fish freshness assessment 2020.pdf

Food Research International 133 (2020) 109157 Contents lists available at ScienceDirect Food Research Inte...

Food Research International 133 (2020) 109157 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres Review A comprehensive review on freshness of fish and assessment: Analytical T methods and recent innovations Pramod K. Prabhakara, , Siddhartha Vatsaa, Prem P. Srivastavb, Sant S. Pathakc ⁎ a Department of Food Science and Technology, National Institute of Food Technology Entrepreneurship and Management, Kundli, HR, India b Department of Agricultural and Food Engineering, Indian Institute of Technology Kharagpur, West Bengal, India c Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology Kharagpur, West Bengal, India ARTICLE INFO ABSTRACT Keywords: Fish, a highly nutritious, containing a good amount of protein and fatty acids, has TMA and TVB-N present as Fish freshness major factors responsible for quality deterioration during storage and maintaining of fish freshness. Freshness is Trimethylamine (TMA-N) one of the most important parameters in the fish market. There are many methods of estimating fish freshness, Total volatile basic nitrogen (TVB-N) out of which some are very costly while others are not user-friendly. However, with more technological in- Biogenic amines novations, there have been efforts to make a more reliable method of calculating and analyzing freshness. Recent innovations Parameters chosen for assessing the freshness are sensory, physical, chemical and microbiological including the recent trends such as SDS-PAGE, fast protein liquid chromatography, hyper Spectral Imaging Technique, etc. focused on reducing time, destruction and labor. Traditional and recent methods of evaluation of freshness along with their comparison based on several parameters are needed to link them and making it convenient for up- coming researchers to have a detailed study for having a universal indicator for assessing the freshness of fish. Information in the present article has all the methods of assessing the fish freshness been discussed in detail. There has also been focus on bringing the readers knowledge about the comprehensive information related to recent developments. The recommended limit for different indicators signifies the time period for which the particular fish can be stored and it depends upon several factors like species, surrounding environment and enzymatic and non-enzymatic actions. Based on these demands, this paper is uniquely worked upon to review the different literature which brought all the discussions from the past including the recent innovations in assessing the freshness of different fishes with the help of various indicators as well as a complete study of spoilage and toxicity mechanism leading to deterioration in quality, making it easy for the reader and re- searchers to have quick glance over the trends and innovations. 1. Introduction total capture leads to 92.7 million tonnes including both 11.4 MT from inland and 81.2 MT from marine water, at the same time the aqua- The demand for fish has been ever-growing due to the increasing culture production leads to 80 MT of fish with 52 MT from inland and human population and more research in fisheries which has increased 28 MT from the marine population (FAO, 2018). A total of 59.6 million the demand over the last few decades across the world. The recent fish farmers exist in the globe out of which 85 percent are supported preservation techniques have made it possible to make the same quality over capturing and aquaculture belong to Asia. The direct consumption of processed fishes reach across different parts of the world. In 2016, of fish leads to 88% that is 151 million tonnes while only 12% was global fish production was 171 million tonnes, in which 47% of total processed for non-food and aquaculture related requirements (FAO, inclusion is of aquaculture and the other 53 percent comes under non- 2018). food uses (and includes fishmeal and fish oil) (FAO, 2018). Since the Fish is highly nutritive, being full of protein, vitamins, and minerals 1980 s, the production of captured fish has remained constant; the which are required by our body for good health and well being. Fish has continued accelerated growth in the supply of fish for human con- been mainly classified into mainly 3 categories: (1) oily fish, (2) white sumption has only been possible due to aquaculture. The human con- fish and (3) shellfish (Naylor et al., 2000). Oily fish contains a good sumption increased from 130 to 151 million tonnes from 2011 to 2016 amount of vitamins A, D and E. Being rich in omega-3 fatty acids, it while non-food uses reduced from 24 to 19.7 million tonnes. While the keeps the brain healthy, is beneficial for the eye and important for the ⁎ Corresponding author. E-mail address: [email protected] (P.K. Prabhakar). https://doi.org/10.1016/j.foodres.2020.109157 Received 27 December 2019; Received in revised form 25 February 2020; Accepted 7 March 2020 Available online 09 March 2020 0963-9969/ © 2020 Elsevier Ltd. All rights reserved. P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Nomenclature DMA dimethylamine TMAO trimethylamine oxide TMA trimethylamine Hx hypoxanthine TVB-N total volatile basic nitrogen EEM excitation-emission matrices TBA thiobarbituric acid FFFS front face fluorescence spectroscopy FFA free fatty acid POW predictive optimal wavelengths ATP adenosine tri phosphate TPA texture profile analysis