Skip to main content
NCBI home page
Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2022 Mar 15;60(3):966–974. doi: 10.1007/s13197-022-05417-0

Development of novel green methods for preparation of lead-free preserved pidan (duck egg)

Chih-Yao Hou 1, Chia-Min Lin 1, Anil Kumar Patel 2,3, Chengdi Dong 2, Ming-Kuei Shih 4, Chang-Wei Hsieh 5,6, Yu-Lin Hung 1, Ping-Hsiu Huang 7,✉
PMCID: PMC9998813  PMID: 36908336

Abstract

Pidan, a pickled duck egg, is a traditional Chinese cuisine and generally produced by soaking in metal ion containing strong alkaline solution such as NaOH solution. However, nowadays consumers possess negative perception for using strong alkali in food processing. Therefore, the objective of the current study was to determine the potential of incinerated eggshell powder and alkaline electrolyzed oxidized (EO) water for pidan production rather than harmful NaOH use. This study aims to obtain the optimal physicochemical and sensory qualities of pidan. Various dosing (1–5%) of the incinerated eggshell powder solution or alkaline EO water was used as a basic pickling solution. Duck eggs were pickled at 25–27 °C for 15–30 days with 3 days of an observation interval. Actual commercial process commonly undergoes for 14 days of ripening, after 25 days of picking process with incinerated eggshell powder or EO water. Results showed that physicochemical and sensory attributes of pidan obtained by incinerated eggshell powder solution and alkaline EO water were not significantly different (P < 0.05) from the commercial product. This study reports a cost-effective and green alternative method for pidan processing by replacing costly NaOH without compromising their physico-chemical and sensory attributes.

Keywords: Incinerated eggshells powder, Alkaline electrolyzed oxidized water, Pidan, Duck egg

Introduction

Preserved duck eggs (pidan; pídàn), or “thousand-year eggs”, “century eggs” or “millenium eggs” is a traditional Chinese food and popular in many Southeast Asian countries, such as Thailand, Malaysia, and Vietnam (Liang et al. 2020). It is a ready-to-eat food and produced by pickling duck eggs in a salty and highly alkaline mixture. Traditionally, the mixture was composed with clay, wood ash, quicklime, and salt. Presently, the mixture is changed to a solution composed with 4–5% sodium hydroxide (NaOH) and several metal ions including Zn, Mg, and Cu (Zhao et al. 2014). The principle of pidan production is that alkaline substances penetrate the eggshell through their pores, resulting in the denaturalization and gelation of albumen proteins along with the solidification of yolk. This process induces the cascade of biochemical reactions that not only change the texture of the pickled egg but also produces numbers of small molecules developing strong flavor and aroma (Eiser et al. 2009). The texture changes include gelation and white crystalline formation on the surface of albumen called songhua which means pine needle flowers, it has been named due to its similarity with pine needles. The pickled eggs are further ripened for days to enrich with the flavor and aroma. The final pidan product exhibits several typical attributes such as greyish and semi-solidified yolks as well as fully elastic, dark brown to black and translucent albumen. Since it has a strong aroma and flavor, hence people usually do not like it at their first try. Moreover, major misconceptions by people due to its taste is that pidan is spoiled. Though, pidan is a preserved food with such a unique taste. Nevertheless, pidan is an excellent method to preserve the rich nutrients of egg and its special taste and aroma make it an essential dish for many Chinese cuisines. It also retains all beneficial micro-nutrients that are found in fresh eggs, such as vitamin A, D, and B (group) as well as metal ions including iron, selenium, phosphorus (Ai et al. 2020). The major carotenoids in egg yolks are carotene, cryptoxanthin, zeaxanthin, and lutein, which are linked to a lower risk of age-related macular degeneration (AMD), cataracts, heart disease, and some types of cancer. The lecithin and choline containing yolk is also rich in several vitamins which are essential for healthy cell membranes, brain, neurotransmitters, and nervous system (Kuang et al. 2018).

Egg production has increased in recent decades, and has reached a volume of 73 million tons worldwide (Abín et al. 2018). Egg is one of the most consumed food items. The main reason is that eggs are not only a valuable source of protein, but also inexpensive edible. However, eggshell is the main waste generated from eggs processing. The main component of eggshell is calcium carbonate (CaCO3), which converts into calcium oxide (CaO) once incinerated at high temperature (600–900 °C) (Bonnard et al. 2020). When CaO dissolves in water it forms calcium hydroxyl (CaOH2) and generates a highly alkaline solution (Seo et al. 2019). Likewise, other natural shell waste such as oyster shell is also composed of CaCO3 and several studies reported its application (in powder form) to prepare alkaline solution for alkaline treatments. The solution of incinerated oyster powder at 0.01% (v/v) was demonstrated to reduce bacteria populations effectively and a potential ingredient of food cleaner, antiseptic or hand sanitizer (Ro et al. 2015). The mixture of 0.2% oyster and 0.3% eggshell increased the sensory qualities of cooked pork and proved as an alternative substance of artificially synthesized phosphate salts (Cho et al. 2017). In addition, it also increased the sensory qualities and shelf life of pork ham and kimchi (Choi et al. 2006).

