Abstract: Asian carp is a general designation for grass carp, silver carp, bighead carp, and black carp. These fish species belong to the family Cyprinidae. In 2018, more than 18.5 million tons of Asian carp were produced globally. Asian carp can be used for producing surimi, a stabilized myofibrillar protein concentrate that can be made into a wide variety of products such as imitation crab sticks, fish balls, fish cakes, fish tofu, and fish sausage. Surimi is usually made from marine fish, but Asian carp have been widely used for surimi production in China. The quality of surimi is affected by various factors, including the processing methods and food additives, such as polysaccharides, protein, salt, and cryoprotectant. With an impending shortage of marine fish due to overfishing and depletion of fish stocks, Asian carp have a potential to serve as an alternative raw material for surimi products thanks to their high abundancy, less emissions of greenhouse gases from farming, desirable flesh color, and sufficient gel forming ability.
Surimi is a food product widely found in East Asian cuisines, which comes in many shapes and sizes, from fish balls to various kinds of seafood imitation, such as crab sticks. Surimi is made from deboned, minced, and washed fish meat. To be able to imitate the texture of other seafood products, a good gelling property is among the most important characteristics of high-quality surimi. In surimi gelation, myofibrillar proteins, which consist of myosin and actin, play an important role. Although myosin alone can form the gel, actin also cooperates in gelation, which is influenced by the actomyosin ratio. In gelation, heating induces the denaturation of myofibrillar proteins followed by an irreversible aggregation and is cross-linked to form a three-dimensional network [1][2].
Nowadays, there is a wide variety of fish that is currently used as a raw material in surimi production and the majority of them are marine fish. Among those fish species, Alaska pollock is a typical commercial fish used for surimi production as a raw material. It is a cold-water white fish that is available in the North Pacific [3]. The superior gel properties, white flesh, and its availability make it suitable for surimi making. Apart from Alaska pollock, there are several cold-water white fish that are also used in surimi manufacturing, which includes the Arrowtooth flounder, Pacific whiting, and blue whiting [4][5][6][7]. In tropical countries, such as countries in Southeast Asia, tropical fish including threadfin bream, bigeye snapper, and lizardfish are some examples used to produce surimi and surimi products [4]; however, overexploitation of these lean fish species diverts the interest of surimi processing industries towards dark fleshed fish called pelagic fish including sardine, mackerel, etc., but these fish possess weak gelling properties, which are associated with the high lipid, water-soluble protein contents and endogenous proteases firmly attached to the fish muscles [8][9]. Therefore, to overcome the aforementioned problems, freshwater fish could be used as a raw material for surimi production. These freshwater fish have already been used in traditional surimi products, such as fish balls and fish cakes, in China [10].
In general, freshwater fish can be cultured at a low cost and they can attain optimum size in a short time. Therefore, they are gaining more attention to be considered as a potential candidate for surimi manufacturing. Asian carps, namely, bighead carp, grass carp, silver carp, and black carp, are freshwater fish, which can be commonly found in Chinese cuisine. Various recent researches have been performed to improve the gel properties of surimi made from Asian carp [11][12][13][14], and although various collective reports have been available on lean and dark flesh fish surimi gel, no review has been available on the usage of Asian carps in surimi gel preparation and factors affecting gelation. Therefore, this review aims to promote a comprehensive understanding of the Asian carps’ characteristics and their suitability for surimi production. Moreover, factors affecting and solutions to improve the qualities of surimi from Asian carp have also been revisited.
Surimi processing technology was established in the 1960s. At that time, cold-water white fish was used as the main material for surimi production, especially the Alaska pollock; however, the market for surimi and surimi products has continually developed and grown in subsequent years, and various marine fish species have been utilized as a material in the surimi industry such as Arrowtooth flounder, Pacific whiting, threadfin bream, and bigeye snapper [4]. The fish materials for surimi production differ from area to area depending on several factors including ecosystem productivity, fish intensity, management, price, and the quality properties of products.