ADP adenosine di-phosphate TS-HIS time series hyperspectral imaging IMP inosine mono phosphate MLR multivariate linear regression NH3 ammonia QIS quality index scores NH4+ ammonium ion SDAE-NN deionising autoencoder neural network NMDA N-methyl D-aspartate receptor XOD xanthine oxidase nerve development in babies. Their consumption also keeps the heart to less preference by most of the people. healthy and there are enough proofs to assure that its consumption All the methods use a common strategy, the base being the calcu- reduces the risk of cancer and arthritis (Lees, 1990). Therefore, such a lation of total volatile basic nitrogen (TVB-N) and trimethylamine large population today directly or indirectly depends on fish either as a (TMA) over different periods of storage directly or indirectly to assess nutritious diet or as a source of income. But the biggest challenge in the freshness of fish (Table 1). Several methods have been thus devel- fulfilling the needs of all the population is the perishability of fish. Fish oped in the recent past to determine the fish freshness. The sensory is highly perishable and the production of various metabolites re- evaluation uses sight, smell, odor, tactile, etc. to measure the freshness sponsible for its spoilage starts right after it is harvested. Hence, there of fishes. A trained panel can evaluate all these sensory attributes quite has been so much focus on estimating the freshness and behavior of well and each qualitative description is converted in a numeric score fishes in different conditions which are due to the increasing demand which helps to differentiate the samples as well as information about and awareness of fish products both from the nutritional and in- the sample. However, the trained panels are generally expensive and formational factors. Apart from this, the fish industry is a prime eco- not always available at different steps of the fishery chain. Hence to nomic source for trade (international and domestic) in the coastal states satisfy the high-quality based inspection and determination of fish and districts. Human consumption of fish and fish related products freshness, the food industry the initial phase of development of in- around the world is about 128 million tonnes, and this consumption for struments was made in vision to replace it exactly with human senses to a single person is 18.4 kg of fish products per year (Durand & detect the freshness. Some of the examples are texture analyzer for Seminario, 2009). All the fish products make a proportion of 15% of the firmness, electronic nose (EN) for odor, and colorimeter and skin image animal protein intake for 4.3 billion people as per the report of the 30th coherence for skin appearance (Table 3). Dalgaard (2000) developed a conference of Fisheries Commission of Food and Agricultural Organi- microbial inspection to know the remaining shelf life by calculating the zation (FAO, 2012). The methods of evaluating fish freshness have been amount of TMAO consumed by different species of bacteria. The total dated back since the mid-20th century and the advances in the last 3 viable count (TVC) is calculated in the fishery products and thus the decades have been the most rapid and innovative ones. But some of freshness is determined (Tables 1–3). During fish storage, the increase these techniques are easy and simple to use but at the same time, time- in TMA-N has been widely correlated with a decrease in TMAO con- consuming while on the other hand, many techniques take less time to centration. Recent developments after 2009 have included EN tech- show the results but are expensive and complex methods (Prabhakar, nique, hyperspectral imaging technique, and fast protein liquid chro- Srivastav, & Pathak, 2019). matography to assess autolytic and microbiological changes in the fish New and innovative technologies have enhanced both the product samples which proved to be non-destructive, less time consuming, but qualities and maintain the same characteristics throughout the period need highly expert and trained people for performing the experiments from when it was harvested to the point the consumer will intake it as a successfully (Table 2) (Cheng et al., 2013; Cheng, Sun, Zeng, & Liu, meal. There have been regulations according to many countries to es- 2015). tablish the principles which can control and certify the quality warranty The chemical inspection has involved a wide area of research in relating to fish products as a whole. Codex is the international body which different scientists have studied the chemical changes on dif- which makes standards for fish commodities and has constituted var- ferent fish species and using a range of instrumental methods. Hassoun ious committees to look after these standards. For example, under and Karoui (2017) held that the basis for chemical inspection has been commodity committees, comes fish and fish products (Norway), fats the determination of K value, Peroxide value, TVB value, Oxidation and oils (United Kingdom), meat and meat products (West Germany). Reduction Potential, P ratio, K value, etc. Spectral imaging and NMR Similarly, in India, the Food Safety Authority of India (FSSAI) looks spectroscopy have been recent advances being the non-destructive, less after the laws and regulations regarding the production and sale of time-consuming, non-contact and reliable technique. But the major different fish and related products. Physical, chemical, microbiological problem related to this