Electrolyzed oxidized (EO) water has also been used for food sterilization and disinfection, particularly in Japan for more than 20 years (Liu et al. 2021). The acidic/alkaline EO water has been used to disinfect fresh cut vegetables, fruit as anti‐browning/ antimicrobial agents (Iram et al. 2021), and food contact surfaces such as cutting boards (Kim and Hung 2014). The alkaline EO water possesses a high pH (> 11), which has been used as a cleaner in the food industry (Rahman et al. 2016; Khalid et al. 2020), emerging as replacement of polyphosphate (50%) treatment (Lin et al. 2020). So far as one of the most promising sterilization agents for microbial control in the food industry in recent decades (Zhao et al. 2021). Both waste products: Eggshell, a major waste of egg industry (after incineration) and EO water, a by-product of acidic electrolyzed water, exhibit remarkable alkalinity hence finds main application in cleaning/sterilization processes. However, the potential usage of eggshell powder and alkaline EO water to become an alternative alkaline substance of sodium hydroxide (NaOH) in pidan production has not been examined before. Therefore, the objective of this study was to evaluate the effectiveness of the incinerated eggshell powder and alkaline EO water in pidan production. The physio-chemical and sensory characteristics of the pidan produced by the incinerated eggshell powder and alkaline EO water were determined. The interaction of eggshell powder solution concentration with other key parameters e.g., pickling and ripen period were also studied. Subsequently, the pidan was characterized for pH values of albumen and yolk, hardness ratio of yolk, solidification of albumen, and texture analyses including gel strength, chewing force, hardness as well as elasticity.

Materials and methods

Duck eggs, eggshell and electrolyzed water

Duck eggs were purchased from Songgao egg enterprise (Tainan, Taiwan). All duck eggs were laid in less than 3 days of testing. The average weight of the duck egg was 50–60 g. The commercial pidan purchased from the same company was used as the positive control. The chicken eggshells and alkaline EO water were supplied by Fu-Che frozen food Co. Ltd. (Kaohsiung City, Taiwan). The Envirolyte ELA-400ANW (Tallinn, Estonia) with 0.05-0.1% NaCl containing tap water was used as an electrolyzing device to produce alkaline EO water every hour.

Preparation of eggshell powder and pickling solution

The incinerated eggshell powder was prepared by adopting Mohadi et al. (2016) and Tangboriboon et al. (2012) methods with slight modification. After washing with running tap water to remove surface debris, the clean eggshell was incinerated at 900 °C for 12 h. The incinerated eggshell was ground to obtain powder, filtered through a sieve (90 μm, Retsch Test Sieve No. 170, Haan, Germany) and stored in a desiccator. To prepare pickling solution, the eggshell powder was added in the water along with the same mole ratio of Na2CO3 to increase the solution pH. Hence the reaction of Ca(OH)2 and Na2CO3 generated sodium hydroxyl (NaOH) solution and CaCO3 precipitate (Ho et al. 2013; Seo et al. 2019). To prepare a 1–5% range of pickling solution, incinerated eggshell powder was added accordingly into water containing 1.06, 2.12, 3.18, 4.24 and 5.3% Na2CO3 respectively. Subsequently it was stirred for 30 min and placed in room temperature for 24 h. Later It was filtered with 5A filter paper (ADVANTEC, Tokyo, Japan). Other metals were also added in the final solution. Pickling solution with the incinerated eggshell powder filtrates, was composed of 5% NaCl, 0.175% ZnSO4, 0.08% MgCl2, and 0.16% CuSO4. Whereas EO based pickling solution was composed of alkaline EO water (pH 11 ± 0.1) and the abovementioned metal ions at the same concentrations.

Pickling and ripening processes

Twelve duck eggs were pickled in 1 L of pickling solution at 25–27 °C for 15, 18, 21, 24, 27, 30 days to investigate the optimal pickling time. The best physicochemical properties of the above results were used as the pickling conditions, followed by a 14 day ripening process at 25 ± 2 °C as the conditions for further experiments to investigate the best innovative process for pidan. After washing by running tap water, each group was randomly sampled (n = 3) for physicochemical analyses.

Analyses of physicochemical characteristics

Determination of pH values:

The pH values were determined by a pH meter (SP 2500, Suntex Instruments, New Taipei City, Taiwan). The yolk and albumen were separated and homogenized with sterile distilled water at ratio of 1:1 (v/v).

Hardness ratio of yolk:

After removing the unsolidified part, the weight ratio of the solidified yolk and whole yolk was used to deduce the hardness ratio of yolk. Hardness ratio of yolk = the weight of solidified yolk/the weight of whole yolk (Ganasen and Benjakul 2010).

