Effect of Processing and Storage Relative Humidity on Selected Functional Properties of Cocoyam (Colocasia Esculenta) Corm Flour

摘要

The effect of processing and storage relative humidity on selected functional properties of cocoyam flours was investigated. Peeled, sliced (3-5mm) taro corms were washed and divided into three parts that were respectively blanched (5 min) in boiling hot water (BT); sulphited in 0.025% metabisulphite (Na2S2O5) solution (4 h) and blanched (5 min) in the same solution (SBT); and left untreated (NT) (the control). The slices were sundried (34 ± 2oC, 3 days), milled, sieved (65 mesh screen, 0.208 mm) and the flours stored under 11, 33, 53, 67, 75% and ambient relative humidities (RH). Flours were analyzed for bulk density (BD), water and oil absorption capacities (WAC, OAC), foaming capacity (FC) and foam stability (FS) at 0, 1, 3, 5 and 7 months. Blanching significantly increased the BD, WAC and OAC but significantly reduced the FC and FS. Sulphiting has no influence on these functional properties. The BD decreased during storage with significant reduction at 53% RH and above. WAC decreased significantly with increasing storage time and RH. The OAC increased insignificantly during storage and with increasing RH; attaining the maximum increased at 53% RH. The FC increased with increasing storage time and RH. The increase in FC of flours stored under ambient, 11 and 33% RH was insignificant but significant for storage at 53, 67 and 75% RH. Only NT flour retained 7.44 – 8.80% of its foam after 1 h. The stability of the foam was higher under low storage RH. Interaction of storage RH and time were significant in BD and FS but insignificant in WAC and OAC Keyword: blanching, cocoyam corm, functional properties, relative humidity, storage, sulphiting