Polymeric Packaging Applications for Seafood Products: Packaging-Deterioration Relevance, Technology and Trends

Seafood is a highly economical product worldwide. Primary modes of deterioration include autolysis, oxidation of protein and lipids, formation of biogenic amines and melanosis, and microbial deterioration. These post-harvest losses can be properly handled if the appropriate packaging technology has been applied. Therefore, it is necessary for packaging deterioration relevance to be clearly understood. This review demonstrates recent polymeric packaging technology for seafood products. Relationship between packaging and quality deterioration, including microbial growth and chemical and biochemical reactions, are discussed. Recent technology and trends in the development of seafood packaging are demonstrated by recent research articles and patents. Development of functional polymers for active packaging is the largest area for seafood applications. Intelligent packaging, modified atmosphere packaging, thermal insulator cartons, as well as the method of removing a fishy aroma have been widely developed and patented to solve the specific and comprehensive quality issues in seafood products. Many active antioxidant and antimicrobial compounds have been found and successfully incorporated with polymers to preserve the quality and monitor the fish freshness. A thermal insulator has also been developed for seafood packaging to preserve its freshness and avoid deterioration by microbial growth and enzymatic activity. Moreover, the enhanced biodegradable tray is also innovative as a single or bulk fish container for marketing and distribution. Accordingly, this review shows emerging polymeric packaging technology for seafood products and the relevance between packaging and seafood qualities.


Introduction
In 2021, world fishery market trade was forecast to increase by 12% in value and 3.7% in volume, with production projected to increase by 4 million tons from 2020 to 2022 [1]. Fishery product prices, especially shrimp, remained stable until July 2021 and then increased from August 2021 due to high freight costs of US$ 0.70-0.80 per kg for products exported from Asia to North America and Europe. Processed seafood is popular as ready-to-eat meals or snacks equipped with detailed serving instructions that normally involve reheating using a microwave oven [2]. Consumption of frozen packaged foods had predicted a CAGR of 5.98% from 2021 to 2028, while average year-on-year growth of 15.35% in 2020 was attributed to consumer panic buying behavior during the COVID-19 outbreak. Cold chain distribution requires high maintenance of both containers and packaging systems to maintain product quality. Seafood is a rich source of nutrients with specific aromas and tastes, while increasing global seafood production reflects consumer demand for packaged seafood products. lactic acid bacteria also contribute to fish deterioration. Photobacterium phosphoreum together with H 2 S spoilage bacteria trigger the production of trimethylamine during post-harvest metabolism. Production of hypoxanthine from the fish body during storage is triggered by Enterobacteriaceae, Pseudomonas, Shewanella putrafaciens, and Photobacterium phosphoreum.
The effect of microbial growth on changes in other fish quality parameters was reported by Kimbuathong et al. (2019) [10]. Microbial growth was linearly correlated with melanosis and trimethylamine production of Pacific white shrimp stored under MAP (Figure 1). This finding indicated that microbial growth strongly stimulated melanosis formation in shrimp following the mechanism shown in Figure 2, while the peptidoglycan binding protein (Gram positive bacteria) and β-1,3-glucan binding protein (Gram negative bacteria) contributed to pro-polyphenol oxidase activation that then induced melanosis formation [22]. Trimethylamine dramatically increased after the total viable count (TVC) reached 6.8 log cfu/g. These results suggested that reduction of trimethylamine and melanosis was dependent on the microbial inhibition ability of CO 2 . Increasing TVC also inversely reduced the firmness. The microbials consumed nutrients such as lipids or proteins, causing proteolytic denaturation and resulting in a loss of firmness.
onaceae, and lactic acid bacteria also contribute to fish deterioration. Photob phoreum together with H2S spoilage bacteria trigger the production of trimeth ing post-harvest metabolism. Production of hypoxanthine from the fish bod age is triggered by Enterobacteriaceae, Pseudomonas, Shewanella putrafaciens, a rium phosphoreum.
The effect of microbial growth on changes in other fish quality param ported by Kimbuathong et al. (2019) [10]. Microbial growth was linearly co melanosis and trimethylamine production of Pacific white shrimp stored ( Figure 1). This finding indicated that microbial growth strongly stimula formation in shrimp following the mechanism shown in Figure 2, while the p binding protein (Gram positive bacteria) and β-1,3-glucan binding protein tive bacteria) contributed to pro-polyphenol oxidase activation that then ind sis formation [22]. Trimethylamine dramatically increased after the total (TVC) reached 6.8 log cfu/g. These results suggested that reduction of trimet melanosis was dependent on the microbial inhibition ability of CO2. Increa inversely reduced the firmness. The microbials consumed nutrients such as teins, causing proteolytic denaturation and resulting in a loss of firmness.   Several studies have investigated microbial inhibition in seafood products using active packaging. Mohebi and Shahbazi (2017) [23] found that chitosan film containing Ziziphora clinopodioides essential oil and pomegranate peel extract effectively retarded TVC and growth of Pseudomonas spp., Pseudomonas flourescens, Shewanella putrefaciens, Enterobacteriaceae, lactic acid bacteria, and Listeria monocytogenes in shrimp compared to the control and gelatin film, while incorporation of combined nanoparticles (ZnO, SiO, and CuO) into gelatin and polyvinyl alcohol film had antimicrobial activity equal to the positive control against S. aureus, L. monocytogenes, E. coli, P. fluorescens, V. parahaemolyticus, and A. caviae [24]. Microbial activity in seafood products can be controlled via active packaging containing antimicrobial agents that delay post-harvest metabolism and extend the shelf-life.

