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. 2022 Mar 1;31(4):505–514. doi: 10.1007/s10068-022-01048-5

Effect of gelatin nano-coating containing Gardenia pigment on the preservation of pork slices

Yong Liu 1,✉, Zi-Hao Liu 1, Chang-Qi Luo 1, Chun-Tao Xiao 1, Wen-Yu Zhou 1, Wen-Jin Xie 1
PMCID: PMC8994802  PMID: 35464240

Abstract

The nano-coating composed of gelatin and Gardenia pigment (GP) was successfully prepared and showed strong antioxidant activity. The average particle sizes of the nano-coating containing 0.1% and 0.3% GP were 269.58 and 394.13 nm, respectively. The pork slices uncoated and coated with the nano-coating were preserved at 4 °C for 15 days. The pork slices' pH, total volatile basic nitrogen (TVB-N), total viable counts (TVC), water-binding capacity (WHC), and thiobarbituric acid reactive substances (TBARS) were measured to assess the preservation effect of the nano-coating. The results showed that the pork coated with the nano-coating had lower pH, TVC, TVB-N, TBARS, and higher WHC, significantly different (p < 0.05) than the uncoated pork. It is suggested that the proposed nano-coating can be used to effectively improve the pork's quality and shelf life during refrigeration storage.

Keywords: Nano-coating, Gelatin, Gardenia pigment, Pork, Preservation

Introduction

Pork is one of the most consumed meat products globally, and it is an essential source of nutrients such as protein, amino acids, vitamins, and minerals needed by the human body (McGlone, 2013). However, because the pork is rich in polyunsaturated fatty acids, it is prone to lipid oxidation and microbial spoilage, which can cause the deterioration of texture, flavor, color, and other qualities and reduce its nutritional value (Sun et al., 2021). Therefore, more and more researchers have adopted various technologies such as vacuum packaging, modified atmosphere packaging, smart packaging, active packaging, and edible packaging to extend the pork shelf life because it is beneficial to the pork industry (Xiong et al., 2020a).

The edible coating is an effective preservation technology and has unique advantages in meat products preservation (Umaraw et al., 2020). This technology uses edible materials to form a thin film covered on the surface of the food by dipping, smearing, or spraying to maintain an excellent physical morphology and eating quality of the food during food preservation, circulation, and sale (Yu et al., 2019). The edible coating can control the permeation of water vapor, oxygen, or various substances, prevent pollution and inhibit microbial damage, slow down the lipid oxidation reaction rate, and achieve the effect of maintaining the sensory quality of food (Huang et al., 2020). With the deepening of research, the preparation of edible coating by adding active substances such as antibacterial agents and antioxidants has become a research hotspot in food preservation (Ribeiro et al., 2021).

Recently, natural plant extracts have been successfully incorporated into the edible coating for preserving various food products because of their strong antibacterial and antioxidant activity, non-toxic and safe (Ganiari et al., 2017). The development and application of these preservation methods have attracted many researchers' attention. However, the biological activity of natural plant extracts is susceptible to environmental conditions, which destroys their bioactivity and reduces their preservation effect. Encapsulation is a promising technology to conquer these problems. With the further development of edible coating, the concept of release-type food functional packaging coating has been proposed. This packaging technology can slowly release bioactive substances to extend the shelf life of food (McClements, 2010). Therefore, some sustained-release carriers, such as microcapsules, nanoparticles, and nanoemulsions, have been used as food-active packaging to extend food's shelf life (Zhang et al., 2019).

Gelatin is a natural edible macromolecule derived from animal tissues. It has good biocompatibility, film-forming, and gel properties (Alparslan et al., 2016). The edible coating made with gelatin as a matrix can be used as a carrier of antibacterial agents and antioxidants to extend the shelf life of various meats (Abdallah et al., 2018). Gardenia pigment, from Gardenia jasminoides Ellis fruits, is a natural phenolic substance with potent antioxidant and antibacterial activity and has been safely used as a food additive (Liu et al., 2021). It is reported that proteins can interact with plant phenols through hydrogen bonding and covalent bonding to form complexes such as nanoparticles (Buitimea-Cantúa et al., 2018). In this work, the nano-coating was prepared according to the interaction between gelatin and Gardenia pigment. The nano-coating effect on the preservation of pork slices during refrigeration storage was also evaluated in detail.