Texture and color analyses

The appearance of pidan albumen and yolk was thoroughly observed and recorded by pictures. In addition, texture characteristics such as hardness, elasticity, cohesiveness, gel strength, and chewiness were determined by a texture analyzer (Brookfield CT3, Middleboro, USA) based on the methods described by (Zhao et al. 2020). The albumen of pidan was cut into cubes with dimension at 15 mm (length × width × height). The samples were compressed to 50% of their original height by a cylinder plunger (diameter 36 mm) with the pressing speed at 1 mm/s and retrieving speed at 55 mm/s. the samples were pressed twice for chewiness and the interval time between the two press was 5 s. Color characteristics including Hunter’s L (brightness), a (redness–greenness), and b (yellowness-blueness) values were determined by a colorimeter (Nippon Denshoku, SA2000, Tokyo, Japan).

Sensory evaluation

Based on the modified Drake and Delahunty’s method (2017), sensory characteristics including appearances, flavor, taste, texture, and overall acceptance were evaluated by 20 trained panelists. On the day of evaluation, a pidan was sliced equally into 4 parts and label by random number. The commercial pidan was used as the positive control and served as the training standard for panelists. Appearance and texture of albumen and yolk were evaluated separated due to different focuses of the sensory evaluation, for example, the focus of textures for albumen and yolk were elasticity and smoothly tasting, respectively. Each characteristic was evaluated on a continuous scale from 1 to 9 (1 = extremely dislike, 9 = extremely like). The room temperature was maintained at 25 ± 2ºC during evaluation. The panelists tasted one slice from each group, rinsed twice with drinking water between each sample.

Statistical analysis

All experiments were conducted in triplicate and repeated at least twice. All the data were presented as mean ± standard deviation (SD). Data were analyzed by using one-way ANOVA and Duncan’s test by using SPSS version 12.0 (International Business Machines Corporation, Armonk, New York). The criterion for significance was set at P < 0.05.

Results and discussions

Physico-chemical characteristics of pidan

For determining the optimal pickling time, investigations were performed for each group of samples on days 15, 18, 21, 24, 25, 27, and 30 (data not show). During the total 30 days of pickling process, there were no gels formed from duck eggs pickled with incinerated eggshell powder concentrations of 1 and 2%, respectively, whereas those pickled processed with 3 and 4% concentrations have formed gels at 24, 25 and 27 days. On the other hand, the egg pickled in both 5% incinerated eggshell powder and alkaline EO pickling solution had formed a gel showing good performance at day 25. Furthermore, the appearance of both treatments showed that the degree of albumin gelatinization was very similar compared to the negative control group, and yet there were no significant changes in the gelatinization effect when the pickling time was completed in 30 days for these Pidan products. Therefore, the results of formation and gelation we determined the conditions for the 25 days pickling in preparation for an innovative process to investigate further the pidan. Alkaline induced gelation of pidan results in the amber brown pidan white gel mainly due to the Maillard reaction of pidan white (Ganesan and Benjakul 2010). Many studies have proposed that gelation of pidan is caused by strong bases, so there are correlations between the pH values and the degree of gelation (Zhao et al. 2020). Interestingly, the difference in pH value before and after the pickling process was observed in the 1% incinerated eggshell powder group, whose pH value was below 13, while no gelation was formed. Neither complete gelation was formed in the 2% group, even with no statistical difference in pH value (Table 1). For the innovative process, the pH of the pickling solution was required to be above 13.9, as well as there was a positive correlation with the concentration of the incinerated eggshell powder contained. In addition, there were no significant differences observed in pH values as compared with negative control groups in both the 5% incinerated eggshell powder as well as the alkaline EO water treatment groups (P < 0.05). We also know from Table 1 that the pidan ripened for 14 days showed significantly better gelation than the non-ripened ones. Hence, it was determined that the best pickling is processed for 25 days followed by ripening for 14 days. Previous study (Zhang et al. 2015) and current commercial processes have also shown that the ripening process significantly increased the gelation properties of pidan. In the study, it was confirmed that pidan with better gelation properties could be obtained via the ripening process. Because, according to the results in Fig. 1, either the 3 and 4% incinerated eggshell powder did not complete gelation due to the completion of the alkaline pickling process. Following ripening, both these groups have performed well for gelation. The results also showed there were no significant differences in both groups (P > 0.05). Nevertheless, the ripening process was not effective for the groups of 1 or 2% incinerated eggshell powder (Fig. 1 A and B). Both treatment groups of 5% incinerated eggshell powder and alkaline EO water showed the same commercial appearance as the positive control group appears (shown as Fig. 1 E, F, G). Zhang et al. (2015) also used similar conditions (24–26 °C, 28 days of pickling and 14 days of ripening) to obtain consistent results. As thus, in terms of gelation effect and appearance was obtained in the following order from best to worst: alkaline EO water ≥ positive control ≥ 5% incinerated eggshell powder > 4% > 1–3%. After completing the pickling process, the pH values of egg albumen and yolk ranged from 10.81 to 11.24 and 9.69 to 10.46, respectively (Table 2). In addition, these pH values were similar after-ripening process (Table 1P < 0.05). Then, the pH values in whole treatment groups were lower than the pickling solution (pH 12–13), and the yolk was lower than that of egg albumen. Since alkali needed to infiltrate eggs from pickling solution into egg albumen, then the yolk, however the pH decreased from the pickling solution, albumen, then yolk was expected. Similar results were reported by Ai et al. (2020) and Wang et al. (2021). This infiltration of alkali along with salt and cations was the major factor to cause protein aggregation and form the special gel-like structure of pidan (Ganasen and Benjakul 2010). The difference between the pH values of albumen and yolk could be due to the series of biochemical reactions occurring during the pickling process, which produces alcohols, aromatics, heterocyclic compounds among others (Chen et al. 2015; Zhang et al. 2015). The formation of pidan occurred between pH 12.5 and 13, hence tyrosine oxidation experienced a sharp increase between pH 12.25 and 12.5 (Cai and Sweeney 2018). From pH 13 to 13.5, the increase of tyrosine oxidation was slow, and it seems to reach the maximum there. It was also reported that the degradation of ovalbumin gel may be due to the lysis of the protein skeleton when the pH value was greater than 13.5 (Cai and Sweeney 2018). However, in the study, this phenomenon was not observed. On the other hand, these substances contain some volatile basic nitrogen substances, and then dissipate through the pores of the eggshell, resulting in the loss of nitrogen and decrease in the pH value (Luo et al. 2020). Similar to a previous study (Zhang et al. 2015), the rate of yolk hardening was significantly higher in all groups following ripening, especially in the group treated with alkaline EO water (Table 2). Besides alkali, metal ions were critical for the gelation of egg protein (Zhao et al. 2020). The hardening ratio is an index for the completeness of pickling, and it increases gradually during pickling or ripening, irrespective of treatments. Therefore, the penetration of alkali, salt, and cation together cause the main changes of egg yolk protein, especially the aggregation of protein (Ganasen and Benjakul 2010). Given the above, current study added 0.18% ZnSO4, 0.08% MgCl2, 0.16% CuSO4 to enhance the solidification. Pidan produced by the regular commercial process with NaOH solution and the same metal ions carried out with same pickled as well as ripen periods, these were used as the negative control.