Chemical Deterioration
Deterioration in seafood is mainly caused by lipid oxidation in high-fat content pelagic fish (mackerel, sardinella, and herring). Oxidation occurs as a result of the reaction between oxygen molecules and the double bond of the unsaturated fatty acid chain. Fish contain high amounts of mono or polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as major sources of nutrition benefits that are highly susceptible to oxidation. Packaging containing antioxidant agents, such as carvacrol essential oil [25], gallic acid, and clove essential oil [26], loaded polymer reduced lipid oxidation of salmon fillets. Li et al. (2021) [27] reported that MAP combined with εpolylysine, chitosan, and sodium alginate coatings delayed myofibril oxidation by inhibiting carbonyl groups in pufferfish.
Lipid oxidation in fish occurs enzymatically or non-enzymatically. Enzymatic lipid oxidation results from lipolysis by lipases, while non-enzymatic oxidation normally arises in hematin compounds such as hemoglobin, myoglobin, and cytochrome [28]. Myoglobin is present in red meat such as tuna as an oxygen-binding protein similar to hemoglobin. High myoglobin content contributes to the reddish-brown color of the flesh. Undesirable discoloration in red meat is related to lipid oxidation associated with the binding between heme and myofibrillar protein and results in greater discoloration [29]. The red color in tuna can be preserved by using carbon monoxide or nitric oxide that react with myoglobin (MB), resulting in MB-Fe +11 -CO and MB-Fe +11 -NO bonding, respectively [30]. Therefore, Several studies have investigated microbial inhibition in seafood products using active packaging. Mohebi and Shahbazi (2017) [23] found that chitosan film containing Ziziphora clinopodioides essential oil and pomegranate peel extract effectively retarded TVC and growth of Pseudomonas spp., Pseudomonas flourescens, Shewanella putrefaciens, Enterobacteriaceae, lactic acid bacteria, and Listeria monocytogenes in shrimp compared to the control and gelatin film, while incorporation of combined nanoparticles (ZnO, SiO, and CuO) into gelatin and polyvinyl alcohol film had antimicrobial activity equal to the positive control against S. aureus, L. monocytogenes, E. coli, P. fluorescens, V. parahaemolyticus, and A. caviae [24]. Microbial activity in seafood products can be controlled via active packaging containing antimicrobial agents that delay post-harvest metabolism and extend the shelf-life.

Chemical Deterioration
Deterioration in seafood is mainly caused by lipid oxidation in high-fat content pelagic fish (mackerel, sardinella, and herring). Oxidation occurs as a result of the reaction between oxygen molecules and the double bond of the unsaturated fatty acid chain. Fish contain high amounts of mono or polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as major sources of nutrition benefits that are highly susceptible to oxidation. Packaging containing antioxidant agents, such as carvacrol essential oil [25], gallic acid, and clove essential oil [26], loaded polymer reduced lipid oxidation of salmon fillets. Li et al. (2021) [27] reported that MAP combined with ε-polylysine, chitosan, and sodium alginate coatings delayed myofibril oxidation by inhibiting carbonyl groups in pufferfish.
Lipid oxidation in fish occurs enzymatically or non-enzymatically. Enzymatic lipid oxidation results from lipolysis by lipases, while non-enzymatic oxidation normally arises in hematin compounds such as hemoglobin, myoglobin, and cytochrome [28]. Myoglobin is present in red meat such as tuna as an oxygen-binding protein similar to hemoglobin. High myoglobin content contributes to the reddish-brown color of the flesh. Undesirable discoloration in red meat is related to lipid oxidation associated with the binding between heme and myofibrillar protein and results in greater discoloration [29]. The red color in tuna can be preserved by using carbon monoxide or nitric oxide that react with myoglobin (MB), resulting in MB-Fe +11 -CO and MB-Fe +11 -NO bonding, respectively [30]. Therefore, chemical deterioration depends on the chemical structure of the fish meat, while preservation is accomplished using an antioxidant agent or high CO 2 atmosphere.

Biochemical Deterioration
Post-mortem biochemical changes in fish result from autolysis by the action of proteolytic enzymes. Ghaly et al. (2010) [28] explained that proteolytic enzymes are mostly present in the muscle and viscera of fish in the early rigor stages and contribute to postmortem degradation. Proteolytic enzymes break down protein, resulting in free amino acids and peptides during autolysis that lead to fish degradation, with production of the biogenic amines: histamine, tyramine, tryptamine, putrescine, and cadaverine [31], followed by acidity, increased pH, and accumulation of basic nitrogen compounds such as trimethylamine (TMA) and total volatile-based nitrogen (TVB-N). The degradation of adenosine triphosphate (ATP) is also responsible for the biochemical post-mortem degradation of seafood products to form adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine, and hypoxanthine, determined as K value [32]. A higher K value indicates a lower freshness level. Kimbuathong et al. (2019) [10] reported that MAP with a high concentration of CO 2 (above 60%) retained a low TMA value. A combination of MAP and ε-polylysine, chitosan and sodium alginate coatings maintained Ca 2+ -ATPase activity by retaining the protein structure (α and β-sheet) of pufferfish [27], while TVB-N and TMA of salted dried Atlantic mackerel were reduced by vacuum packaging combined with an iron-based oxygen absorber [33]. Biochemical deterioration mostly relates to the amine content in fish meat, and this can be delayed by MAP or active packaging.

Melanosis
Melanosis occurs when a cell cannot regulate pigment production and appears as a black spot. This is a serious issue in crustacean products considering their high commercial value. Melanosis is harmless to human health but significantly decreases sensory market value and acceptance by the consumer. Goncalves and Oliveira (2016) [22] categorized five stages of melanosis formation: (1) Gram positive and negative bacteria and fungi trigger the alignment of serine proteinase, (2) pro polyphenoloxidase then activates to become polyphenoloxidase (PPO), (3) PPO acts as a catalyst to convert phenol into colorless quinone, (4) oxidization of quinone results in melanin, and (5) melanin is responsible for melanosis formation in the crustacean carapace. Melanosis formation is accelerated by microorganisms, oxygen exposure, and high temperatures. Melanosis in crustaceans can be measured by PPO extraction and identification using SDS polyacrylamide gel electrophoresis (SDS-PAGE) [34], color measurement, particularly whiteness [35] or L value [36], image analysis [10,37], or sensory assessment [38,39].
Packaging systems integrated with active compounds are now widely developed to preserve crustaceans, particularly shrimp, by inhibiting melanosis formation on the carapace. MAP with a high CO 2 concentration to prevent melanosis in shrimp [10,35], while Laorenza and Harnkarnsujarit (2021) [37] developed a PBAT/PLA active film containing carvacrol, citral, and α-terpineol essential oils to prevent melanosis. Alparslan et al. (2016) [36] also reported that edible coatings prepared from gelatin containing orange leaf oil retained a high L* value, indicating that melanosis was prevented. Application of packaging technology prevented melanosis in shrimp by minimizing oxidation and growth of melanosis-stimulating microbes.