Nowadays, overfishing and depletion of marine fish stocks are becoming a major concern for the fisheries industry as well as the surimi manufacturing industry. With a decreasing supply of marine fish, Asian carp as an alternative ingredient could be exploited. Asian carp can be produced in a large quantity in a shorter time and at a lower cost as compared to marine fish. The amount of grass carp, silver carp, bighead carp, and black carp produced worldwide in the year 2019 were 5.7, 4.7, 3.1, and 0.7 million tons, respectively. On the other hand, 3.5 million tons of Alaska pollock, 0.4 million tons of pacific whiting, and 0.03 million tons of Arrowtooth flounder were produced in the same year [3]. Moreover, almost all Asian carp are currently cultured in China. Asian carp production has the potential to reach an even higher number if other countries start raising Asian carp for consumption as well. In addition to this, Asian carp also have another advantage. According to a study by Gephart et al. [15], silver carp and bighead carp farming produces the least greenhouse gas, nitrogen, and phosphorus among farmed finfish and crustaceans. This makes silver carp and bighead carp more environment-friendly choices for an alternative raw material for surimi than other farmed fish. Regarding the suitability of Asian carp for surimi production, Asian carp are a white flesh fish.
Grass carp (Ctenopharyngodon idella), the sole member of the genus Ctenopharyngodon, is a member of the family Cyprinidae commonly found in East Asia. Grass carp can grow to a maximum size of around 1.5 m [16]. The main diets of grass carp are aquatic plants. Grass carp is the most produced Asian carp, as well as the most produced fish in aquaculture worldwide and there was 5.7 million tons of grass carp produced in 2018 [3]. Grass carp has white flesh which is composed of 16.70% protein and 0.12% fat [10].
Silver carp (Hypophthalmichthys molitrix) belongs to the genus Hypophthalmichthys which can grow to 1 m in size [16]. The silver carp is an omnivore but feeds mainly on phytoplankton. Silver carp is produced more than other fish species worldwide in aquaculture, second only to the grass carp. According to the Food and Agriculture Organization [3], more than 4.7 million tons of silver carp were produced in 2018, compared to 5.7 million tons of grass carp produced in the same year. Silver carp also has white flesh and is high in protein (15.65%) and low in fat (1.89%) [10].
Common carp (Cyprinus carpio), also known as European carp, is a carp species native to Asia and Europe. Common carp have an average size of 40–70 cm, but can grow up to 120 cm [17]. Similar to other carp species, common carp are omnivorous but prefer insects and crustaceans. In the year 2018, 4.3 million tons of common carp were produced globally [3]. Common carp flesh is composed of 15.4% protein and 1% fat [10].
Bighead carp (Hypophthalmichthys nobilis) belongs to the genus Hypophthalmichthys, the same genus as silver carp. The bighead carp’s maximum size is around 1.5 m [16]. The bighead carp is an omnivorous filter feeder that prefers zooplankton as its main diet. Bighead carp is less produced compared to silver carp and around 3.1 million tons of bighead carp were produced worldwide in 2018 [3]. The bighead carp’s flesh is white and firm, and it contains 17.90% protein and 0.96% fat [10].
Black carp (Mylopharyngodon piceus) is the only member of the genus Mylopharyngodon. The average size of a black carp is not so different from that of the other Asian carp species. Its maximum size is 1.2 m [16]. The black carp’s main diet is mollusks, such as clams and snails. Only 0.7 million tons were produced in 2018, which is the lowest among the other Asian carps [3]. The black carp’s flesh consists of 17.06% protein and 8.58% fat [10], which is the highest fat content compared to other Asian carp.
According to the information mentioned above. Asian carp species, namely, silver carp, bighead carp, common carp, grass carp, and black carp, are being produced in great quantities and have a high availability. Their flesh also contains a high protein content and low fat content. Moreover, the size of Asian carp is more economical to prepare fillets for surimi production compared with the average size of threadfin bream (10–15 cm) [4]. Therefore, Asian carp has the potential to become an alternative raw material for surimi production.
