Surimi Processing Research Articles

Effect and mechanism of different exogenous biomolecules on the thermal‐induced gel properties of surimi: A review

AbstractSurimi products are favored by domestic and foreign consumers due to their distinctive gelatinous texture, rich nutrition, and convenient consumption. Gel properties are key evaluation indicators for the quality of surimi products, which was mainly determined by the gel‐forming ability of the myofibrillar protein (MP). In recent years, the surimi processing industry has faced challenges in product quality that limits the further development, and how to effectively improve the gel properties of surimi products has become one of the key scientific problems to be solved in surimi processing industry. A viable strategy for improving the product quality involves combining surimi with exogenous additives, such as proteins, polysaccharides, and lipids, to enhance the gel‐forming ability of MP. At present, there is limited literature review to systematically investigate the role of these exogenous additives in interacting with MPs in surimi gel system and their effect on the gel properties of heat‐induced surimi. Therefore, in this review, we systematically discussed the formation mechanism and influencing factors of surimi gel, the interactions of exogenous biomolecules (proteins, polysaccharides, and lipids) with surimi protein, as well as their effects on the gel properties of surimi product. The aim of this review was to help us with a better understanding for the intrinsic action mechanisms of complex surimi system and provide some theoretical guidance for the improvement of gel quality and development of surimi products.

Lipoxygenase activity in tropical fish: Changes during surimi processing and some biochemical characterization in lizardfish (Saurida tumbil).

The lipoxygenase (LOX) activity of major tropical fish used for surimi production, including threadfin bream (TB), lizardfish (LZ), and goatfish (GF), was measured in the gills, skin, and muscle. The highest LOX activity was observed in the LZ samples (p<0.05), with the gills exhibiting the greatest activity at 376.56U/mg (p<0.05). The highest peroxide value was detected in the TB samples, particularly in the gills (p<0.05). Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were the main polyunsaturated fatty acids in all the tissues and surimi. The total lipid and DHA contents of washed mince reduced considerably after the screw press process. Although LOX activity decreased during surimi production, a residual activity of 21.33U/g was observed in the finished surimi. LOX was partially purified and characterized from LZ gills. The purification was conducted using two successive chromatographic steps, Sephacryl S-200 and diethylaminoethyl (DEAE)-sepharose, resulting in a 3.52% yield and a 22.43-fold increase in purity. The optimum activity was found at 25°C and pH 7.5, with pH stability between 6.0 and 8.5. The relatively high thermal stability at 4°C-10°C suggested that LOX might contribute to fish lipid oxidation during cold storage. The enzyme was thermally inactivated at 60°C. The preferred substrate was EPA. LOX from the LZ gills was inhibited by 1mM ethylenediaminetetraacetic acid and activated by 1mM Fe2+, Na+, and Ca2+. PRACTICAL APPLICATION: Elucidating lipoxygenase activity and lipid oxidation in various tropical fish tissues, as well as understanding the characteristics of LOX, can help take appropriate postharvest actions to afford high-quality surimi.

Physicochemical Properties and Microstructure of Mixed-species Surimi Made from Decapterus sp. and Priacanthus sp.

The surimi industry plays a substantial role in bolstering Indonesia’s fishing sector. The collapse of the majority of surimi companies can be attributed to the government limitation on trawling, which served as the primary source of demersal fish utilized in surimi processing. This restriction resulted in a significant shortage of raw material for industry. Therefore, it is imperative to explore alternate fish species that can serve as viable raw materials for the production of surimi. Alternative fish species are needed as raw materials for surimi. The objective of this work was to investigate the physicochemical characteristics and microstructure of surimi produced from two distinct Indonesian fish species: Decapterus sp., a pelagic species, and Priacanthus sp., a demersal species. Five ratios of Decapterus sp and Priacanthus sp; 1:0 (F1: control 1), 3:1 (F2), 1:1 (F3), 1:3 (F4), and 0:1 (F5: control 2) were tested. The proximate composition showed that the addition of Decapterus sp. to the formula increased the protein and fat content of mixed surimi. The formula F4 showed the highest value for almost all textural profile parameters; there were springiness, cohesiveness, gumminess, chewiness, and resilience. The same result also presented in the gel strength, F4 also has the highest value. The Water Holding Capacity value was low, and it showed no difference between all formulas. The whiteness value was in the range of 66-68, and it showed no difference between all formulas. Protein patterns showed no myosin heavy chain in all formulas. Microstructure analysis showed that only F5 (control 2) was compact and denser, but the other formulas (F1, F2, F3, and F4) showed a large number of loose and porous structures. In the microbial analysis, all formulas showed the Total Plate Count value ( 6 x 105 cfu/g) was under the maximum acceptable value (107 cfu/g). The findings of the study indicated that the mixed-surimi, consisting of Decapterus sp and Priacanthus sp at a ratio of 1:3, exhibited the highest level of gel strength. In conclusion, Decapterus sp has the potential to serve as a viable raw material when combined with Priacanthus sp.

