Effect of different alkali treatments on the chemical composition, physical properties, and microstructure of pidan white

Abstract

Changes in chemical composition, physical property and microstructure of pidan white treated with 4.5 % NaOH or 5.5 % KOH were monitored during pickling up to 4 weeks, and followed by aging for another 2 weeks. As the pickling and ageing times increased, moisture content of pidan white decreased and salt content increased for both (4.5 % NaOH and 5.5 % KOH) treatments (P <0.05). Free alkalinity and pH of pidan white treated with 4.5 % NaOH increased as pickling proceeded, but decreased during ageing for both pickling treatments (P <0.05). At week 4 of pickling, pidan white treated with 5.5 % KOH had higher hardness, cohesiveness, gumminess and chewiness than those treated with 4.5 % NaOH. After ageing, higher springiness, elastic modulus (G') and viscous modulus (G") were generally found in pidan white treated with 5.5 % KOH (P <0.05). As the pickling time increased, lower L*, b* values and higher a* value were observed in pidan white from both treatments (P < 0.05). As visualized by scanning electron microscope, the aggregation of egg proteins took place in pidan white gels, irrespective of pickling treatments used. Nevertheless, closer and more orderly protein aggregates with denser network were founded in pidan white treated with 5.5 % KOH.

Effects of temperature on quality of preserved eggs during storage

“…In addition, the fresh duck egg yolk is acidic (pH = 6.50), and the egg white is alkaline (pH = 8.94) ( Xu et al., 2017 ), which made the pH of the egg white increase more easily than that of yolk under the action of alkali solution. One of the reasons why the pH of the preserved egg white and yolk decreased with time might be that a series of biochemical reactions will occur in the preserved eggs during the pickling process, producing substances such as alcohols, aromatics, and heterocyclic compounds ( Chen et al., 2015 , Zhang et al., 2015 ), which contain some volatile basic nitrogenous substances, then dissipated to the outside through the pores of the eggshell, which eventually leads to a decrease in pH. This kind of speculation also appeared in previous studies ( Ganasen and Benjakul, 2011a , Ganasen and Benjakul, 2011c ).…”

Nondestructive Detection of the Gel State of Preserved Eggs Based on Dielectric Impedance

“…The measurements were made on individual eggs without removing the shell. Each pair of numbers (1)(2)(3)(4) in Figure 2b represents one pair of contact positions of the parallel plates; the data from the four different pairs of positions were averaged after the measurements were taken.…”

“…Using this method, the time taken to produce the preserved eggs depends on the concentration of the alkaline solution, the type and concentration of metal compounds used, and the immersion temperature. Generally, in this way, preserved eggs can be produced in a shorter time than using traditional methods that work at room temperature [ 3 , 4 ]. Combined method: This method involves a combination of the coating and immersion methods.…”

Study on Detecting the Gelling of Preserved Eggs by Using Dielectric Method

“…The preserved eggs utilize the pickling of alkaline substances to cause protein chemical reactions inside the duck eggs to solidify. In general, the production method of preserved eggs can divide into three techniques: coating method, immersion method, and combined methods [2][3][4]. After the interaction between the duck egg and the alkaline substance, the duck egg will become a preserved egg.…”