Conventional Polymer-Based Packaging
Conventional polymer-based packaging, including polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl alcohol (PVOH), and polyamide (PA), still dominates the packaging industry with excellent mechanical, barrier, and thermal properties compared to plastic from other sources. Seafood is usually produced as frozen products, with a temperature during freezing of less than −40 • C and a frozen storage temperature −18 • C. Frozen seafood packaging must withstand low temperatures without cracking. Most frozen products become hard with sharp edges under freezing conditions due to their transition into an amorphous glassy state, causing impingement through flexible films and loss of package integrity. Glass transition temperature (Tg) plays a key role in the choice of packaging material properties. Polymers with higher Tg than freezing and storage temperatures are unsuitable for use with frozen products. Polyethylene has low glass transition temperature at up to −100 • C compared to other petroleum-based polymers, suggesting that it would be a suitable packaging material for products stored at extremely low temperatures [40]. Petroleum-based packaging for seafood products is usually in a flexible (pouch, bag, or pocket) or rigid (tray or box) form. Flexible packaging is made from PP, PE, or nylon due to the high elongation at break, while rigid packaging is normally made from PET or PS due to poor elongation at break.
The development of conventional polymer-based packaging for seafood products includes functional polymeric packaging and MAP that delays microbial growth. Dong et al. (2018) [41] found that the incorporation of rosemary and cinnamon essential oils into polyethylene reduced the degradation temperature and barrier properties of polypropylene film because the hydroxyl groups reacted with oxygen or water molecules and retarded shrimp deterioration. Nylon has excellent barrier properties and is mostly used as vacuum packaging in processed seafood products. Vacuum packaging with very low oxygen permeability maintained seafood quality by removing undesirable gases to minimize post-harvest metabolism [42], while incorporation of anthocyanin originating from plants with polyvinyl alcohol could monitor the freshness of shrimp [43].
Rigid and semi-rigid packaging such as PET-based trays play an important role in fishery product marketing, particularly in retail or convenience store fresh produce displays. Reduction of water-holding capacity in muscle structures causes high-drip loss of seafood products. This adversely affects appearance and consumer satisfaction. Liquid absorption pads are commonly used in the meat industry but are not popular in seafood packaging. The water absorbance pad is placed in direct contact with the fresh product and the water is still in contact with the product. Many patents of water-absorbent discs based on PLA modified material provided indirect contact water absorption between the fresh product and the absorption pad [44]. They designed an outer dish body and a depository dish body in an overlapped mode containing a water accumulation cavity between them. The water absorption sponge is placed inside the water accumulation cavity. The water absorption sponge has a lower size than the height of the accumulation cavity so that the system allows for the absorption of the water in irreversible contact with the product. Rigid packaging is also used to reheat food, and PET, PP, PE, and PS are suitable for microwave heating. A tray can also be used as a seafood MAP to maintain quality and mitigate oxidation and microbial growth.
Thermal insulation is also important for seafood packaging. Seafood is highly prone to microbial and enzymatic degradation, and temperature control is important to maintain product quality. Polystyrene-based rigid packaging such as a tray or box is usually used as a thermal insulator in seafood product delivery to maintain low temperatures. Several types of box insulation packaging have been commercially produced and registered as patents such as insulator bags made from glass wool and non-woven fabric [45], rectangular parallelepiped-based insulator boxes with sodium polyacrylate [46], intermediate foam fish boxes from olefin [47], Styrofoam boxes with intermediate lids [48], and insulator boxes with inflatable bags and wood pulp-based absorbance as wave-shaped convex strips [49]. Recently, conventional packaging still dominates in the packaging industry due to its excellent properties, processability, and lower price compared to bio-degradable polymers. However, end-use disposal of conventional polymer-based packaging is a serious problem; they are non-biodegradable due to their complex chemical structure of stable carbon-carbon linkages and are not broken down by microorganisms. Blending with biodegradable materials with high compatibility will improve the biodegradability without interfering with the properties.

Bio-Based Packaging
The majority of bio-degradable packaging originates from natural biopolymers and synthetic degradable polymers such as polysaccharide-based materials, which are environmentally friendly in terms of disposal and end life. Starch is one of the primary materials used in bio-degradable packaging, which is a renewable source derived from plants [50]. Starch is dominated by a hydroxyl group, resulting in a rigid network [51] and can be molded according to desirable shapes [52]. Thus, it is suitable for rigid packaging such as a tray, which is now dominated by a conventional polymer. The tray is commonly used to protect food from damage caused by undesirable environmental conditions such as shock, vibration, pressure, and deformation.
Polysaccharide-based trays or foam were developed to replace Styrofoam as an environmentally friendly packaging. A patent regarding a starch-based foam tray with at least two slots in the tray body combined with two fasteners, on which the tray body can be stacked and mutually form-embedded through the tray's grooves and fasteners. This tray contains plurality holes, can accommodate loads up to 80 kg [53], and can be used as a fish bulk container. A patent was also registered for biodegradable resin foam sheets prepared from cellulose acetate as the main component with a starch and talc or eggshell powderbased modifier. This had high water-resistant properties as cup trays [54] for high water product packaging. Xiqing et al. (2021) [55] patented a biodegradable tray composited from starch, bamboo pulp, succinic acid, fiber, paper pulp fiber powder, calcium alginate fiber, milk protein fiber, polyethylene resin, and a toughening agent (polyvinyl alcohol or acrylate rubber), which automatically degrades after use.
Antimicrobial trays made of high-amylose corn starch and cinnamyl aldehyde were patented by Zhaohui et al. (2016) [56]. They developed the trays by ultrasonic waves without added surfactant to prolong product shelf-life due to the slow release of cinnamyl aldehyde. Mclaughlin and Yapp (2022) [57] patented a food packaging tray equipped with a sealed compartment using a gasket and cold-seal adhesive with no hot-sealing process. This packaging is to carry the reheated food from the store to keep the food safe and hygienic. They created the easy reseal system by reactivating the cold seal adhesive between the adhesive surface and another surface contacted together. Therefore, the tray plays an important role in seafood packaging, particularly in the selling and distribution, to keep products safe and hygienic for the consumer. Recently, starch-based rigid packaging has been widely developed and commercialized for tableware, packaging, cushioning, and insulation. The application of starch in this field still has limitations due to low water resistance since seafood products have high water content. Future research can be focused on improving the water resistance of starch by chemical modification, lamination, or blending with other materials that have great water resistance.