5.3.1. Traditional Methods
A heating treatment is one of the common processes to induce surimi gel. The quality of surimi products could be dependent on the temperature, heating rate, and heating method. Temperature plays an important role in the denaturation and unfolds of the gel formation. The traditional process of surimi products has been to heat it in a two-step process by a water bath treatment; the first step heated to below 30 °C for the cross-linking of myofibrillar protein, followed by cooking at 90 °C for forming a 3-dimensional protein network and the inactivation of various indigenous enzymes [2][63]. However, water bath heating obtains a heat transfer from the outside surface to the inside of the surimi paste, and causes a slow gel-formation during the fast cooking of surimi products [64][65]. To obtain a fast cooking time with surimi products, several treatments such as microwave heating and radiofrequency have been employed [66][67]. Feng et al. [68] investigated the comparison of microwave heating (100 and 300 w) and water bath heating on the physicochemical properties of fish protein from silver carp. The results showed that the water bath treatment resulted in a surimi gel that had a higher denaturation and aggregation of actomyosin than the microwave; however, the microwave heating (300 w) showed a protective effect on the conformational change of fish protein and improved the quality of surimi. Radiofrequency results in a dielectric heating of the meat product with a low rate of electromagnetic waves. Moreover, radiofrequency has been applied in the surimi heating process to decrease the heating time and reduce nutritional losses, and to improve the quality of surimi products compared with the traditional treatment [67].
5.3.2. Novel Non-Thermal Methods
In addition, non-thermal technology, an acid-induced gel, and 3D printing, have also been developed and applied to the production of Asian carp surimi products [69][70][71](Table 1). Non-thermal technology is used as an alternative to traditional heating methods due to its minimal effect on the color, aroma, flavor, and nutrients of food products [72]. The applications of non-thermal technology in surimi products include high-pressure processing, high-intensity ultrasound, and E-beam irradiation.
High-pressure processing, also known as ultra-high-pressure processing or high hydrostatic pressure processing, is a food processing technology that utilizes a high pressure (from 100 MPa up to 900 MPa) [73]. The pressure can cause physicochemical changes and improve the functional properties of food products by enhancing the moisture–protein or protein–protein interactions [74]. The effectiveness of high-pressure processing on the quality of fish products is dependent on the amount of pressure applied and the type of product itself [75]. Liang et al. [69]compared the effectiveness of a high-pressure treatment (100, 200, 300, 400, and 500 MPa) and a two-step heating treatment (40 °C for 30 min and 90 °C for 20 min), on the gel characteristics of surimi from bighead carp. The results showed that the high-pressure treatment gave a higher gel strength and springiness compared with the traditional heating treatment, especially when 500 MPa of pressure was applied.
High-intensity ultrasound is a technique used for improving the physicochemical properties of food products, such as firmness, ripeness, acidity, and sugar content, by applying a low frequency mechanical wave (16–100 kHz) [76]. This technique can also be used for improving the gel properties of surimi products [77]. For example, Gao et al. [12] studied the effects of pre-treatment using high-intensity ultrasound on the gelation properties of surimi from silver carp. The results showed that applying a high-intensity ultrasound pre-treatment before mixing the mince with salt was the most effective pre-treatment mode for promoting the gelation of surimi. The pre-treatment increased the breaking force and prevented deformation of the surimi gel by promoting the formation of non-disulfide bonds and S–S bonds. Moreover, the efficiency of the high-intensity treatment on the gelation properties of surimi is also dependent on the salt contents [78].
Electron beam (E-beam) irradiation is a technique that involves utilizing high-energy electrons for a variety of applications such as pasteurization and sterilization. It is completed by shooting electrons through the product using a linear accelerator [79]. The E-beam generally uses electricity, making it safer compared to gamma ray irradiation using radioisotopes (Co60 or Cs137). The recommended dose for applying E-beam on food products is ≤10 kGy [80]. Electron beam irradiation is, however, not without flaws. Brewer [81] reported a probability that E-beam can cause off-odors and off-flavors in food products. Zhang et al. [82] reported that the application of E-beam irradiation (1–7 kGy) in combination with microwave heating (70 °C) on grass carp surimi produced more volatile compounds than an E-beam irradiation treatment alone, while the control treatment produced the least volatile compounds.
