Effects of Osmotic Treatments on Modulating Bitter Flavanones Glycosides Contents and Microstructure of Citrus aurantium Peels

Abstract

This study investigated the use of wet and dry osmotic dehydration for modulating the bitter taste of Citrus aurantium peels, imparted by the predominance of flavanones glycosides in their albedo; namely naringin, neohesperidin, and neoeriocitrin. For this purpose, the peels were subjected to dehydration-impregnation by soaking (DIS) in 40°Brix sucrose solution at 25°C and in 60°Brix sucrose solutions at 25 and 50°C and to dry osmotic dehydration (DOD) at 25°C for 6 h. The peels had not shown the immediate dewatering phenomena in the DIS process but rather an imbibition of sucrose solution, reflected in water and sugar gains. Such a tendency has shown to be ascribed to the porous structure of the albedo which fostered the capillary inflow of external liquid. The imbibition was observed during 6 h of treatment in low concentrated sucrose solution whereas in high concentrated ones, it was followed by the dewatering phenomenon thereby inducing an increase of pore volume together with a decrease of cells size. Conversely, in the DOD process, the expected cross transfers of water and sugar were markedly observed. The water was removed from both albedo and flavedo. Indeed, the essential oil cavities exhibited elongation of their shape in line with shrinkage of the peel. The two techniques allowed loss of bitter compounds and gain of sucrose. Nonetheless, The DIS gave rise to higher gain of sucrose and losses of flavanones glycosides than DOD.

Flavedo and albedo of five citrus fruits from Southern Italy: physicochemical characteristics and enzyme-assisted extraction of phenolic compounds

“…Excepting SA, albedo showed lower BD than flavedo. Most likely, albedo being highly porous materials [23,24] were made of less dense and lighter particles. On the contrary, flavedo being rich in oils [25] delivered particles that aggregated and formed bigger complexes.…”