Active Polymer Technology for Seafoods
Active packaging was described by Labuza in 1987 [58] as packaging, packaging materials, or packaging solutions that can interact with food and have a specific function beyond protecting food from the outside environment. The definition of active packaging was then expanded as technology advanced to face new problems. Nowadays, active packaging is defined as a packaging material that releases or treats substances from or into food or the environment. Active packaging methods can be divided into oxygen scavengers [59], carbon dioxide generating systems, ethylene scavengers, flavor and odor absorbers, antioxidants, and antimicrobials [60]. The technology of inserting the active compound into the packaging can be divided by coating [61], incorporating [41,62], surface modification [63], and adding directly into the packaging (i.e., essential oil into MAP) [64], which are able to modify and improve product quality, achieving desirable purposes [65]. The active agents are mostly applied in a polymer and effectively preserve the seafood quality (Table 1), including essential oils [23,37,66], plant phenolic compounds [67], or nano minerals [24,68]. Films showed a yellowish color and improvement in water tolerance, elasticity, and antioxidant activity (56-85% of ABTS inhibition).
Fillets packed in active film had a pleasant smell and flavor, an increase in golden color, and higher stiffness than fillets packed in control film. [67] Chitosan or lysozyme PLA Grass carp fillet The film provides an antimicrobial agent to form an amine bond to inhibit E. coli and S. aureus.
Active film prolonged the fillet up to 3 days. PLA/chitosan was more effective in inhibiting bacterial growth than PLA/lysozyme. [70] Essential oil (Carvacrol, citral and α-terpineol)

PLA/PBAT Pacific white shrimp
Essential oil modified barrier properties and microstructure affected by polymer-essential oil interacted via hydrogen bonding and carbonyl groups.
Shrimp deterioration was prevented by active film. Citral and carvacrol more effectively stabilized protein conformation in muscle tissues, retained drip loss and adhesion between the cephalothorax and abdomen. [37] Green tea ground waste Potato starch, gelatin, carboxymethyl cellulose (CMC)

