Sensory characteristics of accessions of Cleome gynandra harvested at different developmental stages

Abstract

Spider plant is one of indigenous vegetable whose consumption is fast rising both in rural and urban areas. This study was designed to determine the effect of Calcium Ammonium Nitrate (CAN) fertilizer and cattle manure on the accumulation of total phenolics, total flavonoids, tannins and alkaloids as the secondary metabolites of interest during growth and storage of vegetable spider plant (var. Cleome gynandra L). Field trials were set up at the JKUAT Horticultural Farm and Ruiru in 2011 and 2012. This was followed up by two seasons of green house trials set out in the greenhouse in JKUAT between March and June, and June and September 2012. Five accessions of spider plant; Control, MLSF17, UGSF14, UGSF36 and UGSF9 were grown at three fertilizer levels in a split-plot design in field trials. Vegetables were harvested at 4, 5, 6, 7, and 8 weeks after planting. Nitrogen fertilization improved the nutritional quality of spider plants in terms of proximate and mineral compositions. Use of CAN fertilizer led to significant increases in accumulation of nitrates and alkaloids, and significant reductions in the amount of total phenolics, total flavonoids and tannins. Antioxidant activity positively correlated with both the total polyphenols and total flavonoids recorded. Nitrogen did not however, show any significant difference with sensory attributes. MLSF 17 and UGSF 14 exhibited superior characteristics in nutritional and phytochemical compositions. The 6th week after planting proved the most optimum harvesting period to derive the maximum nutrition. Spider plants have therefore a high potential to contribute to the reduction in malnutrition, especially among people in rural areas where it constitutes an important part of the diet. In addition, they grow quickly, require little input and can xv be harvested within a short period of time (4-9 weeks after planting). This is especially so when produced using CAN rates of not more than 2.6g N/plant or 40Kg N/ha. With proper fertilizer management, it is possible to obtain boost high yields and at the same time ensure high quality C.gynandra. In addition, maturity at harvest influences the vitamin and phytochemical contents. The phenolic content including that of quercetin, are also enhanced by use of manure, low levels of N as CAN and with advancing maturity of the vegetables at harvest. Application of manure/fertilizer and the stage of maturity of Cleome gynandra are critical in determining the phytochemical, nutritional and sensory characteristics of the vegetable.