Table 1. The process progress to improve surimi quality.
Processing/Treatments |
Name of Fish Species |
Experimental Conditions |
Analysis |
Optimum Amount/Treatment Conditions |
Reference |
Acid-induced gel preparation |
Silver carp |
Acid-induced gel (acetic acid solution 1:4 (w/v)), and heat-induced gel (30 °C for 1 h and 90 °C for 15 min) |
Moisture content, pH, TPA, expressible water content, whiteness, SDS-PAGE, SEM, and protein solubility |
Acid-induced gel |
[70] |
3D printing |
Silver carp |
Printing systems; nozzle diameter size (0.8, 1.5, 2.0 mm), nozzle height (5, 10, 15, 20 mm), nozzle moving speed (20, 24, 28, 32 mm/s, and extrusion rate (0.002, 0.003, 0.004, 0.005 cm3/s) |
Rheological characterization, gel strength, WHC, microstructure, LF-NMR, extrusion rate, and resulting diameter |
Nozzle diameter 2.0 mm, nozzle height 5.0 mm, nozzle moving speed 28 mm/s, and 0.003 cm3/s |
[71] |
Non-thermal |
|
|
|
|
|
High pressure |
Bighead carp |
Heating treatment (40 °C for 30 min and 90 °C for 20 min), and pressure treatments (100, 200, 300, 400, and 500 MPa, at 25 °C for 30 min) |
Gel strength, TPA, WHC, whiteness, turbidity, protein solubility, SDS-PAGE, SEM, and protein content |
Pressure treatment at 500 MPa |
[69] |
High intensity ultrasound |
Silver carp |
0–5% NaCl, ultrasonic treatment at 100 kHz, 300 W for 10 min |
puncture, microstructures, WHC, dynamic rheological properties, SH content, chemical interactions, solubility, TCA-soluble peptides, and SDS-PAGE |
0–2% NaCl |
[78] |
E-beam irradiation |
Grass carp |
Irradiation doses; 0, 1, 3, 5, and 7 kGy in combination with microwave heating 70 °C |
Volatile compounds, and fatty acid profile |
5 and 7 kGy |
[82] |
Oils have been widely used as a texture modifier, color enhancer, or processing aid for surimi production [108]. Numbers of studies have reported the addition of oils such as peanut oil, soybean oil, and fish oil in silver carp surimi [63][153][154]; however, excessive oil contents could reduce the breaking force due to an interference in the formation of a gel network. Furthermore, the replacement of oil for water may enhance the protein concentration in the matrix of a gel [153][154].
Table 2. The functional ingredients and their optimum conditions to enhance the quality of surimi and surimi products.
Food Additives |
Name of Fish Species |
Experimental Conditions |
Analysis |
Optimum Amount/Treatment Conditions |
Reference |
Carbohydrate |
|
|
|
|
|
Potato starch, corn starch |
Silver carp |
8% potato starch (modified starch, native starch), and 8% corn starch |
TPA, penetration force, gel strength, color evaluation, microstructure, and paraffin section |
8% potato starches |
[87] |
Wheat flour |
Silver carp |
0%, 10%, 20%, and 30% of surimi combination with wheat flour, setting using microwave heating at 2450 MHz |
Temperature distribution, and DSC |
10% and 30% of surimi |
[91] |
Modified starch |
Silver carp |
Acetic acid esterification starch (AAES), cross-linked esterification starch (CES), cross-linked hydroxypropylated starch (CHS), hydroxypropylated starch (HS), and sorbital combination with sucrose (1:1; wt), storage conditions; temperature −20 °C for 90 days |
Gel Strength, Ca²⁺–ATPase activity, SSP content, and SH content |
AAES and HS |
[95] |
Konjac glucomannan (KGM) |
Grass carp |
0%, 0.5%, 1%, 1.5%, and 2% KGM, storage conditions; temperature −18 °C for 30 days |
TPA, WHC, whiteness, SEP content, Ca²⁺ ATPase activity, SH content, and active sulphydryl content |
1% KGM |
[97] |
Starch gum |
Silver carp |
1.37% hydroxypropylated cassava starch (HCS), 0.44% curdlan (CD), 0.22% κ-carrageenan (KC), and mixtures of 1.37% hydroxypropylated cassava starch, 0.44% curdlan and 0.22% κ-carrageenan (HCK) |