Radio frequency heating induced 3D printed white croaker (Argyrosomus argentatus) surimi gelation: Effectiveness and gel quality evaluation

Two-stage water bath (WB) heating is commonly used in surimi gelation as an effective thermal treatment method but produces wasted water. Radio frequency (RF) has the potential substituting the WB heating with its fast, volumetric and adjustable heating characteristics for saving treatment time and water usage. This study examined the effectiveness of RF to substitute one of or both stages of WB heating on surimi prepared with conventional and 3D printed methods. Four treatments including two-stage WB heating, RF heating, and different combinations (RF-WB and WB-RF) with the same target temperature of 85 °C were conducted and the essential quality parameters of surimi products were analyzed. Results showed that RF heating had the highest heating rate of ∼8.6 °C/min with a linear heating curve, among which the 3D printed surimi samples had a slower heating rate than conventionally prepared ones. RF heating resulted in higher water holding capacity (67.24%) comparing to traditional WB method (59.60%). The gel strength of the conventionally prepared surimi samples was not significantly different among four treatments. However, the 3D printed surimi samples treated with WB had lower gel strength than those RF-induced ones. Also, the 3D printed surimi gel had a more compact and uniform gel network structure compared to traditionally prepared ones among all treatments. The proposed non-contact RF treatment method protects the delicate shape of samples from deforming. The results of this study assist the development of more efficient and emission-free surimi processing techniques.

Pepsin Hydrolysate from Surimi Industry-Related Olive Flounder Head Byproducts Attenuates LPS-Induced Inflammation and Oxidative Stress in RAW 264.7 Macrophages and In Vivo Zebrafish Model.

Fish head byproducts derived from surimi processing contribute about 15% of the total body weight, which are beneficial to health because they contain essential nutrients. In this study, olive flounder (OF) was the target species in order to maximize the byproduct utilization. In RAW 264.7 macrophages, the seven hydrolysates from OF head byproducts were examined for their inhibitory potential against inflammation and the oxidative stress induced by lipopolysaccharides (LPS). The pepsin hydrolysate (OFH-PH) demonstrated strong anti-inflammatory activity via the down-regulation of NO production, with an IC50 value of 299.82 ± 4.18 µg/mL. We evaluated the inhibitory potential of pro-inflammatory cytokines and PGE2 to confirm these findings. Additionally, iNOS and COX-2 protein expressions were confirmed using western blotting. Furthermore, the results from the in vivo zebrafish model demonstrated that OFH-PH decreased the LPS-elevated heart rate, NO production, cell death, and intracellular ROS level, while increasing the survival percentage. Hence, the obtained results of this study serve as a platform for future research and provide insight into the mediation of inflammatory disorders. These results suggest that OFH-PH has the potential to be utilized as a nutraceutical and functional food ingredient.

Perubahan Nilai Gizi dan Alergenisitas Produk Olahan Intermediat Surimi dan Otak-Otak Ikan Tenggiri Siap Santap

Fish is one of the nine major food allergens. Avoiding consumption of fish is a common preventive measure to mitigate fish allergies. On the other hand, food processing may potentially alter the allergenicity of fish, and thus, it is important to identify the most effective fish processing methods that can reduce its allergenicity. This research aimed to characterize the nutritional value, intensity of allergens, and allergenicity from the processing of tenggiri fish processing to produce surimi as intermediate food and ready to eat (RTE) otak-otak. The processing steps consisted of washing and adding cryoprotectant during surimi processing, and using deep and air frying methods in RTE otak-otak processing. Changes in the nutritional value and intensity of allergens of fish meat and its processed products were measured using proximate analysis and SDS-PAGE electrophoresis, respectively. The alterations in the allergenicity were investigated using immunoblotting and ELISA. The results revealed changes in the nutritional value due to the processing. Surimi production successfully removed a protein band of 10-–13 kDa, which is suspected to be an allergen. Additionally, both deep and air frying methods effectively removed allergenic proteins with molecular weights above 100 kDa. Immunoblotting assay showed the allergen only appeared in fish meat absent in all of the processed products. The allergenicity rates of surimi and otak-otak was reduced by 90.78 and 98.68%, respectively, as compared to the fish meat. In conclusion, the nutritional value of air-fried otak-otak is superior while the allergenicity is lower than the deep-fried ones. Therefore, air frying processing method for tenggiri fish can be potently used to produce hypoallergenic fish products.