Material and methods

Chemicals

Gardenia pigment was prepared according to the previous method (Liu et al., 2021). Trichloroacetic acid, gelatin, 2,2-diphenyl-1-picrylhydrazyl (DPPH), ethylenediaminetetraacetic acid, 2-thiobarbituric acid, 1,1,3,3-tetraethoxypropane, and magnesium oxide were from Macklin Co. Ltd. (Shanghai, China).

Preparation of gelatin nano-coating

Gelatin (GT) and Gardenia pigment (GP) were first dissolved in distilled water to obtain GT and GP solutions. Under constant stirring, the GP solution was slowly added to the GT solution, and the mixed solution was continuously stirred to react for two hours. Then the mixed solution was sonicated with an ultrasonic generator (F-020SD, 150 W, 40 kHz, Fuyang, China) for 20 min to obtain the nano-coating. Three coating groups were prepared, in which the GT content was 2.0%, and the GP content was 0.0%, 0.10%, and 0.30%, respectively. They were recorded as GT-0.0%GP, GT-0.10%GP, GT-0.30%GP, respectively.

Determination of antioxidant activity and particle size distribution of coating

The particle size distribution of coating was determined by a laser particle size analyzer (NanoBrook Omni, Brookhaven, USA). The antioxidant activity of coatings was evaluated according to the DPPH method (Liu et al., 2013) with some modifications. Briefly, 1.0 mL of DPPH solution (40 μg/mL) was added to 3.0 mL of sample solution to react for 30 min in the dark. Then the reaction solution's absorbance was recorded at 517 nm. The DPPH radical scavenging effect (%) was calculated as (A0 + A2—A1)/A0 × 100, where A0, A1, and A2 were the control, sample, and blank absorbance, respectively. The ascorbic acid (Vc) was used as a standard to express the antioxidant activity as mg of Vc per mg of sample (mg Vc/mg).

Pork preparing and coating

Fresh pork loins were bought from a local market, and their fascia and excess fat were removed under aseptic operation conditions, and then they were sliced into strips of 5 cm × 3 cm × 2 cm for coating storage. Each pork slice was soaked in the coating solution for 30 s, taken out and drained for 10 s, then placed individually into a sterile petri dish, and subsequently wrapped with polyethylene plastic film, and stored in a refrigerator at 4 °C for 15 days. The pork slices were divided into four groups: uncoated pork slices (recorded as control), pork slices with coating of 2.0% GT and 0.0% GP (recorded as GT-0.0%GP), pork slices with coating of 2.0% GT and 0.10% GP (recorded as GT-0.10%GP), and pork slices with coating of 2.0% GT and 0.30% GP (recorded as GT-0.30%GP). The samples were taken out and analyzed at days 0, 1, 3, 6, 9, 12, and 15 of storage.

Determination of pH values

The pH values of the pork samples were determined by Yuan's reported method (Yuan et al., 2021) with some modifications. A 5.0 g of pork sample was placed into 45 mL of distilled water and then homogenized for 30 s at 5000 rpm. After standing for 10 min, a pH meter was used to determine the pH values.

Determination of total viable counts

The total viable counts (TVC) were measured by Ruan's proposed method (Ruan et al., 2019) with some modifications. A 25.0 g of the minced pork and 225 mL of sterile physiological saline were mixed in a sterilized cooking bag and homogenized for 1.0 min at 10,000 rpm. The above solution was taken for tenfold gradient dilution (ten times of dilution up to 10–10) and inoculated on a standard plate count agar, and then placed the plate in a 37 °C incubator and incubated for 48 h. The colonies were enumerated and expressed as log CFU/g.

Determination of water-binding capacity

The water-binding capacity (WHC) was measured according to Sánchez-Alonso's method (Sánchez-Alonso et al., 2011) with some modifications. The meat samples were cut with a scalpel into 3 cm × 1 cm × 1 cm slices. Each slice was wrapped with filter papers and put in a centrifuge tube to centrifuge at 2252 × g for 15 min, and the slice was taken out and weighed. The water-binding capacity (%) was calculated as M1/M0 × 100, where M0 and M1 were the mass of the sample before and after centrifugation, respectively.