is that these techniques do not apply to all and biochemical changes occurring post-mortem in fishes, resulting in a varieties of fish and there needs more research after which the same progressive loss of food characteristics in terms of taste and quality. parameter can be applied to all kinds of fish related products. Moisture Storage time and temperature are key factors for the final quality of the measurement, volatile compounds measurement, protein changes in product. The rate of spoilage however also depends on many other post-mortem storage, lipid oxidation monitoring, ATP decomposition, K factors such as kind of fish species, the sanitary conditions on board, value indicator are important parameters of measuring chemical in- and the amount of food in the guts (Ghaly, Dave, Budge, & Brooks, spection for fish freshness. 2010). When it comes to consumers’ point of view, the taste is, of Physical properties measurements include color measurement and course, the most important aspect which is directly proportional to the texture measurement specifically while the shape, size, volume and fish freshness and hence the most required property. How taste is re- weight also play a major role in determining the freshness (Olafsdottir lated to the freshness of fish needs to be understood by the fact that et al., 2004). Color and textural changes have a direct impact on the with days passing after the freshly harvested fish, the volatile products freshness of fish. Initially, the only colorimeter was used to detect the responding to the smell and the change in texture while chewing leads color in fish, but now we have many novel methods for investigating 2 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 1 Freshness determination methods based on microbial changes. Name of author Method used Approach and Interpretation Remarks 2 4 Gram and Dalgaard (2002) TVC index (for general set of Initial total viable counts are 10 –10 CFU/g and this Advantage: aquatic animals) indicator is used to detect degree of freshness and prediction of remaining shelf life of fish. Can be used for variety of aquatic products. Disadvantage: Time consuming, cumbersome and destructive. 6 Özogul, Özyurt, Özogul, Kuley, and TVC acceptability limit (esp. The acceptable limit was set up as 10 after series of Advantage: Polat (2005) for eel) experiments. Then the shelf life of eel was discovered to be 2 weeks in ice and 1 week without ice. Exact detection of shelf life for which limit is set. Disadvantage: Limits need to be set up differently for different species. Chantarachoti, Oliveira, TVC limit Fish of Alaska pink salmon stored at 14© had shelf life of Advantage: Himelbloom, Crapo, and 3 days while in ice it lasted for 16 days McLachlan (2006) Comparison of TVC based on storage condition helpful for many species. Disadvantage: Destructive consuming technique and time Song, Liu, Shen, You, and Luo Comparison of chilling and Sensory rejection and sensory assessment based on TVC Advantage: (2011) freezing storage based on TVC values of fish being 5.74 and 4.66 log CFU/g for chilling and limit partial freezing respectively. More accuracy based among other TVC analysis tests Disadvantage: Kyrana and Lougovois (2002) Shewanella putrefaciens count The count is directly proportional to the sulphide More cumbersome and difficult. Advantage: production, an indicator of fish spoilage. Easy and mathematically convenient approach Disadvantage: Requires high precision and accuracy both in counting and calculations. Taliadourou, Papadopoulos, Correlation of H2S production Behaviour of H2S producing bacteria of whole-ungutted and Advantage: Domvridou, Savvaidis, and and TVC filleted sea bass during ice storage was studied and related Kontominas (2003) with TVC values. The TVC values were found to be always higher in case of fileted sea bass. Mixture of several techniques leading to more accurate results and correlation between them. Disadvantage: Time consuming and not applicable to fishes that do not involve sulphide production. El Barbri et al. (2009) EN technique Three stages of freshness determined for sardines and the Advantage: results were in good agreement with results based on TVC values. Novel technique. Non-contact and less time consuming. Disadvantage: No further developments till date other than sardine samples. Peng (2011) Hyper Spectral Imaging Rapid prediction tool for freshness quality of fish by fast Advantage: Technique (HIS) monitoring of autolysis and microbiological changes in any sample. Non-contact, Non-destructive, fast, accurate measurement. Disadvantage: The method is fast but still there is a need for rapid microbial inspection and a universal indicator for all samples. Kuznetsov, Mutaeva, and Fast Protein Liquid Uses Nucleotides elution Delay time (Δt) as a freshness Advantage: Kuznetsova (2017) Chromatography (FPLC) index. Delay time can easily be converted into K values by the equation:K = 0.0173 Δt − 3.15 × 10-5 (Δt)2 − 1.3757 Quickest determination of fish freshness available till now. Uses combination of protein and nucleotide elution chromatograms in one action by which delay times are Can be used in labs as well as in retail chains. calculated. The sharp peak is obtained for protein and broad Environment friendly. bands for the mixture of AMP, ADP, IMP, Hx, etc. Low cost, reliable (continued on next page) 3 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 1 (continued) Name of author Method used Approach and Interpretation Remarks Less