a combined or a sequential context, for preservation or improvement of quality performance in storage. Freshly harvested corms, at 10 and 11 months stage of maturity, were dipped in 1% sodium hypochlorite solution, and packaged in jute bags and perforated plastic bags with holes of 8 mm in diameter and 10 cm in spacement. Products were thereafter placed in storage shelves covered with a metallic net. A second lot of corms of the two selected varieties were, following harvest, wounded and bruised, in simulation of mechanical damages, and placed in mounds before storage. A last lot of corms were harvested 1 and 2 weeks after pruning of cocoyam plants and placed in storage. Performance records obtained after 2 months of shelflife have shown a significant (p<0,05) hight improvement of the overall postharvest visual quality of tubers harvested after 10 and 11 months of maturity (31,90 % and 33,90 % respectively). The use of perforated plastic bags significantly (p<0,05) reduced weight loss in stored cocoyam corms (25,90 %), in comparison with that in jute bags (30,65 %) or the records obtained with control products (29,89 %). Dipping of corms in a 1 % NaOCl bactericide solution was ineffective in rotting control. The white cocoyam corms has produced a more (p<0,05) developed sprouting (8,05 %) as opposed to that of the red cocoyam (0,36 %). Regardless of the variety , corms harvested at 10 and 11 months of maturity significantly (p<0,05) produced more elongated sprouting (4,69 % and 5,03% respectively) than the products harvested at 8 and 9 months after planting, which developed respective and comparable sprout formations of 3,67 % and 3,46 %. The red cocoyam has recorded a significantly (p<0,05) higher weight loss (32,48 %) than the level obtained in white cocoyam (25,33 %). Mounding of wounded or injured corms prior to storage has produced a noticeable shelflife quality preservation, and has contributed to 10 % and 14 % drops in water loss in white and red cocoyam respectively. Contrarily to the expected positive effect , mounding was ineffective (p>0,05) in wound healing, and in decay and sprouting prevention. Similarly, pruning did not yield a significant impact on weight loss, sprouting and decay control of cocoyam. Pruning of plants 2 weeks before storage favored a higher total sugars accumulation (80 %) in the tubers whereas delaying of that operation for 1 week or until harvest time led to the respective and reduced records of 77 % and 70 %. In addition, a relatively lesser reduction of 5 % in starch content was recorded in tubers from plants pruned 2 weeks before storage as compared to higher proportions obtained when plants were pruned 1 week prior to storage (8 %) and when pruning were done on harvest day (10 %). Moreover, pruning has significantly (p<0,05) improved the organoleptic quality of cocoyam. Corms from plants that were pruned 2 weeks and 1 week before storage have received higher and comparable preference records (56,44 % and 59,83 % respectively) than the reduced record (48,25 %) attributed to control products.