Effect of Adding Egg White Powder on Surimi Quality Based on Pangasius and Catfish Flesh

The variety of raw materials from demersal fish in small quantities has resulted in the development of freshwater fish-based surimi processing technology. This study aims to determine the best concentration of egg white powder based on pangasius and catfish on the quality of surimi by physically, chemically, and sensory. The experimental design used was a Completely Randomized Design (CRD) with the addition of egg white powder at concentrations of 0%, 1%, 2%, 3%, and 4%. The surimi quality characteristics tested in this study included texture profile, degree of whiteness, pH, moisture, ash, protein, fat, water holding capacity, sensory and folding tests. The results showed a significant effect (P < 0.05) on whiteness, fat, water holding capacity, texture profile, folding and sensory tests. However, it did not affect (P > 0.05) on ash, protein, and pH. The results showed that the concentration of 1% egg white powder was able to improve surimi gel based on quality.

Study on the effect and mechanism of chicken breast on the gel properties of silver carp (Hypophthalmichtys molitrix) surimi.

Adding appropriate exogenous substances is an effective means to improve the quality of freshwater fish surimi. This study investigated the effects of chicken breast on the gel properties of mixed minced meat products. With the increase in the proportion of chicken breast, the breaking force of mixed gels gradually increased. When the addition ratio was 30/70, the gel strength of mixed gels had the highest strength of 759.00 g·cm and also the highest water holding capacity of 87.36%. Compared with surimi gels (0/100), the hardness, adhesiveness, and chewiness of mixed gels were significantly improved. The increase in the proportion of chicken breast increased the thermal stability of the mixed sol and improved the rheological properties of the mixed sol. When the proportion was 40/60, the area of immobile water (A22 ) in the mixed gel increased significantly, and the highest A22 was 3463.24. The hydrophobic interactions and disulfide bonds in the mixed gel were significantly increased due to the addition of chicken breast. The results of microstructure, electrophoresis, and Raman spectroscopy indicated that the addition of chicken breast promoted the cross-linking of the proteins in mixed gels, which facilitated the transformation of the protein secondary structure from α-helical to β-folded structure, thus forming a more uniform and orderly network structure. These results suggest that improving the gel properties of silver carp surimi by using chicken breast has practical implications for the development of new blended products for surimi processing. This article is protected by copyright. All rights reserved.

Comparing Efficiency of Green Methods for Surimi Skin and Bone Gelatin Extraction

Globally, the surimi processing industry produces a large amount of by-products in the form of head and viscera, skin, bones, scale, etc. The aim of this study was to assess the combined biomass of pink perch skin and bones obtained from the surimi industry as a potential source of raw material for gelatin production and identify a green method of gelatin extraction by comparing four green processes. Four green gelatin extraction processes were compared for their gelatin extraction efficiency. Among the four processes, process 1 and process 2 comprised of two-step extraction viz pre-treatment with NaCl and extraction with hot water. Process 3 and process 4 comprised of single-step wherein pre-treatment and extraction were done simultaneously with acidic water using acetic acid. The gelatin extraction efficiency was determined based on the yield and L-hydroxyproline content of the extracted gelatin. Further, the extracted gelatin was characterized for their proximate and amino acid composition. The acetic acid based single-step method was found to be more efficient in the extraction of gelatin than the NaCl pretreatment method. The gelatin extracted with this method had a higher yield (4.2%), protein content (79.6%), and imino acid (27.3%) content than the NaCl pretreatment method, which had 1.51% gelatin yield, 48.1% protein content, and 13.1% imino acid content. The results suggested that the single-step extraction method can be effectively utilized for the extraction of gelatin from pink perch skin and bones combined biomass. This study provides a method for the valorization of the surimi industry by-product into a high value product with potential application in various industries.

