Total Volatile Base Research Articles

Inhibition of Melanosis and Quality Changes on Indian White Prawn Treated with Lemon and Pomelo Peel Extracts Conjugated with Copper Sulfide Nanoparticles during Chilled Storage

ABSTRACT The study was aimed at the assessment of lemon peel extract (LPE) and pomelo peel extract (PPE) conjugated with copper sulfide nanoparticles (CuSNPs) influence on melanosis formation and improving the quality of chilled stored Indian white shrimp (Fenneropenaeus indicus) after 15 days. Biochemical indices, microbial count, and sensory analysis was performed at 3 day intervals. The trimethylamine, total volatile base nitrogen, free fatty acid, and peroxide value of control was 18.01 ± 0.79 mgN/100 g, 45.08 ± 1.1 mgN/100 g, 0.14 ± 0.01% of oleic acid, and 16.42 ± 0.612 milliequivalents/kg, whereas LPE+PPE+CuSNPs was 10.94 ± 1.04 mgN/100 g, 17.51 ± 1.1 mgN/100 g, 0.091 ± 0.01% of oleic acid, and 7.57 ± 0.38 milliequivalents/kg, respectively, at the 15th day of storage. The biochemical indices, microbial count, and sensory score of the treated sample was significantly lower (P < .05) than the untreated sample at day 15. This study aimed to determine the effectiveness of this biopreservation technique, which could provide a new alternative in preservation techniques, as well as impact shelf life and product safety.

Synergistic effects of ε-polylysine hydrochloride and gallic acid on Shewanella putrefaciens and quality of refrigerated sea bass fillets

The abundant nutrients of raw sea bass are excellent media for specific microorganisms like Shewanella putrefaciens, which cause fish spoilage. In this study, gallic acid (GA), protocatechuic acid (PA) and chlorogenic acid (CA) were tested for their synergistic antibacterial effects with ε-polylysine hydrochloride (PL). A strong synergistic inhibitory effect against S. putrefaciens was observed in PL and GA treatment. The combination of 1/8 MIC PL and 1/4 MIC GA completely inhibited S. putrefaciens growth and caused cell death. This combination significantly damaged the cell structure, and induced serious leakage of electrolytes, nucleic acid, and protein. GA, PL and PL-GA treatments significantly reduced sensory deterioration, total viable counts, total volatile base nitrogen and thiobarbituric acid value of sea bass fillets during 4 °C storages, with PL-GA showing the best effect. The results suggested that the combination of PL and GA might be an effective preservative to control marine fish spoilage.

Effect of vacuum packaging on shelf‐life extension of cooked and peeled harpiosquillid mantis shrimp (Harpiosquilla raphidea) during refrigerated storage

SummaryEffects of vacuum packaging (VP) on quality changes of cooked and peeled harpiosquillid mantis shrimp (HMS) during storage at 4 °C of 15 days were investigated. VP inhibited bacterial growth as ascertained by the lower rate of increases in total viable and psychrotrophic bacteria counts as well as other pathogenic and spoilage bacteria counts. VP samples had lower total volatile base and trimethylamine contents as compared to the sample packed in air (AP). Clostridium perfringens was undetectable in both samples. During storage, VP samples possessed lower pH than AP counterpart. Exudate and TCA‐soluble peptide (TSP) contents of sample increased during the storage, regardless of packaging atmospheres. Fatty acid (FA) content, especially PUFA and MUFA, was decreased after 9 and 15 days of storage for AP and VP samples, respectively. The cooked and peeled HMS contained 32 volatile organic compounds, consisting of several aldehydes and alcohols. Carnobacterium and Pseudomonas were mainly involved in spoilage in samples as confirmed by next generation sequencing.