Salmon
The film had high water vapor permeability (WVP) but limited germination due to a low pH. The DPPH radical scavenging of the tray containing tea waste was 80.75%.
The active tray + film provided potential inhibition against biogenic amine accumulation, 19% lower spoilage bacteria of salmon than the control after 6 days of storage. [71]  The incorporation of essential oils in the polymer takes advantage of the volatility of antimicrobial agents that migrate from the packaging to the food inside. Laorenza and Harnkarnsujarit (2021) [37] found that incorporation of carvacrol, citral, and α-terpineol essential oils released from the PBAT/PLA matrix into the headspace. The release behavior of these essential oils was related to shrimp quality with lower microbial growth, lipid oxidation/thiobarbituric acid reactive substance (TBARS), and melanosis formation, while films containing essential oils delayed glycogen metabolism revealed in FTIR absorbance at wavenumbers 2800 to 3040 cm −1 , which also agreed well with the protein degradation and head loss retardation. Shrimp packaged in films containing carvacrol, citral, and α-terpineol essential oils are shown in Figure 3.
The incorporation of essential oils in the polymer takes advantage of the volatility of antimicrobial agents that migrate from the packaging to the food inside. Laorenza and Harnkarnsujarit (2021) [37] found that incorporation of carvacrol, citral, and α-terpineol essential oils released from the PBAT/PLA matrix into the headspace. The release behavior of these essential oils was related to shrimp quality with lower microbial growth, lipid oxidation/thiobarbituric acid reactive substance (TBARS), and melanosis formation, while films containing essential oils delayed glycogen metabolism revealed in FTIR absorbance at wavenumbers 2800 to 3040 cm −1 , which also agreed well with the protein degradation and head loss retardation. Shrimp packaged in films containing carvacrol, citral, and αterpineol essential oils are shown in Figure 3.  Ziziphora clinopodioides essential oil and pomegranate peel extract in chitosan and gelatin film showed a synergistic effect, and were effective in inhibiting microbial growth in shrimp [23]. Essential oils were also applied in bilayer packaging to control the release direction of volatile compounds. Arancibia et al. (2014) [81] developed bilayer agar and alginate film containing cinnamon essential oil for chilled shrimp packaging. They found that cinnamon essential oil in agar was effective in inhibiting microbial growth due to essential oil interaction differences between agar and alginate. Dong et al. (2018) [41] also developed bilayer active packaging from low density polyethylene (LDPE) containing rosemary and cinnamon essential oils as an inside layer. They found that films containing combined rosemary and cinnamon essential oils were more effective in reducing TVB-N, TBARS, and microbial count. Essential oils containing strong antimicrobial and antioxidant activity were released from the packaging and brought into contact with the food to preserve quality.
Plant extracts with antioxidant properties incorporated into polymers as seafood packaging were also reported ( Figure 4). Lopes et al. (2021) [67] loaded potato peel extract onto starch film. The 2,2 -azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) inhibition of the film was measured at 56-85% within 7 days and increased the golden color of smoked sea bream fillet. Grapefruit seed extract incorporated with sodium alginate retarded the microbiological limit of shrimp for up to 4 days longer than the control, with lower TVB-N, pH values, and off-flavors due to dispersion of nanoparticles from the packaging to the shrimp [82]. Nagarajan et al. (2021) [83] developed an active coating prepared from gelatin and chitosan incorporated by longkong pericarp extract. They found that the active coating effectively inhibited melanosis and polyphenol oxidase activity of black tiger shrimp, while lipid (TBARS, peroxide value, and anisidine value) and protein oxidation (loss of sulfhydryl group) were inhibited. These results indicate that the incorporation of plant extracts rich in antioxidants into polymers has the potential to preserve the quality of shrimp. However, further investigation is required regarding the stability of plant extracts, particularly thermal and oxidative degradation. onto starch film. The 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) inhibition of the film was measured at 56-85% within 7 days and increased the golden color of smoked sea bream fillet. Grapefruit seed extract incorporated with sodium alginate retarded the microbiological limit of shrimp for up to 4 days longer than the control, with lower TVB-N, pH values, and off-flavors due to dispersion of nanoparticles from the packaging to the shrimp [82]. Nagarajan et al. (2021) [83] developed an active coating prepared from gelatin and chitosan incorporated by longkong pericarp extract. They found that the active coating effectively inhibited melanosis and polyphenol oxidase activity of black tiger shrimp, while lipid (TBARS, peroxide value, and anisidine value) and protein oxidation (loss of sulfhydryl group) were inhibited. These results indicate that the incorporation of plant extracts rich in antioxidants into polymers has the potential to preserve the quality of shrimp. However, further investigation is required regarding the stability of plant extracts, particularly thermal and oxidative degradation. Nanoparticles were also reported as a potent antimicrobial agent incorporated with polymers ( Figure 4). With their small molecule size, large surface area, and reactivity via the hydroxyl group, nanoparticles are easy to insert into a polymer [84]. Silicon dioxide (SiO2) [85], zinc oxide (ZnO) [86], and titanium dioxide (TiO2) [87] are common nanoparticles used in food applications. Al-Tayyar et al. (2020) [84] reviewed the active functions of nanoparticles. They found that the semiconductive properties of nanoparticles were able to generate reactive oxygen species (ROS) and that Zn 2+ antimicrobial ions were provided by nanoparticles in polar media. The nanoparticles interacted with carboxyl and amine groups on the bacterial membrane surface [88]. Another possibility was oxidative damage of the bacterial cell surface membrane by hydrogen peroxide by nanoparticles. Shao et al. (2021) [24] prepared active films from gelatin and polyvinyl alcohol containing SiO, ZnO, TiO, and copper oxide (CuO). They found that films with these nanoparticles significantly reduced the total viable Shewanella putrefaciens, Enterobacteriaceae, and Pseudomonas spp. counted in shrimp and L. monocytogenes, S. aureus, and E. coli inoculated from shrimp. Moreover, polyvinyl alcohol and gelatin film containing ZnO and TiO2 extended the shelf-life of shrimp by up to 6 days longer than the control [68].
Several patents have been registered regarding active packaging, including beta-cyclodextrin and essential oil inclusion compounded in polyvinyl alcohol [89]. They found no mold in the film after 18 days of incubation under 90% RH at 28 °C. A patent on multilayer active packaging was registered by Roberto et al. (2014) [90]. They developed a Nanoparticles were also reported as a potent antimicrobial agent incorporated with polymers ( Figure 4). With their small molecule size, large surface area, and reactivity via the hydroxyl group, nanoparticles are easy to insert into a polymer [84]. Silicon dioxide (SiO 2 ) [85], zinc oxide (ZnO) [86], and titanium dioxide (TiO 2 ) [87] are common nanoparticles used in food applications. Al-Tayyar et al. (2020) [84] reviewed the active functions of nanoparticles. They found that the semiconductive properties of nanoparticles were able to generate reactive oxygen species (ROS) and that Zn 2+ antimicrobial ions were provided by nanoparticles in polar media. The nanoparticles interacted with carboxyl and amine groups on the bacterial membrane surface [88]. Another possibility was oxidative damage of the bacterial cell surface membrane by hydrogen peroxide by nanoparticles. Shao et al. (2021) [24] prepared active films from gelatin and polyvinyl alcohol containing SiO, ZnO, TiO, and copper oxide (CuO). They found that films with these nanoparticles significantly reduced the total viable Shewanella putrefaciens, Enterobacteriaceae, and Pseudomonas spp. counted in shrimp and L. monocytogenes, S. aureus, and E. coli inoculated from shrimp. Moreover, polyvinyl alcohol and gelatin film containing ZnO and TiO 2 extended the shelf-life of shrimp by up to 6 days longer than the control [68].
Several patents have been registered regarding active packaging, including betacyclodextrin and essential oil inclusion compounded in polyvinyl alcohol [89]. They found no mold in the film after 18 days of incubation under 90% RH at 28 • C. A patent on multilayer active packaging was registered by Roberto et al. (2014) [90]. They developed a multilayer film consisting of paper (outer layer), polyethylene, or biodegradable plastic materials, an optional third metallic layer with an adhesive layer in the interposition, and an inner layer containing Rosmarinus officinalis, Citrus limon, or Vitis vinivera in contact with the packaged food. Results showed that the biogenic amine of fish samples was inhibited by up to 45%, 36%, and 39% after 2, 4, and 7 days of incubation, respectively. Obaiah et al. (2012) [91] developed another patent in active packaging as a dual function O 2 absorbing and CO 2 emission pouch for fishery products. Sodium bicarbonate, citric acid, and iron powder effectively absorbed O 2 with less than 1% concentration remaining within 24 h, while CO 2 remained high (80%) within 48 h. They explained that O 2 absorption was based on the principle of iron oxidation, whereas CO 2 emission came from the reaction between bicarbonate compounds and acids from citric acid releasing carbon dioxide along with the formation of other compounds. Furthermore, a patent for active amine scavenging for fish packaging was registered by Karlheinz and Francesca (2003) [92], consisting of at least one layer of ethylene with an unsaturated carboxylic acid group neutralized by a metal ion capable of adsorbing an undesirous amine from the headspace of the package. Active packaging is designed to have an active compound/system with the purpose of preventing deterioration factors and extending the shelf-life of food products. Active packaging has started to be commercialized; however, the production volume is still low due to safety and regulation. The low stability of active agents also becomes a major factor in causing the short shelf-life of active packaging. Future research focuses on protecting the active agent from damage such as oxidative and undesirable release amounts by microencapsulation as control release, lamination, or multilayer consisting of the high barrier layer.