qualified staff can also work. Non-destructive, less time consuming. Quickly determine shelf life of almost all varieties of fishes. Disadvantage: Still needs universal acceptance and more research to be done. the same (Table 3). But these novel methods require in-depth research Nottingham, 1998). Although performing analysis of TVB-N is quite for more samples and varieties of fishes as compared to other methods easy, it indicates the later stages of advanced spoilage and thus only the of inspection. The connection of the research with mathematical initial ten days of chilled storage, it is not considered so reliable for the modeling has made it possible to have a valid and authentic proof for measurement of spoilage (Sykes et al., 2009). Cheng, Sun, and Wei every experiment the scientists have conducted. In one or more ways (2016) detected the TVB-N of grass carp fillet during frozen storage finally, all the models are interconnected being able to finally detect with a new algorithm of Physarum Network coupled with a genetic fish freshness and at the same time, the approaches of each technique algorithm based on 6 selected optimal wavelengths. PLSR and LS-SVM are quite unique and different from each other. Hence, there has been were applied to establish the prediction model. It is very useful for the much research and development regarding the determination of fresh- measurement of quality in cephalopods such as squid, industrial fish for ness of fish but the world today still needs a much faster and simple to a meal. However, the values do not specify the mode of spoilage that use universal indicator which would be applicable to all the fishes and whether it has followed the bacterial pathway or the autolytic one, and the research regarding this is already going and it is assumed that re- the method of conduction of analysis affects the results to a good extent. searchers will be successful to achieve this target till next decade. 2.2. Free fatty acids (FFA) and thiobarbituric acid value (TBA) 2. Chemical indicators of fish spoilage During the storage of fishes, quality deterioration in fishes is also 2.1. Trimethylamine (TMA) and total volatile basic nitrogen (TVB-N) caused by lipid oxidation. The biggest problem of all the big and small fish markets is that of the limited shelf life of fish. A check on the TMA, a biogenic amine, is considered as a biochemical index for the oxidation of these lipids in the fish has become an important object of quality and shelf life assessment of fish and sea fish. Prabhakar et al. concern with increasing consumption (Salonen et al., 1995). With an (2019) and Peleg (2016) explored that this deterioration process is increase in FFA and TBA, the quality of fish deteriorates. The FFA value characterized by the synthesis of TMA. Trimethylamine is mainly re- is measured in milliequivalents (mEq) peroxide per kg of lipid as well as sponsible for the fishy odor which is highly associated with foul fish, in percentage of oleic acid, while TBA shows absorbance at a fixed bacterial infections, and bad breath. Bevilacqua, Corbo, and Sinigaglia wavelength and is measured in form of mg malonaldehyde (MDA) per (2016), Méndez and Abuín (2012) explained that it is also associated kg of lipid (Table 2). With the chemical reactions ongoing inside the with taking large doses of choline trimethylamine (TMA). During the fish muscle, the lipid gets oxidized and is broken into simpler com- storage of unfrozen fish, there is a development of total volatile bases pounds such as free fatty acids, peroxides and thiobarbituric acid which which consist mainly of ammonia and trimethylamine (TMA). De- result in muscle spoilage (De Abreu, Losada, Maroto, & Cruz, 2010). pending on the species (ground fish, pelagic species, and shellfish), it is Work for TBA value was done by Xu, Riccioli and Sun (2015a, 2015b), a useful measure of freshness quality (particularly flavor and odor as- who monitored the lipid oxidation of Atlantic Salmon during chilled pects) of a variety of seafood, but it depends upon the season and/or the storage for up to 12 days by using multivariate linear regression (MLR) location of catch, stage of spoilage, type of processing, and/or storage, and particle analysis to predict TBA values. and method of analysis (Botta, 1995). Trimethylamine accurately indicates bacterial spoilage in some of 2.3. K-value the species. It is responsible for the fishy smell when the fish spoils and the amine is a pungent and volatile gas. Howgate (2009) unfolded the K value described by Saito, Arai, and Matsuyoshi (1959) was de- presence of TMA in stored fish as a result of reduction by bacteria, termined after analyzing the ATP break-down products as per Ryder present under the tissues of many marine fish species. Gram and Huss (1985). K value, as per Ehira and Uchiyamna (1987), is one of the best (1996) explained that the correlation with bacterial numbers proved indicators of the freshness of fish which is obtained from the autolytic not to be too good often in many species, although TMA has always decomposition of adenosine triphosphate (ATP). K value is the ratio of been considered as a result of bacterial spoilage. Now, it is believed to the final by-products formed after the decomposition of ATP and the occur because few “specific spoilage” bacteria are present which may or summation of all the products in the cycle starting from ATP (Fig. 1). may not represent compounds related to spoilage such as TMA. The