Gel strength, TPA, WHC, whiteness, soluble protein content, SEM, raman spectroscopy, and sensory analysis |
HCK |
[98] |
Pectin gum |
Silver carp |
1% pectin gum and 0.2% CaCl2 with different degree of methoxylation, 27–33%, 27–33%, 60%, 65%, 69–72%, and 72% |
Torsion test, TPA, and expressible water |
Low methoxyl (27–33%) |
[99] |
Apple pectin, KGM |
Silver carp |
0.025%, 0.05%, 0.075%, and 0.1% apple pectin combined with 1%, 1.5%, 2%, and 2.5% KGM |
Gel strength, TPA, WHC, whiteness, SDS–PAGE, and soluble protein |
0.025% apple pectin combined with 2% KGM |
[100] |
Chitosan |
Silver carp |
Chitosan with molecular weight (MW), 299, 410, 600, 706, and 880 kDa combination with different degree of deacetylation, 60.5%, 65.4%, 70.8%, 77.3%, and 86.1% |
Rheological characteristics, gel strength, WHC, SEM, and molecular forces |
Chitosan with MW 880 kDa combination with deacetylation 77.3% |
[103] |
Nanosized okara |
Silver carp |
0%, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8% microsized okara insoluble dietary fiber (MIDF) and nanosized okara insoluble dietary fiber (NIDF) |
TPA, LF-NMR, MRI, light microscopy observation, and FTIR-ATR |
0.8% NIDF |
[105] |
Seaweed |
Silver carp |
27.7 g/kg Ulva intestinalis seaweed powder, and 5 g/kg U. intestinalis sulphated powder, storage conditions; temperature −18 °C for 6 mouths |
Proximate compositions, cooking yield, pH, instrumental color evaluation, peroxide value, TBARS, sensory evaluation, and TPA |
U. intestinalis sulphated powder |
[106] |
Chicory polysaccharide |
Silver carp |
0%–8% chicory polysaccharide |
Sensory evaluation, fuzzy mathematical, factor weight set, hardness, elastic, TVB-N, pH, TBARS, fatty acids, and microbial analysis |
3% chicory polysaccharide |
[107] |
Protein |
|
|
|
|
|
Egg white protein |
Silver carp |
Egg white protein (EWP), and β-cyclodextrin (βCD) mixture, 0%, 2%, 4%, and 6%, storage conditions; temperature −18 °C for 60 days |
FI, circular dichroism, dynamic rheological properties, water loss, TPA, and microstructure |
6% EWP-βCD |
[111] |
Soy protein isolate |
Silver carp |
0%, 10%, 20%, 30%, and 40% soy protein isolate, cooking conditions; direct cooked 85 °C for 30 min, cooked after setting at 30 °C for 60 min, cooked after 40 °C for 60 min, and cooked after 50 °C for 60 min |
Gel strength, breaking force, and breaking distance |
10% soy protein isolate cooked after setting at 50 °C for 60 min |
[113] |
Soy protein isolate |
Bighead carp |
0%, 10%, 20%, 30%, and 40% soy protein isolate, setting conditions; 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C for 30, 60, and 120 min |
Gel strength, and microstructure |
10% soy protein isolate with setting condition at 35 °C to 40 °C for 60 min |
[116] |
Whey protein concentrate (WPC) |
Silver carp |
1–9% WPC combinate with 1–59 mmol/kg CaCl2 setting at 30–90 min |
Gel strength, and bending test |
5% WPC and 15–18 mmol/kg CaCl2 with setting at 60 min |
[118] |
Microbial transglutaminase (MTGase) |
Silver carp |
0 and 15 U/g MTGase, digestion time; 0, 5, 30 and 120 min |
Extent of cross-linking, TPA, dry matter digestibility, particle size, microstructure, tricine-SDS-PAGE, amino acid composition, and LC-MS |
Digestion at 30 min |
[127] |
MTGase |
Silver carp |
0 and 9 U/g MTGase, storage condition; temperature −18 °C for 0, 1, 3, 5, 7, 10, and 15 days |
TPA, WHC, extent of cross-linking, free amino concentration, TGase activity, SH content, disulfide bond, S0, turbidity, and CD spectrum |
5–7 day for promoting the cross-linking |
[129] |
Salts |
|
|
|
|
|
NaCl |
Silver carp |
