A Comparative Analysis of the Physico-Chemical Properties of Pectin Isolated from the Peels of Seven Different Citrus Fruits

In the present research work, pectin was isolated from the peels of seven citrus fruits (Citrus limon, Citrus limetta, Citrus sinensis, Citrus maxima, Citrus jambhiri, Citrus sudachi, and Citrus hystrix) for a comparison of its physicochemical parameters and its potential use as a thickening agent, gelling agent, and food ingredient in food industries. Among the seven citrus fruits, the maximum yield of pectin was observed from Citrus sudachi, and the minimum yield of pectin was observed from Citrus maxima. The quality of each pectin sample was compared by using parameters such as equivalent weight, anhydrouronic acid (AUA) content, methoxy content, and degree of esterification. It was observed that all seven pectin samples had a high value of equivalent weight (more than 1000), suggesting that all the pectin samples had a high content of non-esterified galacturonic acid in the molecular chains, which provides viscosity and water binding properties. The methoxy content and degree of esterification of all the pectins was lower than 50%, which suggests that it cannot easily disperse in water and can form gel only in presence of divalent cations. The AUA content of all isolated pectins samples was above 65%, which suggests that the pectin was pure and can be utilized as a food ingredient in domestic foods and food industries. From the FTIR analysis of pectin, it was observed that the bond pattern of Citrus maxima, Citrus jambhiri, and Citrus hystrix was similar. The bond pattern of Citrus limon, Citrus limetta, and Citrus sinensis was similar. However, the bond pattern of Citrus sudachi was different from that of all other citrus fruits. The difference in the bond pattern was due to the hydrophobic nature of pectin purified from Citrus limon, Citrus limetta, Citrus sudachi, and Citrus sinensis and the hydrophilic nature of pectin purified from Citrus maxima, Citrus jambhiri, and Citrus hystrix. Hence, hydrophobic pectin can be utilized in the preparation of hydrogels, nanofibers, food packaging material, polysoaps, drug delivery agents, and microparticulate materials, whereas hydrophilic pectin can be utilized for the preparation of gelling and thickening agents.