Inactivation of Salmonella in steamed fish cake using an in-package combined treatment of cold plasma and ultraviolet-activated zinc oxide

An intervention technology combining in-package atmospheric discharge cold plasma (CP) treatment with ultraviolet (UV)-activated zinc oxide (ZnO) treatment was developed to decontaminate steamed fish cakes in commercial plastic packages. Efficacy of the simultaneous treatment of UV-activated ZnO treatment and CP treatment (ZnO&CP treatment) in inactivating Salmonella (1.8 log CFU/g) did not differ significantly from that of the CP-only treatment (P > 0.05). The CP treatment immediately after UV-activated ZnO treatment (ZnO-CP treatment) led to higher inactivation of Salmonella (2.4 log CFU/g) than the ZnO-only (0.4 log CFU/g) or CP-only (1.7 log CFU/g) treatments. Inactivation of Salmonella by ZnO-CP treatment increased as the ZnO or CP treatment time increased, the number of samples in the package decreased, and upon shaking the package during the CP treatment. The difference in Salmonella counts between ZnO-CP treated and untreated samples were maintained at 1.3–1.8 log CFU/g and 1.1–1.6 log CFU/g when samples were stored at 4 °C and 10 °C for 21 days, respectively. The ZnO-CP treatment did not alter the moisture content, water activity, color, pH, and gel strength of the steamed fish cake at both storage temperatures. However, the ZnO-CP treatment reduced the total volatile base nitrogen content in the steamed fish cake stored at 10 °C. These results demonstrated the potential of applying a combined treatment approach for microbial decontamination of steamed fish cake in plastic packages.

Effect of Salting on Mechanical Drying of Pangasius hypophthalmus

A study was conducted during 2016 to evaluate the effect of salt and mechanical drying on Pangasius at Central Institute of Fisheries Education, Andheri, Mumbai, India. In this study, the salted and unsalted Pangasius was mechanically dried at 60°C temperature and the quality of the dried Pangasius was evaluated. The quality parameters include the changes in proximate composition, physicochemical parameters [total volatile base nitrogen (TVBN), peroxide value (PV), free fatty acid (FFA), pH, thiobarbituric acid reactive substances (TBARS), salt, water activity], microbial enumeration (total viable count (TVC), Escherichia coli, Staphylococcus spp.) and sensory evaluation. The colour characteristics, percentage yield and storage stability of the product was also evaluated. From the results, it was observed that the protein and ash content of unsalted dried Pangasius was higher than salt dried Pangasius. From the results of physicochemical changes, it was observed that PV, FFA, TVBN, TBARS and salt content were higher in salt dried Pangasius. The TVBN, PV and salt content of salt dried Pangasius were 24.75 mg N 100 g-1, 4.17 meq O2 kg-1 fat and 14.55% respectively which were higher than the Unsaltd dried Pangasius. The salt dried Pangasius had higher L* value but lower a* and b* value than unsalted dried Pangasius. The unsalted dried Pangasius was unstable during storage whereas salt dried Pangasius was stable. Based on the results, it was concluded that salt drying is the most effective method of preservation for drying Pangasius at 60°C.

Quality evaluation of vacuum‐pack ready‐to‐eat hot smoked pangasius fillets during refrigerated storage

In this study, Pangasius was evaluated as a candidate species for hot smoked ready-to-eat product, and its quality and shelf life were assessed during refrigerated storage under vacuum packing. Initially, smoking conditions were optimized based on analysis of water-phase salt and sensory scores. The optimized conditions were dipping fillets in 20% brine solution for 60 min, pre-drying at 50°C for 30 min, and smoking at 80°C for 3 h. The optimized vacuum-packed smoked and nonsmoked fillets were analyzed for proximate, biochemical and instrumental, amino acid, and fatty acid degradation, microbiological, and sensory parameters at refrigerated temperature (4 ± 1°C). Benzopyrene content was analyzed for optimized salted smoked fish in comparison with salted nonsmoked fish. The major changes observed in total volatile base nitrogen, total viable count, and sensory scores on the 49th and 63rd day of storage were 41.86 and 35.89 mg N/100 g, 7.21 and 6.54 log CFU/g, and 4.83 and 5.88 for nonsmoked and smoked Pangasius, respectively. During storage, the saturated fatty acids in both smoked and nonsmoked samples increased and unsaturated fatty acids values decreased, which might be due to lipid oxidation. Sensorily, salted nonsmoked (control) and salted-smoked fillets were acceptable for 35 and 63 days. Novelty impact statement Though Pangasius has good demand in the international market, Pangasius cultured in India is having low demand and the production cost is more than the selling price. Hot smoking can be an alternative method of preservation to increase the utilization of Pangasius and create demand in the international market. Smoked fishery products are a delicacy in many countries, especially hot smoked products prepared from salmon, trout, whitefish are being exported to many countries. Pangasius being a major export item from Asian countries can be used as an alternate species for hot smoked products.

