Quantitative and qualitative changes in coleus (Solenostemon rotundifolius (Poir) J.K.Morton) tubers during development and storage

Abstract

Studies were conducted at Regional Agricultural Research Station, Pattambi and the College of Horticulture, Vellanikkara to analyse the quantitative and qualitative changes during development and storage of coleus tubers. During the development the total fresh biomass of the plant increased up to 90 days after transplanting in all the varieties. The absolute growth rate was highest between 75-90 days after transplanting. The leaf fresh biomass increased up to 60 OAT in all the varieties and at this stage more than 50 per cent of dry matter was present the leaves. The stem fresh biomass of stem increased up to 120 OAT, the fresh biomass of root also increased up to 120 DA T and the rate of accumulation of root dry matter was high up to 120 OAT. The fresh biomass of tuber and dry matter accumulation showed an increasing trend along with maturity of tubers. The higher growth rate was between 135- 150 OAT stages. Total number of tubers, length, diameter, peel thickness and peel percentage were found to increase with maturity of tubers. The peel colour changed from yellowish brown to brown and the flesh colour changed from yellowish cream to whitish cream during maturation. The starch and polyphenol content increased with the maturity of tubers, where as the soluble sugar increased up to 135 OAT and thereafter declined. The nematode infested tubers showed higher sugar and polyphenol content and lower starch content compared to non-infested one. The sensory evaluation indicated that the overall acceptability, increased with the advancement of maturity. Storage behaviour of coleus tuber was assessed under different conditions of storage. Sprouting and physiological loss in weight was lowest under the zero energy cool chamber storage. Room temperature and pit storage were rated next to zero energy cool chamber. The spoilage was minimum in tubers stored under room temperature followed by zero energy cool chamber. The starch content of tubers decreased and sugar content increased in storage.

No definite pattern was indicated in the polyphenol content during storage. Tubers turned dark brown under low temperature storage conditions. The tubers stored under zero energy cool chamber showed better sensory characters. Peeled tubers could be stored for two days with minimum spoilage at 8-10°C. Hot air oven dried product had a higher rehydration ratio and better sensory quality compared to sun dried one.