Determination of thiobarbituric acid reactive substances

Lipid oxidation of pork samples was measured according to the thiobarbituric acid reactive substances (TBARS) assay (Xiong et al., 2020b) with some modifications. Briefly, 7.5 g of trichloroacetic acid (TCA) and 0.1 g of ethylenediaminetetraacetic acid (EDTA) were dissolved in 100 mL of distilled water to prepare a TCA solution. 5.0 g of the minced pork sample and 20 mL of the TCA solution were mixed and homogenized for 1.0 min at 7508 × g and then filtered through a Whatman No. 1 filter paper after standing for 20 min. 5.0 mL of the filtrate was taken to mix with 50 mL of 0.02 M 2-thiobarbituric acid (TBA) solution and reacted at 90 °C for 30 min. The mixture was quickly cooled to room temperature by running tap water, and then its absorbance was determined at 532 nm. The malondialdehyde (MDA) content was calculated according to the standard curve of 1,1,3,3-tetraethoxypropane, and the TBARS value was expressed as mg of MDA per kg of the sample (mg MDA/kg).

Determination of total volatile basic nitrogen

The total volatile basic nitrogen (TVB-N) was measured using a semi-micro nitrogen determination device (Beijing Beibo Bomei Glass Co., Ltd., China) according to GB 5009.228-2016 (the national food safety standard for the determination of volatile basic nitrogen in food issued by the National Health Commission of China). 20.0 g of the minced meat sample was mixed with 100 mL of distilled water, and the mixture was shaken for 30 min and filtered. 10.0 mL filtrate was injected into the reaction chamber through the tiny glass cup of a semi-micro nitrogen determination device. Then the tiny glass cup was washed with 10 mL of distilled water and allowed to flow into the reaction chamber, and then the rod-shaped glass stopper was tightly plugged. 5.0 mL of magnesium oxide suspension (10 g/L) was injected into the reaction chamber. The glass stopper was immediately covered tightly, and distilled water was added to the tiny glass cup to prevent air leakage. 10.0 mL of boric acid solution (20 g/L) and five drops of mixed indicator solution (0.67 g/L methyl red and 0.33 g/L methylene blue) were added to the receiving flask. The lower end of the condenser tube was inserted below the liquid surface of the boric acid solution. The screw clamp was clamped when the distillation started. After distillation for 5 min, the distillate receiving flask was moved so that the liquid surface left the lower end of the condenser and then distilled for another 1 min. Then the outside of the lower end of the condenser tube was rinsed with a small amount of distilled water. The distillate receiving flask was removed to titrate with a standard hydrochloric acid titration solution at the endpoint. The amount of TVB-N (mg/100 g) was calculated as [(V1 – V0) × C × 140]/m × 100, where C and V0 were the HCl standard titration solution's concentration (mol/L) and volume (mL), respectively, V1 was the blank volume (mL), and m was the sample weight (g).

Statistical analysis

All the tests were measured in triplicate, and the results were expressed as an average value. The OriginPro 8.5 software was used for mapping analysis. The significant difference of the test data was statistically analyzed by SPSS 20.0 software with the Tukey's test, and p < 0.05 was statistically significant.

Results and discussion

Particle size distribution and antioxidant activity

It was reported that phenolic substances could cause changes in protein properties such as the molecular structure, solubility, surface hydrophobicity, and antioxidant activity through cross-linking with proteins (Liu et al., 2017). By comparing the changes in particle size distributions of GP, GT, and their hybrid solutions, their interaction in the solution can be judged. As seen in Fig. 1A and B, the 0.10% GP, 0.30% GP, and 2.0% GT solution's average particle sizes were 26.35, 28.62, and 205.81 nm, respectively. After adding GP into the GT solution, the average particle sizes of the GT-0.10%GP and GT-0.30%GP solutions increased to 269.58 nm and 394.13 nm, respectively. The changes in the average particle sizes indicated that GT and GP have interacted and formed a nano-coating solution. The greater the concentration of GP, the stronger the interaction between GT and GP, and the larger the formed particle sizes (Huang et al., 2017).

Fig. 1.