Effect of Storage Conditions on the Quality Attributes of Value-added Cutlets Produced from Low-cost Silver Carp (Hypophthalmichthys molitrix)

ABSTRACT The study was conducted to develop a high-quality value-added product, fish cutlet, using a low-priced fish, silver carp (Hypophthalmichthys molitrix). Skinless and boneless fish fillets were minced to prepare the fish cutlet, which was stored in both refrigerator (4 ± 1°C) and freezing conditions (−18 ± 2°C) to evaluate various quality attributes through biochemical, microbiological, and sensory analysis. Results revealed that the proximate composition of the prepared cutlet changed significantly (p < .05) after 16 days of refrigeration (moisture = 54.3%; protein = 14.2%; lipid = 10.63%; ash = 4.42% of wet tissue) and 120 days of freezing (moisture = 57.1%; protein = 15.48%; lipid = 8.26%; ash = 5.7%) compared to 0 day (moisture = 61.16%; protein = 18.47%; lipid = 6.17%; ash = 3.40%). The pH, total volatile base nitrogen, peroxide value, and bacterial counts of the products increased significantly (p < .05) with the storage time but were within permissible limits across the treatments. However, sensory scores of the products exhibited a declining pattern with the increase of storage duration. Overall, this study concludes that the storage conditions have significant effect on product quality and shelf life.

Sensory Characteristics and Microbiological Quality Changes of Nile Tilapia Fillet Processed by Various Sous-vide Conditions During Chilled Storage

Sensory characteristics and microbiological quality of Nile tilapia cooked with various sous-vide (SV) conditions including 50 and 60°C, for 30, 45 and 60 min (S5-30, S5-45, S5-60, S6-30, S6-45 and S6-60) and their changes during storage (4°C) were investigated, compared with control (cooking with boiling water). The result found that increasing temperature and time of SV accelerated protein degradation, both myofibrillar protein and connective tissue. This affected to the lower water-holding capacity (WHC) and shear force of samples treated with severe SV conditions (S6-45 and S6-60) (P&lt;0.05). SV technique may less contribution to the flavor formation, particularly lipid oxidation products, since there were no differences in total volatile base nitrogen (TVB-N) content and thiobarbituric acid reactive substances (TBARS) value among all samples (P&gt;0.05). However, SV cooked samples had higher sensory scores than control, both at day 0 (before storage) or throughout the storage time. This suggested the potential to improve consumer acceptability by this technique. In this study, SV at 60°C, 60 min seem to be the optimal condition for tilapia fillet, which can preserve at 4℃ for at least 6 weeks without any spoilage.

Development of real-time intelligent films from red pitaya peel and its application in monitoring the freshness of pork.

Red pitaya peel (RPP) is a good source of polysaccharides, which can be used in the production of biodegradable material. Betacyanins in it possess antioxidant and pH-sensitive properties. However, RPP is commonly discarded during fruit processing. This study aimed to develop real-time intelligent film using RPP to evaluate pork freshness. Real-time intelligent films were developed with film-forming substrates (FFS) composed of 60-100% (w/w) RPP and 0-4% (v/w) glycerol in pH4.3 ~ 8.0. Rheology tests revealed that the FFS exhibited shear-thinning behavior. Fourier-transform infrared (FTIR) analysis showed that molecules in the RPP interacted with glycerol and formed hydrogen bonds. It showed that the film developed with FFS of 80% RPP and 2% (v/w) glycerol had strong molecular interaction, dense structure, and optimal tensile strength and elongation at break. Film with pH adjusted to 7.0 had greater sensitivity to ammonia than film that was prepared at an original pH of4.3, so this film was used to monitor freshness of pork. A visible change in the color of the film was observed during the spoiling process of pork, which correlated with the accumulated total volatile base nitrogen. Based on its sensitivity to ammonia, the film made of 80% (w/w) RPP and 2% (v/w) glycerol at pH7.0 was recommended for use in monitoring the freshness of protein-rich food. Our findings are of great significance for ensuring meat quality and safety and for reducing food waste. © 2022 Society of Chemical Industry.