Watanabe, Nagumo, Hoshi, Konagaya, and Tanaka (1987) and Luong, area where TMA lags behind as a great indicator is that TMA does not Male, and Huynh (1991) have shown that k values increases with show anything during the early stages of spoilage and is applicable to spoilage. Although representing so many species, it is not an effective certain fish species (Gill, 1990). TVB-N is a parameter in which the way of indicating the freshness of many other tropical fishes like presence of volatile nitrogenous bases in the original material (fish- salmon, halibut, and, yellowtail according to Isono (1990). For such meal) is measured. Ricque-Marie et al. (1998) explained that it gives an cases, K value is used which is the ratio of the sum of hypoxanthine and accurate estimation of the final product’s quality to be obtained. TVB-N inosine to that of inosine monophosphate added to the previous one is very commonly specified as a major parameter for assessing the fish (Table 2). Although these methods are successful in giving exact results, freshness. Huss (1988) revealed that for estimating the degree of de- but they effectively work for fish extract, and also need more skills composition of fish muscle, TVB-N is the most widely preferred para- along with time as a big constraint (Niu & Lee, 2000). K value is a meter nowadays. It mainly measures all the nitrogenous compounds function of temperature and storage duration. This is mainly due to the which cause spoilage of seafood (Chinivasagam, Bremner, Wood, & rapid reduction of HxR and accumulation of Hx with the storage time 4 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 2 Analytical and advanced freshness determination methods based chemical changes. Name of author Method used and type of Fish used Approach and interpretation Remarks Khodabux, L’Omelette, NIR spectroscopy (skipjack tuna and Comparison of NIR with traditional oven-drying and electronic Advantage: Jhaumeer-Laulloo, yellowfin tuna) moisture analyser was done. NIR resulted in more accurate and Ramasami, and Rondeau (2007) fast analysis as compared to other two. Fast and accurate Disadvantage: Limited costly. research work done and Li (2000) Electronic Nose (Red Fish, cod and haddock) The fresh sense could sense the difference in odour of fresh and spoiled fishes with help of standard compounds present Advantage: Comparison of behaviour of ice- in the mixtures. Portable, has high sensitivity and stored and MAP stored fish. The CO sensor increases earlier than the other sensors and is most likely responding to short chain alcohols and carbonyls specificity and is also non- destructive. formed during the storage of red fish. Disadvantage: The NH3 and H2S sensors are sensitive to amines and sulphur compounds respectively formed in high concentrations at the end of the storage period. It was found High efficiency e-nose is unavailable as it can test limited analytes, is also that MAP storage was better than ice storage. quite expensive and the biggest limitation is that it detects advanced spoilage in later stages and cant detect initial spoilage in fishes. Huang et al. (2003) Short wavelength NIR using Partial 600–1100 nm SW-NIR was used for moisture determination with Advantage: Least Square Regression (PLSR) and PLSR and ANN. PLSR and ANN gave good and similar results of Artificial Neural Networks (ANN) calibration methods of moisture R2 = 0.799 and 0.784 Advanced NIR technique, being more reliable and covering more determination. Cured Atlantic varieties. Salmon Disadvantage: Expensive, requires high skill and precision. Unable to determine spoilage in initial phase. Wold et al. (2006) NIR multispectral imaging (70 dried salted coalfish) & NIR interactance PLSR 2 prediction models obtained correlation value of R = 0.92 with RMSECV = 1.07% for online determination Advantage: multispectral imaging (six species of of moisture content in fishes. Covering more varieties. Gives fillets) Other species identified by spectroscopy: Cod, sardine, salmon, Spectral region of 760–1040 nm helped to determine water content and distribution of the same in the fillets. information about water distribution also and it is suitable for high speed abalone, Sea bass, Trot, Halibut assessment of quality parameters of water content and distribution in fillets. Disadvantage: Costly, needs to be universal, unable to detect spoilage in initial growth of microbes. Duflos, Coin, Cornu, Antinelli, and Malle Solid phase Micro Extraction, Headspace analysis, Gas Headspace analysis identified 24 ions that could be used as markers of food spoilage. Advantage: (2006) Chromatography. (Whiting Cod and Mackerel, scallops) SPME identified 86 compounds out of which 20 can be used to assess freshness including alcohols, ketones, aldehydes Non-destructive, reliable, sensitive, accurate and recent technology and esters (C2-C11) covering large proportion of chemical compounds inside fish. Uses volatile compounds as a basis for checking spoilage. Disadvantage: Incompounds HS, the concentration of the 20 common to the three species and characteristic of spoilage fluctuate significantly from one species to another, reflecting the difficulty of defining common markers between species of fish. Hard to trace the source of spoilage (can’t track the mode). Özogul et al. (2005), Taliadourou et al. (2003) Estimation of acceptability limit of TVB-N (General for all types) Freshness was indicated as the limit of TVB-N. As the limit of the value is higher than 10 mg TVB-N per 100 g flesh, the N/A