Polymeric Sensors for Seafood
Intelligent packaging is defined as a system equipped with tools that are sensitive to environmental changes and continue to inform the users about the changes [93], while also providing information related to the function and properties of the packaged foods [94]. Intelligent packaging facilitates decision-making, warning of potential risks, food safety, and freshness [95]. Intelligent packaging can be divided into time-temperature indicators or gas indicators, biological sensors, humidity indicators, barcoding techniques, and radio frequency identification systems [96]. Food deteriorates during storage due to microbial activity, producing metabolites such as volatile amines and organic acids, which react and are then detected by the sensor-equipped intelligent packaging system that makes significant visible changes as a signal to assess the freshness level of the product [97]. Bioactive compounds extracted from plants have been widely investigated as freshness indicators in intelligent packaging. Bhargava et al. (2020) [97] compiled freshness indicators such as anthocyanin, curcumin, betalains, chlorophyll, carotenoids, tannins, quercetins, and brazilin, while chemical-based sensors incorporated with polymers were developed, including alizarin [98], pelargonidin [99], cyanidin-3-glucoside [100], and rhodamine B [101].
Biological/bioactive sensors are the most common intelligent packaging applied to seafood products, with metabolism outcomes such as ammonia, volatile nitrogenous compounds, and acidity (pH value) (Table 2 and Figure 5). You et al. (2022) [102] explained that anthocyanin loses the cations on the original oxygen atoms in C-ring and decreased the original salt ion concentration, resulting in a yellow color, and gradually turned blue in response to an increase in pH. Curcumin is susceptible to humidity changes and is suitable for use as a humidity indicator. Higher humidity promoted contact between ammonia and water molecules, resulting in ammonium cations and hydroxide, leading to a more alkaline environment and accelerating red color formation [103]. Metal-based colorimetric indicators such as gold, silver, or copper nanoparticles were also reported to be able to detect meat spoilage. Metal colorimetric indicators are suitable as volatile sulfuric compound detectors due to the high affinity between bonded metallic cations and sulfide anions. However, metal-based indicators, particularly Cu, were reported to have high stability in pH changes or no changes were found in variant pH values [104]. They also found that copper nanoparticles changed from dark yellow to red and finally black in response to an increase in hydrogen sulfide concentration in the fish. Fish spoilage results from the reaction of the volatile sulfur gas hydrogen sulfide with metals.
Common derivatives of anthocyanin include delphinidin, peonidin, pelargonidin, cyanidin, petunidin, and malvidin [99]. Pelargonidin was applied in intelligent packaging of tilapia fillets by   [99]. They found that the orange-red color originating from the flavylium cation was reduced due to the formation of quinone, resulting in carbinol pseudobase formation. Absorbance increased with increasing pH from 7 to 10 as a result of the redshift phenomenon that commonly occurs in anthocyanin. Anthocyanin as cyanidin-3-glucoside was also applied in intelligent packaging for tilapia fillets. The red color at pH < 4 originated from the flavonoid cation and then turned colorless in the pH range of 5-6 due to the conversion of the flavonoid cation to carbinol pseudobase and chalcone, while cyanidin shifted to quinonoidal anhydrobase with a purple/blue color at pH 6-8 [100].
Dye-based colorimetric indicators have been used as potential sensors. Alizarin contains a phenolic hydroxyl group that can easily deproteinize in neutral pH, resulting in color changes from yellow to red, while the second deproteination of the phenolic hydroxyl group occurs in alkaline pH (9)(10)(11), resulting in a purplish red color [98]. Liu et al. (2022) [101] found that the AIE-stimuli-responsive polymer tetraphenylethylene/polymethacrylic acid (TPE/PMMA) with rhodamine B acted as an acidity-dependent indicator that changed polymer conformation by ionization of the carboxylic acid group, thereby exhibiting a change in fluorescence intensity. This indicator was more sensitive in response to amines (trimethylamine and dimethylamine) than ammonia in salmon. Intelligent packaging based on poly (3,4-ethylenedioxythiophene) and polystyrene sulfonate as flexible ammonia gas sensors for fish meat by coating them onto metal electrodes was patented by Yabo et al. (2022) [105]. The response value increased with increasing ammonia up to 94%, with humidity reaching 85%. Intelligent packaging now monitors food consumption safety using sensors that can detect various deterioration factors. The natural-based biosensor has a high potential as a dual-function biosensor as well as an antimicrobial agent to monitor the freshness and preserve the quality of seafood products.  Color change from pale-blue to yellow-green in response to shrimp spoilage. [112] Malva sylvestris anthocyanins PLA, polyethylene glycol (PEG), and calcium bentonite (CB) Shrimp, fish roe, meat and chicken fillet pH-sensitive Color change from light red (pH 2) to green (pH 11) and more sensitive to shrimp and fish roe rather than chicken and meat correlated to TVB-N value. [113] Anthocyanin-rich purple potato extract 2,2 6,6tetramethylpiperidine-1-oxyradical, oxidized bacterial cellulose and thymol shrimp Volatile ammonia detector Color changed to dark purple in response to shrimp spoilage after 32 h. [114] Curcumin nano capsules Soy protein isolate and cellulose nanocrystals shrimp pH-sensitive, ammonia detector, anti-radical scavenging The yellow (pH 3-7) color becomes reddish-brown (pH 8-11) in response to TVB-N changes in shrimp during storage. [103] Curcumin Corn starch, polyvinyl alcohol