Study on microbial community and physicochemical properties of braised chicken during processing and storage microbial community of braised chicken

AbstractBraised chicken is a popular meat product with an attractive appearance, delicious taste, and rich nutrition. High‐throughput sequencing technology (HTS) was utilized to comprehensively characterize the dynamics of the microbial community during processing and storage (4°C). The physicochemical properties (pH, moisture content, total volatile base nitrogen (TVB‐N), and the thiobarbituric acid reactive substances (TBARS)) and colony counts were also evaluated. The microbial community of braised chicken was different between processing and storage. Weissella and Psychrobacter were the dominant genera during processing; Acinetobacter, Pseudomonas, Enterobacter, Aeromonas, and Aneurinibacillus were the dominant genera in storage. The microbial counts (total viable count [TVC], Pseudomonas, LAB, and Enterobacteriaceae) decreased gradually during hot working processing, but increased during storage. After the warranty, TVC and Enterobacteriaceae counts exceeded the limit for cooked meat products. TBARS and TVB‐N increased from 0.089 to 0.400 mg/kg and 0.52 to 2.03 mg/kg, respectively, during processing and storage, and TVB‐N content exceeded the limit of cooked meat products after the warranty. Spearman's correlation analysis showed that Pseudomonas, Enterobacter, and Aeromonas were significantly positively correlated with the spoilage index (TVB‐N and TBARS). Amino acid metabolism and carbohydrate metabolism were also significantly positively correlated with them，indicating that Pseudomonas, Enterobacter, and Aeromonas may be the main microorganisms that cause spoilage of braised chicken. This study revealed the possible spoilage microorganisms of braised chicken during processing and storage, which was helpful to improve the quality and safety of braised chicken.

A Preliminary Study on the Use of Rice Husk-Based Smoke Powder for Meatball Preservatives

This study examines the use of smoke powder derived from rice husks as a preservative for chicken meatballs. Rice husks were pyrolyzed in a slow pyrolysis reactor at the temperatures of 300°C (T1), 350°C (T2), and 400°C (T3) to produce liquid smoke. Each of the liquid smoke was distilled at 190°C and then converted into smoke powder by spray drying method. The smoke powder’s feasibility as a meatball preservative was examined by total plate count (TPC), total volatile base (TVB), most probable number (MPN) test of E. coli, and organoleptic (aroma, texture, and color) tests. The results showed that the TPC and TVB increased with storage time. At the storage time of 76 hours, the meatballs were no longer suitable for consumption as the TPC had exceeded the minimum limit. In meatballs with T3 smoke powder at 72-hour storage, the number of colonies was 6.87 × 104 CFU/g, indicating the TPC value has not exceeded the threshold yet. The TVB test showed that up to 72 hours of storage, the meatballs remained fresh with a TVB value of less than 0.20 mgN/g. The result of the organoleptic test also showed that meatballs could last for 72 hours. The MPN test, on the other hand, revealed that the E. coli was still permissible after 68 hours of preservation.

Combined effects of calcium-alginate coating and Artemisia fragrance essential oil on chicken breast meat quality.