Impact of Washing with Antioxidant-Infused Soda-Saline Solution on Gel Functionality of Mackerel (Auxis thazard) Surimi.

Mackerel (Auxis thazard), a tropical dark-fleshed fish, has the potential to be used in the production of surimi. It is necessary to identify the optimal washing method to make better use of this species since efficient washing is the most important step in surimi processing to ensure maximal gelling and high-quality surimi. The purpose of this study was to evaluate the combined effect of cold carbonated water (CW) with NaCl and antioxidants in washing media, so-called antioxidant-infused soda-saline solution, on lipid and myoglobin removal efficacy, biochemical characteristics, gelling properties, sensory features, and the oxidative stability of mackerel surimi in comparison with unwashed mince (T1) and conventional water washed surimi (T2). Mackerel mince was washed with CW in the presence of 0.6% NaCl at a medium to mince ratio of 3:1 (v/w) without antioxidant (T3) or with the addition of 1.5 mM EDTA plus 0.2% (w/v) sodium erythorbate and 0.2% sodium tripolyphosphate (T4), 100 mg/L gallic acid (T5), and 5 mM citric acid containing 8 mM calcium chloride (T6). During the first washing cycle, the antioxidants were mixed into the washing medium. The second and third washing cycles were then completed with cold water. The yields of all treatments were roughly 75-83%, based on the gross weight of the raw mince. The pH of the surimi was in a range of 5.47-6.46. All of the surimi had higher reactive sulfhydryl (SH) content and surface hydrophobicity but lower Ca2+-ATPase activity than unwashed mince (p < 0.05). After washing, lipids decreased significantly (p < 0.05), accounted for a 65-76% reduction. The T2 surimi had the highest peroxide value (PV). T1 had the lowest conjugated diene value. T1 and T4 surimi had the lowest TBARS value (p < 0.05). A lower non-heme iron level was found in all antioxidant-treated samples than in T1. Washing can increase the redox stability of myoglobin regardless of the washing media, as seen by the relatively low metmyoglobin levels. According to the dynamic viscoelastic behavior, all surimi and unwashed mince underwent the same degree of sol-gel transition following heat gelation. T1 showed the lowest breaking force, deformation, gel strength, and whiteness (p < 0.05). Surimi made from T4 or T5 had the highest gel strength when both breaking and deformation were considered, but the latter's expressible drip was noticeably higher. Surimi gel appears to be stabilized against lipid oxidation, as demonstrated by low PV and TBARS levels, when produced with T4. Because of the low level of TBARS, all 10 panelists rated rancid odor as low (~1 out of 4), with no significant variations across treatments. Only treatments with T4 and T6 tended to have a lower fishy odor score as compared to unwashed mince. Scanning electron microscope demonstrated that surimi gels washed with all washing media exhibited microstructures that were very comparable, with the exception of the T6 treatment, which had big pores and aggregates. Based on the quality features, T4 appeared to be the optimal medium to enhance the gel functionality of mackerel surimi.

Analysis of Consumer Preferences and Nutritional Composition of Analogue Shrimp Made from African Catfish Surimi with Addition of Flavor

African catfish is one of the freshwater fish species that is cultivated intensively and is quite abundant in Indonesia, but has a relatively low selling price so that needed innovation through surimi processing for the development of various commercial products such as analog shrimp and other processed products. The purpose of the study was to examine the level of consumer preferences, nutritional composition and quality deterioration of analog shrimp. The study used a completely randomized design with the addition of shrimp flavoring treatment (0%, 1%, 2%, 3%). The addition of 1% shrimp essence is a treatment that is highly favored by consumers with an average preference value of 3.60 and water content (69.96%); ash (2.13%); protein (12.08%); fat (3.52%) and carbohydrate (11,59%). The total calories produced by analog shrimp from fat (32 calories), protein (48 calories) and carbohydrates (46 calories) is 126 calories, thus the serving size of the product per 100 grams contains 126 kcal. The content of TPC and TVB-N were 3.17 log cfu/gram and 10.12 mg/100 gram, respectively, on the last (5th) storage day, indicating that analog shrimp was still fit for consumption.