Pangasius bocourti
(catfish) pH-sensitive Color changed from yellow to orange in the range acidic (pH 3) to neutral (pH 7), and turned to red at pH 8-10 in response to TVB-N changes. [115] Copper nanoparticles Salmon trout Volatile sulfur compound The color of white, yellow and brown as a colorimetric indicator related to fresh, semi-fresh, and spoiled salmon, respectively. [104] Alizarin Gelatin and lavender essential oil shrimp pH-sensitive and ammonia detector, antimicrobial activity The color changed from yellow to red-brown in response to increasing TVB-N in shrimp after 3 days of storage. [98] Donor-π-acceptor (D-π-A) Cellulose Fish Amine detector The color changed from red to yellow in response to putrid fish, while the emission changed to bright cyan. [116] Pelargonidin Bacterial cellulose Tilapia fillet pH-sensitive The color change from red to colorless in response to the TVB-N value and sensory changes of tilapia fillets. [99] Cyanicin-3-glucoside Bacterial cellulose Tilapia fillets pH-sensitive Color changed from red to green in pH range 3-10. During application, rose-red fresh tilapia turned to purple (acceptable) and lavender (spoilage). Color change from pink (fresh) to dark blue (spoilage) was linearly correlated with TVB-N, indicating that the sensing label was feasible and non-destructive for quantitative TVB-N.  [105]. The response value increased with increasing ammonia up to 94%, with humidity reaching 85%. Intelligent packaging now monitors food consumption safety using sensors that can detect various deterioration factors. The natural-based biosensor has a high potential as a dual-function biosensor as well as an antimicrobial agent to monitor the freshness and preserve the quality of seafood products.

Modified Atmosphere Packaging for Seafood
Modified atmosphere packaging (MAP) controls the gaseous atmosphere surrounding the food inside its packaging using specific polymeric packaging materials with appropriate levels and gas barriers to maintain gas transfer from and to the environment for food preservation ( Figure 6) [117]. MAP is a non-thermal technology with multiple advantages for extending seafood shelf-life [35]. Lipid oxidation, protein degradation, microbial growth, and melanosis can be prevented by providing poor O 2 , rich CO 2 [118], and argon (Ar) [119]. Gas concentration inside the MAP changes during storage due to gas-food interaction. Oxygen decreased due to consumption by microorganisms, while CO 2 decreased due to muscle absorption by seafood or meat [10,35]. A reduction of CO 2 also occurred due to gas transfer from the packaging into the environment. They also found that higher O 2 concentrations showed greater CO 2 losses. However, the phenomenon of gas absorption activity requires further detailed investigation. and horse mackerel. This finding indicated that hydrogen incorporation gave advantages to biogenic amine inhibition due to the presence of antioxidant properties. Moreover, hydrogen gas is a permitted food additive with the code of E949. A patent about the application of MAP on fisheries products was registered by Jing et al. (2020) [125] for gas concentrations of 40-60% CO2, 0-10% O2, and 30-40 N2. They found that a gas composition of 60:5:35 of CO2:O2:N2 with a ratio between gas volume and puffer fish of 3:1 was optimal for packaging in terms of puffer fish quality. Packaging systems with low O2 and various concentrations of CO2, N2, Ar or H effectively preserved seafood quality and prevented lipid oxidation and biogenic amine production. Seafood products have different nutritional values, especially protein and lipid profiles, required specific gas concentration, gas permeability of packaging, and environmental conditions, to optimize MAP efficacy on seafood products. Modelling of MAP system for handling and storage which in turn influence shelf life of foods has been previously reviewed [126]. Future research needs to be focused on investigating, calculating, or modeling the appropriate MAP for seafood products with a specific characteristic.  CO2:O2:N2 ratio 1) Increased CO2 to 60-80% effectively reduced microbial growth, melanosis, and lipid oxidation. O2 de- CO 2 is the mainstay gas used in MAP due to its ability to maintain product quality, particularly limited microbial growth. However, CO 2 is generally highly soluble in meat, particularly in muscle or fatty tissue, and is influenced by pH, lipid type, and lipid content. Abel et al. (2020) [120] applied NaCl in salmon to reduce CO 2 solubility in MAP. They found that increasing NaCl concentration effectively reduced CO 2 solubility in salmon meat, due to changes in water fraction affected by increase in electrolyte concentration, leading to salting-out phenomena and resulting in inbound and unfree water content no longer available for CO 2 uptake.
The incorporation of hydrogen gas into MAP, called reducing atmosphere packaging (RAP), was investigated by Sezer et al. (2022) [124]. The use of RAP with 4% hydrogen significantly inhibited the formation of biogenic amines, namely heterocyclic, aromatic, and aliphatic di-amines (histamine, tyramine, putrescine, cadaverine) in rainbow trout and horse mackerel. This finding indicated that hydrogen incorporation gave advantages to biogenic amine inhibition due to the presence of antioxidant properties. Moreover, hydrogen gas is a permitted food additive with the code of E949. A patent about the application of MAP on fisheries products was registered by Jing et al. (2020) [125] for gas concentrations of 40-60% CO 2 , 0-10% O 2 , and 30-40 N 2 . They found that a gas composition of 60:5:35 of CO 2 :O 2 :N 2 with a ratio between gas volume and puffer fish of 3:1 was optimal for packaging in terms of puffer fish quality. Packaging systems with low O 2 and various concentrations of CO 2 , N 2 , Ar or H effectively preserved seafood quality and prevented lipid oxidation and biogenic amine production. Seafood products have different nutritional values, especially protein and lipid profiles, required specific gas concentration, gas permeability of packaging, and environmental conditions, to optimize MAP efficacy on seafood products. Modelling of MAP system for handling and storage which in turn influence shelf life of foods has been previously reviewed [126]. Future research needs to be focused on investigating, calculating, or modeling the appropriate MAP for seafood products with a specific characteristic. ε-polylysine, chitosan and sodium alginate coatings and MAP delayed myofibril oxidation, preserved Ca 2+ -ATPase activity, α-helix and β-sheet contents, and stabilized tertiary structure during cold storage. [27]