The objective of the present study was to evaluate the effects of calcium‐alginate (CA) containing Artemisia fragrance essential oils (AFEOs) as a potential antioxidant and antimicrobial coating on quality attributes and shelf life of chicken meat throughout keeping period (4°C). Five treatments were produced as follows: T1 (distilled water as control), T2 (2% CA), T3 (2% CA +500 ppm AFEOs), T4 (2% CA +1000 ppm AFEOs), and T5 (2% CA +1500 ppm AFEOs). The chicken meats packaged in polyethylene bags at atmospheric condition and physicochemical, microbiological, and organoleptic properties were assessed at days 1, 4, 8, and 12. There was no remarkable difference in proximate composition (moisture, ash, protein, and fat) of meat samples by treating with CA or AFEOs. The results revealed that CA +AFEOs coating reduced significantly the pH, total volatile base nitrogen (TVB‐N), and thiobarbituric acid reactive substances (TBARS) values and also displayed higher contents of the total phenolic content (TPC) and redness value when compared with control. According to results, 2% CA +1500 ppm AFEOs reduced 58.3 (mg MDA (malondialdehyde)/kg) and 0.63 (mg/100 g) of TBARS and TVB‐N values when compared to control, respectively. The microbiological count showed that CA +AFEOs had a significantly higher inhibitory impact on the total viable count (TVC), coliforms, molds and yeasts. At day 12, 6.89 Log CFU (colony‐forming units)/g was recorded for TVC in 2% CA +1500 ppm AFEOs, which was the lowest overall. This treatment also displayed the reduction of 2.97 Log CFU/g in coliforms and 3.3 Log CFU/g in molds and yeasts in comparison with uncoated samples. The outcomes of pH, TBARS, TPC, color values, microbiological count, and organoleptic properties suggested 2% CA +1500 ppm AFEOs as an efficient coating for quality stability and improving the shelf life of chicken breast meat without negative impact on organoleptic properties.

Effect of Lentinan on Lipid Oxidation and Quality Change in Goose Meatballs during Cold Storage.

The effects of different concentrations of lentinan (LNT) (0, 0.5, 1, 2 and 4%) on the oxidation characteristics and physicochemical properties of goose meatballs were investigated during different cold storage (4 °C) stages (3, 7 and 12 days). After adding LNT, the thiobarbituric acid reactive substances (TBARS) and total volatile base nitrogen (TVB-N) of goose meatballs significantly decreased compared to the LNT-free sample during cold storage, which indicated that LNT can inhibit the fat oxidation and the release of nitrogenous substances. Meanwhile, the presence of LNT makes microstructure of the goose meatball samples become denser during the whole storage time. The headspace solid phase microextraction gas chromatography-mass spectrometry (SPME-GC-MC) results showed that the proportion of aldehydes in the 4% LNT group reached 0 during storage, suggesting that high LNT concentration inhibits the formation of oxidized products in meat products. The sensory evaluation showed that the addition of LNT improved the color, appearance, flavor, and overall acceptance of goose meatballs, and the 2% LNT group had the highest score in overall acceptance. In summary, the addition of LNT could delay lipid oxidation and improve the quality of goose meatballs during cold storage.

Effect of nanocomposite alginate-based film incorporated with cumin essential oil and TiO2 nanoparticles on chemical, microbial, and sensory properties of fresh meat/beef.

The environmental problems of synthetic plastics in food packaging have led researchers to synthesize biodegradable films. In this study, nanocomposite alginate‐based films containing TiO2 nanoparticles (1%) and cumin essential oil (CEO, 2%) were fabricated and the potential of these films to protect beef from chemical [pH, total volatile base nitrogen (TVBN), peroxide value, and thiobarbituric acid reactive substances (TBA)] and microbial [total viable count, Enterobacteriaceae, lactic acid bacteria, Listeria monocytogenes, and Pseudomonas spp.] spoilage was evaluated during 24 days of storage (4°C). The active films significantly induced the reduction in lipid oxidation, microbial growth, and TVBN values, improved the sensory attributes of treated samples, maintained the redness of meats for a longer time, and increased the shelf life of beef from 4 to 16 days. The results of this study showed that TiO2/CEO alginate‐based nanocomposite film has a great potential for application in meat and meat products.

Effect of chitosan/starch aldehyde-catechin conjugate composite coating on the quality and shelf life of fresh pork loins.