Table 1.

The change of pH value and gelation of pidan under different conditions during the process of pickling for 25 days and ripening for 14 days

Groups pH value Degree of gelation
Before pickling After pickling Pickling Ripening
Negative control # 13.47 ± 0.07a 13.27 ± 0.21ab  + + +   + + + 
Concentration of incinerated eggshell powder (%) 1 13.33 ± 0.06a 12.92 ± 0.09b – –
2 13.44 ± 0.05a 13.24 ± 0.03a – –
3 13.50 ± 0.03a 13.39 ± 0.01a  +   + + 
4 13.57 ± 0.03a 13.51 ± 0.07a  +   + + 
5 13.51 ± 0.06a 13.41 ± 0.03a  + + +   + + + 
Alkaline EO water 13.62 ± 0.04a 13.47 ± 0.01a  + + +   + + + 
Positive control* / 10.60 ± 0.42c  + + +   + + + 
Open in a new tab

#The composition of commercial process was 4.2% NaOH and 5% NaCl

*Positive control was commercial products

All groups (n = 18) were adding with 3 metal ions and concentration are as follows, Zn: 0.18% ZnSO4·H2O, Mg: 0.08% MgCl2, Cu: 0.16% CuSO4, respectively

Degree of gelation comparison of appearance and commercial products, the following symbols represent: “ + ” partially gelled, “ + + ” gelled, “ + + + ” perfect gelled, “–” ungelled, /: no observation, respectively

Fig. 1.

Fig. 1

Open in a new tab

Images of pidan in different treatments during pickling for 25 days and ripening for 14 days. A–E The concentration of incinerated eggshell powder is 1–5% in order. F Alkaline EO water G Positive control. C–G Left & Right, the difference is pickling and ripening, respectively

Table 2.

The pH values of albumin and yolk, hardening percentage of yolk in different conditions during pickling and ripening process