Fabrication, performance and curcumin-controlled release of electrospun sarcoplasmic protein nanofiber films via layer-by-layer self-assembly

The recycling and high-value application of fish sarcoplasmic protein (FSP) from the surimi rinsing wastewater can promote the sustainable development. This work successfully fabricated monolayer nanofiber films and three-layer nanofiber films with cellulose acetate (CA) nanofibers as the outer layer to encapsulate curcumin (CUR) based on chitosan flocculated and direct freeze-dried FSP (CFSP and DFSP) through electrospinning and layer-by-layer (LBL) self-assembly, and investigated the films microstructure, performance and CUR release behavior. The nanofibers exhibited uniform, smooth, and beadless morphology, with a clear interface but strong interactions between the adjacent layers for three-layer films. The CA-CFSP/CUR-CA three-layer film possessed the best flexibility (elongation at break 6.5%), surface hydrophobicity (water contact angle 130.5° ± 2.6°) and thermal stability, suggesting its potential application in food packaging. The CUR release kinetics in all nanofiber films well fitted to First-order model, reflecting a release driven by concentration gradient. The monolayer films quickly released CUR in neutral PBS. The CA-DFSP/CUR-CA three-layer film could resist gastric acid and controllably released ∼18% CUR in the first 60 min and cumulatively up to 45.2% within 480 min, following diffusion-controlled Fickian release in simulated gastric-intestinal fluid (SGF-SIF), implying great applications potential in sustained release. This study can not only advance the surimi processing field by recovering and utilizing FSP from the surimi rinsing wastewater, but also expand the application of FSP for food packaging and drug delivery fields.

Effect of heating temperature on electrical properties and gel properties of carp surimi

AbstractFor better application of ohmic heating technology in the food industry, it is necessary to study the variation of the electrical properties of food materials with temperature. In this paper, various initial heating temperatures were applied to investigate the impact of temperature on the electrical properties of rinsed and unrinsed carp surimi. An impedance analyzer was utilized to measure the electrical parameters of carp surimi within the frequency range of 20 ~ 120 MHz. The frequency and temperature characteristics of electrical parameters were explained based on biological and electromagnetic theories. These findings furnish theoretical references and experimental evidence for applying ohmic heating technology. The results showed that the parallel inductance (Lp), parallel capacitance (Cp), parallel resistance (Rp), and impedance (Z) of surimi decreased as the internal temperature of the surimi increased. The greater the heating temperature of the water bath, the larger the parameter values. The Lp, Cp, Rp, and Z values were lower for unrinsed surimi than for rinsed surimi. During the heating and cooling process, the parameter values at the same temperature point differed due to the different states of the surimi gel. As the frequency increased, the Rp and Z of surimi showed different regular changes, with similar trends at the same temperature. Rinsing has been demonstrated to improve the gel properties of surimi effectively. Prolonged periods in the temperature range of 60 ~ 70°C can cause the modori phenomenon (gel degradation), leading to reduce the gel strength of surimi. Thus, it is essential to pass through this temperature zone as soon as possible during the preparation of surimi gel. The relationship between the internal microstructure of surimi gel and the electrical parameters needs to be further investigated.Practical ApplicationsAs an emerging technology for food heat treatment, ohmic heating has the characteristics of uniform heating and fast heat production. As a homogeneous material, surimi is ideal for ohmic heating. However, the heating process is not easy to control when the electrical parameters are unknown, so the purpose of this study is to explore the changes of the electrical parameters of surimi at different heating rates and temperatures, provide data reference for the heat treatment of surimi by ohmic heating, and promote the application of ohmic heating in surimi processing.

Unrinsed Nemipterus virgatus surimi provides more nutrients than rinsed surimi and helps recover immunosuppressed mice treated with cyclophosphamide.

The rinsing process in the production of surimi can cause the loss of some important nutrients. To investigate the differences in nutritional properties between rinsed surimi (RS) and unrinsed surimi (US), this study compared the elemental composition, amino acid composition, fatty acid composition, proteomics, and an immunosuppression mouse model of surimi before and after rinsing, and analyzed the nutritional and immunological properties of RS and US. The results showed that the protein, fat, and ash contents of RS were decreased compared with those of US; specifically, the contents of essential amino acids, semi-essential amino acids, non-essential amino acids, saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids were decreased. In the non-labeled quantitative proteomics analysis, three high-abundance quantifiable protein contents and 68 low-abundance quantifiable protein contents were found in RS (P-values < 0.05, ratio > 2). Immune function experiments in mice revealed that both RS and US contributed to the recovery of immunity in immunocompromised mice. The effect of US was better than that of RS. The rinsing process in surimi processing leads to the loss of nutrients in surimi. US promotes the recovery of immunity in immunocompromised mice more effectively than RS. © 2023 Society of Chemical Industry.