Fig. 1

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Mean particle size distribution and antioxidant activity of the coatings. GP: Gardenia pigment; GT: gelatin; 0.10%GP: 0.10% Gardenia pigment solution; 0.30%GP: 0.30% Gardenia pigment solution; GT-0.0%GP: coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, and D) show significant differences (p < 0.05) of various samples on day 0 and day 6. Lowercase alphabets (a and b) indicate significant differences (p < 0.05) on each sample between day 0 and day 6

Figure 1C displays that the antioxidant activity of the new nano-coating solution (GT-0.10%GP and GT-0.30%GP) on day 0 was slightly lower than that of 0.10%GP and 0.30%GP, but their differences were not significant (p > 0.05). The formation of the complex that reduces the antioxidant activity of GP may be due to the decrease in GP's hydroxyl groups as a result of the interaction with gelatin (Staszewski et al., 2011). Similar results were also observed in the interaction between gelatin and polyphenols (Huang et al., 2017). The antioxidant activity of the samples except GT-0.0%GP was significantly (p < 0.05) lower on day 6 than that on day 0. However, after six days, it was worth noting that the antioxidant activity of the nano-coating solution was higher than that of GP instead. This result is because the interaction between GT and GP can increase the GP's chemical stability and effectively protect its antioxidant activity (Dai et al., 2019), which is beneficial to improve the fresh-keeping effect of the prepared nano-coating.

pH value

The pH value is a crucial indicator to evaluate pork freshness. The changes in pH values of pork in different treatment groups are depicted in Fig. 2. With the storage time extension, the pH of each treatment group showed an upward trend, and the pH values varied significantly between the treatment groups (p < 0.05). This result may be that nutrients like protein were decomposed under the action of microorganisms and their physiological conditions to produce alkaline amines and ammonia substances in the subsequent storage process, which led to a gradual rise in pH values (Ruan et al., 2019). The pH values of the control group rose fast, but that of the coated groups rose slowly, especially for the nano-coated groups. The pH changes may be due to the micro-atmosphere environment formed by the coating on the pork surface, which weakens the substance exchange between the pork and the surrounding environment, and to a certain extent, slows down the reproduction of microorganisms and the rate of protein decomposition (Zhang et al., 2020). Besides, nano-coating also has good antioxidant and antibacterial properties. It can continuously release GP slowly, effectively reduces the rate of amine and ammonia alkaline substances produced by the reproduction and metabolism of microorganisms, and slows down the rate of pH rise (Kim et al., 2016). Zhang et al. (Zhang et al., 2020) reported a similar result from the nano-encapsulated tarragon essential oil incorporated into the chitosan–gelatin coating for pork slices. The pH of fresh pork is generally between 5.10 and 6.36, and the highest quality pork is at a pH range from 5.7 to 6.0 (Zhang et al., 2020). The initial pH value of pork was 5.35. The pH values of the control, GT-0.0%GP, GT-0.1%GP, and GT-0.3%GP groups increased to 6.19, 6.22, 6.23, and 5.96 on the 6th, 9th, 12th, and 15th days, respectively, indicating that the nano-coating can effectively inhibit microbial reproduction and protein degradation, better maintain the quality of pork, and extend its shelf life.

Fig. 2.

Fig. 2

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Variations in pH values of differently treated pork during refrigeration at 4 °C. GP: Gardenia pigment; GT: gelatin; Control: uncoated samples; GT-0.0%GP: coated samples with coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coated samples with coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coated samples with coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, and D) indicate significant differences (p < 0.05) on each treatment as a function of storage time. Lowercase alphabets (a, b, c, and d) show significant differences (p < 0.05) of various treatments at the same storage time

Total viable counts

Bacterial growth is one of the main factors that cause meat spoilage. The bacteria can use the protein and glycogen in the meat to multiply rapidly, which leads to the increase of TVC value. Therefore, the TVC value is usually used as an essential indicator to measure the degree of meat spoilage. The variations in TVC values of pork in each treatment group are depicted in Fig. 3. With the increase of the storage time, the pork' TVC values gradually increased. The uncoated pork's TVC value increased rapidly, while the coated pork's increased slowly. Generally, each treatment group's TVC values varied significantly (p < 0.05). The TVC value of 7.0 log CFU/g can be regarded as the threshold for the acceptable freshness of pork meat (Huang et al., 2014). If the TVC value is higher than the threshold, the pork meat may be spoiled by microbial growth. The initial TVC value of pork was 2.89 log CFU/g. The TVC values of the control and GT-0.0%GP groups exceeded the threshold (7.38 and 7.47 log CFU/g, respectively) on the 9th and 12th day, respectively, which was unacceptable. However, the GT-0.1%GP and GT-0.3%GP groups' TVC values on the 15th day were 6.68 and 5.19 log CFU/g, respectively, which was still lower than the maximum acceptable value (7.0 log CFU/g). These different changes in the TVC values of the samples may be related to the antioxidant, antibacterial, and sustained release properties of GP in the nano-coatings. GP can effectively and continuously prevent bacteria from infecting the samples so that the TVC values increase slowly and the shelf life of pork is prolonged (Zhang et al., 2019). The tea polyphenol incorporated into chitosan film on preserving pork meat patties also had a similar result (Qin et al., 2013).

