Effect of marine biopolymers as edible coatings incorporated with cinnamon essential oil on shelf-life extension of black pomfret steak stored under refrigeration storage

Introduction

Seafood is a crucial component of a balanced diet due to its high protein content, low-fat levels, and rich supply of long-chain polyunsaturated fatty acids like EPA and DHA, offering various health benefits (Hassoun et al., 2022;Petricorena, 2015;Carlucci et al., 2015). However, postharvest deterioration occurs rapidly due to biochemical, physicochemical, and microbial processes, leading to protein degradation, oxidation, and spoilage (Liu et al., 2013;Zhan et al., 2018;Wang, 2019). Traditional preservation methods like drying, curing, and fermentation help slow deterioration (Hassoun et al., 2020a;Hassoun et al., 2020b;Tavares et al., 2021), but incorporating natural preservatives in low concentrations provides additional antimicrobial and antioxidant benefits (Baptista et al., 2020;Hassoun & Çoban, 2017;Batiha et al., 2021). These can be applied directly to seafood or integrated into edible coatings and packaging materials (Hassoun et al., 2022). Edible coatings, made from biopolymers like polysaccharides, proteins, and lipids, form a thin protective layer on food surfaces (Ju et al., 2019;Santhosh et al., 2020). Polysaccharide-based coatings, such as chitosan and seaweed extracts, offer limited moisture barriers but can be enhanced with essential oils (EOs) like oregano, cinnamon, and thyme, which improve antibacterial action and prolong shelf life (Dehghani et al., 2018;Aider, 2010;Ju et al., 2019). Combining polysaccharide coatings with functional EOs provides strong antimicrobial and antioxidant properties, effectively preserving seafood quality (Ju et al., 2019) [1, 3, 4, 6, 7, 13-16, 21, 25, 32, 33, 37, 39, 40] . Edible coatings are thin layers of edible biopolymers, such as polysaccharides, proteins, and lipids, applied to food surfaces via immersion or spraying to enhance preservation (Ju et al., 2019;Santhosh et al., 2020). Polysaccharide-based coatings like chitosan and seaweed extracts offer limited moisture barriers due to their hydrophilic nature but can be improved with essential oils (EOs) like oregano, cinnamon, and thyme, which enhance antibacterial activity and prolong shelf life (Dehghani et al., 2018;Aider, 2010;Ju et al., 2019). Cinnamon (Cinnamomum zeylanicum L.), rich in cinnamaldehyde and terpenes, exhibits strong antibacterial and antioxidant properties by disrupting bacterial cell walls and enzyme formation (Tzortzakis, 2009;Helander et al., 1995). Chitosan, a biodegradable and biocompatible polysaccharide, is widely used in food coatings and packaging due to its potent antimicrobial and antioxidant effects (Li et al., 2013;Kulawik et al., 2019). Similarly, gelatin-based coatings offer strong mechanical properties and act as effective barriers against oxygen and moisture, reducing oxidation and extending food shelf life (Hanani et al., 2013;Molinaro et al., 2015; Krochta & Mulder-Johnston, 1997) [1, 7, 12, 17, 21, 22, 23, 24, 28, 38] . Mainly fishery products develop objectionable odours and flavours due to bacterial activity during refrigerated storage. So, natural bio-preservatives are used to prevent or destroy the growth of these spoilage bacteria and improve the quality of the fish product (Gilliland & Ewell, 1983). Therefore, this work aimed to evaluate the effect of marine biopolymers such as chitosan and gelatin-based coatings incorporated with the essential oil such as cinnamon essential oil on the shelflife extension of Black Pomfret, Parastromateus niger, steak during refrigerated storage [10] .

material and methods

Preparation and treatment of fish samples 2.1.1

Fish preparation: Fresh black pomfret (Parastromateus niger) were purchased from Veraval fish landing center, (Gujarat) and kept in an insulated box in iced condition with a temperature range of 0-2 ℃ and transported to the Fish Processing Laboratory of the Department of Fish Processing Technology, College of Fisheries Science, Kamdhenu University, Veraval. After that, the fish was washed and dressed. Then dressed fish was cut into the steak and again washed with chilled potable water.

2.1.2Preparation of coating solutions and treated steaks

Chitosan and Gelatin powder purchased from Myochem Pvt. Ltd. For preparing chitosan coating solution, first of all, Chitosan dissolved in 1% glacial acetic acid overnight and then filtered with Whatman filter paper no. 3 and then make up a solution with distilled water and add0.75ml/gm glycerol as plasticizer and stir for 10 minutes. For preparing a gelatin coating solution, gelatin powder is dissolved in distilled water on a magnetic stirrer at 35 ℃ for 15 minutes. Then, cool down the solution at 7 ℃ for 15 minutes and allow the solution to swell. Again, warm the solution at 55 ℃ for 30 minutes in a hot air oven. 0.2 ml of Tween 80 was added in 1 ml of cinnamon essential oil as an emulsifier for complete dispersion of oil into the above biopolymers coating solutions. After dressing fish were divided into 4 groups, such as T0(C), T1, T2, and T3. In T0, it was considered a control treatment where no treatment was given. In the T1 treatment, the fish steaks were treated with 1% chitosan with 1% cinnamon essential oil coating solution. In the T2 treatment, the fish steaks were treated with 1% gelatin with 1% cinnamon essential oil coating solution. In the T3 treatment, the fish steaks were treated with 1% chitosan and 1% gelatin coating blended with 1% cinnamon essential oil coating solution.