Group After 25 days of pickling After 14 days of ripening
pH value Hardening rate (%) pH value Hardening rate (%)
Albumin Yolk Albumin Yolk
3 10.92 ± 0.12aA 9.69 ± 0.23aA 51.47 ± 5.66aA 9.86 ± 0.18abB 9.45 ± 0.15aB 72.81 ± 3.46abB
Concentration of incinerated 4 11.07 ± 0.25aA 10.32 ± 0.53bA 69.45 ± 8.72bA 10.06 ± 0.18cB 9.92 ± 0.32bB 84.87 ± 4.67cB
Eggshell powder (%)
5 11.12 ± 0.31aA 10.46 ± 0.31bA 71.53 ± 5.86bA 9.96 ± 0.08abcB 9.89 ± 0.18bB 79.99 ± 6.61bcB
Alkaline EO water 11.01 ± 0.14aA 10.00 ± 0.12abA 61.94 ± 3.10bA 9.82 ± 0.13aB 9.43 ± 0.07aB 68.04 ± 5.50aB
Negative control# 11.24 ± 0.27aA 10.43 ± 0.18bA 71.43 ± 3.55bA 10.03 ± 0.07bcB 9.86 ± 0.19bB 76.98 ± 6.92bcB
Positive control* 10.81 ± 0.30aA 9.96 ± 0.52abA 72.50 ± 10.61bA 10.3 ± 0.21cC 9.84 ± 0.25bB 77.50 ± 10.6abB
Open in a new tab

#The composition of commercial process was 4.2% NaOH and 5% NaCl

*Positive control was commercial products

All groups (n = 12) were adding with 3 metal ions and concentration are as follows, Zn: 0.18% ZnSO4·H2O, Mg: 0.08% MgCl2, Cu: 0.16% CuSO4, respectively

Data are presented as average ± standard deviation. A (horizontal axis) and a (Vertical axis) averages with different letters in the same column are significantly different (P < 0.05)

Textural properties

Hardness of pidan white of all treatments increased continuously and reached its maximum during pickling and ripening process (P < 0.05). Hardness was achieved in the following order: 5% incinerated eggshell powder > positive control > alkaline EO water > negative control. This was most likely because of the higher aggregation of egg white protein mediated by calcium hydroxyl (CaOH2), which could penetrate through shell and shell membrane. Furthermore, proteins with negative charge under alkaline conditions could interact with each other in the presence of cations via lowering the repulsive force between protein molecules (Chang et al. 1999). Therefore, the hardness of the 5% incinerated eggshell powder group was the highest.

Interestingly, springiness and cohesiveness reflected the development of internal bonding in a 3-dimensional albumin gels network (Zhang et al. 2015). No difference in springiness and cohesiveness was observed in pidan albumin obtained from each treatment (P < 0.05) during pickling and ripening, while an increase in gel strength and chewiness was obtained in pidan albumin from the 5% incinerated eggshell powder treatment (P < 0.05). At the same time, no difference in gumminess was found between pidan albumin obtained from alkaline EO water and positive control (P > 0.05). However, the chewiness of pidan albumin from 5% incinerated eggshell powder treatment was higher than that from other treatments (P < 0.05), indicating the stronger gel-like structure of albumin. This result might be attributed to the lowered moisture content of albumin. The cohesiveness of yolk obtained from pidan treated with ZnCl2 or CaCl2 was higher than those from other treatments. In general, cohesiveness can be used as an indicator of a gel’s ability to maintain an intact network structure. A high cohesion value indicates that the product can withstand a complete network structure (Ganasen and Benjakul 2011). However, in the results of this study, cohesiveness of the other treatments was not significantly different from that of control (P > 0.05). Since only the samples processed by 5% incinerated eggshell powder, alkaline EO water, and negative control had solidified albumen and yolk, hence the analyses of the textural profiles of these samples were compared with the positive controls (as shown in Table 3). There was no statistically significant difference between the 5% incinerated eggshell powder, alkaline EO water, and control (P < 0.05). Results of texture analyses for each group were as follows (from high to low): 5% incinerated eggshell powder, positive control, alkaline EO water, negative control. These results were correlated with the observation of gel formation (Fig. 1).

Table 3.

Texture characteristics of albumin and yolk, gelatinization percentage of egg yolk in different concentrations of incinerated eggshell powder or alkaline EO water during pickling and ripening process

Group Hardness (g) Springiness Cohesiveness Gel strength Chewiness (mJ)
5% of incinerated eggshell powder 94.36 ± 17.42ab 0.85 ± 0.03b 0.96 ± 0.02bc 90.89 ± 16.57ab 4.55 ± 0.84ab
Alkaline EO water 79.50 ± 13.44a 0.77 ± 0.07b 0.91 ± 0.04b 71.72 ± 9.87a 3.33 ± 0.44a
Negative control# 81.10 ± 13.08a 0.82 ± 0.05b 0.95 ± 0.02bc 76.44 ± 11.08a 3.92 ± 0.55b
Positive control* 60.0 ± 14.14c 0.82 ± 0.09b 0.95 ± 0.03bc 55.0 ± 14.14c 2.43 ± 0.60c
Open in a new tab

#The composition of commercial process was 4.2% NaOH and 5% NaCl

*Positive control was commercial products

All groups (n = 6) were adding with 3 metal ions and concentration are as follows, Zn: 0.18% ZnSO4·H2O, Mg: 0.08% MgCl2, Cu: 0.16% CuSO4, respectively

Data are presented as average ± standard deviation. A (horizontal axis) and a (Vertical axis) averages with different letters in the same column are significantly different (P < 0.05)

