Effects of Acids and Salts on Physicochemical and Rheological Properties of Pickled Duck Eggs (Meidan)

• Main Authors: Shu-Ying Cheng, 鄭淑瀅
• Other Authors: Po-Yuan Chiang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/64141161053565602698

碩士 === 國立中興大學 === 食品科學系 === 93 === Plum brine (salinity 23.24%, pH 2.98, and titratable acidity level of citric acid of 2.35%) is the transudate which produced by pickling plums with salt, containing plum extraction, high salt content, organic acids content and plum flavors. Because the salinity of plum brine is similar to saturated saline (26%), and its organic acids may accelerate the pickling, we used it for pickling duck eggs and hope a pickled product as the traditional osmotic dehydration. The study considered the pathway of both acid and salt into duck eggs at the same time, contrasted meidan with salted egg which brined by immersion method, and investigated the components, microstructure, physicochemical and rheological properties and the correlation among them. During pickling, eggshell thickness, calcium and magnesium content and collagen content of meidan eggshell were decreased. Scanning electron micrographs showed an increase of pore size and rough porous inner palisade layer of eggshell that promoted NaCl infiltration because it was reacted with acid. NaCl concentration, total solid, Q value, apparent viscosity, hardness, yolk index and tan δ of meidan yolk increased (r2 ＞ 0.80) with dehydration and its surface sulfhydryl group decreased during pickling period. On the 30th day, the scanning electron microstructure of meidan and salted egg look like polyhedral grains. NaCl concentration, total solid, apparent viscosity and albumen index of meidan white increased with dehydration; apparent viscosity and albumen index of salted egg white decreased, their surface sulfhydryl group were decreased during pickling. In dynamic rheological test, G’ (storage modulus), G” (loss modulus) and tan δ (loss angle) of meidan white depended on frequency; in salted eggs there was no appreciable difference between moduli. Because denaturation of protein or its structure changed by dehydrating or reacting with NaCl or acids, showed that physicochemical properties of pickled eggs influenced its own physical properties, and the physical properties influenced its own viscoelasticity. During pickling, eggshell surface of meidan eroded by organic acids of plum brine which made it crumbly and porous that increase infiltration of component of plum brine into eggs. In sensory evaluation, the overall acceptance of the 24th day meidan yolk got the better grade which got salinity of 2.10% and hardness of 228.35 g. The panelists advised meidan yolk could be the main product, because its unique plum flavour, we advised just commercialize meidan yolk. Meidan was not only salvaged the waste liquid (plum brine) of mei processing, but also developed it to form a new egg product.