Fresh pork is susceptible to oxidation and spoilage. Edible coating containing antioxidant and antimicrobial agents can create moisture and oxygen barriers around pork and inhibit oxidation and microbial growth in the pork. In this study, chitosan in combination with starch aldehyde-catechin conjugate (SACC) was used as a novel edible coating material for preserving fresh pork loins at chilled storage (4 ± 1°C) for 14 days. Effect of chitosan/SACC composite coating on the quality of pork loins including weight loss, colour, pH value, microbial spoilage, lipid oxidation, protein oxidation, texture and sensory attributes during chilled storage was determined. Chitosan and SACC had synergistic antioxidant and antimicrobial actions. As compared with uncoated and chitosan coated pork loins, chitosan/SACC coated pork loins showed lower weight loss (7.16%), pH value (5.99), total viable count (7.11 log CFU g-1 ), total volatile base nitrogen content (130.2mg kg-1 ), lipid oxidation level (0.47 mg malondialdehyde kg-1 ), protein oxidation level (0.047 mmol free thiol group g-1 ) and shear force (27.40 N) on day 14. Meanwhile, chitosan/SACC composite coating effectively maintained the colour, micro-structure and sensory attributes of pork loins throughout chilled storage period. The shelf life of pork loins was extended from 8 days (uncoated samples) to 14 days by chitosan/SACC composite coating. Chitosan/SACC composite coating effectively retarded the oxidation and spoilage of pork loins during chilled storage. © 2022 Society of Chemical Industry.

Effects of bioactive substances to prolong the shelf‐life and inhibit the formation of black spots in black tiger shrimp (Penaeus monodon) preserved at 0 degree C

AbstractThe objective of this study was to extend the shelf‐life and inhibit the process of black spots formation in giant black tiger shrimp (Penaeus monodon) by using 1.5 % solutions of the bioactives including: gallic acid, caffelic acid and cinnamaldehyde. Shrimp samples were dipped in the solutions for ten minutes, at 4°C and stored at 0°C for 15 days. Total viable count (TVC), melanosis evaluation method, chemical quality indexes including total volatile base nitrogen (TVB‐N), trimethylamine nitrogen (TMA‐N), pH and hypoxanthine values were used to evaluate the effectiveness of the treatments. TVC values, melanosis score of shrimp samples treated with bioactive compounds appeared more slowly, TVB‐N and TMA‐N values changed exponentially, hypoxanthine values increased linearly with storage time, and pH decreased on day 2, then increased gradually. Shelf life of treated samples were found to be longer than that of the control sample (8 days), and had a better ability to inhibit melanosis, in particular, the samples treated with a solution of cinnamaldehyde had the longest shelf life of 14 days, compared with 13 days of samples treated with caffelic acid and 12 days of the ones treated with gallic acid.

THE EFFECT OF VACUUM PACKAGING ON THE QUALITY AND SHELF LIFE OF PINDANG COB PATCHES (Auxis tharzad, Lac).

This an comparative experimental study that compares the quality of pindang cob packed with vacuum and non-vacuum at the shelf life of 0, 2, 7, 14, and 28 days at room temperature (30-33oC). The processing of fishery products plays an important role in post-harvest activities considering fishery products are perishable goods. Vacuum packaging technique is currently a packaging technique that is currently popular among the public. The purpose of this study was to determine the effect of vacuum packaging techniques on the quality and shelf life of pindang cobs (Auxis tharzad, Lac). The parameters evaluated included chemical parameters, namely moisture content, salt content, histamine levels, total volatile bases levels, and trimethylamine levels; microbiological parameters such as the number of bacteria, the number of coliforms, and the number of Escherichia coli; and organoleptic parameters including appearance, smell and texture. Based on the results of the research, the quality of the storage capacity of frigate mackerel which is vacuum packed at room temperature storage of 30-33oC, can only be stored &lt; 7 days and there is a significant difference in quality and shelf life between vacuum packed and non-vacuum packed frigate mackerel.