All treatment solutions were mixed with the help of a centrifuge for 5 minutes at 9,000 rpm. Then after, the fish steaks were dipped for 30 seconds in a solution. Then allow standing for 2 minutes. After that, again immersed for 30 seconds in a solution. Then remove from the solution and allow to drain for 2 minutes. After that, put it in a hot air oven for 15 minutes at 35 ℃ for proper coating. After that, treated fish steaks were packed in air packaging of an LDPE bag and stored at 4±1 ℃ refrigerated storage. The biochemical and microbial analysis was conducted at every 5 days of interval to determine the overall quality of fish steaks.

Proximate Analysis

The moisture content and crude ash were determined in an oven at 105 and 550 ℃, respectively, until the weight became constant. The total crude protein was determined by the Kjeldahl method. The crude lipid was determined by the Soxhlet extraction method (AOAC, 1984) [2] .

Microbial Analysis

Total Plate Counts (TPC) and Psychrotrophic Bacterial Counts (PBC) were determined by preparing serial decimal dilutions of homogenized fish steaks and inoculating them onto plate count agar using the pour plate method. The plates were incubated at 37°C for TPC (2 days) and at 7°C for PBC (5 days). The results were expressed in log CFU/g. For E.coli determination, a 0.1 ml aliquot of aseptically prepared serial dilutions was spread onto Tergitol-7 agar plates using a sterile glass rod, followed by incubation at 37±1°C for 24 hours. Yellow colonies with a pinkish tinge were counted, and E. coli counts were reported as CFU/g. Staphylococcus aureus in fish samples was determined using the AOAC (2006) method by plating 1 ml of food homogenate on Baird Parker Agar, followed by incubation at 35-37°C for 1 hour upright and 45-48 hours inverted. Results were expressed as S. aureus CFU/g [2] .

Biochemical Analysis

Total volatile base nitrogen (TVB-N) was determined using the micro-diffusion method of Beatty & Gibbons (1937). The unreacted acid in the inner chamber of the diffusion unit, after overnight reaction with TCA extract and potassium carbonate, was titrated against 0.01N NaOH using Tashiro's indicator. Results were expressed as mg% TVB-N. Trimethylamine (TMA) was determined using the microdiffusion method of Beatty & Gibbons (1937). After reacting the TCA extract with formaldehyde and potassium carbonate in a sealed diffusion unit overnight, the unreacted acid was titrated with 0.01N NaOH using Tashiro's indicator. Results were expressed as mg% TMA [5] .

Statistical Analysis:

Data were statistically analyzed using a completely randomized design, with analysis of variance (ANOVA) conducted as per Snedecor and Cochran (1989). Experimental data were processed using IBM BASIC Windows release 1.13 to identify significant differences among treatment combinations and determine the optimal treatment [35] . with 75.5±0.3% moisture, 2.4±0.1% crude fat, 19.9±0.4% crude protein, and 1.7±0.04% ash. Jai Ganesh et al. (2011) also reported comparable values except for a lower crude protein content of 14.4±0.5%. These results confirm that all proximate characteristics are within the prescribed limits, indicating the freshness of the fish used in this study [19, 20, 27, 36] . 2005) reported a higher initial TPC (5.52 log cfu/g) at 20°C compared to the present study [8,9,11,26,29,30,31,34] .

Results and discussion

The changes in Total Volatile Base Nitrogen (TVB-N) content of Black Pomfret steak are presented in

Conclusion

The findings of the present investigation revealed that edible coatings prepared from marine biopolymers and incorporated with cinnamon essential oil were effective in preserving the quality of Black Pomfret (Parastromateus niger) steaks during refrigerated storage. The treated samples exhibited slower microbial proliferation compared to the untreated control, indicating the antimicrobial potential of the coating materials. Among the different treatments, the combination of chitosan, gelatin, and cinnamon essential oil showed the best preservation effect by maintaining lower microbial counts throughout the storage period. The coated fish steaks also showed delayed spoilage and better retention of freshness during storage, which may be attributed to the barrier properties of chitosan and gelatin along with the antioxidant and antimicrobial activities of cinnamon essential oil. The synergistic interaction of these natural components helped in minimizing quality deterioration under chilled conditions. Overall, the study suggests that marine biopolymer-based edible coatings enriched with cinnamon essential oil can serve as an effective and sustainable preservation method for refrigerated seafood products. The use of such natural bioactive coatings may contribute to extending shelf life, improving product quality, and reducing post-harvest losses in fish and fishery products.

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