Physicochemical Variability of Pectin from Different Okra Phenotype

Okra (Abelmoschus esculentus L.) is a readily available plant in Ghana and considered an abundant source of pectic polysaccharides which are useful ingredients for the functional food industry. Pectin extracts from eight different okra samples obtained from different sources were evaluated for their physicochemical and functional properties. The structural and molecular characteristics were analysed by means of Fourier transform infra-red (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (NMR) and size-exclusion coupled to multi-angle light scattering (SEC-MALS). The water absorption, oil absorption and emulsification capacities of the pectin extracts were determined. Results showed that the crude okra pectins had total carbohydrate contents in the range of 59.2 to 70.2% whereas protein content varied from 8.0 to 15.1%. The FTIR and¹H-NMR spectra revealed similar structural features whereas the weight average molecular weight (Mw) ranged widely from 320×10³ to 7600×10³ gmol^–1 in the order Pora < Akrofo < Asha < Asontem < Penkrumah (Techiman) < Sengavi < Penkruma (Kenkeso) < Agbagoma.The water/oil absorption capacity and emulsification capacity of the pectin isolates also varied depending on the geographical source. The relatively high galacturonic acid content of the pectins conferred hydrophilic characteristics that positively influenced the water absorption capacity of the polymers in solution. Pectin from the okra phenotypes Sengavi and Agbagoma shown to have low RG-I fractions demonstrated increased oil holding (378g/100g and 384g/100g respectively) and emulsification capacities (45%). The present findings indicate that the differences in pectin characteristics among the okra phenotypes have the potential to be exploited for different technological applications.