freshness is degraded. Whereas Taliadourou showed that acceptability limit of TVB-N for filleted fish was 26.77 mg N per 100 g flesh and for whole-ungutted bass, it was 26.88 mg N per 100 g flesh. Chang et al. (2017) Electrochemical biosensor (amine gas sensor) to detect volatile Inin the a very short time of 60 s, NH3, TMA, DMA were detected raw fish and the results showed good correlation with Advantage: ammonia gas in raw fish (Mackerel the TVB-N results’ analysis. Quick response, high sensitivity, and Beltfish, Tilapia) Insensor case of Tilapia (a freshwater fish with low TMAO), the gas became more effective than TVB-N analysis. specificity and minimum cross reactivity (continued on next page) 5 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 2 (continued) Name of author Method used and type of Fish used Approach and interpretation Remarks Disadvantage: Weak electric signal and biological agents less stable, hence degrade with making them not reusable. Borisova et al. (2016) Enzyme biosensor based on Construction of a XOD/MNP-PAMAM-PtNP/rGO-CMC/GCE Advantage: decomposition and vaporization of electrode to determine the extract of hake. A linear relationship ATP (Cod fillets, Hake) was obtained between steady current and concentration of Xanthine (50 nm-12 µM) with LOD of 13 nm and sensitivity of Simple, fast and easy to use, takes lesser number of steps than HPLC to 9.9 mA/M. XOD (Xanthine Oxidase) is involved in reaction chain detect volatiles. of ATP responsible for its’ disintegration. Disadvantage: More research to be done, Extraction of enzyme is quite a laborious and intelligent task and requires skilled labour. Heising, Dekker, Bartels, and Ammonium ion-selective electrode An innovative method which uses ammonium ion-selective Advantage: Van Boekel (2012) method (NH4 + -ISE) Cod Fillets electrode (NH4 + -ISE) to measure signal changes of NH4 + -ISE , due to the changes in ammonia content of fish being developed and the results were in good correlation with Highly sensitive and effective evaluation of spoilage of fish. the TVB-N content in the cod fillets. Disadvantage: High range of data which makes it difficult to interpret and simultaneously give results based on statistics. It requires skilled personnel to do the job. Herrero (2008) Raman Spectroscopy Identification of structural change of proteins during storage and Advantage: this change was implicated in the loss of fish freshness quality Quick response, high sensitivity, specificity and less time consumed Disadvantage: Sivertsen, Kimiya, and Heia VIS/NIR Spectroscopy Studied the oxidation degree of fish proteins (haemoglobin and Costly, needs to be universal. Advantage: (2011) myoglobin) by means of VIS/NIR spectroscopy during freezing- thawing and cold storage in ice, and predicted that this change was correlated with most of the variations seen in the visible Covering more varieties. Gives information about water distribution region of spectrum. also and it is suitable for high speed assessment of quality parameters of water content and distribution in fillets. Disadvantage: Costly, needs to be universal, unable to detect spoilage in initial growth of microbes. Martinez, Šližytė, and SDS-PAGE Cods Sodium Dodecyl Sulphate-polyacrylamide gel electrophoresis Advantage: Daukšas (2007) (SDS-PAGE) technique was used to reveal the protein patterns of wild and framed cod and the results implied that wild cod muscle had a different expression and post-mortem degradation Highly sensitive and effective evaluation of spoilage of fish. pattern from framed cod. Disadvantage: It is organism specific and thus not applicable to many fishes.It requires skilled personnel to do the job. Godiksen, Morzel, Hyldig, SDS-PAGE Trout fillets He correlated protein band intensities and firmness of rainbow Advantage: and Jessen (2009) trout fillets by the SDS-PAGE technique and found that the textural change of trout could lead to breakdown of protein structure. Highly sensitive and effective evaluation of spoilage of fish. Disadvantage: It is organism specific and thus not applicable to many fishes.It requires skilled personnel to do the job. Taliadourou et al. (2003) TBA value Whole-ungutted and With the help of TBA value, the degree of lipid oxidation was Advantage: filleted seabass known and the values changed from 1.55 and 10.21 mg MDA per kg muscle to 8.15 and 26.27 mg MDA per kg muscle for whole- ungutted and filleted sea bass after 16 days of storage Easier and simpler way of determining freshness of fish. respectively. Disadvantage: Storage temperatures need to be prefixed and less accurate and non-universal. Herrero (2008), Özogul et al. Traditional quality method and Peroxide value and fatty acid composition were known using Advantage: (2005) Raman Spectroscopy technique. All these techniques which was related to freshness of fish fishes Quick response, high sensitivity, specificity and less time consumed (continued on next page) 6 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 2 (continued) Name of author Method used and type of Fish used Approach and interpretation Remarks Disadvantage:Costly, needs to be universal Guillen and Ruiz (2004) Nuclear Magnetic Resonance Spectra An NMR spectrum was applied on salmon lipids, and the study Advantage: Salmon was useful for determining the proportions of different acyl groups. The oxidative stability and the oxidation degree thus obtained were useful to indicate fish freshness. Non-destructive, non-contact, fast, responsive and