The color characteristics

The brown albumen and the blackish-green yolk are representative features of pidan. As a result, good color and appearance is an important part of commercialization. Three parameters were tested for color: L value (1–100) stands for lightness and darkness. The parameter a stand for red and green. The parameter b stands for yellow and blue. Through the analysis, it was known that the yolk brightness of all groups was reduced during processing, the yellow gradually disappeared, and the color turned darkened significantly. The observation of pidan samples showed the egg albumen gradually turned translucent or opaque (Fig. 1), it was alike that of the previous study (Zhao et al. 2020). The values of Hunter whiteness (Wh) between the samples processed by alkaline EO water, 5% incinerated eggshell powder, and positive control were not significantly different (Table 4). The main mechanism for color alteration and gel formation during pidan processing was alkali mediated degradation of egg proteins into small peptides, which reacts with metal ions and form a stable metal ion-peptides complex (Zhao et al. 2014). In addition, some amino acids were degraded and produced H2S or NH3, which have reacted with other organic substances and offered the special aroma of pidan (Cartus 2017). The lipid compounds of eggs were also solidified due to high pH and metal ions presence, these procedures were similar to saponification (Zhao et al. 2020). In this study, the solutions of 5% incinerated eggshell powder and alkaline EO water both were able to provide a high pH environment, which was favourable for pidan processing. Thus, both solutions were potential candidates to replace NaOH for pidan preparation which claims commercial value.

Table 4.

Changes in color of pidan in concentrations of 5% incinerated eggshell powder and alkaline EO water

Group Wh L a b
5% incinerated eggshell powder 77.11 23.01 ± 2.60c 4.07 ± 0.18c 1.26 ± 0.28a
Alkaline EO water 82.22 17.88 ± 3.87a 3.72 ± 0.81b 1.45 ± 0.25a
Negative control# 76.64 23.62 ± 0.91c 6.21 ± 0.76d 1.17 ± 0.35a
Positive control* 81.05 18.99 ± 1.53b 2.4 ± 0.46a 1.34 ± 0.15a
Open in a new tab

#The composition of commercial process was 4.2% NaOH and 5% NaCl

*Positive control was commercial products

Data are presented as average ± standard deviation. Averages with different letters in the same column are significant different (P < 0.05)

Wh: Hunter whiteness = 100−[(100−L)2 + (a2 + b2)]1/2

Sensory evaluation of pidan

The samples of positive control and alkaline EO water showed the highest and lowest scores for sensory evaluation, respectively (Table 5). Overall, sensory performance decreased in the following order: Positive control > Negative control > 5% incinerated eggshell powder > alkaline EO water group. For overall performance, the Positive control and 5% incinerated eggshell powder group had the highest and lowest scores among all treatment groups. The results were similar with other evaluation indexes, these indicators were appearances, flavor, taste, and mouthfeel, respectively. Nevertheless, the scores of the samples of 5% incinerated eggshell powder were closely similar to the positive control than alkaline EO water samples. Thus, using 5% incinerated eggshell powder could be an effective alternative source to replace commercially expensive NaOH for pidan processing. It is noteworthy that the proposed use of eggshell waste material also helps in effective remediation or reuse of waste. Hence ensures the environmental protection and resource reuse aspects.

Table 5.

Effects of different conditions on sensory parameters of pidan (n = 9)

Group Appearances Mouthfeel
Color of egg white Soft-boiled of yolk Flavor Taste Elasticity of egg white Texture of egg yolk Overall
Negative control# 6.82a 6.59a 5.94a 5.68a 6.35a 6.26a 6.38a
Positive control* 6.15b 6.03b 5.56b 5.91a 6.59a 6.32a 6.29a
5% incinerated eggshell powder 6.09b 6.09b 5.53b 5.65b 6.28a 5.93b 5.98b
Alkaline EO water 5.00c 4.53c 4.97c 5.00c 4.59b 4.94c 4.71c
Open in a new tab

#The composition of commercial process was 4.2% NaOH and 5% NaCl

*Positive control was commercial products

Data are presented as average ± standard deviation. Averages with different letters in the same column are significant different (P < 0.05)

Conclusion

The outcome of the current work suggests that both incinerated eggshell powder and alkaline EO water offer adequate alkalinity to facilitate processing of commercial grade pidan. Especially, 5% incinerated eggshell powder containing solution was effective to produce quality pidan exhibiting similar physio-chemical characteristics and sensory attributes with the commercial products. In addition, eggshell powder application not only fits constraints of the recycling economics but also is environmentally friendly. Therefore, more investigation must be carried out to establish the eggshell powder as a potential green alternative resource to replace NaOH for pidan processing.

Acknowledgements

The authors would like to thank all the individuals who volunteered for this study.