Correlation between Water Characteristics and Gel Strength in the Gel Formation of Golden Pompano Surimi Induced by Dense Phase Carbon Dioxide.

The relationship between the gel quality of golden pompano surimi treated with dense phase carbon dioxide (DPCD) and changes in water characteristics was evaluated. Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to monitor changes in the water status of surimi gel under different treatment conditions. Whiteness, water-holding capacity and gel strength were used as the quality indicators of the surimi gel. The results showed that DPCD treatment could significantly increase the whiteness of surimi and the strength of the gel, while the water-holding capacity decreased significantly. LF-NMR analysis showed that, as the DPCD treatment intensity increased, the relaxation component T22 shifted to the right, T23 shifted to the left, the proportion of A22 decreased significantly (p < 0.05) and the proportion of A23 increased significantly (p < 0.05). A correlation analysis of water characteristics and gel strength showed that the water-holding capacity of surimi induced by DPCD was strongly positively correlated with gel strength, while A22 and T23 were strongly negatively correlated with gel strength. This study provides helpful insights into the quality control of DPCD in surimi processing and also provides an approach for the quality evaluation and detection of surimi products.

Effects of heating process on 3D printing properties of Pennahia argentata surimi: Water distribution, gel formation, rheology, chemical bonds

AbstractThe gel is an important factor in 3D printability of Pennahia argentata surimi. While surimi gel is sensitive to temperature and influenced by chemical bonds changes. Hence, preheating effects on printing and material properties of surimi were investigated. Results shown hydrogen bonds and ionic bonds contents in surimi under different heating conditions decreased about 20%–90%. Meanwhile, hydrophobic force and disulfide bonds increased about 0.2–6 times. These changes formed more gel, as well as 6.5% at most immovable water transferred into free water which enhanced texture properties and made solid properties of rheology in surimi dominant. This phenomenon occurred significantly in temperature range of gel formation (35–40°C, 90°C) while became extinct at 45°C with 10–30 min due to gel degradation. These made surimi by heating exhibit strong mechanical strength, which is conducive to forming process when printing after extrusion. However, if they occurred before extrusion, these could increase extrusion difficulty to make filamentous materials be broken easily after extrusion, weakening printing effect. Hence, preheating of surimi before extrusion was not suitable for 3D printing. While short‐time heating during or after extrusion might be more appropriate for printed surimi, promoting the application of surimi in 3D printing technology.Practical Applications3D printing is a new technology in food processing that refers the process of connecting or curing materials to form 3D objects by continuously adding layers of materials. Surimi is one of the suitable materials which can promote the process of printing. While the material properties of surimi are affected by temperature that influences the printing effects. The purpose of this study was to investigate the effects of different temperatures on the material properties of Pennahia argentata surimi, and determine the suitable heating process of printed surimi products. These results could promote the application of 3D printing technology in surimi processing.

Inulin for surimi gel fortification: Performance and molecular weight-dependent effects

Inulin is a prebiotic carbohydrate widely used in food industry due to its health benefits and unique rheological properties. For the first time, this study explores the potential of natural inulin as a sustainable food additive to enhance surimi gel characteristics, specifically focusing on understanding its molecular weight effects. The good solubility of inulin facilitates the conversion of α-helix to other secondary conformations which are favorable for protein denaturation and aggregation during gelation. Moreover, the abundant –OH groups at the surface of inulin can boost the chemical forces within surimi proteins to reinforce the gel network. Compared to short-chain inulin, long-chain inulin can alleviate proteolysis, enhance hydrophobic interactions and intertwine with myosin molecules, thereby reinforcing the gel network. A more viscous long-chain inulin solution formed within surimi gels fills the space between aggregated proteins and facilitates the lock of water molecules, improving the water-holding capacity (WHC). Thus, an addition of 12 % long-chain inulin leads to an enhanced hardness of surimi gel from 943 to 1593 and improved WHC from 72 % to 85 %. A new inulin-myosin interaction mechanism model is also proposed to provide useful guidelines for surimi processing and expanding the application of inulin within the food industries.