highly sensitive. Disadvantage: High precision and accuracy required, expensive. Nortvedt, Torrissen, and Application of NIR spectroscopy NIR spectroscopy was successful to predict the lipid oxidation Advantage: Tuene (1998), Folkestad, Atlantic Halibut Fillet Tuna fish and degree of Atlantic halibut fillet, Tuna fish and yellow fin. Rørvik, Kolstad, and Mørkøre (2008) and yellow fin Fast and accurate Disadvantage: Khodabux et al. (2007) Limited research work done and costly. ElMasry and Wold (2008) Spectral Imaging Technique Six Quantitative measurement of fat distribution was done using Advantage: species of fish fillets spectral imaging technique, the results showing correlation of 0.91 with the traditional measurements. Non-destructive, non-contact, fast, responsive and highly sensitive. Disadvantage: High precision and accuracy required, expensive. Ehira and Uchiyamna (1987) Freshness value indicator based on K Correlation between the changes of fish muscle and ATP content, Advantage: value some preliminary studies have been conducted and fluctuating metabolite contents of ATP decomposition were reported. K value was defined by them as the ratio (%) of the total amount of Widely accepted method of evaluating fish freshness giving a inosine and hypoxanthine to that of ATP-related compounds direct correlation between ATP K-value (%) = (HxR + Hx)/ decomposition and fish quality. (ATP + ADP + AMP + IMP + HxR + Hx) Disadvantage: Non-destructive methods to calculate K value yet to be known with cost effective and short time approach. Raatikainen et al. (2005), Ion Mobility Spectrometry technique Presentation of details on ATP derived products and K value Advantage: Tejada (2009), Alasalvar, determination showing it to be useful for fish freshness Grigor, and Ali (2010) measurement. More useful and cost- effective approach being highly precise. Disadvantage: Ocaño-Higuera et al. (2011) Exponential measurement of K value The K value increased exponentially from an initial value of Not applicable for all kind of fishes. Advantage: 4.7% to a final value of 47.5% indicating the signs of freshness and deterioration. Mathematical determination of fish freshness by K value showing the direct measurement. Disadvantage: Requires precision. high accuracy and Agustini et al. (2001) Oxidation-Reduction Potential A relation between ORP and K value was established in which it Advantage: method (ORP) was shown that ORP increased proportionally to K value when it was in the range of 0.30–0.38 V, and then decreased further with increasing values of K depending on the storage temperatures. Easier and simpler way of determining freshness of fish by ORP. Disadvantage: Storage temperatures need to be prefixed as it tends to rapidly change the relation between the two. Hamada-Sato, Usui, K1 value evolved from K value At 0°Celsius, the contents of ATP, ADP, and, AMP values Advantage: Kobayashi, Imada, and decreased rapidly and, HxR and Hx contents increased when Watanabe (2005), Li et al. (2011) IMP content decreased. In this case, contents of ADP and AMP were found to be negligible. Thus, K value was substituted to a Itvalue is more useful and effective than K for evaluating fish freshness. new K1 value as:K1 (%) = {(HxR + Hx)/ Disadvantage: (IMP + HxR + Hx)} × 100 It’s only useful for monitoring early stage of stored fish. Barat et al. (2008) Amperometric flow injection system An amperometric flow injection system with 16-way switching Advantage: valve and immobilized enzyme reactors to determine the freshness of sea bream stored at 4 °C. The K1 value thus obtained had correlation of 0.992 with storage time. High correlation coefficient proving it to be an efficient method of evaluation of fish freshness. Disadvantage: (continued on next page) 7 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Table 2 (continued) Name of author Method used and type of Fish used Approach and interpretation Remarks Ithighly is a destructive technique and is expensive method. Watanabe, Tamada, and Non-destructive quality evaluation Non-destructive quality evaluation sensor was proposed to Advantage: Hamada-Sato (2005) sensorSashimi determine sashimi freshness quality and the result showed a good relationship between K1 value and remaining days of shelf life. Non-destructive, responsive. specific, sensitive, Disadvantage: K1 value can’t be used to determine loss of acceptability or monitoring at end of storage life. Table 3 Freshness determination methods based on physical properties. Author Method Approach and Interpretation Remarks Karoui and Blecker (2011), Costa et al. Colorimetric imaging by The differences in the freshness under four Advantage (2013) multivariate partial least squares of refrigeration modalities has been developed with whole external body of sea breams the help of non-destructive method based on the colorimetric imaging of the whole external body of Merging different image analysis techniques had the ability of the method for sea breams to evaluate through multivariate automatic assessment of fish freshness. partial least squares. Disadvantage The results produced quantitatively possible colorimetric differences between fresh and non- fresh fish. There is a need for the reduction of hyperspectral data redundancy, and the acceleration of detection speed. Wallat, Luzuriaga, Balaban, and A colour computer vision Live A machine vision system was designed and used to Advantage Chapman (2002) Goldfish analyse the fish skin colour development in live