Author contribution

C-ML and C-YH; Data curation, C-ML and C-WH; Funding acquisition, Y-L H and C-YH; Investigation, Y-L H, M-K S and C-YH; Methodology, Y-L H and C-YH; Project administration, C-W H; Resources, M-K S and P-H H; Software, C-ML and C-YH; Supervision, M-K S C-DD, and C-WH; Validation, C-PH, Y-L H, AKP, and P-H H; Visualization, C-YH and P-H H; Writing—Original draft, C-ML, C-YH, AKP, C-DD, and P-H H; Writing—Review & editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Ministry of Science and Technology, Republic of China (Grant no. 110-2320-B-992-001-MY3 and 110-2622-E-992-012-).

Data availability

Not applicable.

Code availability

Not applicable.

Declarations

Conflict of interest

The authors declare no conflict of interest.

Ethics approval

Not applicable.

Consent to participate

Not applicable.

Consent for publication

All authors have read and agreed to the published version of the manuscript.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. Abín R, Laca A, Díaz M. Environmental assesment of intensive egg production: a Spanish case study. J Clean Prod. 2018;179:160–168. doi: 10.1016/j.jclepro.2018.01.067. [DOI] [Google Scholar]
  2. Ai M, Zhou Q, Guo S, Fan H, Cao Y, Ling Z, Zhou L, Jiang A. Characteristics of intermolecular forces, physicochemical, textural and microstructural properties of preserved egg white with Ca(OH)2 addition. Food Chem. 2020;314:126206. doi: 10.1016/j.foodchem.2020.126206. [DOI] [PubMed] [Google Scholar]
  3. Bonnard M, Boury B, Parrot I. Key insights, tools, and future prospects on oyster shell end-of-life: a critical analysis of sustainable solutions. Environ Sci Technol. 2020;54(1):26–38. doi: 10.1021/acs.est.9b03736. [DOI] [PubMed] [Google Scholar]
  4. Cai J, Sweeney AM. The proof is in the pidan: generalizing proteins as patchy particles. ACS Cent Sci. 2018;4(7):840–853. doi: 10.1021/acscentsci.8b00187. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Cartus A. Chapter 12 - d-amino acids and cross-linked amino acids in food. In: Schrenk D, Cartus A, editors. Chemical contaminants and residues in food. 2. Woodhead Publishing; 2017. pp. 251–278. [Google Scholar]
  6. Chang HM, Tsai CF, Li CF. Quantification of racemization of amino acids in alkaline-treated duck eggs by micellar capillary electrophoresis. J Agric Food Chem. 1999;47(2):479–484. doi: 10.1021/jf980796+. [DOI] [PubMed] [Google Scholar]
  7. Chen Z, Li J, Tu Y, Zhao Y, Luo X, Wang J, Wang M. Changes in gel characteristics of egg white under strong alkali treatment. Food Hydrocolloids. 2015 doi: 10.1016/j.foodhyd.2014.10.026. [DOI] [Google Scholar]
  8. Cho MG, Bae SM, Jeong JY. Egg shell and oyster shell powder as alternatives for synthetic phosphate: effects on the quality of cooked ground pork products. Korean J Food Sci Anim Resour. 2017;37(4):571–578. doi: 10.5851/kosfa.2017.37.4.571. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Choi YM, Whang JH, Kim JM, Suh HJ. The effect of oyster shell powder on the extension of the shelf-life of kimchi. Food Control. 2006;17(9):695–699. doi: 10.1016/j.foodcont.2005.04.005. [DOI] [Google Scholar]
  10. Drake MA, Delahunty CM. Chapter 20 - sensory character of cheese and its evaluation. In: McSweeney PLH, Fox PF, Cotter PD, Everett DW, editors. Cheese. 4. San Diego: Academic Press; 2017. pp. 517–545. [Google Scholar]
  11. Eiser E, Miles CS, Geerts N, Verschuren P, MacPhee CE. Molecular cooking: physical transformations in Chinese century eggs. Soft Matter. 2009;5(14):2725–2730. doi: 10.1039/b902575h. [DOI] [Google Scholar]
  12. Ganasen P, Benjakul S. Physical properties and microstructure of pidan yolk as affected by different divalent and monovalent cations. LWT Food Sci Technol. 2010;43(1):77–85. doi: 10.1016/j.lwt.2009.06.007. [DOI] [Google Scholar]
  13. Ganasen P, Benjakul S. Effects of green tea and Chinese tea on the composition and physical properties of pidan white. J Food Process Preserv. 2011;35(6):907–916. doi: 10.1111/j.1745-4549.2011.00544.x. [DOI] [Google Scholar]
  14. Ho W-F, Hsu H-C, Hsu S-K, Hung C-W, Wu S-C. Calcium phosphate bioceramics synthesized from eggshell powders through a solid state reaction. Ceram Int. 2013;39(6):6467–6473. doi: 10.1016/j.ceramint.2013.01.076. [DOI] [Google Scholar]