0.1, 0.2, 0.3, 0.4, 0.6, 1, 2, and 3 M NaCl, setting conditions; temperature 4 °C |
Confocal laser scanning microscopy, UV absorption spectra, Ca²⁺-ATPase activity, S0, SH content, reactive sulfhydryl, turbidity, solubility, and particle size |
1–3 M NaCl |
[132] |
NaCl, KCl, MgCl2, CaCl2 |
Grass carp |
The same concentrate (0.6 mol/L) of NaCl, KCl, MgCl2, and CaCl2 with 0.1 g/100 mL MTGase, setting conditions; temperature 4 °C |
WHC, color evaluation, gel strength, dynamic rheological, microstructure, and raman spectrum |
KCl > MgCl2 > CaCl2 |
[135] |
NaCl, KCl, CaCl2 |
Silver carp |
NaCl, KCl, and CaCl2 at corresponding to ionic strength of 0.51, 0.34, and 0.17 |
TPA, WHC, gel strength, chemical bonds, rheological analysis, SH content, solubility, and SEM |
KCl |
[136] |
Cryoprotectants |
|
|
|
|
|
Sucrose, sorbitol, trehalose, polyphosphate |
Grass carp |
4% + 4% sorbitol + 0.3% polyphosphate, 6% trehalose, and 6% trehalose + 0.3% polyphosphate, storage conditions; temperature −18 °C for up to 25 weeks |
Ca²⁺-ATPase activity, SH content, SEP content, and gel-forming ability |
6% trehalose, and 0.3% polyphosphate |
[143] |
Protein hydrolysate |
Silver carp |
4% sucrose (S), 2% surimi by-products hydrolysate by trypsin + 2% sucrose (TS), and 2% surimi by-products hydrolysate by alcalase + 2% sucrose (AS), storage conditions; temperature −18 °C for 3 months |
MW distribution, degree of hydrolysis, ABTS radical scavenging activity, reducing power, Fe2+-chelating activity, SSP, SH content, carbonyls concentration, Ca²⁺-ATPase activity, fluorescence intensity, S0, gel strength, TPA, water distribution, and expressible water content |
TS and AS |
[144] |
Protein hydrolysate |
Bighead carp |
1% hydrolysate from neutral protease, 2% hydrolysate from neutral protease, and 4% sucrose, storage conditions; temperature −18 °C for 4 months |
MW distribution, DPPH radical scavenging activity, chelating activity, SH content, disulfide bonds, carbonyl concentration, Ca²⁺-ATPase activity, SSP, S0, gel strength, TPA, and LC-MS |
1% and 2% hydrolysates by neutral protease |
[138] |
Polyphenols |
|
|
|
|
|
Tea polyphenols |
Grass carp |
0, 5, 10, 20, 50, and 100 μmol/g tea polyphenols |
Amino acid side-chain groups, raman spectra, S0, SDS–PAGE, gel strength, TPA, particle size, and turbiscan stability index |
5 and 10 μmol/g tea polyphenols |
[150] |
Young apple polyphenols |
Grass carp |
0%, 0.05%, and 0.10% young apple polyphenols, storage conditions; temperature at 4 °C for 7 days |
TBARs, TVB-N, PV, color evaluation, soluble myofibrillar protein content, SDS-PAGE, emulsifying activity, emulsifying stability index, S0, gel strength, TPA, and sensory evaluation |
0.10% young apple polyphenols |
[152] |
Oil |
|
|
|
|
|
Vegetable oils |
Silver carp |
10, 20, 30, 40, and 50 g/kg of soybean oil, peanut oil, corn oil, and rap oil |
Punch test, expressible water, color evaluation, dynamic rheological, transmission electron microscopy, and sensory evaluation |
10% peanut oil |
[153] |
Soybean oils |
Silver carp |
0%, 1%, 2%, 3%, 4%, and 5% soybean oils |
Punch test, TPA, and color evaluation |
<3% soybean oil |
[154] |
Fish oils |
Silver carp |
0, 3, 6, 9, and 12% fish oils, heating condition; under two-step water bath heating (40 °C for 30 min and 90 °C for 20 min), and water bath-microwave heating (40 °C for 30 min and power intensity 5 w/g for 96 s) |
TPA, color evaluation, expressible moisture content, SEM, LF-NMR, and lipid oxidation |
6% fish oil, under water bath-microwave heating |
[63] |
6.1. Inferior Gel Forming Ability