Fig. 3.

Fig. 3

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Variations in TVC of differently treated pork during refrigeration at 4 °C. TVC: total viable counts; GP: Gardenia pigment; GT: gelatin; Control: uncoated samples; GT-0.0%GP: coated samples with coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coated samples with coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coated samples with coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, D, F, and G) indicate significant differences (p < 0.05) on each treatment as a function of storage time. Lowercase alphabets (a, b, c, and d) show significant differences (p < 0.05) of various treatments at the same storage time

Total volatile basic nitrogen

TVB-N refers to the ammonia and amino nitrogen substances produced by protein decomposition due to the joint action of endogenous enzymes and bacteria in the muscle during animal food storage (Goulas and Kontominas, 2007). It is one of the essential indicators to measure the spoilage of meat products. The variations of pork's TVB-N values with the prolonged storage time are shown in Fig. 4. The TVB-N values of the control and coated groups all gradually increased with the storage time increase. The control group's TVB-N value increased the fastest, while that of the GT-0.3%GP group increased the slowest, and the TVB-N values of each group varied significantly (p < 0.05). This rising trend is because the reproduction of microorganisms accelerated the decomposition of pork proteins, increasing the TVB-N content. According to Sun et al. (Sun et al., 2021), the TVB-N value of 15 mg/100 g can be used as the threshold for the upper limit of acceptability for pork freshness. As seen from Fig. 4, the TVB-N value of pork was 3.75 mg/100 g on the 0th day, while the control group had reached 15.69 mg/100 g on the 6th day, and the GT-0.0%GP and GT-0.1%GP groups had exceeded the threshold (16.52 and 15.68 mg/100 g, respectively) on the 9th day, but the GT-0.3%GP group did not exceed the threshold (16.57 mg/100 g) until the 15th day. These results indicated that the nano-coating with good antibacterial and antioxidant activity can effectively inhibit the bacteria growth, decrease the rate of bacterial decomposition of protein, and thus slow the increase in TVB-N values (Ruan et al., 2019), which can be mutually confirmed with the TVC tendency. The result was similar to nanoemulsion-based edible coatings containing fennel essential oil to preserve pork meat patties (Sun et al., 2021).

Fig. 4.

Fig. 4

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Variations in TVB-N of differently treated pork during refrigeration at 4 °C. TVB-N: total volatile basic nitrogen; GP: Gardenia pigment; GT: gelatin; Control: uncoated samples; GT-0.0%GP: coated samples with coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coated samples with coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coated samples with coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, D, and F) indicate significant differences (p < 0.05) on each treatment as a function of storage time. Lowercase alphabets (a, b, c, and d) show significant differences (p < 0.05) of various treatments at the same storage time

Lipid oxidation

Due to the high content of unsaturated fats, meat products are easily oxidized to produce malondialdehyde (MDA). The TBARS value is related to the MDA content and is often used as an essential indicator to evaluate the lipid oxidation degree (Ulu, 2004). The changes in TBARS values of pork are shown in Fig. 5. The TBARS values of the control and coated groups all increased with the time extension, and their TBARS values changed significantly (p < 0.05). The TBARS values of the coated groups were lower than that of the control group with a longer refrigeration time. The TBARS values of the control, GT-0.0%GP, GT-0.1%GP, and GT-0.3%GP groups increased from 0.12 mg MDA/kg on the 0th day to 1.46, 1.24, 0.91, and 0.56 mg MDA/kg on the 15th day, respectively, indicating that the nano-coating had a good effect on inhibiting lipid oxidation in pork. This result may be because the coating can serve as a barrier to limit external oxygen penetration into the contact samples, which slows down the lipid oxidation rate (Sathivel, 2005). At the same time, the slow release of GP in the nano-coating continues to inhibit the free radical chain reaction in samples due to its good antioxidant activity (Ahmad et al., 2012), further reducing the rate of lipid oxidation in the samples and extending the pork shelf life. A similar tendency obtained by Sarvinehbaghi et al. (Sarvinehbaghi et al., 2021) was that the native seed gums coating containing red onion extract nanoencapsulation had a significant effect in inhibiting lipid oxidation of beef fillets.