  15. Iram A, Wang X, Demirci A. Electrolyzed oxidizing water and its applications as sanitation and cleaning agent. Food Eng Rev. 2021;13(2):411–427. doi: 10.1007/s12393-021-09278-9. [DOI] [Google Scholar]
  16. Khalid NI, Sulaiman NS, Ab Aziz N, Taip FS, Sobri S, Mahmud Ab Rashid N-K. Optimization of electrolysis parameters for green sanitation chemicals production using response surface methodology. Processes. 2020;8(7):792. doi: 10.3390/pr8070792. [DOI] [Google Scholar]
  17. Kim MJ, Hung Y-C. Effect of alkaline electrolyzed water as an inhibitor of enzymatic browning in red delicious apples. J Food Biochem. 2014;38(6):542–550. doi: 10.1111/jfbc.12086. [DOI] [Google Scholar]
  18. Kuang H, Yang F, Zhang Y, Wang T, Chen G. The impact of egg nutrient composition and its consumption on cholesterol homeostasis. Cholesterol. 2018;2018:6303810. doi: 10.1155/2018/6303810. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Liang Y, He L, Zhang M, Liu X, Jin G, Jin Y, Ma M. Preserved egg digests promote the apoptosis of HT29 and HepG2 cells. Food Biosci. 2020;36:100661. doi: 10.1016/j.fbio.2020.100661. [DOI] [Google Scholar]
  20. Lin H-M, Hung Y-C, Deng S-G. Effect of partial replacement of polyphosphate with alkaline electrolyzed water on the quality of catfish fillets. Food Control. 2020;112:107117. doi: 10.1016/j.foodcont.2020.107117. [DOI] [Google Scholar]
  21. Liu Y, Wang J, Zhu X, Liu Y, Cheng M, Xing W, Song P. Effects of electrolyzed water treatment on pesticide removal and texture quality in fresh-cut cabbage, broccoli, and color pepper. Food Chem. 2021;353:129408. doi: 10.1016/j.foodchem.2021.129408. [DOI] [PubMed] [Google Scholar]
  22. Luo W, Xue H, Xiong C, Li J, Tu Y, Zhao Y. Effects of temperature on quality of preserved eggs during storage. Poult Sci. 2020;99(6):3144–3157. doi: 10.1016/j.psj.2020.01.020. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Mohadi R, Anggraini K, Riyanti F, Lesbani A. Preparation calcium oxide from chicken eggshells. Sri J Env. 2016;1:32–35. doi: 10.22135/sje.2016.1.2.32-35. [DOI] [Google Scholar]
  24. Rahman S, Khan I, Oh D-H. Electrolyzed water as a novel sanitizer in the food industry: current trends and future perspectives. Compr Rev Food Sci Food Saf. 2016;15(3):471–490. doi: 10.1111/1541-4337.12200. [DOI] [PubMed] [Google Scholar]
  25. Ro EY, Ko YM, Yoon KS. Survival of pathogenic enterohemorrhagic Escherichia coli (EHEC) and control with calcium oxide in frozen meat products. Food Microbiol. 2015;49:203–210. doi: 10.1016/j.fm.2015.02.010. [DOI] [PubMed] [Google Scholar]
  26. Seo JH, Park SM, Yang BJ, Jang JG. Calcined oyster shell powder as an expansive additive in cement mortar. Materials. 2019;12(8):1322. doi: 10.3390/ma12081322. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Tangboriboon N, Kunanuruksapong R, Sirivat A. Preparation and properties of calcium oxide from eggshells via calcination. Mater Sci Pol. 2012;30(4):313–322. doi: 10.2478/s13536-012-0055-7. [DOI] [Google Scholar]
  28. Wang Y, Xiong C, Luo W, Li J, Tu Y, Zhao Y. Effects of packaging methods on the quality of heavy metals–free preserved duck eggs during storage. Poult Sci. 2021;100(5):101051. doi: 10.1016/j.psj.2021.101051. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Zhang X, Jiang A, Chen M, Ockerman HW, Chen J. Effect of different alkali treatments on the chemical composition, physical properties, and microstructure of pidan white. J Food Sci Technol. 2015;52(4):2264–2271. doi: 10.1007/s13197-013-1201-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Zhao Y, Tu Y, Xu M, Li J, Du H. Physicochemical and nutritional characteristics of preserved duck egg white. Poult Sci. 2014;93(12):3130–3137. doi: 10.3382/ps.2013-03823. [DOI] [PubMed] [Google Scholar]
  31. Zhao Y, Cao D, Shao Y, Xiong C, Li J, Tu Y. Changes in physico-chemical properties, microstructures, molecular forces and gastric digestive properties of preserved egg white during pickling with the regulation of different metal compounds. Food Hydrocoll. 2020;98:105281. doi: 10.1016/j.foodhyd.2019.105281. [DOI] [Google Scholar]
  32. Zhao L, Li S, Yang H. Recent advances on research of electrolyzed water and its applications. Curr Opin Food Sci. 2021 doi: 10.1016/j.cofs.2021.03.004. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Not applicable.

Not applicable.

Articles from Journal of Food Science and Technology are provided here courtesy of Springer

RESOURCES