Quality attributes of Black-Chin Tilapia (Sarotherodon melanotheron) surimis treated with different cryoprotectants

This baseline investigation tried four surimi formulations using three common cryoprotectants namely sucrose, sorbitol and sodium tripolyphosphate for Black-Chin Tilapia (Sarotherodon melanotheron), an invasive species and known prolific pest in Philippine farm ponds, and then compared the quality attributes of the products across formulations and against those reported from previous studies that utilized more popular species in surimi processing. The quality parameters analysed were pH level, functional properties (water holding capacity, foamability and emulsifiability) and gel strength and elasticity. The surimi formulation that yielded the best quality attributes was the 6% sucrose with 0.5% STPP. The formulation yielded a pH value of 6.33-6.47, a water holding capacity of 3.87-3.98 mL/g, a foaming capacity of 23.06-30.70%, a foaming stability of 13.31-15.19%, an emulsifying capacity of 47.50-47.83%, an emulsifying stability of 81.17-85.00%, a folding test score of 5.00, and a biting test score of 9.00. Still, a better understanding of the effects of different concentrations of cryoprotectants (presently used and other kinds) on the functionality of S. melanotheron surimi is recommended to rationally improve the quality attributes. Also, frozen storage analyses are needed for several and longer periods to see how long the S. melanotheron surimi can withstand freezing for specific formulations. It is concluded that S. melanotheron surimi, with the right formulations, can be at par with quality with those made from traditional raw materials.

Effects of Potato Protein Isolated Using Ethanol on the Gelation and Anti-Proteolytic Properties in Pacific Whiting Surimi.

Pacific whiting is a primary species utilized for surimi processing in the Pacific Northwest of the US. However, endogenous protease in Pacific whiting surimi deteriorates the quality during slow cooking. The demand for clean-labeled and economically competitive protease inhibitors has been increasing. In the present study, the anti-proteolytic effect of potato protein isolate (PPI), a by-product from the potato starch industry, prepared using 20% ethanol on the endogenous protease activity of Pacific whiting (PW) surimi was investigated. The ohmic heating method was carried out for a better assessment of the anti-proteolytic activity of inhibitors. A factorial design was carried out in which the independent variables were the four types of inhibitors and their concentration (0, 0.5, 1, 2, and 3% w/w) at two heating conditions. The heating condition was used as a blocking factor. All experiments were randomized within each block. The addition of 2% PPI which demonstrated the highest anti-proteolytic activity among five different concentrations significantly increased the breaking force, penetration distance, and water retention ability of PW surimi gel as the endogenous proteases were effectively inhibited when heated ohmically at 60 °C for 30 min prior to heating up to 90 °C. In addition, SDS-PAGE disclosed that PPI successfully retained the intensity of myofibrillar heavy chain (MHC) protein of PW surimi gels even under the condition at which proteases could be activated at 60 °C. The whiteness of gels was not negatively affected by the addition of PPI. Comparing all samples, a denser and more ordered microstructure was obtained when PPI was added. A similar trend was found from the fractal dimension (Df) of the PPI-added gel’s microstructure. Therefore, PPI could be an effective and non-allergenic protease inhibitor in PW surimi leading to retaining the integrity of high gel quality.

Study on the mechanism of protein hydrolysate delaying quality deterioration of frozen surimi

The surimi processing industry generates a large number of underutilized by-products. The aim of this study was to evaluate the protein oxidation, protein degradation, and gel property of surimi during frozen storage to investigate the mechanism of cryoprotective effects of surimi by-product protein hydrolysates on surimi. The results showed that compared with Control and Cryoprotectant surimi, surimi by-product protein hydrolysates groups had lower thiobarbituric acid content, carbonyl content and surface hydrophobicity, higher Ca2+-ATPase activity, total sulfhydryl groups and salt-soluble proteins (P < 0.05), which significantly delayed the freezing denaturation and oxidation rate of surimi myofibrillar protein during frozen storage. Aggregation of surimi proteins occurred during frozen storage, and surimi by-product protein hydrolysates could inhibit the degradation of myofibrillar protein and effectively induce protein cross-linking, which led to the formation of a denser gel network in surimi. In summary, surimi by-product protein hydrolysates was expected to be a natural and green cryoprotectant and gel texture enhancer in surimi.