Thermal Insulation Packaging
Maintaining the freshness of seafood products is important, particularly during handling and distribution. The cold chain system is the main stage for the fresh seafood product supply chain until it reaches the consumer safely. Low temperatures are mostly obtained by ice (flake ice, tube ice, block ice, crushed ice). However, packaging equipped with thermal insulation is necessary to stop the ice from melting during storage and distribution. Expanded polystyrene, polyurethane foam, and expanded polyurethane foam are common thermal insulators used for cold chain distribution [133]. They contain many pores filled with air and have very poor thermal conduction properties that inhibit the flow of heat energy (Figure 7). Sormin et al. (2016) [134] reported that Styrofoam had better cool temperature maintenance, resulting in a faster cooling rate of fish (0.13 • C/min) compared to the cool box insulator "ela sago" (0.045 • C/min). Patents for insulator boxes for fisheries' products are listed in Table 4.
Nowadays, environmentally friendly thermal insulators have attracted research attention to replace conventional material-based products in cool chain systems. Ariany et al. (2018) [135] found that cellulose-based insulators with low thermal conductivity could be applied to fishery products to reduce the magnitude of heat flux on the fish to 61.31% of the maximum heat flux, although the system required further improvements, particularly the thickness. Thermal insulation-equipped packaging prepared from feathers had low thermal conductivity compared with expanded polystyrene [133]. The feathers were extremely lightweight and environmentally friendly, with good mechanical properties and high thermal insulation due to the hollow shaft structure. Cardboard-based thermal insulators consisting of double E-fluted corrugated board sandwiches between PE laminated and metalized E-fluted cardboard had similar thermal insulation properties to commercial expanded polystyrene; however, the complex structure of cardboard-based insulator thermal insulators requires further investigation for foldability and manufacturability performance [136]. Rigid packaging that can maintain low temperatures is required in the seafood supply chain to preserve product quality and prevent loss. Natural-based thermal insulators have started to be investigated to replace conventional polymers. Future research needs to investigate the durability of the natural-based insulator to meet the requirement for an insulator box for distribution and storage. It could be conducted by simulation with heat transfer and distribution, shock, and vibration taken into consideration. larly the thickness. Thermal insulation-equipped packaging prepared from feathers had low thermal conductivity compared with expanded polystyrene [133]. The feathers were extremely lightweight and environmentally friendly, with good mechanical properties and high thermal insulation due to the hollow shaft structure. Cardboard-based thermal insulators consisting of double E-fluted corrugated board sandwiches between PE laminated and metalized E-fluted cardboard had similar thermal insulation properties to commercial expanded polystyrene; however, the complex structure of cardboard-based insulator thermal insulators requires further investigation for foldability and manufacturability performance [136]. Rigid packaging that can maintain low temperatures is required in the seafood supply chain to preserve product quality and prevent loss. Natural-based thermal insulators have started to be investigated to replace conventional polymers. Future research needs to investigate the durability of the natural-based insulator to meet the requirement for an insulator box for distribution and storage. It could be conducted by simulation with heat transfer and distribution, shock, and vibration taken into consideration.   Table 4. Patents related to thermal insulators and box packaging for fishery products.

Patent Title Invention Details Application Patent Source
Containing bag for fresh fish A bag contained waterproof material at the outer most portion, equipped with outer heat insulating material made from glass wool and nonwoven fabric. The cooling system, prepared from nitrogen gas sealed in the hollow layer reached cooling temperature of −1 • C to −5 • C. The mouth of the bag was equipped with fastener material (Velcro fastener or waterproof fastener).
Transportation and storage bag for high-economical commodity, particularly tuna and camellia in cold insulation state.
JP1995243741 [45] Portable cool box The component of the cooling box was hollow with a rectangular parallelepiped case body, a lid, cold insulator, and support mechanism. The insulator material contained highly water-absorbing polymer sodium polyacrylate sealed in a hollow plastic case to maintain high water absorbency by forming a gel structure.
Portable cool box for retaining the freshness of fish or other objects which can be easily used in fishing or camping.
JP2013085550 [46] Intermediate dish of foamed fish box The overlapped box containing two outer boxes and an upper layer made from cold resistant olefin sheet-based raw material. The depth of the main container was adjusted by calculating the amount of ice required. An edge over the upper layer created an overlapped insulator box.
Container for fresh fish at processing site or for transportation.
JP2018135150 [47]  Non-direct contact cooling system using cold air for fresh products. KR1020180112388 [48] Corrugated carton suitable for transportation and packaging of fish tank A corrugated box for transporting fish tanks equipped with an inner and outer groove on the foam base. The inner groove is equipped with a rubber sleeve and the fish tank is placed on the outside of the rubber sleeve on the outer groove. Between the fish tank and rubber sleeve, rubber supporting feet are attached with a soft rubber cushion, EPE pads protect the fish tank and are reusable.
Corrugated paper box for fish tank transportation and packaging.
CN209427201 [49] Circular fish tank buffering packaging box formed by one piece of paper A fish box formed by one piece of paper packaging as the main body, with linings and a handle, comprising a bottom plate, four end plates, a top plate, four lining plates and a bottom plate. The handle comprises two triangular top plates. Prevents fish transportation damage with reduced amounts of foam, reduced production cost, and material saving.
Paper box for fish transportation to minimize damage. CN209720191 [137] Packaging box for refrigerating fresh fish meat A box with an inside structure, including an inflatable bag with an inflatable interface on the top, foam plastic board, absorbent paper made from wood pulp layer and a non-woven layer on both sides, and a wave-shaped convex strip in the inner wall. A sealing gasket is attached between the box cover and box body, with a support pad placed in the bottom of the box.

Conclusions and Future Perspective
This paper highlighted seafood's post-harvest deterioration and reviewed recent advances in polymeric packaging technology. Novel technology regarding polymeric active packaging, intelligent packaging, MAP, as well as rigid insulation packaging for seafood products has been developed and patented. Furthermore, the removal of the smell of seafood products related to their chemical compounds has also become a challenge in terms of packaging technology. New active compounds have been successfully used to preserve product quality, such as essential oils, nanoparticles, and plant extracts, while intelligent bioactive sensors, such as anthocyanin and metal and dye-based sensors, have been used to monitor the freshness of seafood. Biodegradable insulator packaging for seafood is at the novel development stage. From these recent results, biodegradable and sustainable polymers will be increasingly investigated for packaging applications in the future. Functionalized materials as well as improve the stability and packaging performance of biodegradable materials for seafood packaging applications will be explored by global researchers. Chemical and physical modification of polymers, lamination, coating, and blending with other sustainable materials are the technologies to improve water resistance and performance for seafood packaging. Further research is required to scale-up the polymeric-based packaging to industrial market production to meet the needs of the fishery market and promote a circular economy in the post-pandemic situation.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.