goldfish. Quick and responsive method of evaluating physical parameters. Disadvantage Wu, Sun, and He (2012) Infrared Hyperspectral Imaging To measure the colour distribution in salmon fillet, Not applicable to all kinds of fishes. Advantage system a long wave infrared HSI system was studied for Salmon fillet the same. Results also showed it had high potential in fish Rapid and non-invasive method of analysis. Disadvantage colour measurement in rapid form. The problem of choosing optimized wavelength for HSI and in-depth research for improving the precision of prediction still exists. Misimi, Erikson, and Skavhaug (2008), Yagiz, Gokceoglu, Sezer, and Comparison of machine vision and HIS system Quevedo showed that there was a good relationship between the freshness shown by Limitations: Iplikci (2009), Quevedo, Aguilera, and Pedreschi (2010) Salmon fillets, irradiated Atlantic Salmon sensory evaluation and machine vision based on Roche colour card industrial standard. Although having so many advantages, the accuracy of the analysis results is subject to Misimi proposed that the computer vision and HIS technique to be a powerful tool for external factors which play a crucial role in the internal characteristics. replacing manual vision in fish processing. Concerning the HIS technique, further in- Yagiz compared the results of machine vision and HIS system with Minolta colorimeter and depth research needs to be carried out for improving the precision of the prediction the values were matching for irradiated model Atlantic salmon thus confirming its excellence. Steen and Lambelet (1997) Low field nuclear magnetic Textural changes were measured in frozen cod Advantage: resonance spectroscopy cod Using this method and it was found to be an effective alternative tool to investigate its textural modifications. Non-destructive, non-contact, fast, responsive and highly sensitive. Disadvantage: High precision and accuracy required, expensive. Costa et al. (2011) VIS/NIR Spectroscopy The texture in sea cage cultured fish showed Advantage: To discriminate between concrete higher values of measured force (N) with respect tank cultured sea bass from sea cage-cultured sea bass based on to fish reared in concrete tanks at 48-hour post- mortem. Instead 96 h results showed opposite Fast and accurate Disadvantage: textural changes. results. Limited research work done and costly. Wu et al. (2012), Coope et al. (2002) HSI , VIS Farmed Atlantic Salmon It offered fair predictions of Kramer shear force to Advantage: analyse the texture profile. Fast and accurate Disadvantage: Limited research work done and costly. 8 P.K. Prabhakar, et al. Food Research International 133 (2020) 109157 Fig. 1. Metabolism in fish muscle (autolysis). due to the breakdown of nucleotides mainly resulting from autolytic enzymatic oxidation and microbial growth includes the cycle of reduction of activity of nucleotide degrading enzymes such as adenosine tripho- bases of nitrogen and other amines to simpler forms thus deteriorating the sphatases, adenosine monophosphate deaminase and inosine mono- keeping quality (Sallam, Ahmed, Elgazzar, & Eldaly, 2007). phosphate phosphohydrolas (Mohan, Ravishankar, Ashok Kumar, & Srinivasa Gopal, 2019). 4. Fish spoilage, freshness and its mechanisms K value = (HxR + Hx )/ ATP + ADP + AMP + IMP + HxR + Hx After the fresh fish is caught, the spoilage process is too fast. In the (1) tropics with ambient climatic conditions, the spoilage starts within 12 h where HxR is Inosine, Hx is hypoxanthine, IMP is inosine 5′-mono- after their catchment. Rigor mortis is responsible for all the changes in phosphate, AMP is adenosine 5′-phosphate, and ADP is adenosine di- the fish after its death. In this process, fish lose their flexibility because phosphate. the muscles become stiff after a few hours the fish dies. All the digestive enzymes, surface bacteria causing spoilage along with partial and complete oxidation is responsible for the degradation process (Olayemi, 3. Usefulness as a chemical indicator of fish freshness Adegbola, Bamishaiye, & Awagu, 2012). The breakdown and formation of compounds are simultaneous during the fish spoilage. Semeano et al. Sea fish contains TMAO (Trimethylamine-oxide) which is broken down by bacteria to form TMA. Although some individual species of bacteria do (2018) developed a gas-sensitive hybrid gel material as an optical e- nose to monitor the spoilage of tilapia. It worked on a relationship not reduce TMAO to TMA, sufficient TMAO-reducers are always present in the normally mixed microflora on fish so that TMA will always be formed as between the changes of optical signals with time which was consistent with the reproduction of microorganisms. Morsy et al. (2016) proposed per Dheeragool (1989). Nazir and Magar (1963) found that very little or no TMA is present in the muscle immediately after the fish has been caught and a colorimetric sensor to monitor spoilage of Atlantic Salmon containing sixteen chemo-sensitive substances that were sensitive to typical spoi- killed. By measuring the amount of TMA that accumulates in fish muscle one can obtain a fairly good indication of the extent of bacterial dete- lage inducing compounds like TMA, DMA, Cadaverine, Putrescine. All these compounds together bring changes in the sensory, physical and rioration that has taken place (Lougovois & Kyrana, 2005; Prabhakar et al., 2019). Hence, TMA and TVB-N act as true chemical indicators of fish chemical characteristics of the fish muscle. spoilage.