Fig. 5.

Fig. 5

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Variations in TBARS of differently treated pork during refrigeration at 4 °C. TBARS: thiobarbituric acid reactive substances; GP: Gardenia pigment; GT: gelatin; Control: uncoated samples; GT-0.0%GP: coated samples with coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coated samples with coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coated samples with coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, D, and F) indicate significant differences (p < 0.05) on each treatment as a function of storage time. Lowercase alphabets (a, b, c, and d) show significant differences (p < 0.05) of various treatments at the same storage time

Water-binding capacity

It is well known that after food is frozen and thawed, the food's internal ice crystals melt into water. If the water cannot be absorbed by food tissues and return to its original state, it will be separated and become into loss liquid. The loss liquid contains water, proteins, salts, vitamins, and other nutrients. Consequently, the liquid loss can reduce food quality and loss of texture, nutrients, and flavor (Farajzadeh et al., 2016). The liquid loss is negatively related to the meat products' WHC. Therefore, the WHC can be an essential indicator for evaluating food quality. The WHC changes in Fig. 6 showed that each group's WHC gradually decreased. The WHC value on the 0th day was 99.02%, while the values of the control, GT-0.0%GP, GT-0.1%GP, and GT-0.3%GP groups on the 15th day reduced to 79.95, 87.31, 90.18, 92.68%, respectively. The lowest WHC value was the control group, and the highest was the GT-0.3%GP group. They were significantly different (p < 0.05). The decrease in the samples' WHC values may be related to the loss caused by microbial activity and enzymatic autolysis to promote protein degradation and dissolution in the loss liquid (Abdoua et al., 2018). GP has good antibacterial and antioxidant effects, which can effectively inhibit the growth and reproduction of microorganisms and delay protein degradation. Besides, the coating's lower water vapor transmission coefficient is also conducive to the WHC stability. Therefore, the nano-coating has a better ability to maintain the higher WHC values. A similar report was also found on the hyaluronic acid coating to preserve the crucian carp during the partial-freezing storage (Guo et al., 2017).

Fig. 6.

Fig. 6

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Variations in WHC of differently treated pork during refrigeration at 4 °C. WHC: water-binding capacity; GP: Gardenia pigment; GT: gelatin; Control: uncoated samples; GT-0.0%GP: coated samples with coating solution of 2.0% gelatin and 0.0% Gardenia pigment; GT-0.10%GP: coated samples with coating solution of 2.0% gelatin and 0.10% Gardenia pigment; GT-0.30%GP: coated samples with coating solution of 2.0% gelatin and 0.30% Gardenia pigment. Capital alphabets (A, B, C, and D) indicate significant differences (p < 0.05) on each treatment as a function of storage time. Lowercase alphabets (a and b) show significant differences (p < 0.05) of various treatments at the same storage time

In summary, the nano-coated pork under cold storage can significantly control microorganisms' growth, reduce protein's autolysis and decomposition speed, slow down lipid oxidation and spoilage rate, and improve water-binding capacity. Therefore, the proposed nano-coating can effectively extend the shelf life of chilled pork and may be used as an edible active coating for refrigeration preservation of other meat products.

Acknowledgements

This work was financially supported by the University Student Innovation and Entrepreneurship Training Program of Guangdong Province (No. S202010580071).

Declarations

Conflict of interest

The authors declare no conflict of interest.

Footnotes

Publisher's Note

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

Contributor Information

Yong Liu, Email: lygdut@163.com.

Zi-Hao Liu, Email: 278061606@qq.com.

Chang-Qi Luo, Email: 771170800@qq.com.

Chun-Tao Xiao, Email: 2603831005@qq.com.

Wen-Yu Zhou, Email: 806426835@qq.com.

Wen-Jin Xie, Email: 1040767373@qq.com.

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