Asian carp species are known to have a relatively low gel-forming ability. Luo et al. [155] have completed a study on the gel-forming ability of Asian carp species (common carp, grass carp, and silver carp) compared to that of an Alaska pollock, the marine fish species commonly used for surimi production. The result of this study showed that the Asian carp species had a lower gel-forming ability than an Alaska pollock; however, the Asian carp species still had enough gel-forming ability to be utilized in surimi production [155]. The gel-forming ability of the muscle protein can be affected by several factors such as the muscle sources, protein concentration, heating rate, and heating time. Protein plays an important role in the determining of gel properties [2] and the protein muscle sources can influence the gel-forming ability [2]. Chan et al. [156] reported that the differences in gel-forming abilities of three fish species (cod, herring, and silver hake) were related to the cross-linking abilities of the myosin helical tail. Meanwhile, a number of studies compared the network structure between marine fish and freshwater fish by using microstructure [157][158]. Riebroy et al. [158] reported that marine fish (Atlantic cod) myosin obtained a higher interconnected and finer network structure than freshwater fish (burbot) myosin. The gel-forming ability was increased due to higher myofibrillar protein concentrations [159]. Asian carp species have white flesh which on average is composed of 16.65% protein content [10], while marine fish such as Alaska pollock flesh is composed of 17.5% proteins [160]. A strong and orderly 3-dimensional surimi gel structure can be achieved when surimi gelation occurs under a slow heating rate and a previous study showed that Asian carp species (common carp, grass carp, and silver carp) required a higher temperature and longer duration for surimi gelation compared with Alaska pollock [155].
Although Asian carp species have a relatively low gel-forming ability compared to marine fish species, they are usable in surimi manufacturing and their low gel-forming ability can be improved by using various additives such as pectin, curdlan, κ-carrageenan, gelatin, and starch [11][98][99]. Moreover, this gel-forming ability is sufficient for surimi processing and its products.
6.2. Muddy Odor
Off-odors and off-flavor represent a significant problem for fish and their products, which affects consumer acceptance [161]. The compounds of off-odors are generally derived from enzymatic reactions, microbial activity, lipid oxidation, and environmental or thermal reactions [162]. The off-odors of fish are mainly caused by the odor components of alcohols, aldehydes, and ketones such as hexanal, nonanal, 1-octen-3-ol and 2, 4-heptadienal (E, E) [163]. In addition, the muddy odor or taste in fish is also considered as one of the major problems in carps or other aquaculture fishes. Generally, geosmin and 2-methylisoborneol (MIB) are the main causes of an earthy or muddy odor, which is produced by cyanobacteria and actinomyces [161]. The accumulation of a muddy odor is also dependent on management practices and water quality [164]. On the other hand, a fishy odor is generally related to diatom, chrysophyte, cryptophyte and dinoflagellate. The polyunsaturated fatty acids (PUFAs) present in those algae could result in the production of unpleasant odors [165]. In addition, the fishy odor of fish is also directly related to lipid oxidation. Due to their high content of PUFAs, the lipids of fish muscle are more prone to oxidation than in other animals. The lipid oxidation is mainly catalyzed by heme proteins and irons, as well as lipoxygenase [166]. Fu et al. [167] reported that the lipid oxidation and fishy odor of silver carp muscle were caused by 12-lipoxygenase.
