The onion is a major export crop in Argentina and obtaining consistent quality is a matter of concern to remain competitive internationally. Grading is generally done according to Mercosur standards but quality assurance programs are necessary at the packinghouse level. The objective of this study was to develop a first approach for characterizing sorting and sizing efficiency. During the 1998 season five onion packinghouses located in the Valle Bonaerense del Río Colorado (Buenos Aires Province, Argentina) were randomly selected. In all of them, variables measured were: sorting table width, bulb transport and rotation speed as well as number of bulbs/sorter/hour. Before and after sorting, samples of 100 bulbs of each size category were randomly taken and closely inspected and their diameters were measured. Sizing efficiency was determined and a Chi-square test was performed to compare observed frequencies of defects with the expected ones within each category. All the studied packinghouses failed to meet the established limits for slight defects and only one of them was able to comply with the standards for basic requirements when preparing Extra class onions. Even when equipment and operational setup were different among packinghouses, the operational flux (bulbs/sorter/hour) was similar for all of them. Differences in sorting performance can be attributed mainly to the sequence of operations and speed of belt conveyors. Equipment and its calibration affected sizing efficiency, with better results obtained with the diverging roller system. The proposed methodology for characterizing efficiency could be considered as a simple and useful tool for monitoring quality at onion packinghouses.
Allium cepa; packhouse; sorting; quality; postharvest; Allium cepa; beneficiamento; clasificação; qualidade; pós colheita
