Respiratory rate and vital heat of some specialty vegetables at various storage temperatures

Abstract

Respiratory rate was measured and vital heat calculated for 18 specialty vegetables {arugula or roquette [Eruca sativa Miller], banana flower bud [Musa x paradisiaca L. var. paradisiaca], bitter gourd [Momordica charantia L.], cassava [Manibot esculanta Crantz], chayote [Sechium edule (Jacq.) Swartz], Chinese chive [Allium tuberosum Rottler ex Sprengel], Chinese water chestnut [Eleocharis dulcis (Burm. f.) Trin. cx Henschel], drumstick [Moringa oleifera Lam.], giant or elephant garlic [Allium scorodoprasm L.], guar [Cyamopsis tetragonoloba (L.) Taub.], hyacinth bean [Lablab purpurus (L.) Sweet.], Jerusalem artichoke [Helianthus tuberosus L.], jicama [Pachyrhizus erosus (L.) Urban], methi [Trigonella foenum-graecum L.], salsify [Tragopogon porrifolius L.], tindora [Coccinia grandis (L.) Voigt], tomatillo [Physalis ixocarpa Brot. ex Hornem.], and tumeric [Curcuma longa L.]} at 0, 5, 10, and 20 °C. Respiration rates increased more or less exponentially with increasing storage temperature in all the vegetables tested, CO2 varying from 28 to 302 mg·kg-1·h-1 at 20 °C for tumeric and drumstick, respectively. At 0 °C, the same products had the lowest and highest respiration rates of the products measured (i.e., CO2 at 4.5 and 28 mg·kg-1·h-1, respectively). Among the vegetable tested, above ground plant parts such as leaves, fruit and flowers generally had higher respiration rates than subterranean storage organs such as roots, corms and tubers. Vital heat produced range from 49 J·kg-1·h-1 for tumeric at 0 °C to 3272 J·kg-1·h-1 for drumstick at 20 °C.