Common methods have been used to remove the off-odor in aquatic products such as adsorption, microcapsules, fermentation, and removal by antioxidants [168],but the removal of off-odor is also dependent on deodorizing agents. Thus, the deodorizing agents should be safe and have a mild odor [169]. The deodorizing of surimi products generally involves washing with saline agents. Currently, several methods have been utilized to remove or reduce the off-odor of Asian carp surimi such as ozone treatments and yeast glucan additions [61][170].
Apart from the utilization of Asian carp to substitute for less available marine fish as mentioned earlier, the utilization of Asian carp as a raw material for surimi manufacturing can contribute to the Asian carp problem in the United States as well. Asian carp species, namely, grass carp, silver carp, bighead carp, and black carp are considered as invasive species in the U.S. Their fast reproduction and growth rate are desirable characteristics if they are raised for commercial use but they have no natural predators, making them a threat to native species and the environment. The U.S. government has expended significant effort in attempting to control Asian carp numbers and in preventing their further spread. Using Asian carp as an alternative to marine fish in surimi processing can increase the consumption of Asian carp and lead to a decline in the Asian carp population; however, various things must be undertaken in order to make this strategy work.
First, the customers’ views on Asian carp must be changed. Currently, Asian carp in the U.S. have a bad reputation and people often view Asian carp as a dangerous, inedible and invasive species. Moreover, its off-flavors and intermuscular bones have also made them unappealing. Consumers or farmers should be educated about the nutritive values as well as their cultural practices to control the Asian carp population growth. According to Li et al. [10], more than 60% of American consumers are willing to purchase products from Asian carp after being informed about their benefits. Processing Asian carp into surimi will remove the intermuscular bones and off-flavor, changing the Asian carp into a more appealing and convenient product.
Moreover, there are several other challenges for the production of Asian carp surimi in the US. Li et al. [10] suggested that four reasons have made Asian carp surimi in the U.S. currently unsuccessful. Those reasons are (1) Asian carp is not abundant enough, (2) catching Asian carp has a higher risk, (3) the price of Asian carp is not competitive to other fish, and (4) a lack of skilled workers. The problems with the abundancy and price of Asian carp exist because Asian carp are yet to be raised and produced as a commercial fish. For skilled personnel, experienced personnel from countries familiar with handling Asian carp could be hired from Asian countries, such as China. Asian carp are important freshwater fish species in China and in 2020, the production of Asian carp in China reached 13 million tons. The consumption demand for surimi products in China is increasing, with the production volume of surimi products in China recorded at around 1.3 million tons in 2020 [171]. Asian carp have also been used to produce a variety of surimi products in China, such as fish balls, fish tofu and fish cakes. Due to this increasing demand for surimi products in China, there is pressure increasing for the production of surimi material resources, especially Asian carp. Currently, there is huge progress in the development of aquaculture technology, such as new feeding techniques, breeding methods, and farm management practices [172][173][174], which have led to increases in the production of Asian carp. Asian carp have the potential to be produced in far greater numbers than marine fish.
As the demand for Asian carp in the U.S. grows and Asian carp begins to be raised for consumption, their reputation will be changed from being a dangerous, inedible and invasive species to a nutrient-rich and easy-to-produce commercial fish.
Asian carps have a great potential in surimi manufacturing. Their great abundance, appealing white flesh and decent gel-forming ability have made them viable alternatives to marine fish, which are currently used in surimi production. In this review, we have summarized the challenges faced in the production of Asian carp surimi along with solutions to improve their quality. The utilization of Asian carp in surimi production also can contribute to solving the threat from Asian carp in the U.S. as well.
This entry is adapted from the peer-reviewed paper 10.3390/foods11091318