Drying the green herb shado beni (Eryngium foetidum L.) in a natural convection cabinet and solar driers.
1994
Sankat C.K. | Maharaj V.
The food flavouring herb Eryngium foetidum L. commonly called "shado beni" or "bhandanya" in Trinidad, "ngo gai" in Vietnam or "ketumbar jawa" in Malaysia was dried in a natural convention cabinet drier at 35 degreeC, 45 degreeC and 65 degreeC to determine its drying characteristics. Drying in the falling rate period was strongly temperature dependent with two drying periods adequately describing the drying behaviour. Drying constants were 0.064 h-1, 0.265 h-1, 0.296 h-1 and 0.782 h-1 for the first falling rate period (m.c. > 8) at 35 degreeC, 45 degreeC, 55 degreeC and 65 degreeC, respectively. In two similar low cost, natural convection, solar driers of the direct and indirect types operating at average daily temperatures of 39.5 degreeC and 37.6 degreeC respectively, the herb's moisture content was reduced from an initial average value of 835 (dry basis) to 9 and 20 for the direct and indirect driers respectively, in 5 days. On drying, the volatile oil content of the herb dropped from 0.84 (dry matter basis) to 0.12 and 0.19 for the direct and indirect driers respectively. Blanching the herb in hot water at 96 degreeC using a quick dip step followed by drying in the indirect drier reduced the loss of green colour normally observed on direct drying without pre-treatment. Blanching did not affect the drying rate behaviour of the herb.
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