Changes in bacterial community structure and quality characteristics during fermentation of stinky variegated carp ( Aristichthys nobilis )

Bacterial metabolism greatly affects the quality and flavor of traditional, low-salt fermented fish. We assessed changes in the bacterial community structure and quality characteristics of “stinky” variegated carp (Aristichthys nobilis) during fermentation at 20°C. The total viable count (TVC), firmness, chewiness, tackiness, total volatile base nitrogen (TVB-N) and thiobarbituric acid-reactive substance (TBARS) levels, and relative peak area of volatile compounds significantly (p < .05) increased, while the pH, weight, and elasticity dramatically decreased, during fermentation. The total free amino acid (FAA) content decreased early during fermentation (from 0–2 d) and then significantly (p < .05) increased (from 3–5 d). The levels of flavorful AAs (aspartic acid, glutamate, phenylalanine, tyrosine, alanine, and glycine) increased markedly after 4 d of fermentation. Solid-phase microextraction-gas chromatography–mass spectrometry (SPME-GC–MS) revealed that the levels of ketones, ethers, and nitrogenous compounds increased significantly (p < .05) during fermentation. Illumina MiSeq sequencing identified Plesiomonas as the dominant bacterial genus during fermentation, followed by Aeromonas, Cetobacterium, Vibrio, and Hathewaya. These bacteria may contribute to the flavor and aroma of stinky variegated carp. The association between bacterial succession and the flavor and taste of stinky fish was also discussed. Practical applications Variegated carp could be processed to create stinky fish. In this study, bacterial community structure and quality characteristics analysis were assessed. FAAs and volatile compounds related to flavor and aroma were found. A potential starter culture that could improve the quality of stinky variegated carp was identified. Our findings provide a theoretical basis for the industrial production of fermented stinky fish.

Assessment of Spoilage Microbiota of Rainbow Trout (Oncorhynchus mykiss) during Storage by 16S rDNA Sequencing

Due to the high contents of protein and fat in rainbow trout, it is highly susceptible to spoilage, which limits the storage and transportation processes. Exploring the spoilage microbial community during rainbow trout storage is essential to develop an effective preservation method. Here, the changes in the total bacterial colony and total volatile base nitrogen (TVB-N) during the storage of rainbow trout were investigated. Storage at 0 °C can effectively slow down the spoilage process with bacterial counts and TVB-N contents decreased from 8.7 log CFU/g and 18.7 mg/100 g obtained at 4 °C to 5.6 log CFU/g and 14.5 mg/100 g, respectively. 16S rDNA high-throughput sequencing results showed that the diversity of microbial genera decreased during storage. Acinetobacter, Pseudomonas, and Shewanells gradually became the dominant spoilage genera with contents of 59.9%, 18.6%, and 1.7%, respectively, in the late stage of storage. The spoilage abilities of bacteria belonging to the Pseudomonas and Shewanells genera were analyzed. Shewanella sp. S5-52 showed the highest level of TVB-N content (100.6 mg/100 g) in sterile fish juice, indicating that it had a strong spoilage ability. This study confirmed the dominant spoilage bacterial genera and evaluated the spoilage abilities of isolated strains during the storage of rainbow trout, which laid the foundation for further investigation of the spoilage mechanism of rainbow trout and other aquatic products.

Changes in physicochemical properties of silver carp (Hypophthalmichthys molitrix) surimi during chilled storage: The roles of spoilage bacteria

Chilled surimi has become increasingly popular owing to its superior texture and freshness. In this study, changes in the microbiota and gel properties during chilled surimi storage, and the contributions of dominant bacteria to the physicochemical properties of chilled surimi were investigated. The results showed that Pseudomonas gessardii, Aeromonas media, and Acinetobacter johnsonii were the dominant bacteria during chilled surimi storage. P. gessardii was the key bacteria that degraded protein in the process of surimi spoilage, which led to high total volatile base nitrogen (TVB-N), trichloroacetic acid (TCA)-soluble peptides as well as poor gel properties. Both P. gessardii and A. media were high putrescine producers, whereas only A. media produced cadaverine. In this study, spoilage microorganisms in chilled surimi were investigated for the first time, and it was found that P. gessardii had the greatest influence on surimi quality, which provides a research basis for in-depth study on the mechanism of microbial spoilage and the preservation of chilled surimi.